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, 
along 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 М. Certes (Acad. Royale de Belgique, 
Bull VIL, 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 no signs of fermentation. 
This pressure is equal to a depth of nearly 
4,000 fathoms. 
