THE DEEP SEA AND ITS CONTENTS. 345 



considerably exceeding that exerted by the hydraulic presses used 

 for packing Manchester goods. Even the "protected" ther- 

 mometers specially constructed for deep-sea sounding were 

 frequently crushed ; and a sealed glass tube containing air, having 

 been lowered (within a copper case) to a depth of 2,000 fathoms, 

 was reduced to a fine powder almost Hke snow by what Sir Wyville 

 Thomson ingeniously characterized as an mplosion, the pressure 

 having apparently been resisted until it could no longer be 

 borne, and the whole having been then disintegrated at the same 

 moment. The rationale of the resistance afforded by soft-bodied 

 animals to a pressure which thus affects hard glass is simply 

 that they contain no air, but consist of solids and liquids 

 only ; and that since their constituent parts are not subject to 

 more than a very trifling change of bulk, while the equality of the 

 pressure in every direction will prevent any change in their form, 

 there is really nothing to interfere with the ordinary performance 

 of their vital functions. 



The entire absence of solar light, which constitutes another 

 most important peculiarity in the conditions of deep-sea life, would 

 seem at first sight to be an absolute bar to its maintenance. Ex- 

 perimental evidence has not yet, I believe, been obtained of the 

 direct penetration of the solar rays to more than 100 fathoms ; but 

 as I dredged slow-growing red calcareous Algse (true corallines) 

 in the Mediterranean at a depth of 150 fathoms (at, or below, 

 which Edward Forbes also would seem to have met with them), 

 the actinic, if not the luminous, rays must probably penetrate to 

 that range. Below what Edward Forbes termed the coralline 

 zone, it would seem impossible that any other type of vegetable 

 life can be sustained, than such as has the capacity of the fungi 

 for growing in the dark, living, like them, upon material supplied 

 by the decomposition of organic compounds. Such lowly phmts 

 have been found by Professor P. M. Duncan in corals dredged 

 h^om more than 1000 fathoms' depth. 



Upon what, then, do deei)-sca animals feed ? In tlie early 

 stage of this inquiry it was ascertained by Dr. Frankland that the 

 samples of water procured by the Porcupine not only at con- 

 siderable distances from land, but also from bottoms exceeding 

 500 fathoms' depth, contained so much organic matter not in a 



