546 THE JOURNAL OF GEOLOGY. 



Amount of Folding. — Folded structure implies, of course, an 

 alternation of anticlines and synclines. The number of these 

 varies with the intensity of the folding. In the Coast Range 

 there are apparently four or five anticlines and corresponding 

 synclines. In the Sierra they cannot be counted, but there must 

 be very many so closely appressed that the strata seem to be a 

 continuous series dipping all in the same direction, i.e., steeply 

 toward the axis, for at least 30 miles. They cannot form a 

 single series, for this would make an incredible thickness. It 

 must be a series repeated several times by extreme folding ; how 

 many, it is impossible now to say. In the Appalachian, accord- 

 ing to Claypole 1 , there are about 19 anticlines and synclines in 

 65 miles and in one part — Cumberland valley — there are eight in 

 16 miles. In the Vaudoise Alps, according to Renevier, there 

 are at least seven 2 , and in Savoy as many as 1 5 3 . In many cases the 

 foldings are so extreme that the strata first rise as folds, then are 

 pushed over beyond the base as overfolds, and finally broken at 

 the crest and upper limb of the fold is pushed over the lower limb 

 many miles horizontally. In the Highlands of Scotland, accord- 

 ing to Peach 4 , by overthrust, the Archaean is brought over the 

 Silurian and overrides it for ten miles. In the Rocky Moun- 

 tains of Canada, according to McConnell 5 , the Cambrian is 

 brought over the Cretaceous and overrides it for seven miles. 

 In the Appalachian of Georgia, according to Hayes 6 , by over- 

 thrust, the Cambrian is made to override the Carboniferous for 

 eleven miles. 



4. Cleavage Structure. — Closely connected with the last, and 

 having a similar significance, viz., lateral squeezing and mashing, 

 is another structure — cleavage. This structure is often asso- 



1 Am'n Nat'st, Vol. 19, p. 257 and seq. 



2 Archives des Science, Vol. 59, p. 5, 1877. 

 3Archives, Vol. 28, p. 608, 1892, and 25, p. 271, 1893. 

 4 Nature, Vol. 31, p. 29, 1884. 



s Geol. Surv. Can. 1886, Rep. D. p. 33. 

 6 Bull. Geol. Soc. Am. Vol. 2, p. 141. 



