OF THE TEMPERATURE, Of the SUBTERRANEALL REGIONS. As to Heat and Cold. CHAP. I.

IF when I used to visit mines, I had thought of writing on the subject I am now about to treat of, and had design'd to satisfie my selfe about the Temperature of the Subterraneall Air, as much as I did about the other Subjects I was then concern'd to be inform'd of, I think I should have enabled my selfe to deliver much more upon my own observation, then I shall now pre­tend to doe. But though for the reason newly intimated, and because of my being particularly subject to be offended by any thing that hinders a full freedom of Respiration, I was not solicitous to goe down into the deep mines; yet after ha­ving discours'd of the Temperature of the Air a­bove Ground, I presume it may not be impro­per or unwellcome to say something of the Tem­perature of the Subterraneall Regions and of [Page 4]the Air reaching thither. For deep mines being places which very few have had the opportunity, and fewer have had the curiosity to visit, and of which I have scarce found any thing at all obser­vable by Classick Authors, and by other writers, but very little, especially that I think probable enough to make use of, I presume it will not be unacceptable to you, if of Regions so little fre­quented, and less known, I report what I have been able to learn (by diligent enquiry purposely made) from the credible Relations of severall Eye-witnesses differing in nation, and for the most part unacquainted with each other.

Though I do not think it absurd to suspect that in some places of the Earth, the peculiar constitution of the Soil, and other circumstances, may make it reasonable to assign those places fewer or more Regions then three; yet speaking in the Generall, the Ternary number seems not inconvenient to be assigned to the Subterraneall Regions, not so much upon the score of the Ana­logy, that by this Division will be established be­tween the Regions of the Earth and of the Air, as because there seems to be a reason of the Divi­sion included in the Division itselfe. And indeed Experience appears to favour it in the Subterra­neall Cavity, that I have hitherto been able to procure an account of, from any Ocular witness, and (very few excepted) one of the deepest that we yet know of, in the world. And since it has been received for a Rule among Philosophers, [Page 5]that which is perfectest or compleatest in its kind, ought to be the Standard whereby the rest are to be measured, or estimated, I shall begin the re­maining part of this Essay by a Relation that I obtained from a Chymist, that had purposely travelled into Hungary, and other places to visit the mines those parts are justly famous for, and who bringing me the honour of a Complement from a Prince, to whom he belonged gave me the opportunity of asking him divers Questions, his Answers whereunto (which I presently after put into writing,) afforded me the ensuing ac­count.

CHAP. II.

THat very near the Orifice of the Groove, he felt the Air yet warm; but afterwards de­scending towards the lower parts of the Groove, he felt it cold, till he came to such a depth, as he had scarce attained by a quarter of an hours descent, and that the Cold he felt during this time seem'd to him considerable, especially when in descending he had reached to a good depth.

That after he had passed that Cold Region, he began by degrees to come into a warmer one which increased in heat, as he went deeper and deeper. So that in the deeper veins he found the Workmen digging with only a slight garment over them; and the Subterraneal heat was much [Page 6]greater, then that of the free Air on the top of the Groove, though it were then Summer.

[What is here mention'd of a cold region in the Earth, has been since confirmed to me by an ingenious Physitian, upon an observation made in another Hungarian mine (near a Town whose name I remember not) that was not of Gold, but Copper; and of much lesser deepnesse then that newly spoken of. For this Relator answer'd me that in going down, he felt a considerable degree of Cold. And when I ask'd whether he found the like in his Return upwards, he told me, he ob­servd it then too. And when I further inquired after the extent of this cold Region, he replyed, that not expecting to be ask'd about such Circum­stances, he had not taken particular notice of them: but thus much Information my Questions procur'd me, that he began to feel the above men­tion'd coldnesse when he could receive no more light at all by the mouth of the Groove, and that this cold Region lasted till he came somewhat near the bottom, which was estimated to be about an 100 fathom or more distant (in a strait Line) from the Top.]

This Relation agrees well enough for the main, with that short, but considerable one of Morinus, (which I elsewhere cite) who above forty five years agoe, visited the deep Hungarian-mines in the month of July, and takes notice, that when he came down to the burrows, as he calls them, he did not find any heat, as at the mouth of the [Page 7]Well; but the beginning of a very Cold, as well as considerably thick Region: though I easily beleive him, when he confesses, that he felt it much the Colder, because he had left of his own Clothes, and put on the slight Garments used there by the Diggers. He further informs his Reader, that when they had descended about 80 fathoms beneath the surface of the Earth, he be­gan to feel a breath of an almost luke-warm air; which warmth increased upon him, as he descen­ded lower, pleasing him not a little, because it freed him from the troublesome scents of his former coldnesse. Adding that the Overseer of the mine who conducted him, affirmed to him, as also the Officers of other Hungarian mines un­animously did, that in all their mines, at least all the deep ones, after a thick tract of Cold Earth, there succeeds a Lower Region, that is alwaies hot. And that after they arriv'd at such a depth, they felt not any more Cold, but alwaies Heat, how deep soever they digg. And to add upon the by, though this Learned Man lay much weight upon Antiperistasis; yet in the next page to those that contain what I have been just now relating, he either very candidly or inconsiderately takes notice, that they inform'd him, that their mines, whether more or lesse deep, they observed that at some times in the year, a somewhat intenser heat was felt, and the two Times that he expresly names, are those oppositely qualified Seasons of Summer and Winter.

Having laid down these generall narratives, I now proceed to consider the Earths Regions in particular, about which the Summe of what I yet have to propound, may be conveniently enough compriz'd in the 4 following Propositions.

CHAP. III. Proposition the 1.

THe First Region of the Earth is very variable, both as to Bounds, and as to Temperature.

The former part of this observation will not be difficult to prove, since 'twill be easily granted, that the manifest operation of the Sun-Beams is (caeteris paribus) greater, and reaches further in hot Climates then in Cold ones; in the midst of Summer, then in the depth of Winter.

The Second part of the Observation may be proved by the same Arguments as the First; to which may be added, as to some places, the Solidity or porousness of the Earth, as also the na­ture of some Salts, Marchasites, and other Bodies contained in it, which by their natural Tempe­rature may dispose the Soil to Coldness or Heat. As I shall have occasion to shew, when I come to speak of the second Region.

In the mean time I have this to observe fur­ther, That in this First Region, the Air is usually more temperate, as to Cold and Heat, then that [Page 9]above the surface of the Earth, and that this Re­gion is not wont to be considerably deep: Both parts of which Observation are capable of being made good by the same Reasons, and therefore I shall endeavour to prove them jointly.

That in the uppermost Region of the Earth, it should be less cold then above the surface, seems reasonable to be allowed upon this Consideration, That the Subterraneall Cavities of the Earth are sheltered by the thickness of the sides, from the direct action of the Sun-Beams, the Winds, &c. and is also kept from an immediate, or at least from so full a contact of the externall Air, when that is vehemently, either heated or refri­gerated.

