Relation of Secular Decay of Bocks. — Tan\ 41 
seclimeuts are probalil}- for the greater part the rapidly removed 
products of long-continued, protected disintegration and decom- 
position." 
Changes in the amount of river load from the limpid stream of 
a low lying countrj', to the turbid stream flowing with rapid cur- 
rent over a recently elevated region covered with a residual soil, 
aside from the rapid accumulation of much fine sediment, must 
have an important effect upon the life of the region, which may 
be almost entirely exterminated by the incursion of the mud bear- 
ing waters. A coral fringed coast would lose its character with 
such an incursion and an entire change of fauna result. How 
many times this has happened in the past it is entirely impossi- 
ble to tell at present, but a search among the geological records 
may very likely show many such changes which can be traced to 
this cause. 
(/) Bi/ the Sea. 
The depression beneath the sea of a country bearing a residual 
soil would produce similar though more widespread results. The 
fine sediments swept out to sea and the coarser remnants de- 
posited nearer the point of origin would rapidl}' produce exten- 
sive deposits, at the same time undoubtedly changing the charac- 
ter of the fauna. 
One recorded instance of this method of origin of sediments 
is all that has been found in the geological literature examined. 
It is so interesting that it is given here in some detail. For the 
complete account I refer to professor Pumpell3"'s paper.* 
In the Hoosac mountains in western Massachusetts there is a 
central core of true granitoid gneiss characterized by a blue 
quartz. Above this and separating it from the overlying schists 
is a band of rock, which, though stratigraphically continuous, is 
widely different in its various parts. It wraps around the granit- 
oid core or island, and on the east is a quartz ite, on the north a 
conglomerate, while on thp west it is a white gneiss. By transi- 
tional beds these pass downward into the granitoid gneiss bj' 
direct stratigraphical conformity. The conglomerate contains, 
besides blue quartz pebbles, many pel)bles of feldspar with an un- 
altered nucleus bordered by a kaolinized feldspar, which, since 
its production, has been altered to a secondarj' feldspar by meta- 
*The Relation of Secular Rock Disintegration to certain Transitional 
Crystalline Schists. Bull. Geol. Soc. Am., 181)1, ii, 209-2'24. 
