Review of Recent Geological Literatwre. 201 
Tlte Geology of Cape Ann, Massachusetts. By Nathaniel Sottthgate 
Shaler. pp. 529-611 ; plates xxxii-lxxvii : figures 42-51. (Accompany- 
ing the ninth annual report, U. S. Geol. Survey.) The glacial and 
structural geology of a tract about ten miles long, extending into the 
ocean on the northeast coast of Massachusetts and including Gloucester 
and Rockport, is here well described, with abundant illustrations sup- 
plied from photographs. Only a single drumlin, Pigeon hill, is found 
on Cape Ann, but this is a large, smoothly rounded, typical example of 
its class of till accumulations. Boulders are spread in profusion, on a 
morainic belt about two miles wide, which trends from northeast to 
southwest at right angles with the average direction of the glacial stria- 
tion. They are mostly like the granite aud other bed-rocks of the cape, 
which are exposed in multitudes of outcrops. There are also narrow 
bands of excessively rocky moraine, with boulders of all sizes up to ten 
and twenty feet in diameter piled promiscuously together. The systems 
of joint planes in the granite and diorite bed-rocks have been carefully 
studied, and a great number of dikes of diabase and quartz porphyry are 
tabulated and mapped, mostly along the ocean shore and in the exten- 
sive quarries near Rockport. 
Formation of Travertine and Siliceous Sinter by tlie Vegetation of Hot 
■S}>rings. By Walter Harvey Weed. pp. 613-676; plates lxxviii- 
lxxxvii: figures 52-56. (Accompanying the ninth annual report, U. S. 
Geol. Survey.) Some of the results of the investigations published in 
this memoir have been recently given by the author in the Geologist 
(Jan. 1891, pp. 48-55). His field of special study has been the Yellow- 
stone National Park, whose hot springs and geysers are forming, through 
the agency of algae, extensive deposits of silicious sinter, but at only one 
locality are they known to be depositing travertine, or calcareous tufa, 
of any considerable extent. This place is the Mammoth Hot Springs, 
where the heated waters rising through Mesozoic limestone reach the 
surface heavily charged with carbonate of lime. The wbite travertine 
here mostly deposited upon white filamentary alga?, has a maximum 
thickness of probably 250 feet, resembling an immense snow-bank, and 
contrasting remarkably with the pine-clad sides of the narrow valley in 
which it is enclosed, so that it has been compared by Archibald Geikie 
to the terminal front of a glacier. The formation of siliceous sinter by 
plant life is taking place in many parts of the Park, among which the 
Upper Geyser Basin of the Firehole river is selected for particular 
description. Forty-eight geysers, including the Giant, Bee Hive, and 
Old Faithful, are known in this area of about two square mile-. The 
maximum depth of the sinter or geyserite around several of the older 
vents is about 30 feet. Wherever the hot waters Mow, multitudinous 
tints of red and yellow, green and brown, are produced by the growth of 
alga?, which thrive best at the temperature of about 140° P., hut are 
able to endure is:, . 
The structure "fa portion of tin Sierra Nevada of California. By 
