Revietv of Rccoit Geological Literature, 53 
and tonalyte, on the east side tonalyte alone, on the west tonalyte bor- 
dered by the granite; while cutting the granite and the surrounding 
schists, pegmayte occurs in immense quantity. The granite areas are 
"reservoirs which have partly forced and partly melted their way up 
through the schists, absorbing much of the material of the latter in 
their progress, and sending upward and outward a complex radiating 
network of dikes. The two great stocks of "tonalite" are partially de- 
nuded domes of these great granite batholites, which have melted so 
much of the gneiss and hornblende-schist into their mass that their 
composition has been greatly changed, but which, penetrated more 
deeply, would change to ordinary granite." It is not clear whether 
the granite and tonalyte grade into each other where they lie together 
•on the west, or no. The hornblende of the tonalyte is in some places 
seen to be derived from diallage, which still remains in part, and the 
rock here is a quartz-gabbro: probably that was the original condition 
of all the tonalyte. The relation of these rocks to the surrounding 
schists and to each other shows that they are of late Devonian or Car- 
boniferous age and that their order of succession is (i) tonalyte and 
granitite. (2) pegmatyte, (3) albitic granite, — a series in which min- 
■cralizers took an increasing part. The contact efifects on the sur- 
rounding rocks are often marked, especially about the tonalyte. 
Schists become feldspathic, limestones coarsely crystalline, hornblende 
schists pyroxenic or feldspathic, and (about the granite) slates become 
chiastolite schists. 
The Triassic. The valley of the Connecticut is mainly underlaid by 
Triassic sandstones and shales. These are the M't. Toby conglomerate 
and Sugarloaf arkose about the border, Chicopee shales along the 
center of the valley, with the Longmeadow' sandstone on either side of 
the shale, between it and the coarser border deposits. "These rocks . 
ar^e not chronologically successive, but are synchronous facies, de- 
pending for their variety on the character of the shore rocks from 
which they were derived, on the strength and direction of the tidal 
currents by which they were carried and on the varying distance from 
the shore and the varying depth of the water in which they were de- 
posited." These rocks, estimated at considerably more than a mile in 
original thickness, show constant evidence of shallow water deposition 
and must have been laid down in a gradually deepening trough. Their 
deposition was thrice interrupted by volcanic outbursts producing suc- 
cessively (i) two large and probably synchronous submarine over- 
flows of diabase whose outcrops now form Mt. Holyoke and Deer- 
field mountain, (2) a thin- double sheet and the core from which it 
flowed, followed immediately by the Granby tixflf, and (3) a series of 
intrusive dikes and plugs along the line of fissure which may have 
communicated originally with surface volcanoes, since removed by 
trosion. Triassic and post-Triassic deformation produced a general, 
though not great, dip to the east and southeast and resulted in con- 
siderable faulting, especially along the eastern border, whereby the 
valley bottom was still farther dropped relative to the uplands on either 
side. 
