102 BIBLIOGRAPHY AND INDEX OF N. A. GEOLOGY, [bull. 135. 
630 Whittle (Charles Livy). The occurrence of Algonkiau rocks in 
Vermont and the evidence for their subdivision. 
Jour, of Geol., vol. ii, pp. 396-429. 
Describes the topographic and geologic features of the Green Moun- 
tains, and the lithologic and structural differences in the different 
divisions of the Algonkian series. 
631 The general structure of the main axis of the Green Moun- 
tains [Vermont]. 
Am. Jour. Sci., 3d ser., vol. xlvii, pp. 347-355. 
Describes the rocks which underlie the Olenellus horizon in this 
region, which are referred to the Algonkian, and the orographic dis- 
turbances which they have suffered, and discusses the character of the 
folding of the Green Mountains. 
632 Williams (E. H., jr.). South Mountain glaciation [Pennsylvania]. 
Geol. Soc. Am., Bull., vol. v, pp. 13-15. 
Describes glacial phenomena of this region which form a fringe of 
the great terminal moraine in Pennsylvania. 
633 Extra-morainic drift between the Delaware and the Schuylkill 
[Pennsylvania]. 
Geol. Soc. Am., Bull., vol. v., pp. 281-296, pis. 9-11. 
Abstract: Am. Geol., vol. xiii, p. 221 (ip.). 
Describes the topographic features, draiaage systems, and the gla- 
cial deposits and underlying rocks of the region. 
634 The age of the extra-morainic fringe in eastern Pennsylvania. 
Am. Jour. Sci., 3d ser., vol. xlvii, pp. 34-37. 
Describes the glacial deposits in the vicinity of Bethlehem, Pa., 
and concludes that they are of recent formation, and that the Ice age 
was of short duration. 
635 Williams (George Huntington). The Appalachian region. 
Int. Cong. Geol., Compte Rendu, 5th session, pp. 268-273. 
Describes the geologic formations of the Appalachian region, with 
special reference to the portion crossed by the Rocky Mountain excur- 
sion of the International Congress of Geologists. 
636 Washington, D. C, to Cumberland, Md. Itinerary. 
Int. Cong. Geol., Compte Rendu, 5th session, pp. 274-279. 
Describes the geologic features along the route traversed by the 
excursion. 
637 The distribution of ancient volcanic rocks along the eastern 
border of North America. 
Jour, of Geol., vol. ii, p. 1-31. 
Abstracts: Am. Jour. Sci., 3d ser., vol. xlvii, pp. 140-141; Am. Geol., 
vol. xiii, pp. 212-213 (1 p.). 
Reviews the opinions of various writers on the nature of ancient 
volcanic rocks and describes the distribution of the volcanic areas of 
eastern North America and gives the author's general conclusions. 