And first as to the heat of the Sun, that That does much less powerfully affect such places as are sheltered from its action by solid Bodies, may appear by the Conservatories of Ice and Snow, wherein frozen water is kept in that State during all the Heat of Summer, and that often­times in Cavities that are at no considerable depth beneath the Superficies of the Earth. Nay I remember that having had occasion, (for the perfecting of some Conclusions I was trying) to keep Ice many weeks after the frosty Weather was gone, and a milder Season was come in, I was able to doe it, (contrary to the expectation of some Curious men,) without either digging to a notable depth in the ground, or building any substantiall Structure over the Cavity. For wan­ting [Page 10]conveniencies, I contented my selfe (though 'twere in a champain place) with a pit somewhat broad at the bottom, of about four foot deep or lesse, whose mouth was shelter'd only by a little low thatch'd hovell, that was wide open to the North, and only skreen'd the mouth or vent of the little pit from the direct Beams of the Sun. And though I will not deny, that in deep Con­servatories of Snow, the naturall Coldnesse of the Earth, especially in some places, may contri­bute to the effect; yet I remember, that discour­sing once with a Traveller and Schollar that was born in hot Countries, of a conjecture of mine that in an arch'd building, whose walls were suffi­ciently thick, and whose Air were carefully kept from all avoidable intercourse with the externall Air, one may without digging so much as a mans depth into the Ground, make a sufficient Con­servatory for Ice in very open and unshelter'd places, and even such as Salisbury plain it selfe; discoursing (as I began to say) with this Travel­ler about this Conjecture, he told me, that at a place he nam'd to me, in the Southern part of France, whose heat seem'd to me to exceed that of divers parts of Italy, some Curious persons that were resolv'd at any rate, to have Ice in Sum­mer, though the Soil were such, that they could not dig 4 foot without meeting with water, were yet able to make use of Conservatories by covering the Brick-Building they made over their pits, with Clay and Sand to a very considerable [Page 11]thicknesse, and taking care that the only place that should permit accesse to the outward Air, should be a small Northern Door to go in and out at, fitted to shut exactly close, and fenc'd with a little porch furnished with another Door. And by this means he affirms these Gentlemen to reserve the included Ice not only all the Summer long, but sometimes for two or three years to­gether, the heat of that Region making many of their Winters too mild to recruit them with Ice.

To all these things I shall add, that even where the intercourse is not quite debarr'd, but left free enough betwixt the Subterraneall and the superior Air, the operation of the Sun-Beams may be very much lesse in a Cavity though but shallow, beneath the Surface of the Ground then above it. For besides that Tryalls have in­form'd me, that Liquors that differ in little else then in consistence, will not so easily pervade each other, as a man would surmise; unlesse some ex­ternall motion hasten their intimate mingling with one another. I remember that one morning pretty late, having had the Curiosity to descend into a pit where they were digging out Iron Oar; though this Cavity had no very narrow Orifice, and was dugg directly downwards, and exceeded not ten or twelve foot in depth: yet I found not the heat at all troublesome whilst I staid there, Though the pit were in an open feild unshaded by Trees, and though the Air abroad were much [Page 12]heated at that time of the year, which was in that season (or at least very near it) that is wont to be call'd the Dogg-Daies.

CHAP. IIII.

ANd as we have shewn, that the Subterra­neal Air, even in the first Region is usually much less heated, then the Superterrestriall Air; so we may also easily observe, that That Inferi­or Air is (Caeteris paribus) wont to be much less refrigerated by the grand Efficients of intense Cold, then the Superior Air.

I will not urge on this occasion what I have observed by a surer way, then for ought I know has been before practised, about the smoaking of some Springs in Frosty Weather; because I doe not know but that those Springs may have come from, or passed a good way through, some place very deep beneath the Surface of the directly incum­bent ground, and perhaps from a Soil peculiarly fitted to warm them: whence the water may have deriv'd a warmth considerable enough not to be quite lost, till it began to spring out of the ground, where it needed only not to be quite Cold to appear to smoke; the intense Coldness of the Air making those exhalations visible in Frosty Weather, which would not be so in mil­der: As is evident in a mans Breath, which ap­pears like a smoak in such weather, though it be not visible in Summer.

That therefore, which I shall propose in favour of our observation, is first taken from the nature of the thing, which may perswade us, that the Subterraneall Air being though comparatively cool, yet indeed moderately warm in Summer, ought not to be affected with Winters Cold, so much as that contiguous to the Surface of the Earth, from whose immediate Contact, it is by a thick arch of Earth (if I may so call it) defen­ded; and that the Cold reigns most in the free Air; and the Superficiall parts of the Terrestriall Globe, may appear by Waters beginning to freeze at the Top, not at the Bottom. To which Reason from the nature of the thing, I shall add only this from experience, that we see that in Cellars that are arch'd and carefully kept close from the Communication of the outward Air, Beer, and other Liquors may be kept from free­zing in frosty, and snowy Weather. As I have ob­served in a cellar that was but shallow, but well arch'd in a Winter that was sharp to a wonder, and froze stronger Liquors then Beer in another Cellar very near it, that differed not much from it in depth, but had not so thick and solid a roof. And that not only here in England, where the Cold is less violent, but even in Russia it selfe, where it is wont to be so extream, it reaches not near so deep as one would think, I learn'd by Inquiry purposely made of an ingenious Physiti­an that lived at Mosco, who answered me, that others and he himselfe, did in that City keep all [Page 14]the Winter long, not only their Wine but their Beer from freezing in Cellars that were not a­bove 12 or 14 foot deep, but well cover'd above, and carefully Lin'd with plankes of Firr, without any entrance, but a small trap-Door (commonly at the top,) which was fitted so exactly to the Orifice it was to close, as to exclude (as much as was possible) all communication between the internall and externall Air, that the latter might not affect the former with it's Coldnesse.

I have indeed suspected that in some Cellars, the comparative warmth we find there, may be partly due to Subterraneall Exhalations that are pent up in them: and perhaps too in some measure from the Steams of the fermenting, or fermented Liquors lodg'd in those places. And I was somewhat confirmed in this Suspition, by an Information my Inquiries obtained from the newly mentioned Doctor, who told me upon his own observation, that in one of the Cellars he made use of at Mosco, having occasion to open the above mentioned trap-door, after the Cellar had for a good while been kept very close shut, there came out at the vent that was thereby given, a copious Steam in the forme of smoak, which to them, who had their Bodies affected with the externall Air, was very sensibly warm, and was almost unfit for Respiration. Which Circum­stance increased my suspition that there might be among these steames, some of the nature of those, [Page 15]that have been observed to come from fermen­ting Liquors, especially Wine, and so abound in some Cellars, as almost to stiffle those that ven­tured into those Vaults, And to kill some of them outright. Which effects the long abode of Sub­terraneall Steams in stagnating Air, even in many places, where no metalline Oars at all, not other noxious mineralls have been found, has enabled that Air to produce. Of which divers sad Instan­ces have been given within lesse then a mile of this place, upon mens first going down into pitts or Wells, that had not in a long time been open'd or made use of: (but this is here mentioned only upon the By) nor have we any necessity to fly to Subterraneall Exhalations, for the Comparative warmth that good Cellars in generall afford in frosty weather; since that Phaenomenon may be ac­counted for, by the reason formerly given, That the closenesse of the Cavity, and the thicknesse of the sides and Roofe, keep it from being vehement­ly affected with the Cold of the Ambient Air.

