314 



THREE CRUISES OF THE " BLAKE. 



in solution in the sea. This broth probably remains serviceable 

 for quite a period of time ; the decomposition of the organic 

 material which has found its way to the bottom takes place 

 gradually, and its putrefaction must be very slow.^ This broth 

 is derived not only from the pelagic fauna and flora, but also, 

 alono- the littoral and continental zones, from the decomposition 

 of animal and vegetable detritus washed from the shore belts, or 

 swept by the rivers into the sea, or carried into deeper water by 

 slowly moving currents. Though we are only beginning the 

 investigation of the physical conditions of the ocean, we have 

 learned enough to see how necessary to any exposition of the 

 evolution of the present condition of our earth is a knowledge 

 of the physics of the sea. 



1 M. Certes (Acad. Royale de Belgique, 

 Bull. VII., No. 6, 1884) has shown the 

 presence of microbes at considerable 

 depths, 250 to 2,500 fathoms, and of a 

 large number of tests he made, only four 

 have given no result. He submitted a 

 bacterium to a pressure of 600 atmos- 

 pheres, and found that this did not affect 

 it. He seems to think the effect of pres- 

 sure varies with each species, and that no 



littoral species can resist an excessive or 

 prolonged pressure. 



Regnard (Comptes Rendus, Mars 24, 

 1884, p. 745), who also experimented on 

 the effect of great pressure, found that 

 while under a pressure of six hundred at- 

 mospheres yeast mixed with a solution of 

 sugar showed uo signs of fermentation. 

 This pressure is equal to a depth of nearly 

 4,000 fathoms. 







