REVIEWS 763 
on the chemical relations of the rocks of this region. It may be 
that the analyses will explain certain difficulties which have suggested 
themselves, almost as a matter of course, in the way of explaining the 
formation of such minerals as hornblende and olivine (especially the 
latter) in the endomorphic zone of recrystallization. IRS) JS IDY Wie 
RECENT BIBLIOGRAPHIES. 
Libliography and Index of North American Geology, Paleontology, 
Petrography, and Mineralogy for 1896. By F. B. WerEks. 
(Bull. U. S. Geol. Surv., 149, 152 pp. Washington, 1897.) 
Bibhiografia Geolbgica y Minera de la Repiblica Mexicana. By 
R. Acuiar y Santillan. (Bol. 10, Inst. Geol. de Mexico. 
158 pp. Mexico, 1898.) 
Students and workers in geology everywhere will be glad to receive 
the two papers here mentioned. The value of a well compiled and 
carefully edited bibliography is too well recognized to need any men- 
tion. ‘To ail active workers such books are indispensable. The two 
under review, fortunately, are both excellent. Mr. Week’s good work 
in this line needs no introduction. It only remains to commend and 
to note the broadened scope of the bibliography. In its preparation 
108 serials were examined, the number including several devoted to 
economic phases of geology and not previously listed. As usual the 
abstracts are concise, but are quite sufficient to determine the scope of 
the paper. The full indexes are especially valuable. 
The bibliography of Mexico is especially helpful, because of the 
previous absence of any paper thoroughly covering the field. The 
author has had more than the usual difficulties, due to poor library 
facilities, the scattered and incidental nature of the papers, and the 
presence of broken sets of short lived serials. In the face of such 
materials there must necessarily be a certain amount of selection. Not 
all the papers listed are strictly geological but all will doubtless be 
helpful. At first glance the 1953 titles included seem formidable, and 
one is surprised at the amount which has been written, but a more 
careful examination shows, as remarked by the Director in his introduc- 
tion, that the great majority of the papers written on the geology of 
Mexico are really technical engineering papers, and deal with geology 
