Ji'er/eir of Jiecent Geoloiiical LiterafKrc. J^li 
American Geologist (vol xvi, pp. 61, 113, July and August. 1895); a 
paper entitled "The Potable Waters of eastern United States," also by 
Mr. McGee, in 47 pages, with five figures: "Natural Mineral Waters of 
the United States," by A. C. Peale. in pages 49-88, with two maps: 
"Results of Stream Measurements," by F. H. Newell, in pages 89-15.3, 
with two plates, and 19 figures: "The Laccolite Mountain Groups of 
Colorado, Utah and Arizona," by Whitman Cross, in pages 157-241, 
with ten plates and 19 figures; "The Gold-Silver Veins of Ophir, Cali- 
fornia," by Waldemar Lindgren. in pages 243-284, with two plates; 
"Geology of the Catoctin Belt" [beginning in the south edge of Penn- 
sylvania, extending across Maryland and into Virginia], by Arthur 
Keith, in pages 285-395. with 21 plates and one figure: "Tertiary Revo- 
lution in the Topography of the Pacific Coast," by J. S. Diller, in 
pages 397-434, with eight plates and four figures: "The Rocks of the 
Sierra Nevada," by H. W. Turner, in pages 4.35-495, with twelve plates 
and three figures (a paper which was summarized by the author in the 
American Geologist for April and May, 1894): "Pre-Cambrian igneous 
rocks of the Unkar terrane. Grand Canyon of the Colorado, Arizona," 
by Charles D. Walcott, with notes on the "Petrographical Character 
of the Lavas," by Joseph Paxson Iddings, in pages 497-524, with six 
plates and two figures: "On the Structure of the Ridge between the 
Taconic and Green Mountain Ranges in Vermont," V)y T. Nelson Dale, 
in pages 525-549, with five plates and eleven figures; "The Structure of 
Monument Mountain in Great Harrington, Massachusetts," also by Mr. 
Dale, in pages 551-565, with two plates and eight figures, and "The 
Potomac and Roaring Creek Coal Fields in West Virginia," by Joseph 
D. Weeks, in pages 567-590, with two maps and three figures. 
Presenting so many reports of important special investigations, this 
volume is one of the most valuable in its series. The longest of these 
reports, l)y Mr. Keith, gives the following approximate ratios of the du- 
ration of Tertiary and Quaternary time, derived from comparisons of 
their relative siinounts of denudation in the district comprising the Ca- 
toctin mountain, namely, the Tertiary era. regarded as extending to the 
end of the Lafayette period. 134: the early part of the Pleistocene j)eriod, 
1; its later part, "'[o : and the Recent period, a small fraction. If the Ice 
age and subsequent time have included aliout 60,000 years, Tertiary time 
was, according to this estimate, about 4,000,000 years, and the geologic 
record from the dawn of life on the earth would be, according to Dana's 
ratios for the great eras, some sixty to a hundred inillion years, w. u. 
Republication of JJt'scriptions of FohhUs from the Htill Collection in 
the American Museum of Natural History, from the Report of Prog- 
gress for isai of the Geological Surreij of Wisconsin, t»j James Hall, 
ifitli illustrations from the origiital type specimens not heretofore fig- 
ured. By R. P. Whitkikli). (Memoirs Amer. Mus. Nat. Hist., vol. i, 
pt. 2, roy. 4to, pp. 39-74. pis. iv-xii, 1895.) Professor Whitfielil has done 
a genuine service to American paleontology in the illustration of these 
hitherto almost unrecjognizable Silurian species published nearly 
thirty-five years ago. Paleniitologists whu liiivc tuid occasion to study. 
