Three tracts written by Robert Boyle.

RELATIONS About the BOTTOM OF THE SEA.

RELATIONS about the Bottom of the Sea.

The First SECTION.

I Do not pretend to have visited the Bottom of the Sea, but since none of the Naturalists whose writings I have yet met with, have been there any more then I, and 'tis great rarity in these cold parts of Europe to meet with any men at all that have had at once the Boldnesse, the oc∣casion, the Opportunity and the Skill to penetrate into those conceal'd and dangerous Recesses of Nature, much less to make any stay there, I pre∣sume it will not be unpleasant, if about a subject, of which, though none of those very few Natura∣lists that write any thing at all, write otherwise then by hear-say, I recite in this place, what I have learn'd by Enquity from those Persons that among the many Navigators and Travellors I have had opportunity to converse with, were the likeliest to give me good Information about these Matters.

It would be needless here to take notice, that the Sea is usually Cold and Salt at the bottom, nor to repeat those other Things that I have al∣ready

delivered in other Discourses. I shall there∣fore begin what I have to say in this, by relating that one of the chief things that I was solicitous to enquire after about the Bottom of the Sea, was, the inequality I supposed to 〈◊〉〈◊〉 in the Soil. For though the surface of th•• Sea when 'tis not agi∣tated by the winds, appears very plain and levell, and though it be indeed, at least i•• this or that particular Sea, Sphaericall and (Physically speak∣ing) concentricall to the earth; yet I could not think it probable, for Reasons not necessary to be here discoursed of, that the Bottom, the Super∣ficies of the Ground, or of the Vess ll that con∣tained it, should be either flat or levell, or regu∣larly concave.

To satisfy my selfe about this matter, I enqui∣red of a Person that had visited the famous Pearl fishing at the little Island of Manar (near the rich Isle of Ceylon) in the East Indies, and had by his stay there much opportunity to see Divers at their Work and converse with them. By the An∣swers of this man who was a Scholler, I learnt, that the Divers had assured him, That they found the Floor of the Sea, if I may so call it, in divers places exceedingly unequall, in some places be∣ing flat, in others asperated with crabby Rocks a considerable height, and elsewhere sinking into precipitous depths in which they found it very cold.

Besides the recited Testimonies of the Divers, I enquired of severall Pilates and other Naviga∣tors,

that had made long Voyages, what gradu∣all or abrupt inequality they had observ'd at their Soundings in very neighbouring places; it being easy to be gat••ered from thence, whether the Sea were there uniformly deep, or did at least with some regularity alter its depth by degrees, or whether as I suspected, there were not at the bottom of the Se••, ••illy places, and steep Praeci∣pices, and perhaps deep Vallies or Wells, as we observe in the discovered part of the Terrestriall Globe.

By these inquiries I obtained severall Observa∣tions, whereof the most materiall are those that follow.

First, An ancient Sea-Commander, that had many years frequented Africa and the Indies, told me as others had don before, that when they sail'd in the Ocean very far from sight of Land, they did not often put themselves to the trouble of Sounding, but that as far as they had Sounded, he had usually found the depth of the Sea, to in∣crease or decrease gradually, without very great irregularities, excepting some places, instancing particularly in the Excavation that makes the Bottom of the Sea, within sight of the Cape of good Hope, where though for the most part, he found the water to deepen more and more as he sailed farther from the shore, yet in one place, he and others had met with a Bank (as he conceived it to be) at a considerable distance from the sur∣face of the Water. So that though when they

were as they imagined near the edge of that bank, they found but a moderate number of fathoms, yet when sailing a very little way farther, they had gone beyond it, they found the Sea of an immense depth. In short, I gathered from his Answers, that in the greater Seas, he had found for the most part, the ground at the bottom, to fall away by degrees; but nearer the shores, that is, with∣in a moderate number of Leagues, he observed in divers places that the Submarine Ground was ve∣ry unequall, and had as it were, Hills and Prae∣cipices.

A man of Letters, that had sailed both to the East and West Indies, and in divers other Regi∣ons besides, and had made some of his Voyages in ships of such great burden, as obliged the Mar∣riners to be very frequent and carefull in sound∣ing, informed me, that some times at considera∣ble distances from shore, he had observed the Sea to be 20, 30, or perhaps 40 fathom deeper when they cast the sounding Lead from one side of the ship, then it had been just before, when they had sounded from the other, and from other Things that he told me, I found my self much confir∣med in the above proposed Opinion.