I know 'tis pretended that the warmth we speak of, proceeds from an Antiperistasis, but not now to engage in a controversy that would take up too much time, it may here suffice to represent, that in our case there appears no necessity of recurring to it, the Phaenomenon being solvable by the Re­gion newly cited, which may be confirmed by this Experiment, that in the Vaulted Cellar above mention'd, wherein Beer was kept from freezing, [Page 16]in an almost prodigiously sharp Winter, the in­cluded Air, though sensibly warm, to those that came out of the free Air, had not so intended its native heat, as the Assertors of An [...]iperistasis would have expected; being Colder then the free Air commonly is in that place, not only in the heat of Summer, but in other seasons, when the weather is Temperate; As I was assur'd by com­paring my own observations made at other times, with the account brought me by a skillfull per­son, whom I employ'd into that Cellar at late hours, in one or two of the sharpest nights of the forementioned cruell winter with the same excel­lent seal'd weather-glass that I had long kept sus­pended within a stones cast of that place.

CHAP. V.

HAving said thus much about the Earths up­permost Region, I now proceed to that which lies next beneath it; whose Temperature I cannot so conveniently give an account of, in less then two Propositions, whereof the First is this;

CHAP. 6.

THe second proposition relating to the Tem­perature of the second Region of the Earth, may be delivered in these Terms.

CHAP VII

I Omit to speak of the transient changes that may be occasion'd in the temperature of the se­cond Region of the Earth by severall Accidents, and especially by the Subterraneall Exhalations, that in some places and times copiously ascend out of the lower Regions of the Earth. Nor shall I insist upon any of the other causes of a more durable difference of temper in some parts of the second Region, such as may be the Vicinity of Subterraneall Fires in the third Region that heat the incumbent Soil; because I would hasten to the Third and last part of this Discourse: which yet I must not do without premising this advertise­ment, that I think my selfe oblig'd to speak the more hesitantly and diffidently about the Tempe­rature of Subterraneall Air; because mineralists have not had the Curiosity to examine it by Weather-glasses, which would give us much more trusty Informations then our sense of fee­ling powerfully preaffected by the cold or heat of the externall Air. I did indeed send fitt Instru­ments to some daies journey from this place, to examine the Air at the bottom of some of our [Page 24]deep mines: but through some unlucky casu­alties upon the place, the attempt miscarried. But when I shall (God assisting) recover an op­portunity that I have since wanted, I hope an ac­curate seal'd Weather-glasse, join'd with a porta­ble Baroscope will give me better Information then mineralists have yet done. I say a seal'd Weather-glasse because though common Ther­moscopes had been employed by miners, I durst not rely upon them; being perswaded by tryalls purposely made, as well as by the Reason of the thing, of the Fallaciousnesse of such Ther­moscopes: for in them the included Air is liable to be wrought upon, not only by the Heat and coldnesse, but by the weight or Pressure of the ex­ternall Air. So that if a Thermoscope be let down from a very considerable height, at the top of which the station of the pendulous Liquor be well markt, that Liquor will be found to have risen, when the Instrument rests at the bottom, as if the included Air were manifestly refrigerated: though the temper of the externall Air may be in both places alike, the cause of the pendulous Li­quors rising being indeed that the Aereall pillar incumbent on the stagnant Liquor, is higher and heavier at the bottom, where the Instrument rests, then that which lean'd upon it, at its first or upper station nearer the top of the At­mospher. From whence 'twill be easy to conclude that at the bottom of a deep Groove, where the Atmosphericall pillar that presses the stagnant [Page 25]water will be much longer and heavier then at the top, the Air may appear by the Instrument to be colder in places, where 'tis really much hotter, the increased weight of the incumbent Air being more forcible to impell up the pendulous Liquor then the indeavour of expansion procur'd in the in­cluded Air by the warmth of the place is to de­presse it.

CHAP. VIII.

THat which challenges the third and last part of my discourse, is the lowermost Region of the Earth, about whose temperature I shall com­prize, what I have to say in the following Pro­position.

CHAP. IX.

THat manifest Steams oftentimes are found in Grooves, especially in deep ones is evi­dent, by the damps that infest most of them, and that in distant Regions, as in severall provinces of Germany, Bohemia, Hungary, &c. as also in seve­rall parts of England in Grooves, some of which I have received Relations from the mine-men themselves. By which it appears, that severall of these Exhalations ascending from the entralls of the Earth are sulphureous & Bituminous in smell and in some Grooves (one whereof I elsewhere mention my selfe to have visited) these Steams are apt, actually to take fire.

The warmth of many Subterraneall Exhations I thinke may be made further probable by some other Observations. For though these newly [Page 30]mentioned are not to be rejected, and may be employed for want of better; yet I have severall times questioned, whether I ought to acquiesce in them alone. For I do not thinke the easy in­flammableness of Bodies to be alwaies a sure proofe of the actuall sensible warmth of the mi­nute parts it consists of, or may be reduced into. For though Salt-peter be very inflammable, yet being by a solution in fair water reduced to invi­sible Corpuscles, it highly refrigerates that Li­quor. Nor have I observed its fumes, (when far from the Fire,) to have any heat sensible to our Touch. And the like may be said of the Exhalati­ons of highly rectifi'd spirit of Wine; which yet we know is itselfe totally inflammable. Nay I know not whether, (for a Reason elsewhere de­clared) copious Exhalations may not ascend from the lower parts of the Earth, and yet be rather Cold then Hot. For (in another Paper) I menti­on a way by which I made a mixture that plenti­fully enough enitted Steams, of whose being ra­ther of a Cold, then hot nature, there was this probability, that the mixture whence they ascen­ded even whilsts its component Ingredients were briskly acting upon one another, was not only sensibly, but considerably Cold.

One main thing therefore that induces me to assent to the Opinion, whereto the former Instances do but incline me, is, That having purposely in­quired of an observing man that frequented deep mines, (wherein he had a considerable share,) [Page 31]he answered me, that he plainly observed the fumes that came out of the mouths of the deep pits, to be actually and sensibly warm, and that in a warm season of the year. And Morinus (above cited) speaking of the deep Hungarian­mines, makes it the first Epithite of the copious Exhalation that ascended from the bottom, that it was hot. And a few pages after he says, that at the mouth of the Well, the ascending Fumes were sensibly hot in Summer it selfe. And the same Arguments that I have elsewhere given to shew that there are very hot places, and as it were Ae­stuary in the Bowells of the Earth, may serve to make it probable that the steams ascending thence may be actually warm.

That also in many places of the Earth, where no Grooves are dugg, and no visible Exhalations are taken notice of, they may yet pervade the Soil, and exercise some operations of warmth, may be probable by this, that the experienced Agricola himselfe reckons it among the signs of a latent minerall vein, that the hoar-frost does not ly upon that tract of the Surface of the Earth, under which a vein (though perhaps very deep) runs. The like Directions I have known given by the skillfull in England, for the Discovery of pla­ces that contain Coal-mines. And I remember a near relation of mine shewed me a great scope of Land of his, which (though in an outward ap­pearance, likely to be as cold as any place there­abouts,) he affirm'd would not suffer Snow to ly [Page 32]upon it above a day or two in the midst of Win­ter.

