644 LEWIS G. WESTGATE 
Brégger,’ Williams,? Crosby,3 and others, the presence of one or 
more parent masses of less acid plutonic rocks is to be expected in 
such regions of abundant pegmatite dikes. The pegmatite dikes 
of central Connecticut are abundant, and are widely known for 
the variety and beauty of the minerals they have furnished col- 
lectors. They occur in dike-like masses in both gneisses and 
schists, but more abundantly in the latter, and they both cross 
and run parallel to the foliation of the enclosing rocks. Their 
contact with the gneisses and schists is sharp and they frequently 
contain inclusions of the same. There are two other considera- 
ble areas of granitic biotite-gneiss in the region, one to the south 
and the other to the north of the area under consideration. The 
former shows no sign of igneous origin and seems to be the basal 
member of a series of conformable gneisses and schists which 
form a northward pitching anticline. The study of the latter 
area is not yet completed. The evidence so far collected seems 
to indicate that it is largely composed of eruptive material; but 
even so the Middletown granite-gneiss ‘s more centrally located 
with reference to the dikes and would more likely be the rock 
genetically connected with them. The schists which surround 
it are more filled with pegmatite. The hills near the Connecticut 
River, just west of the granite-gneiss, are known as the ‘“‘ White 
Rocks,” from the prominent outcrops of pegmatite, and the 
schist east of the granite-gneiss is also cut by quantities of the 
same rock. This abundance of pegmatite dikes would lead us 
to expect one or more centrally located masses of granite with 
which they could be connected, and the area of granite-gneiss 
we have been describing seems to answer the expectation It 
does not appear that the dikes radiate from it; rather they 
follow in a general way the foliation of the schist. They do, 
however, appear to grow more abundant toward the granite-gneiss. 
In connection with the evidence brought forward to show the 
eruptive nature of the granite-gneiss it is interesting to know 
* Zeit. fiir Kryst., Vol. XIV, 1890, or Canadian Rec. Sci., Vol, VI, p. 33. 
2 Fifteenth Ann. Rept. U. S. Geol. Surv., p. 680. 
3CRosBy and FULLER, American Geologist, Vol. XIX, p. 151. 