Hearing of a Sea-Captain of extraordinary skill in Maritine Affairs, that was come home this year from East-India, his reputation made me endeavour to have a little conference with him, about the subject of this discourse; but his occasions hastening him to another place before

I could send to him, I procur'd from the chief Persons that employ'd him, a sight of some Notes, touching his last Voyage, which he had left with them; hoping to sind there something at least, about the Soundings of so accurate a Sea∣man, and accordingly I met with a Passage, very pertinent to my purpose, and worthy to be here transcribed.

Febr. 12. After our Observation, (he means a former one very agreeable to this) seeing the ground under us, we heav'd the Lead, and had but 19 fathom rocky ground, then hal'd by N.N. E^t. the Wind at N.W. and found our water to shoale from 19 to 10 and 8 Fathom hard Corall Ground, then suddainly deepned again from 8 to 20 and 22 fathom Sandy Ground, and then sud∣dainly saw Rocks under us, where we had but 7 fathom, and the next cast 14 fathom again. And so having run N. N. E^t. from 6 in the morning till 12 at noon about 19 mile, we deepen'd our VVater, from 16 to 25, and the next cast, no ground with 35 fathom of Line.

Lastly, having opportunely met with an Anci∣ent Navigator, who passes for the most experien∣ced Pilate in our Nation for an East Indian voy∣age; I asked him about his own Observations concerning these unequall Soundings, I was an∣swer'd, that he had not only met with them else∣where, but that not far from the mouth of out Channell, he had sometimes found the bottom of the Sea so abrupt, that in sailing twice the

Length of the ship, he had found the VVater deepen from 30 fathom to a hundred, if not also much more.

Since I received these Relations, having the honour to discourse with a Noble Person, who has divers times deservedly had the command of English Fleets, and is no less curious then intelli∣gent in Maritine affairs, I took the opportunity to inquire of his Lordship, whether he had not observ'd the bottom of the Sea to be very unequal in neighbouring places? To which he reply'd, that he had found it exceedingly so. And to satisfy me that he spoke not upon meer cōjecture, he told me that sailing once with his Fleet even in our Chan∣nell, he perceived the VVater to make a rippling noise (as the Sea-men call it) as the Thames does under London Bridge. So that he was afraid they were falling upon some shoale, the VVater being 12 or 14 fathom deep, and going on a little farther, he cast out the Plummet again, and found it about 30 fathom. He added that he made di∣vers such Observations, but took notice of such rippling VVaters only when the Tide was ebbing: and yet in a deep Sea meeting with the like ap∣pearance in the upper part of the water, and thinking it improbable that there should be any shoale there, he ordered the depth to be sounded, and found it to exceed 30 fathoms; and after he had passed on a very little farther, he found the Sea so deep, that he could not fathom it with his ordinary Line.

The Second SECTION.

ANother thing observ'd at the Bottom of the Sea, is the great pressure of the water there against other Bodies. For what ever men may Philosophize in their studies, and may conclude from the Principles that are generally received a∣bout the Non-gravitation of Water in its proper place, yet experience seems very little to favour that Generall Doctrine.

For first, I remember that having caus'd a pretty large Cylinder of Glass, that was open only at one end, to be so depress'd into a large Glass vessell full of water with a conveniently applyed weight of Lead, that none of the air could get out, I could easily discern through the Liquor and Vessells, which were all transparent, that as the inverted Cylinder descended deeper and deeper, the externall Water compress'd the imprison'd air, and ascended higher and higher in the Cavity of the Cylinder, against whose side we had before hand plac'd a row of Marks, whereby to take notice of the graduall ascent and descent of the Internall Water.

Secondly having inquired of two severall ob∣serving Persons, whereof one had with a Diving Engin visited the bottom of the Sea in a Cold Northern Region; and the other had done the like in an Engin much of the same sort, upon the coast of Africk, I found their Relations to agree

in this, that the deeper they descended into the Sea, the more the air they carried down with them was compassed, and the higher the Water ascended above the Lip, or Brim of the Engin into the Cavity of it.

But I shall now add a more considerable ex∣periment or two, to the same purpose. For dis∣coursing one day with an Engineer of my Ac∣quaintance, that had been often at Sea, and loved to try Conclusions, of a way I had thought of, to make some estimate of the pressure of the water at a considerable depth beneath the surface, and shew that the pressure is great there, he told me he could save me the labour of some Tryalls, by those he had made already, and assured me that having divers times opportunity to sail near the Straights Mouth, over a place where the Sea was observed to be of a notable depth, he had found, that if he had let down with a weight into the Sea, not a strong round Glass-bottle, but a Violl, such as the Seamen use to carry their Brandy and strong waters in, such a Vessell which might con∣tain a Pint or a Quart of water, would when it came to be sunk 40 fathom under water, if not sooner, be so oppress'd, by the Pressure of the incumbent, and laterall Water, as to be thereby broken to pieces.