The probability of which Relation was con­firmed to me by the answer I received from a ve­ry ingenious Gentleman who lives among mines, and is not a little concern'd in some of them. For having inquired of him, What he had observed about the lying, or not lying of the Snow on the minerall Soils near the place of his Residence; he replyed, that in some of them, he did not take notice of any peculiar Indisposition to let the Ice and Snow continue on them; which I conceive may proceed, either from the want of such mi­neralls in the Subjacent parts, as were then in the state of Incalescence; or else from this that, (ac­cording to what we have elsewhere observed a­bout the Snows on Aetna) the direct ascension of the hot Steams was hindered by some Layers of Rocks or other Stone, through which the Steams could not penetrate, or could doe it but so slow­ly, as to loose their actuall warmth by the way. But this Gentleman added that in other places, near that of his abode, and such as he knew to have minerall-Veins beneath them, he observed that the Snow, (nor the Ice) would scarce con­tinue at all upon the Surface of the Ground, even in an extraordinarily cold winter.

It will be a considerable Instance to our pur­pose if it be indeed true which some learned men have written that near the Gold-mines in Hun­gary [Page 33]the leaves of the trees, (especially those that respct the Ground) are oftentimes found en­nobled with a golden-colour from the metalline Exhalations of the Gold-mines; which one would think must by reason of their ponderousnesse need a considerable heat to elevate them, especi­ally into the open Air. But though doubting of this Relation, as not made by mineralists or accu­rate Observers, I inquired about it of a person, whose Curiosity carried him purposely to visit those mines, I was answerd that he could not be a witnesse to the truth of the Observation; yet he told me, an observation (which I else where men­tion) that doth not discountenance that Tra­dition.

If it be objected that what has hitherto been said about Latent Fires and heats in the Bowells of the Earth will give an account of the warmth only of those places that are within teach of the action of such Magazines of heat, which probably may be wanting in many places of the Earth, I shall rea­dily confesse, that as I first made this Objection to my selfe, so I do not yet discern it to be unrea­sonable, and that for ought I know if men had occasion to digg as deep and be as far conversant in many other low places of the Earth, where there are no signs of Mineralls, as they have done where the hopes of actuall discovery of veins of metalls, and other mineralls worth working, have in­vited them, divers places in the Third Regi­on of the Earth would be met with, that would [Page 34]bedestitute of the warmth that has hitherto been generally found in places of the same Region that either abound with mineralls themselves, or are near some of the deep and latent Aestuaries a­bove-mentioned.

And as for those parts of the Third Region of the Earth, which men feel not only warm, but troublesomly hot, that incommodious de­gree of heat seems not, (at least in some places) to be derivable from the two above mentioned cau­ses; which must, (to produce so considerable an effect) be assisted by a third cause more potent then themselves: which seems to be the inca­lescence there is produced in many mines, and other Places, by the mutuall action of the com­ponent parts promoted by water of immature and more loosely contexted mineralls, especially such as are of a Marchasiticall nature. That such an Incalescence may by such a way be produced in the Bowells of the Earth, I have elsewhere shewn (in my discourse of Subterraneall Fires & heats) by the examples of such incalescences pro­ducible in minerall Bodies here above ground. That Marchasites which for the most part abound in Vitrioll, are bodies very fit to procure this Subterraneall heat, may be consirm'd not only by the Sulphureous and Saline parts they abound with, and by this, that many of them may be wrought on, as we have tryed, both by simple water, and even by moist Air, which argues the re­solublenesse of their Constitution: but also by [Page 35]this, that having purposely inquired of a Gen­tleman that went out of Curiosity to visit one of the deeper Hungarian mines, he confirmed to me what I had otherwise been informed of, by an­swering me, that in the lower parts of the m [...]ne, he had gathered Vitrioll that app [...]ared above ground to be of a golden nature; and that in a Cave that is on one side of the Groove, in the deep Gold-mine near Cremnitzo, the corrosive smell is so strong and noxious, that men have not dared to dig out the native Gold it richly abounds with, being deterr'd by the ill fate of livers that ventured to work in it. Adding that though he passed by it, in great hast; yet he could not avoid the being offended by the noysome Exhalations. And on this occasion, 'twill not be (I presume) disliked, if I illustrate what I was saving of Im­mature mineralls, by subjoining, That having, asked this Chymist whether the Vitrioll he found very deep underground were all solid, or some of it soft? he affirm'd that as he gathered it, he found some of it soft. And to satisfy my curiosity to know whether it continued that yeilding consi­stence? he further told me, that it was soft in the deeper part of the mine, but when he had brought it into the Superterrestriall Air, it hardened there and appeared to have 9 divers golden streakes in it.

CHAP. X.

ONe thing there is, which must not be here [Page 36]omitted, though it will probably be great news to those that philosophize only in their studies, and have not received information from any that visited the deeper parts of the Earth: The Phaeno­menon is this, That the Diggers in mines having found by unwelcom experience that in deep Grooves, the Air (unless ventilated and renewed) dos in a short time become unfit for respiration, have been put upon this expedient, to sinke at some convenient distance from the Groove where the miners worke, another pit (by some called a vent pitt) that usually tends directly downwards (though sometimes it make Angels) to which our English-minemen do in severall parts of this King­dom give differing names; whereof the most sig­nisicant seems to be that given it in the Leadmines of Darbyshire, where they call it an Air-shaft, and are wont to make it 40, 50, and sometimes 80 or 100 paces off, and, (as one of the cheife and skillfull Miners there informed me) as deep as the Groove or Well; (Though I find that the best German and some English Miners think a less depth will often suffice) From this Air-shaft to the Groove the men work in, there passes a Chan­nell or if I may so call it, Ventiduct to convey the Air from the former to the latter; which is that, that Agricola sometimes (for he employs not the Terme alwaies in the same sense) denotes by his Cuniculu; Lib. V. [...] VI. De re metall. and which though differingly nam'd by our Miners in severall parts of England [Page 37]is in the above mentioned Lead-mines called a Drift, because the Air dos usually in the form of Wind drive thorow it: and thereby enables the Workmen to breath freely and conveniently e­nogh at the very bottom of the Well. On this oc­casion I remember that a very observingrman who much frequented these Mines told me, that at the depth of no less then about 200 yards, be found that by the help of the Air-shaft, the Air was not only very commodious for Respiration, but tem­perate as to heat and Cold. And when I further asked, what time of the year it then was? he told me 'twas about the latter end of August and the beginning of September.

