ONSTRUCTIOX OF THE EARTH. 131 



gressed, BO that the geologist can apply conclusions 

 made in regard to rocks in one quarter of the world to 

 those which exist in any other quarter. There may be 

 omissions, but there is never any change in the order. 

 ki As a bookbinder," says Phillips, "sometimes neglects 

 to bind in a particular leaf, so Nature sometimes omits a 

 particular rock ; but she never misplaces the rocks, as 

 the careless workman sometimes misplaces the pages." 

 There is a very signal example of such an omission in 

 the rocks of this country. We have here the cretaceous 

 or chalk formation that is, the series of rocks so called; 

 but the chalk, which forms so prominent a part of this 

 series in England, France, and many other countries, is 

 wholly absent ; that leaf in the American geological vol- 

 ume is left out. 



214. Flexures of Strata. Though strata are deposited 

 generally either horizontally or nearly so, they are often 

 very much bent, as is represented in Fig. 52. There are 



some magnificent exhibitions of these flexures in some 

 of the mountainous regions. Among the Alps there are 

 mountains thousands of feet high, looking, as Professor 

 Hitchcock says, " as if crumpled together by some migh- 

 ty hand." It would seem as if it were not possible 

 thus to bend rocky strata without breaking them. But 

 probably the rocks were both moistened and heated 

 when this was done. Besides, the bending force un- 

 doubtedly was made to act very gradually. Some light 

 is thrown on this point by some observations in regard to 

 the bending of ice. Though ice is a very brittle solid, 



