58 The American Geologist. j«iy, looi. 
REVIEW OF RECENT GEOLOGICAL 
LITERATURE. 
Nitrates in Cave Earth. By Henry W. Nichols. (Jour. Gcol., Vol. 
IX, pp. 236-243.) 
This is in the main a criticism of the theory advanced by Hess 
{Jour. Geol., Vol. VH, p. 2) that the nitrates of cave earth are not de- 
rived to any great extent from bat guano, as has been formerly sup- 
posed, but from the soil above by a leaching process followed by a 
deposition of the salts on evaporation. The chief objections raised by 
Mr. Hess to the old theory may be briefly summarized as follows : — 
I. Bats do not penetrate far into caves, which makes it difficult to ac- 
count for the' presence of salts derived from guano and their uniform 
distribution in the caves. 2. Cave earths contain little or no organic 
matter. 3. While the total phosphates in the guano and imderlying 
earth are about equal, the soluble pho,sphates are much less in the earth. 
In criticising these objections it is shown, that bats do penetrate into 
remote parts of the caves, that in some instances cave earths do con- 
tain organic matter and that the lack of soluble phosphates in the earth 
is due to a pimple reversion of the soluble to an insoluble form. Among 
other things to which attention is called is the presence of carbonatgs 
in the drip waters of the cave and their absence in the cave earths, 
a fact which Mr. Hess's theory does not account for. It is thought that 
the amounts of phosphates and nitrates taken into solution from the soil 
are too small to account for the amounts found in the earth and that 
the considerable quantities of soluble salts in the bat guano furnish 
a more probable source of supply. The author therefore concludes that 
the old theory agrees with the facts better than the new. c. H. w. 
Moliazvkite. By Joseph W. Richards. (Aui. Jour. Sci., 161, 457-458.) 
Under the name mohawkite a mineral was described bj' Ledoux 
{Eng. & Mill. Jour., Apr. 7, IQOO,) to \yhich he assigned the formula 
(CuNiCo)4As. Later the correctness of his work was called into 
question by Koenig, who appropriated the name mohawkite for a min- 
eral which he described (Am. Jour. Sci., Dec, 1900,) as having the 
composition (CuNi €0)3 As. A new analysis is reported in the present 
paper, confirming the correctness of Ledoux's work and proving the 
existence of a molecule (CuNiCo)4As. The name ledouxite is pro- 
posed as a name for the latter. c. h. w. 
On the origin of the Phenocrysts in the Porphyritic Granites of Georgia. 
By Thomas L. Watson. (Jour. Geol., Vol. IX, pp. 97-122.) 
A detailed petrographical description is given of the porphyritic 
granites of Georgia, within the Piedmont plateau. The different areas 
are taken up according to their geographical distribution. The follow- 
ing facts given by the author concerning these rocks are believed to 
indicate that the phenocrysts (orthoclase) have been formed in place 
and are not of intratelluric origin: — i. The absence of a definite ar- 
rangement or orientation among the phenocrysts. 2. Absence of 