He also averred to me, that having exactly closed an Aeolipille of Metall, and with a compe∣tent weight, sunk it to a great depth in the Sea, as to forty, fifty, or sixty fathom deep, when he

pull'd it up again, he found to his wonder, that the great pressure of the water, had in divers places crusht it inwards. And though I had some suspition, that the coldness of the Sea at such a depth, might by weakning the spring of the in∣cluded Air, something contribute to the effect, yet I did not admire the event, having divers years before had a thin Aeolipile of Copper crusht inwards by the pressure of a much lighter Fluid then Sea-water.

The Third SECTION.

ANother thing observed in the Bottom of the Sea is, the Tranquillity of the VVater there, if it be considerably distant from the surface. For though the VVinds have power to produce vast waves in that upper part of the Sea that is ex∣pos'd to their violence, yet the vehement agitati∣on diminishes by degrees, as the Parts of the Sea, by being deeper and deeper, lye more and more remote from the superficies of the water. So that the Calm being less and less disturb'd to∣wards the Bottom of the water, if that lye con∣siderably deep, the water is there either calm, or scarce sensibly disturb'd.

But that is for the most part to be understood, of places at some distance from the shore; for of∣tentimes in those that are too near it, the progress of the waters being rudely checkt, and other cir∣cumstances concurring, the Commotion of the water is so great, that it reaches to the very bot∣tom, as may appear by the heaps of Sand, the Amber, and in some places, the stones that are wont to be thrown up by the Sea, in, and after stormes.

The above mentioned Calmness of the Sea at the Bottom (will I doubt not) appear strange to many, who admiring the force of stormy Winds, and the vastness of the VVaves they raise, do not at the same time, consider the almost incompara∣bly

greater Quantity, and weight of VVater that must be mov'd, to make any great commotion at the bottom of the Sea, upon which so great a Mass of Salt-water, which is heavier then fresh, is constantly incumbent. VVherefore for the Proof of the propos'd Paradox, I will here set down a memorable Relation, which my inquiries got me from the Diver elsewhere mentioned, who by the help of an Engin could stay some hours under VVater.

This Person then being ask'd, whether he ob∣served any operation of the VVinds at the bottom of the Sea, where it was of any considerable depth? Answered me to this purpose, That the VVind being stiffe, so that the waves were ma∣nifestly six or seven foot high above the surface of the VVater, he found no signe of it at 15 fathom deep; but if the Blasts continued long, then it mov'd the Mudd at the Bottom, and made the water thick and dark. And I remember he told me, which was the Circumstance I chiefly de∣sign'd, that staying once at the bottom of the Sea very long, where it was considerably deep, he was amaz'd at his return to the upper parts of the water, to find a Storm there which he dreamt not of, and which was raised in his absence, ha∣ving taken no notice of it below, and having left the Sea calm enough when he descended into it.

For farther Confirmation, I shall add, that having inquired of a great Traveller, who had as∣sisted at a rich Pearl-fishing in East Indies, whe∣ther

he had not learnt by his Conversation with the Divers, that storms reach not to the bottom of the Sea, if it be of any considerable depth, he answer'd, that he had seen the Divers take the Water, when the Sea was so very rough, that scarce any Vessells, would hazard themselves out of Ports, that those returning Divers told him, that at the Bottom, they had found no distur∣bance of the Water at all. Which is the more considerable, because of the scituation of that place where they dive for Pearls; for this is near the shore of Manar, and that it self is sealed be∣tween the great Iland of Ceylon, and the vast Cape of Comori: and though it may be much nearer the former, is not yet far distant from the latter. Which scituation and the Neighbourhood of the vast Indian Ocean, on the one side of Ceylon, and the great Gulfe of Bengala, (antiently Sinus Gangeticus) on the other, makes the place where the Pearls are fished for, exceeding likely to be subject to very troubled Seas.