Now that which seems to me to deserve a farther and accurate observation about the motion and Temperature of the Air in these Artificiall under ground Cavities, is a Relation of Agricolas which, (though he be the most Classick Author we have about m [...]nes,) has not (that I know of) been taken notice of, in him. For this experienced VVritter, though in his Treatise Idcirco f [...]robes, putei cuni­culi eff [...]ssi complentur exte­riore Aere. Atque ipsum in cos influere imprimis hyema li tempore evidens est in duobus puteis, ad quorum u­trumque ex modico interval­h cuniculus aliquis pertinet. Nam Aer in unum continuo influit rectâque per cunicu­l [...]m permeat & transit ad alterum; atque ex eo rursus evolat foras. de Ortu & causis Subterraneo­rum, he only sayes indefi­nitely, that by means of the Cuniculus or Drist, which connects the Air-shaft & the well, that Air which comes in at one of those two, passes out at the other; yet in his Fifth Book [Page 38] de re metallicâ he gives a more particular and odd account of the course of the Air in these not over clear Terms, Aer autem exterior se suâ sponte sundit in cava terra, atque cum per ea penetrare potest, rur­sus evolat soras. Sed diversâ ratione hoc sieri solet; etenim vernis & aestivis diebus in altiorem puteum influit, & per cuniculum vel fossam latentem perme­at, ac ex humiliori effluit similiter iisdem diebus in altiorem cuniculum infunditur, & interjecto puteo de­fluit in humiliorem cuniculum atque ex eo emanat. Autumnali verò & hyberno tempore, contra in cu­niculum vel puteum humiliorem intrat, & ex altiori exit: verum ea fluxionum Aeris mutatio in tempera­tis Regionibus fit in initio veris, & in fine Antumni: in frigidis autem, in fine veris & in in initio Au­tumni. To which he adds that which is more re­markable; That the Air in both the mentioned times, Sed Aer utroque tempore an­teaquam cursum suum illum cons [...]etum co [...]st [...] teneat plerum [...] di­erum spacio [...] habet mutationes, [...] [...]ltiorem [...] [...]el cuniculum ins [...]a­ens, modo in humiliorem. before its wonted course come to be dura­bly setled, uses to be for the space of a fortnight li­able to frequent changes, sometimes flowing into the upper or higher groove or Drift, and sometimes into the lower, (and passing out at the other.) If this Observation con­stantly hold, though but in some deep Mines, it may hint some odd inquiries, about considerable and [...] changes in the Subterraneall parts of the Earth, or in the Air, or in Both, which though they have not yet been considered, deserve [Page 39]be so. I have endeavoured to learn whether any such thing has been observed in some deep Lead-mines, whence I have procured divers informati­ons about other particulars. But a very observing Person, that had the chief hand in contriving the Subterraneall structures there, assured me that both VVinter and Summer, the current of Air, went constantly the same way: the Air entring in at the Mouth of the Air-shaft, and coming out at the Perpendicular Groove, which takes its deno­mination from a Cave, (or Casa Pu [...]ealas) usu­ally built over the Orifice of it, to shelter the Workmen from rain, and other inconvenien­ces.

And since the writing of this, I found in Mori­nus (his Relation already mentioned) a passage that may somewhat illustrate the darkly exprest Observation of Agricola. For the lately men­tion'd Author writes, that in the deep Hungarian-Mines he visited, the outward Air passed (first) through the Burrows, and so through By waies, (if I may so call them) that tended not directly downwards, reacht at length to the bottom of the VVell, or perpendicular Groove, whence, together with the Steams proceeding from the Mine) is ascended strait upwards. But Morinus taking no notice at all of Agricola's Observation about the differing course of the Subterraneall Air at differing Seasons of the year: though (as I find by what he writes elsewhere,) 'twas Sum­mer when he visited the Mines, and so what he [Page 40]reports, agrees well with one part of what Agri­cola seems to say; yet, as to the other, and prin­cipall part of his Observation, he says not any thing. And the sensible heat he ascribes to the steams ascending out of the perpendicular Well, leaves it somewhat dubious, what interest the Rarefaction of the Air, by the Subterraneous Heat may have in the Phaenomena we have been dis­coursing of.

But to return to what I was saying before I had occasion to mention Morinus. Which per­haps it will not be impertinent to add, that I loarn'd by inquiry, that the Air-shafts, and the Wells, were in these Mines much of a depth. But I hope ere long to have accounts of what happens in other mines, in other parts of Eng­land, as to the course of the Subterraneall Air especially when its issuing out of the Well, or the Air-shaft depend not on the changes of the Winds that blow above ground: And I wish the curious would employ the like endeavours in o­ther Countries.

For indeed what I have hitherto discoursed in this Treatise, is accommodated but to the scant Information I have hitherto receiv'd; and there­fore ought to be rectified or Confirmed by farther Informations if they can be procur'd.

In the mean time, I think I may probably e­nough, gather from the pas't Discourse, that though in some Mines, three Subterraneall Re­gions, and their distinguishing Attributes, may [Page 41]be not inconveniently assigned; yet generally speaking of the whole Body of the Terrestriall Globe (as farr as we know it) both the Bounds and the Temperature of the Regions of the Earth, as well as those of the Air, are various and un­certain enough.

And much less have we any certain knowledge of the Temperature of the more inward, and (if I may so speak) the more Centrall parts of the Earth; in which, whether there be not a continu­ed solidity, or great Tracts of Fluid matter, and whether or no, differing Regions are to be distin­guished, and what their number, Order, thickness, and qualifications may be, we are as yet ignorant, and shall I fear long continue so, For it is to be noted (with which observation I shall conclude) that what has been hitherto discoursed, belongs only to the Temper of those Subterraneall parts, to which men have been enabled to reach by Dig­ing. 'Tis true indeed that some Mines especially in Germany, and Hungary are of a Stupendious depth, in comparison of the generality of ours, and of the more obvious Cavities of the Earth; yet I find it boasted in a Discourse written purposely of the Various Mines, in the VVorld, that the rich Mine at Sueberg is 400 yards deep: And they are scarce believed, that relate one Hungarian-Mine which they visited to be 400 sathom; which though double the depth of the former, reaches not to half a mile. But the deepest of all the mines that I have as yet read or heard of, from any cre­dible [Page 42]Relator, is that which the experienced A­gricola in the Tract he calls Bermannus, Cap. 12. mentions to be at Cotteberg. But this it self though it reach to above 500 fathom, that is, 3000 foot, yet this prodigious depth dos not much exceed halfe a mile & fals short of three quarters, Licet variae de ambitu ter­vae opiniones sint, nobis ta­men propemodum constet, esse ipsam milliarum Italia­rum 26255, quod in maxi­mo ad Terrae superficiem cir­culo respondeant uni gradui milliaria proximè 73. &c. Gassend. Instit. Astronom. Lib: 2. Cap. 13. and how small a part is that of the whole depth of the Terrestriall Globe? whose semidiame­ter, if we admit the recent account of the Learned Gassendus, reckoned at 4177. Italian miles: in comparison of which, (as I was saying), how small a thing is a depth that falls very short of a single mile?

OF THE TEMPERATURE, Of the SUBMARINE REGIONS. As to Heat and Cold. CHAP. I.

THough the Aristotelians who believe wa­ter and Aire to be reciprocally trans­mutable, doe thereby fancy an Affinity between them, that I am not yet convinced of: yet I readily allow of so much Affinity betwixt those two fluid Bodies, as invites me (after ha­ving treated of the Temperature of the Aeriall Regions) to say something of that of the Submarine Regions: which name of Submarine, though I know it may seem Improper, I therefore Scru­ple not to make use of, because even among the Generality of Learned Men use has Authorized the name of Subterraneous Places. For as these are not by this name, and indeed cannot in Reason be supposed to be beneath the whole Bodie of the Earth, but only the Superficiall parts of it: so by the Appellation of Submarine Regions 'tis not to be supposed that the places so called are below [Page 4]the Bottom of the Sea, but only below the sur­face of it.

