666 THOMAS L. WATSON 
the northern ends of the valleys have undergone considerable 
modification from a period of local glaciation, which is now con- 
fined to the northern side of the peninsula, and in its last declin- 
ing stage Owing to the work of local glaciation, more or less 
contrast is observed in the topography of the opposite ends of 
the approximate northwest-southeast trending valleys (see 
Fig. 3). Glacial filling, principally bowlders with some till; 
abundance of typically developed roches moutonnées, glacial 
grooves, striae, planing and _ polishing, conspicuously char- 
acterize all of the major valleys. 
A large number of the major valleys were associated with 
dikes of basic rock. So far as studies were extended, the mass 
of fact pointed to the conclusion, that this type of valley was 
due to differential preglacial decay with subsequent ice erosion. 
The entire set of major valleys, everywhere viewed on the penin- 
sula, are distinctly preglacial; and while their origin was not 
apparent in every case, they have all suffered considerable 
subsequent modification from ice erosion. 
A parallelis probably found in Canada, where Dr. Robt. Bell’ 
has observed greenstone dikes protruded into granites. The 
dikes have subsequently been worn out and at present form 
valleys occupied by lakes and streams. 
Tuomas L. Watson. 
GEOLOGICAL SURVEY OF GEORGIA, 
Atlanta, Georgia. 
IBELL, Dr. Rost., Bull. Geol. Soc. Amer. 1894, V, 364. 
