^0 ^/'C America)) GcoUxjitsf. January, 1895 
drou'rapliic" surveys of all otir coast lines, and esiM'fially in the vicinity 
of tile principal harbors, by the U. S. C'oasl Survey, have been freely 
used by the author, makinjr a very instructive and valuable memoir of 
exceptional popular interest. Concerniii'; oscillations of the land, which 
contribute very larjjely to the formation and changes of harbors. Prof. 
Shaler says: "Althougli tliere is much evidence to show a process of de- 
pression along' the Atlantic coast line, recently operative, and i)robHbly 
still in progress at certain points, and the known facts of the Pacific 
coast point to similar movements there, and although there is, further- 
more, evidence tending to show a very modern uprising along the coast 
from New York northward, the shores of our continent may fairly be 
considered as in a tolerably stable ctjndition." w. v. 
The Mecha)iic» of Appalachian Striu-tu)-e. ]>y JiAiLEY Wilms. (Thir- 
teenth An. Rep., U. S. Geol. Survey, Part II, pp. 211-281, with plates 
xi,vi-xcvi, and figures 16 and 17.) The most common types of moun- 
tain ranges, and the causes and conditions of their formation, are no- 
where better displayed than in the Appalachian mountain belt, stretch- 
ing 900 miles from New York to Alabama, Avith'a width from 50 to 125 
miles. Great thicknesses of Paleozoic sediments, which were titere de- 
posited on the western border of a continental area, are compressed 
into long and narrow parallel folds, sometimes overtvirned atwi over- 
thrust. From the early work of H. D. and W. B. Rogers to the recent 
studies of the long overthrust faults by Hayes and Campbell, this belt 
lias held a prominent place in the growing literature on the structure 
and origin of mountain ranges, to which the present work is probably 
the most important contribution yet made by American authors. Four 
<list.ricts in the Appalachian province are each distinguished by a pre- 
vailing structural type, namely, the district of open folding in the Alle- 
ghany region of Pennsylvania and West Virginia: the district of close 
folding along the Appalachian valley; the district of folding and fault- 
ing in the Southern Appalachian region of Virginia, Tennessee, and 
Georgia; and the district of folding with schistosity in the Smoky 
mountain region. 
Attempting in the laboratory an experimental reproduction of folds 
and faults in alternating hard and soft strata, as had before been done 
by Sir James Hall, Favre, Schardt, and Cadell, the author, used bees- 
wax to repre.sent the rock formations, mixed in varying proportions 
with plaster of Paris to harden it, and with Venice turpentine to soften 
it, so obtaining a range in quality from brittle solid to semi-fluid. Pks- 
ticity in the earth's crust being a result of pressure due to load, this 
condition was imitated by iilacing a body of shot, heavy, but yielding 
.and convenient to handle, above the strata. A maximum weight of 
1,000 pounds was used, evenly distributed over the models, giving a 
pre.ssure of five pounds per square inch. The machine for imitating 
the lateral i^ressure by which the mountain strata were folded and up- 
heaved was a strong oak box with a piston wUich could be advanced by 
a. screw. 