But to come from words to things, I presume it will not be expected that I that never pretended to be a Diver should give of the Regions I am to treat of, an Account build on my own Observati­ons; and I hope it may gratifie a Reasonable Cu­riosity about a subject, of which Classick Authors are so very silent, and about which Philosophers seeme not so much as to have attempted any Ex­periments (for want of Opportunities and mean to make them.) I offer the best Information I could supply my selfe what by purposely con­versing with Persons that have dived some with­out, and some by the help of Engins. To which I have added some reports that I judge fit to be allowed, made me by Persons that had conversed with the Divers upon those Affrican and Indian-Coasts, where the most famous and expert are thought to be found.

And I the rather report the Answers and Relati­onsmy Inquiries procur'd because the Informati­ons they give us concerne a subject considerable as well as vast, about which neverthelesse I among many others am not in a condition to sa­tissie at all my Curiosity by Tryalls of my own making, and because also what I shall say will probably spoile the credit of the Vulgar Er­ror that in all deepe water of which the Sea is the Cheifest, the lowermost are still the warmest parts, unlesse in case that in some very hot Cli­mates [Page 5]or seasons, the superficiall ones happen to be a little warm'd by the Extraordinary or Vio­lent heat of the Sun.

CHAP. II

THough the Air and the Earth have been discriminated as to Temperature into three Regions; yet the Informations I have hitherto met with, invite me not to assign to the Sea any more then two. The former of which may be supposed to reach from the superficies of it, as far downwards as the manifest operation of the variously reflected and refracted Beames of the Sun, or other Causes of warmth penetrates: from which to the Bottom of the Sea, the other Region may be supposed to extend.

According to this Division the Limits of this upper Region will not be alwaies constant; for in the Torrid Zone and other hotter Climates, it will, Caeteris paribus, be greater then in the Frigid Zone or in the Temperate Zones: and so it will be in Summer then in Winter: and in hot weather then in Cold; supposing in these Cases the Heat to come from the Sun and Air; and not, as sometimes it may do, from the Subterraneall Exhalations.

The same causes are likewise proper as 'tis manifest to alter the Temperature as well as the Bounds of this Region, But this Temperature [Page 6]may also be changed in some few places by at least two other Causes; The one is the differing constitution of the Soil that composes the Shore, which may affect the neighbouring water if it doe extraordinarily abound with Nitre, loosely con­texed marchasites, or other substances capable considerably to encrease or lessen the Coldnesse of the water. Another though unfrequent Cause, may be the figure and situation of the lesse deep parts of the Shore, which may in some sort re­verberate the Heat that proceeds from the Sun; and upon such an account may either add to the warmth, or allay the Coldnesse that would else be found in the neighbouring water. For whate­ver the Schools are wont to teach about the Inte­rest of the Attrition of Air in the heat produced by the Sun Beams, I have elsewhere shown by Experiments, that those Beams may considerably operate upon Bodies placed quite under water.

Besides these two Cases that may occasion Ex­ceptions to the generall Observation; I intimated by the words, at least, that there might be others. Because, to mention now but one Example, though it seem probable from what I have else­where delivered concerning the Subterraneall Fires and Heats, that may in some places be met with, even beneath the bottom of the Sea, that the Phaenomenon I am going to recite may be reduc'd to the causes newly intimated; yet I am not abso­lutly certain but that in this case, whereto some o­thers may perhaps be found resebling, some other [Page 7]cause, then those hitherto mentioned, may produce or concurre to the effect. The Relation here meant is afforded us by the following Passage, taken out of the Voyage of Monsieur de Monts into New-France, (whereof he went to be Governor) where the Relator thus recites his observation. About the eighteenth day of June we found the Sea-water during three dayes space very warm, and by the same warmth, our wine also was warme in the bottom of our ship; yet the Air was no hotter then before. And the 21 of the said moneth, quite contrary, we were 2 or 3 days so much compassed with mists and cold, that we thought our selves to be in the moneth of January, and the water of the Sea was extreame cold: which continued with us untill we came upon the Bank by reason of the said mists, which outwardly did procure this cold unto us. This effect he attributes to a kind of An­tiperistasis in the following part of his narrative; which I shal not now either transcribe or examine.

CHAP. 3

And thus much being breifely noted touching the upper Region of the Sea, and the requi­site Cautions (that may perhaps extend further then it) being premised; it remains that I take no­tice of the Temperature of the Lower Region, which, in one word, is Cold (unlesse in some few places to be presently mentioned.) For water be­ing [Page 8]in it's naturall or most ordinary state, a li­quor whose parts are more slowly agitated then those of mens Organs of Feeling, must be upon that account Cold as to sense: and consequently it need not be strange that those parts of the Sea, which are too remote to be sensibly agitated by the Sun-Beams, or wrought upon by the warmth which the Air and upper parts of the Earth may from other Causes receive, should be felt Cold by those that descend into it; unlesse in those few places where the Coldnesse may be either ex­pell'd or allay'd by hot Springs or Subterrestriall Exhalations, flowing or ascending from the sub­jacent Earth, or the lower parts of the shore into the incumbent or adjacent parts of the water.

To justifie my ascribing of this Coldnesse to the second, or lower Region of the Sea, I shall now subjoin some Relations I procur'd from per­sons that had occasion to goe down into it, or o­therwaies take notice of its Temperature in very differing Regions of the World, and at very une­quall depths.

And first as to the Temperature of the lower Region in the Northerne Sea, I had the opportu­nity to converse often, and sometimes to oblige a man bold and curious enough, who for some years got the best part of his subsistence by de­scending to the bottom of the Sea in an Engin, whose structure I elsewhere describe, to seek for, and recover Goods lost in Shipwrackt Vessels. This person I diligently examined about divers [Page 9] Submarine Phaenomena, about which his an­swers may be elsewhere met with. And as to the Temperature of the lower parts of the Sea (the knowledge of which is that alone that concerns us in this place) he severall times complained to me of the Coldnesse of the deep water, which kept him from being able to stay in it so long as he might have been put into a condition of do­ing by the goodnesse of his Engin; for I remember that he related to me that he staid once betwixt an hour or two, at a depth that was no greater then 14 foot and a half upon the coast of Sweden, in a place that was near the shore; and I after­wards learnd that he staid much longer in a dee­per place; (use having probably made the Cold more supportable to him) He told me then, that about two years before he was engaged by a good reward to goe down with his Engin to the bottom of the Sea to fetch up some Goods of value out of a Ship that had been cast away there within a­bout a miles distance from a very little Island, and if I mistake not about 6 miles from the Shore. He farther answered me that though he felt it not at all Cold on the Surface of the Water (his attempt being made in June) yet about the depth of the Ship, it was so very Cold, that he felt it not so Cold in England Winter and Frosty VVeather. And he told me that an excessive Cold was there felt not only by him but by very sturdy men, who invited by his example, would needs also goe down themselves to participate and promote the [Page 10]hoped for Discovery. He told me also, that the upper water did but cool and refresh him; but the deeper he went the Colder he felt it, which is the more considerable, because he had some times occasion to stay at 10 fathoms or even 80 foot under water. And I since found that he in­formed divers Virtuosi, that purposely consulted him, that he found the Coldnesse of the Water encrease with its depth: and gave that for the reason why he could not stay so many hours as otherwise he might, at the bottom of the Sea. Adding that before his Engin was well fitted, he was once so covered over with it, that he was forced to touch the ground with his hands and feet, and the neighbouring parts, to which he found a Coldnesse communicated by the Fundus he lean'd upon; though the closenesse of his dis­ordered Engin made the other, and (whilst he was in that posture) upper parts of his Body, of a very differing Temper.

