in the Ocean at the South Pole. 171 



destitute of trees, then of grass, lastly of lichens and algse, until 

 at the poles ice and death hold solemn reign. 



The greatest depths in the ocean at which Mollusca had been 

 found to exist were, according to the observations of Mr. Cuming 

 in the year 1834, the genera Venus, Cytherea and Venericardia at 

 50, Byssoarca at 75, and Terebratula in 90 fathom water. Ac- 

 cording to Milne-Edwards and Elie de Beaumont, 244 metres, or 

 732 foot, formed the extreme range for the growth of corals and 

 the development of organic matter in the sea off the coast of 

 Barbary. From a 100-fathom depth, Peron drew up in the year 

 1800, off New Holland, Sertularice and a variety of corallines, 

 which were all luminous, and on an average three degrees higher 

 in temperature than the surface of the sea. In 1824 and 1825 

 Quoy and Gaimard, in their valuable researches upon the struc- 

 ture of corals, asserted that branched corallines could occur only 

 in a depth of from 40 to 50 fathom, and that in a 100 fathom 

 of water Retepora alone existed. According to Ellis and Mylius, 

 who wrote in 1753, the greatest known depth from which a living 

 animal had been taken was the Umbellaria Encrinus, which was 

 fished up by Captain Adrian in Greenland from 236 fathom of 

 water, equal to a depth of 1416 foot. Specimens, however, of the 

 sea-bottom have been drawn up from still greater depths ; for at 

 Gibraltar, Captain Smith found in 950 fathom, or 5700 foot of 

 water, sand containing fragments of shells ; and Captain Vidal, 

 according to Mr. Lyell, detected in the mud of Galway Firth, 

 from a depth of 240 fathom, only some Dentalia, the remainder 

 of the sea-bottom from the same depth consisting of pulverized 

 shells and other organic remains devoid of life. 



According to the calculations of Parrot, a column of sea- water 

 at a depth of 1500 foot exercises a pressure of 750 pound, or 

 1\ hundredweight, upon the square inch ; and since the atmo- 

 spheric air inclosed in these animals of a delicate cellular struc- 

 ture descending from the surface of the ocean would produce 

 alternately such extremes of expansion and contraction as to ap- 

 pear destructive to such organisms, just doubts have been raised 

 whether organic life could actually subsist at great depths. 



Wollaston, moreover, in 1840 proved that at the great depth of 

 670 fathom, in the Mediterranean Sea off Gibraltar, the propor- 

 tion of salt in the water was four times greater than at the surface. 

 Very accurate and scientific investigations upon the amount of 

 salts of the sea had been already published by Lenz in Peters- 

 burg during 1830 ; and Mr. Lyell, in his ( Geology ' of 1840, was 

 induced to regard the observations of Wollaston not as simply in- 

 dicating a local phenomenon, but to conclude that at still greater 

 depths the relative proportion of saline matter would be still more 

 remarkable, and must progress in a similar advancing ratio. 



N2 



