302 Dr. Wallich [Jan. 25, 



undoubtedly a highly important one, I hope to be able to prove that it 

 is not of essential value, as has heretofore been laid down, in deter- 

 mining the final limit of animal life in the sea. 



It is almost needless to state that at the sea level there exists a 

 pressure of 15 lbs. on every square inch of surface, due to the weight 

 of the atmospheric column resting upon it ; and that the pressure on 

 the successive strata of water in the sea, as the depth increases, is infi- 

 nitely in excess of this, inasmuch as a column of water only 33 feet in 

 height is capable of counterbalancing the entire atmospheric column, 

 which extends to a height of about 45 miles. Accordingly, for every 

 33 feet of descent in the sea, putting out of consideration the effect of 

 the superincumbent column in actually diminishing the bulk of the 

 portions beneath by augmenting their density, there is an additional 

 15 lbs. At great depths, therefore, the aggregate pressure becomes 

 stupendous. As is well known, pieces of light wood let down to a 

 depth of 1500 or 2000 fathoms, become so compressed and surcharged 

 with water as to be too heavy to float. But there is a fallacy in this 

 experiment; for the contraction of the woody fibre and cells is a 

 necessary consequence of their submission to an amount of pressure so 

 enormously in excess of that under which they originated. With 

 organisms which have been developed, from first to last, under the full 

 operation of any given amount of pressure, the result would not be of 

 this nature ; for the equalization of the pressure, within and without 

 their entire structure, although it might possibly exercise some definite 

 effect in determining their shape, size, or even functions, cannot, I 

 submit, operate in causing the creatures living under it to experience 

 any more detrimental results than we experience from the 15 lbs. on 

 every square inch, or about 14 tons, on the general surface of our 

 bodies near the sea level. 



It can scarcely be wondered at that under such apparently extra- 

 ordinary conditions, the maintenance of life, even in its least developed 

 aspects, should have been deemed absolutely impossible at extreme 

 depths ; and that it should have been almost unanimously recognized as 

 an axiom, that at a depth of 400, or, at most, 500 fathoms, life, whether 

 animal or vegetable, must be extinct. The fact is unquestionable that 

 as we descend beyond the first hundred fathoms, the traces of life 

 become more and more remote ; and it is probably owing to this 

 gradual diminution in the number of animal forms, as the depth exceeds 

 this limit, that it has been assumed, rather as a matter of theory than of 

 observation, that a point is speedily reached at which all the conditions 

 essential to life are extinguished. This view has also derived support 

 from the idea that "animal life depends on the previous existence of 

 vegetable life." In the case of the higher orders of the animal kingdom, 

 the law, no doubt, holds good. Not so, however, in the case of the 

 lower. The conditions essential to the perpetuation of the one are not 

 essential to the perpetuation of the other. Thus, light is indispensable 

 for the healthy respiration and growth of the vegetable. The animal 

 can, on the other hand, respire as freely in the blackest darkness as in 