It will perhaps be thought no slight addition to the fore-going Arguments, if I here add, that meeting one day with an ancient and expert Sea∣man, whom his merit had advanc'd to considera∣ble Employments in his Profession, I was con∣firm'd by the Inquiries I made of him, not only in the Opinion I had about the Calmness of the Bottom of the Sea, but also that the operation of good Gales of VVind, does oftentimes not reach to near so considerable depths into the Sea,

as hath been hitherto supposed, even by Naviga∣tors themselves. For he assured mee, that having sometimes sailed in great Ships that drew much water, as about 12 or 15 foot, he had Div'd to the Keel of the shipps, when they are under Sail, and observ'd the Agitations of the Water, to be exceedingly diminish'd, and grown very languid, even at that small distance, from the upper part of the Waves. And he farther answered, that when in America he learned to Dive of the Indi∣ans, they taught him by their Examples, to creep along by the Rocks and great stones, that lay near the shore at the Bottom of the Water, to shelter themselves from the strokes, and other ill effects of the Billows, which near the shore, and where the Sea was so shallow, as it was there, did often∣hurt and endanger Swimmers and unskillfull Di∣vers. But when they were by this means got fur∣ther from Shore and into deeper VVater, they would securely leave the shelter they had till then made use of, and swim within a few yards of the Surface of the Sea, as fearing there no danger from the To sings and Commotions of the upper parts of the Water.

But lastly, for further satisfaction, I had the op∣portunity to make inquiry about this matter of a great Sea Commander who has both an extraor∣dinary curiosity to make marine Observations, & an unusuall Care in making of them accurate∣ly, I found the Opinion countenanced by his An∣swer, which was in short; That he had lately

been at a place where the Sea was often tempe∣stuous enough, and that they found by a sure mark that the Storm did not reach with any efficacy four fathom beneath the Surface of the Wa∣ter.

About the Tranquillity of the Lower Parts of very deep waters I had a suspition, which though I fear it might seem somewhat extravagant, because I have not met with it in Authors; yet I thought it worth examining for the use it might be of, if re∣solv'd in reference to the Ebbing and Flowing of the Sea.

I made therefore a Solicitous Inquiry whether the Tides did reach to, or near the Bottom of the deeper Seas, but found it exceeding difficult by reason of mens want of Curiosity to obtain any sa∣tissaction about a Problem that most Navigators I have conversed with did not seem to have so much as dreamd of. But thus much I found in∣deed by inquiring of an Engineer who was curious of Marine Observations, that a famous Sea Com∣mander of his Acquaintance being also a great Mathematician, had affirmed to this Relator, that he had divers times observ'd, that when he let down his Plummer to a great depth but yet not to reach ground, it would be quickly carried by a motion quite cōtrary to that of the Shallop whence they sounded and very much qu••cker then it; but I had this only at second hand. Also, if I mis-re∣member not, I was informed by a skillfull Ob∣server that commanded many of our English men

of Warr, that he had near the sound observed the upper and Lower parts of the VVater to move with a considerable swiftness quite different wais; but not having committed this Relation to wri∣ting, I dare not build much upon it. And among the Answers I had received and written down con∣cerning those matters, all that I can yet find a∣mong my Adversaria, is a Relation which though single, will not be unworthy to be transcrib'd in this Place, because the Person who gave it me, is one of the ancientst and most experien'st Pilots of our Nation.

This Person therefore assured me, that sayling beyond the Cape of Good Hope into the South Seas, made Tryalls of the motion of the upper part of the Water above the lower, where sometimes casting out a large and heavy Plummet, he let it down to severall depths short of 50 fathom, without any sensible Operation upon the motion of the Boat, or Shallop he stood in to make the Tryall; but when he let down the Plummet lower, to about an hundred fathom or more, then he found that though the Plummet reached not to the Bottom of the Water, yet upon the score of the standing water beneath, the Superior VVater would make the Bo••t turn towards the Tide or Current, as if it lay at Anchor, and the water would run by the side of the Boat at the rate of about three mile an hour, Thus far this dili∣gent Observer. But how far the inequality of the Soil at the bottom of the Sea, and how far the

various depth of the VVater, and some other cir∣cumstances, may alter the case, and make it hard to determine, what ought to be ascribed to Tides and what to Currents, and are things which I will by no means be positive in; till I can meet with further Information.

[Since the writing of this, hapning to meet with one that spent some time at a famous Ea∣sterne Pearle-fishing, and asked him whether he had inquired of the Divers about the Problem lately proposed, and whether the Sea were there deep enough to make observations of that kind: To the latter part of which Question he replyed, that in some places it was of a very considerable depth, and fit to make the observation in; And to the former he answered, That he had inquired of the Divers, who affirmed to him that sometimes at the Bottom of the Deep waters there seem'd to be a stagnation of the Sea for a great depth, so that till such a height they could rise directly upwards, but that at other heights they would be carried away by the lesse deep-waters; so as to be found when they came to emerge a great way off from that point of the surface which was perpendicu∣lar to that place at the Bottom, whence they be∣gan to ascend.]

FINIS.