71 
LITERATURE. 13 
He also called attention to abrupt east -west shifts in the course of 
le ranges — the first near North Adams, where the Green Mountain 
Jange advances 4 to 5 miles westward ; the second near Bennington, 
»us diere the quartzite and limestone along the foot of the Green Moun- 
lins recede a mile or more eastward; the third at Bear Mountain, 
i Stockbridge and Lee, where the older gneisses advance 3 miles 
westward, deflecting the Housatonic River and the rail and carriage 
an 
l?i 
:|| 
I I 
oads. He attributed these advances and recesses of the range to 
l &r 
ays in the Archean land mass. He also called attention to the sud- 
en turn in the trend of the schist hills between Lenox and Great 
Harrington from north-northeast in Mount Osceola to north-north- 
r est in Monument Mountain, and also to the absence of schist hills 
n the great limestone plain about Pittsfield." 
In 1891 W. M. Davis defined " Cretaceous peneplain " as the prod- 
ct of the denudation in Jurassic and Cretaceous time of the com- 
[ i lined crystalline and Triassic area of Massachusetts, Connecticut, 
q s T ew Jersey, etc. This peneplain was uplifted toward the close of 
I he Cretaceous to the extent of " 1,000 feet in Massachusetts east of 
he Connecticut Valley, of 1,200 to 1,400 or 1,500 feet in the western 
iei »r Berkshire plateau, of somewhat more where the plateau is cut by 
llf he Hudson gorge, of somewhat less in the northern highlands of 
STew Jersey, and thence decreasing southwestward into Pennsyl- 
] rania ; and this uplifted peneplain was eroded in Tertiary time. 
i le thought it probable that the altitude of the Berkshire Valley 
800 to 1,000 feet) is to be explained by its imperfect reduction to 
Dase-level in the Tertiary cycle, more particularly by — 
he absence of any large master river to drain it ; second, by the belts of hard 
rocks that its streams, the Housatonic and the Hoosic, must cross on their way 
o the sea, and possibly, third, by a shift of drainage. * * * The plateau 
jetween the Connecticut and the Berkshire valleys is drained almost entirely 
>y branches of the Connecticut, the divide being close along the western margin 
)f the plateau ; it is quite possible that in the Cretaceous cycle these branch 
streams drained the Berkshire limestone area as well, and that the present 
outlets of the valley are the result of headward cutting of formerly external 
(streams ; if this be true, it is quite natural that the valley should not yet be 
excavated to the same depth as the Connecticut lowlands.^ 
I 
111 1892 B. K. Emerson gave the following order of physical events 
for western Massachusetts: (a) folding; (b) base-leveling, perhaps 
to old sea level of Cretaceous; (c) elevation of about 2,000 feet; (d) 
erosion of gorges. 
ii 
« Am. Tour. Sci. ? 3d ser., vol. 33, 1887, pp. 273-276. 
6 Davis, W. M., The geological dates of origin of certain topographic forms on the 
{Atlantic slope of the United States : Bull. Geol. Soc. America, vol. 2, 1801, pp. 545, 
|568, 580. 
c Outlines of the geology of the Green Mountain region in Massachusetts : Geologic 
Atlas U. S., " Hawley sheet," U. S. Geol. Survey, 1892 (a preliminary folio, not included 
in the regular series), 
