\i DET1 K MI NATION OF R0< 7S 



along the crests and declivities ./onul lines of 



cdding and the vertical lines of the joints. The 

 rocks are cut int.. huge blocks in the process of dcnuda 



and these blocks ar. 1 ami < hi^-llcd 



along the dominant divisional lines. With this 

 linear style of an compare that uf a mass of 



<-, one of the amorphous crystalline rocks (Fi f 

 No parallel systems of lines here catch the eye. The 

 crests are splmun.i. indeed, along ti and these 



- may be traced by a practised eye down 

 and steep declivities of granite 



never show the dcfmiteness, regularity, and alter- 

 nation of prominent and retiring kinds so typical of 



led rocks. The general lines of the mountain are 

 graceful curves rising more and more towards the summits 

 till they often bec<>: aL l 



.stratified rocks, then, are distinguished by 

 arrangement into beds, varying according to the nature 

 of the substance, from the finest lamina: up to large 

 masses many yards in thickness. The amorphous 

 crystalline rocks, on the other hand, are marked by t he- 

 absence of all structure c\< qt their joints. The reader 

 will find this subject further illustrated in succeeding 

 chapters ; but he will learn more by a little practice in 

 ncld than can be easily communicated by books. 



1 The geological sketches of Mr. \V. V. Holmes in the public*, 

 lions of the United States Geological Surveys, and those of 1 



:n his hook on the Mechanism of Mountain-building, and in 

 the Bciiragc of the Swiss Geological Commission, may be profitably 

 by the geological observer as models of artistic and scientific 



