340 The American Geologist. December, i ', 
ing at the time of the accumulation of the material, from which 
petroleum arose as a secondary product, and the latter is, at 
first glance, an indication, at least, of their absence. There is 
only one way of reconciling these two conflicting pieces of 
testimony. That is to allow that the fossil memorials of the 
life of the shah' sea have been in some way or other destroyed. 
That the petroleum is an organic derivative is presumably 
beyond question. No other probable source has ever been 
indicated. The theory of an inorganic origin advocated by 
Mendeleef has no geological or even chemical basis, and would 
never have attracted notice save for the great name and fame 
of its author, lint whether this hydrocarbon is of animal 01 
vegetable nature is a question less easily answered. Dr. Xew • 
berry advocated the latter and likened the water in which 
the black shale was laid down to the Sargasso sea of the pres- 
ent Atlantic, admitting, however, that in some cases and to 
some extent animal remains might have contributed their 
share to the result. This latter view seems the only probable 
and tenable one. The vast amount of material required is in- 
consistent with any other source. As for the fishes, etc., which 
inhabited the sea, if the order of nature was then as it is now, 
probablv few of them were ever allowed to decay. Their 
carcasses wonld be promptly eaten by some of their comrades, 
even if the animals were permitted to die a natural death, 
which i> scarcely likely, save perhaps in the case of some mon- 
ster such as Dinichthys. lint the vast accumulation of vege- 
tation yearly dying and decaying must have supplied to the 
bottom an enormous mass of carbonaceous material, to which 
the blackness of the shale may well be due. 
This conclusion seems to require a very slow rate of ac- 
cumulation for the shale, and this is in exact agreement with 
its extreme fineness and with the known distance from land. 
To include ten per cent of carbonaceous matter in its compo- 
sition must have demanded many years of vegetable decav 
during the accumulation of a very small thickness of the shale. 
This inference is, moreover, in harmony with the already noted 
lack of fossils, for, except in a limestone sea, fossils are best 
- preserved where deposit is rapid. In a shale, sea lime must 
be scarce and it is only a logical deduction that the shells, etc., 
lay on the surface unburied lone: enough to allow of their 
