754 GEOLOGY. 
down by a current is diffused over a part of a bed of living coral, 
it kills the animals of that part. Moreo Bone I learned at Malta 
‘that in the beds which yield the extremely jine-grained stone 
which is used for delicate carvings, scarcely a fossils are found 
save sharks’ teeth; whilst in the coarse-grained beds of the same 
formation, fossils are abundant; and as the former may be re- 
garded as the product of a slow deposit in the deep sea, so may 
the latter be considered as shore beds. Further, I have been in- 
formed by Professor Duncan, that in the Fleisch of the Alps, 
which shows in some parts a thickness of several thousand feet, 
and which is coniposed of a very fine sedimentary material, there 
is an almost entire absence of organic remains. 
There is, however, another condition of the bottom-water of the 
Mediterranean, which is na less unfavorable than its turbidity 
— probably yet more so—to the existence of animal life in its 
depths; namely, the deficiency of oxygen produced by the slow 
decomposition of the organic matter brought down by its great 
rivers. According to the determination which I made in my 
second visit to the Mediterranean in 1871, the gases boiled off 
from water brought up from great depths contained only about 5 
60 per cent. being carbonic acid. w in gases 
the deep water of the Atlantic, the average percentage of oxygen 
was about 20, while that of carbonic acid was between 30 and 
40; even this large proportion of carbonic acid not appearing 
prejudicial to en life of the marine Taten so long as oxy- 
gen was present in sufficient proport 
The rationale of ‘both these oaiit seems obviously the 
m 
stagnant condition. If the doctrine of a vertieal oceanie circu- 
lation be true, ever 'y drop of ocean water is brought in its turn to 
the surface, where it can eat ay iat its siegh naam acid, and take in 
of temperature, than that of the mass of water it overlies, there 
is no agency capable of eter any interchange; the bottom 
water “e with the slowly gravitating sediment is never dis- 
turbed ; the organic matter contained in that n 
consumes ax oxygen so much more rapidly than it can 
“oe nec mesh above by ane through the vast column of super- 
in nt water, that nearly the whole of : is converted into ~ 
carbonic : acid, scarcely any being left for the support of animal 