An inquisitive person of my acquaintance that made a long stay in the Northerne America (at about two or three and forty degrees of Lati­tude) and diverted himselfe often with swimming under water, answered me, that though he scarce remembred himselfe to have dived above two fathoms beneath the surface of the Sea; yet even at that small depth, he observed the water to in­crease in coldnesse, the lower he descended into it. Which argues, that though the Sun-Beams do often penetrate plentifully enough to carry light [Page 11]to a great depth under water; yet they doe not alwaies carry with them a sensible heat: and that at least in some places, the upper Region of the Sea reaches but a little way.

The coldnesse of the Climate in these western parts of Europe, and the want of considerable in­ducements to invite men to dive often to any great depth into our Seas, has kept me from be­ing able to procure many observations about the temperature of their lower Region, but upon the hotter Coasts of Africk, and the East-Indies, the frequent Invitations men have to dive for Corall, pearles, and other Submarine Productions, has made it possible for me to get more numerous observa­tions: some of which I shall now annex.

CHAP. 4.

MEeting with a Person of Quality who had been present at the sishing of Corall upon the shoar of Africa, and Who was himselfe pra­ctised in diving, I inquired of him whether he found the Sea upon the African Coast to be much colder at a good depth, then nearer the surface; whereto he answered me, that though he had sel­dome dived above three or four fathoms deep, yet at that depth he found it so much colder then nearer the Top of the water, that he could not well endure the coldnesse of it.

And when I farther asked him whether when he [Page 12]was let down to the bottom of the Sea in a great diving Bell (as he told me he had been) he felt it very cold, though the water could not come im­mediately to touch him, he replyed that when the bell came first to the ground, he found the Air in it very cold, though after he had staid a while there, his breath and the steams of his Body made him very hot.

That also at a greater depth in those hotter Climates the Sea-water is sensibly Cold may be thus made probable, Inquiring of a famous Sea-Commander who had been upon the Affrican Coast, to what depth he was wont to sinck his Bottles to preserve his Wine any thing coole in that excessive hot Climate, he Answered me that in the day time he kept it in a tolerable temper so as to be drinkable, by keeping it in the Bottom of the ship, and in sand, but in the morning he had it coole enough by sincking his Bottles over night into the Sea, and letting them hang all night at 20 or 30 fathom deepe under water.

Inquiring also of an intelligent Gentleman that was imploy'd to the river of Gambra, & sayl'd up 700 miles in it, in a small frigot, whether he had observed that in the Sea, even of those hot climats, wine may be preserved coole, he told me that it might, and that by the means I hinted to him, which was to let down when the ship came to an Anchor in the Evening severall Bottles full of wine (they used that of Madera) exactly stoped to ten, 12, or 14 fathoms deep, whence being the next [Page 13]morning drawn up, they found the wine coole and fresh (as if the vessels had been in these parts drawne up out of a well) provided it were pre­sently drink, for if that Circumstance were o­mitted, the heat of the Aire on the upper part of the water would quickly warme the Liquor.

I remember too, that having met with a man of Letters that sail'd to the East-Indies in a Portugal-Caraet, I learnt by enquiry of him, that 'twas the practice in that great Vessell for the Captain and other Persons of note, whilst they passe through the Torrid Zone, to keep their Drink, whether Wine or Water, cool, by letting it down in bot­tles to the depth of 80, 90, anc sometimes an hundred Fathom or better, and letting it stay there a competent time; after which he told me he found it to be exceeding cool and refre­shing.

Lastly, to satisfie my selfe as far as I could, to how great a depth the Coldness of the Sea rea­ched; meeting an observing Traveller whose affairs or Curiosity had carried him to divers parts both of the East and VVest-Indies, I enquired of him whether he had taken notice of any extraordinary deep soundings in the vaster seas, To which being answered, that some years agoe sailing to the East Indies in a very great ship, over a place on the o­ther side the Line that was suspected to be very deep, they had the Curiosity to let down 400 Fathom of Line, and found they needed no lesse. Whereupon I enquired of him, whether he had [Page 14]taken notice of the Temperature of the sounding Lead assoon as 'twas drawn up: To which he told me, that he, and some others did; and that the Lead which was of the weight of about 30, or 35 l, had received so intense a degree of coldnesse as was very remarkable; insomuch that he thought that if it had been a masse of Ice, it could not have more vehemently refrigerated his hands: and when I asked in what Climate this observation was made, he told me 'twas in the Antarctick Hemis­phere, but at a great distance from the Line. As indeed I concluded by some Circumstances he mentioned to me, that 'twas about the 35th de­gree of Southern Latitude.

CHAP. 5.

These are the cheife Relations I have hi­therto been able to procure about the Tem­perature of the Sea; which if they be so confir­med by others, as that we may conclude they will generally hold; it wil not be irrational to conceive that in reference to Temperature, those two Fluids, Air and Water, may have this in com­mon, that where their Surfaces are contiguous, and in the neighbouring parts, they happen to be sometimes cold, and sometimes hot, as the parti­cles they consist of, chance to be more or lesse a­gitated by the variously reflected Sun-Beams, or more or lesse affected by [...]ther causes of Heat. [Page 15]But that part of the Air which they call the second, & is superior to the first, as also the lower Region of the Sea, being more remote from the operati­on of those causes, doe retain their naturall or more undisturbed Temperature, which, as to us men, is a considerable degree of coldness, the Agitation of their small parts being usually in those Regions much inferior to that of the Spirits, Blood, & other parts of our Organs of Feeling. So that the Regions of the water and Air seem to answer one another; but in an inverted order of situation, and the Ana­logie might perhaps be carryed further, if I had time and opportunity to doe it in this place. And here I shall not dissemble that I was some­what perplexed by meeting with a traveller that had visited the East- Indian Coast, near the famous Cape of Comory: for asking him some questions touching the neighbouring Sea, I gathered from his discourse, that he concluded from that of some Divers, that the Sea near Ceylom was warmer at the bottom then at the top. And when I there­upon asked him whether this happened not in their Winter, he replyed that it was indeed Winter, though not with us, yet with them; it occurr'd indeed to my thoughts on this occasion, that perhaps in a part of the Torrid Zone so near the Line as about 80 degrees, if the Sea were not of a considerable depth, the heat of the two not far distant shores of Coromandell and Ceylom might have no small influence upon the Tempe­tature of the water. I considered also (which [Page 16]did not a little weigh with me) that in divers parts of the East-Indies, and even in a Region bordering upon Coromandell, where an ingenious Acquaintance of mine lived some years, it has been observed, that Winter and Summer are not so much discriminated by Cold weather & Hot, as by very Rainy weather and very dry. Nay in some places the sultry heat of the Climate is more complained of, in what they call their Winter then their Summer. So that there will be no necessity to recur to an Antiperistasis occasioned by the coldnes of the Winter. I thought too, that it may perhaps be without absurdity suspected, that as the bottom of the Sea in this place had a peculiar Constitu­tion that fitted it more then others for the copi­ous production of pearls: so there might be some peculiarity in the nature of the subjacent Soil, or there may be some Subterraneali Fire or heat be­neath it, which may occasion an unusuall warmth in that part of the Sea, by w ^ch cherishing warmth, perhaps such abundance of shell Fishes teeming with pearls, may be invited to settle there rather then in any of the neighbouring places. But with all these conjectures, I should not have been so well satisfied, as with the answer I afterwards ob­tained by a Gentleman whose Curiosity had car­ried him to be an assiduous Spectator of the famous pearl-fishing near the Island of Manar; between that and the Coast of Coromandell, which reaches near, if not fully to the Cape of Comoris. For this Person having had much Conversation with the [Page 17]Divers for Pearls, not only learn'd from them, that they found the water very sensibly Cold at the bottom which in some places he estimated to be 80 or 100 fathom deep; but observd divers of them at their return to the Boats, to be ready to shake with Cold, and hasten to the fires that were kept ready for them in little Cabines upon the shore: Which Relation being accompanied with divers Circumstances of credibility and arguing the person that made it to have been acquainted with the report above mentioned, and had met with some that had dived in the place whereto it had relation, made me conclude that as to that re­port hither something extraordinary had hap­pened in that place, or that there was some mistake of him to whom 'twas made, or that di­vers did not descend to a sufficiently considerable Depth

