CLARK: TACONIC REVOLUTION. 137 
debt many authors frankly admit. As examples of the par- 
ticular influence of Dana's views on the problem at hand, I shall 
refer to a few of the modern text-books and other writings which 
are compilations of geological data, viz.: 
Ulrich, E. O., and Schuchert, C. Paleozoic seas and barriers 
in eastern North America. Bull. N. Y. State Mus., no. 52, p. 646, 1902. 
Chamberlin, T. C, and Salisbury, R. D. Geology. Second ed., 
vol. 2, p. 333-336, 1907. 
Schuchert, C. Paleogeography of North America. Bull. Geol. 
Soc. Amer., 1910. 
Chamberlin, R. T. Diastrophism, etc., VII, Perir licity of paleozoic 
orogenic movements. Journ. Geol., vol. 22, p. 318 321, 1914. 
Blackwelder, Eliot. A summary of the orogenic epochs in the 
geologic history of North America. Journ. Geol.. vol. 22, p. 639-643, 
1914. 
Scott, W. B. An introduction to geology. Second ed., p. 567, 1909. 
Schuchert, C. Text-book of geology, part 2, p. 636, 1915. 
Cleland, H. F. Geology, physical and historical, p. 422, 1916. 
A study of these writings will show the existence of a concerted 
opinion among geologists to-day that there was a period of in- 
tense folding accompanying uplift at the close of Ordovician 
time. Direct evidence of such a condition is said to be seen at 
localities where Silurian rocks overlie unconformably folded 
rocks of Ordovician age. These localities may be arranged 
according to both geographical distribution and similarity of 
geological structure as follows :^ — 
1. Nova Scotia. 
2. New Brunswick and Eastern Quebec. 
3. Central New England. 
4. Montreal and vicinity. 
6. Hudson Valley region. 
6. Shawangunk Mountain. 
7. The Taconics and the Green Mountains. 
8. The crystalline rocks of New York City, Now Jersey Highlands, 
and southward. 
It is proposed to consider (;ach of these areas separately. 
Nova Scotia. 
In the fourth edition of his Manual, Dana stated (see page 136 
above) that '"unconformability between the Upper Silurian and 
