Review of Recent Geological Literature. Ill 
Warm, moist climates are most favorable to rock decay, which is 
found more general and extending to greater depths as one travels 
from north to south along the crj'stalline Piedmont belt of Archtean 
age or in the great Appalachian valley of Paleozoic strata. Along the 
Shenandoah, James and New rivers in Virginia the decay of limestone 
has yielded a red clay sometimes fifty feet deep ; but in the colder and 
somewhat less humid climate of the driftless area in Wisconsin the 
average thickness of the residual deposits is only seven feet. Little 
decomposition of the rocks is observable in the arid region of the Rocky 
mountains and the Great Basin, and the colors of the soils there are 
gray and light brown ; but on the west slope of the Sierra Nevada, 
which has plentiful rains and temperature nearly like that of the 
southern part of the Appalachian belt, deep rock decay has taken 
place and the soil is red. In Nicaragua, the West Indies, Brazil and 
southern Europe and Asia, extensive rock decomposition and red soils 
prevail. The red earth of Bermuda, the "terra rossa" of southeastern 
Europe and the "laterite" of India are apparently identical, both in 
composition and in method of accumulation, with the red residual 
soil of the south part of the Appalachian valley. 
Turning to the rock formations of previous eras, we find that the 
red and brown colors of the Newark sandstones, and of many other 
sandstones, as on lake Superior, are due to incrustations of ferric 
oxide which coat the surfaces of the gmins of quartz and feldspar 
forming the strata and cement them together. The author therefore 
concludes that these beds consist of the debris of land8 that had long 
been expo^^ed to the action of a warm, moist atmosphere. Previous 
hypotheses of Ramsay, Dawson, Dana, Cofik, Newberry, Newton, 
Green and others, are discussed ; and there is appended a bibliography 
of papers relating to the subai-rial decay of rocks. 
The geology of Nantucket. By Nathaniel Southgate Shaler. pp. 54; 
with ten plates and 16 figures in the text. (Bulletin of the U. S. Geol. 
Survey, No. 53, ISSH). Glacial and recent deposits form the entire 
island of Nantucket. Through its central part there extends from 
west to east a series of low but extremely numerous and irregularly 
shaped hills of glacial drift (gravel and sand with boulders), culmi- 
nating in Shawkemo, Altar rock, and Foulger's hills, and Sankaty 
Head, 75 to 100 feet above the sea. On the southern half of this 
island this line of low drift hills, which is shown by its topographic 
features and material to be a terminal moraine of the continental ice- 
sheet, is bordered by a plain of gravel and sand which descends with 
a gentle slope from the hills to the sea and terminates in low bluffs 
rarely more than 20 feet high. 
The lowest deposit exposed on Nantucket is a bed of clay, generally 
blue and compact, scantily intermingled with pebbles and sand. 
Though exhibiting an obscure stratification, it is probably to be classed 
as till or boulder clay. Its pebbles are occasionally scratched, and 
throughout they have the angular or faceted character common to 