If I had been furnished with opportunity, I would have engaged some ingenious Navigators to examine the Temperature of the Submarine-Regions, both of differing seasons of the year (especially the hottest part of Summer and Coldness of Winter, & with Hermetically seal'd Weatherglasses in order to the Discovery of such Particulars as these, Whether there be in some Seas any such varying Differences of Tempe­rature, as may invite us at least in some places, to make more then two Submarine Regions. Whether the Submarine Coldnesse do at the bottom of the Sea, or elsewhere either Equall or [Page 18]surpasse that degree which we here find sufficient to freez [...] common water. Whether the parts of the Sea-water are still the Colder, as they are the deeper, And Whether or no this increase of Coldnesse be regular enough to be reducible to any settled proportion. But for the resolving of these and the like Questions, I did not cause­lessely intimate that a sealed Weather-glass was to be employed; for I take a common one to be al­together unfit for such purposes, not only because the Sea-water would mingle with such Liquors as are wont to be employed in it, for that In­conveniency I could easily remedy, by substi­tuting, as I have severall times don in other cases, Mercury instead of ordinary Liquors: but cheifely because the incumbent Sea-water would gravitate upon the restagnant Liquor of the Weatherglass, and thereby render its Informations false or un­certain. According to what I have had occasion to observe in another Tract.

Whereto, that there may not in this place be any need to recur, I shall add a slight experiment that I made for the satisfaction of some Ingenious men not w [...]ll acquainted with Hydrostaticks, or not rightly principled in them. And this Tryall I shall the rather mention, because many will not allow Water to press upon Me [...]cury immersd therein, t [...]s being a far more ponderous Liquor then that; and others will expect, that the inclu­ded Air, having no place to escape out at, should resist the ascension of the subjacent Mercury, more [Page 19]than indeed it will. We made then a small Weather-glasse differing from common ones, (besides the bignesse,) in that it was turnished with Mercury instead of Water; and in that we em­ployed to contain the stagnant Mercury, a Glass Viall with a narrow neck, wherein (by a piece of Cork or two) the Stem of the Glass ball was well fastened that this globula put of the Instru­ment might not be lifted up when it was under water. Then having by applying cold water to the outside of the Ball endeavoured to reduce the Air to the same Temper with the Water, or at least to an approaching degree of Coldnesse; and ha­ving taken notice of the Station of the Mercury in the shanck or stem above mentioned; we did, (by strings tyed about the neck of the small Vial) let the Instrument gently down into a large tall glas Body filled with fair water that the Liquor and Vessell being both transparent, we might easily perceive the motions of the Mercury in the slender pipe. By which means it appeared, that as the Thermometer descended deeper and deeper into the Water, the Mercury was pressed up higher and higher in the Stem. And that it may not be suspected, that this ascension proceeded only, or cheifely, from the refrigeration of the Air by the Water, I shall add to what I have just now noted, that though the Coldnesse of the VVater may well be supposed uniform as at least to sense; yet the whole instrument being leasurely removed sometimes to the upper sur­face [Page 20]of the VVater. (The like Experiment we might have tryed with a Thermoscope furnished with VVater and let into Oyl; or with deli­quated Salt of Tartar and pure Spirit of VVine instead of Mercury and Water: if we had been furnished with sufficient quantities of those Li­quors and had judged it to be requisite.) But this Circumstance, I thought fit to admonish the spectators of, that tis not to be expected, that the Mercury should rise as much in proportion when it is (for example) a foot under water, as when it is but two or three Inches; because according as the Instrument is let down deeper and the Air crowded into a less room, the Spring of that com­pressed Air becomes the stronger and makes the more resistance. VVhich Advertisement agreed well with the Experiment, whose other Phaeno­mena I pas over as not pertinēt to this place, where I would only justifie what I said of the unfitnesse of Weather-glasses made (though with other Liquors) after the Common waies for ma­king the Submarine Tryalls I proposed.

But till such Artificiall Observations can be ob­taind we may from what has been above delive­red, probably gather that though the lowermost of the Submarine Regions be very sensibly Cold, yet VVater, at least that of the Sea, does not by these Phaenomena appear to be the Summum Frigidum. Though I have been severall times a­ble to produce Ice in Saltwater, yet I find not by any Observation, that there has been Ice met with [Page 21]and generated at the bottom of the Sea, under which the Earth has been found unfrozen by our Divers; and appears to be soft at depths excee­dingly surpassing the greatest they have reacht; as is evident by the Mudd, Gravell, &c. fetch'd from the bottom of the Sea by sounding plum­mets, let down to 80 or 100 fathom, or even a depth, whereof examples may be met with in the Journalls of Navigators; n [...]y, my curio­sity procur'd me this account, from the sober Commander of a ship, that came this year from the remoter parts of the great Ocean, that at a­bout 35 degrees of Southern Latitude, the tal­low with which his sounding Lead was annointed brought him up gray Sand from the immense depth of no less then two hundred & twenty Fa­thom. But to this Observation tis just to annex this Caution, That we cannot safely conclude from mens finding no Ice at the bottom of the Sea, that the Cold there cannot be very intense; for as I have found by more then one Relation ( Notes aboat the Salt­nesse of the Sea. elsewhere re­cited) that, whatever the Schools surmise, the Sea is at least as Salt at the bottom, as at the top: so I have more then once tryed, that Salt water will without freezing ad­mit a much greater degree of Cold, then is ne­cessary to turn fresh Water into Ice.