U8 A HISTORY OF 



In order to extend our knowledge of the sea to greater depths, re- 

 '.ourse has been had to the plummet ; which is generally made of a 

 iump of lead of about forty pounds weight, fastened to a cord.* This, 

 however, only answers in moderate depths ; for when a deep sea is to 

 be sounded, the matter of which the cord is composed, being lighter 

 than the water, floats upon it, and when let down to a considerable 

 depth, its length so increases its surface, that it is often sufficient te 

 prevent the lead from sinking ; so that this may be the reason that 

 some? parts of the sea are said to have no bottom. 



In general, we learn from the plummet, that the bottom of the sea 

 is tolerably even where it has been examined ; and that the farther 

 from the shore, the sea is in general the deeper. Notwithstanding, in 

 the midst of a great and unfathomable ocean, we often find an island 

 raising its head, and singly braving its fury. Such islands may be 

 considered as the mountains of the deep ; and, could we for a mo- 

 ment imagine the waters of the ocean removed or dried away, we 

 should probably find the inequalities of its bed resembling those that 

 are found at land. Here extensive plains, there valleys, and, in many 

 places, mountains of amazing height. M. Buache has actually given 

 us a map of that part of its bottom, which lies between Africa and 

 America, taken from the several soundings of mariners : in it we find 

 the same uneven surface that we do upon land, the same eminences, 

 itnd the same depressions. In such an imaginary prospect, however, 

 there would be this difference, that as the tops of land-mountains ap- 

 pear the most barren and rocky, the tops of sea-mountains would be 

 found the most verdant and fruitful. 



The plummet, which thus gives us some idea of the inequalities 

 of the bottom, leaves us totally in the dark as to every other par- 

 ticular ; recourse, therefore, has been had to divers : these, either 

 being bred up in this dangerous way of life, and accustomed 

 to remain some time under water without breathing, or assisted 

 by means of a diving-bell, have been able to return some confused 

 and uncertain accounts of the places below. In the great diving-bell 

 improved by Dr. Halley, which was large enough to contain five men, 

 and was supplied with fresh air by buckets, that alternately rose and 

 fell, they descended fifty fathom. In this huge machine, which was 

 let down from the mast of the ship, the doctor himself went down to 

 the bottom, where, when the sea was clear, and especially when the 

 sun shone, he could see perfectly well to write or read, and much more 

 to take up any thing that was underneath : at other times, when the 

 water was troubled and thick, it was as dark as night below, so thai 

 he was obliged to keep a candle lighted at the bottom. But there 

 was one thing very remarkable, that the water which from above was 

 usually seen of a green colour, when looked at from below, appeared 

 to him of a very different one, casting a redness upon one of his hands, 

 like that of damask roses :t a proof of the sea's taking its colour not 

 from any thing floating in it, but from the different reflections of the 

 lays of light. Upon the whole, the accounts we have received from 

 the bottom, by this contrivance, are but few. We learn from it, an<\ 



* Boyle, vol. ii. p. 5. t Newton's Optics, p. 56 



