STRUCTURE AND POSITION. 



175 



of water, but oftener far in the interior of continents and high up the 

 slopes of mountains ; sometimes they are still horizontal though ele- 



Fig. 141. 



vated (Fig. 141) ; but often, especially in mountain-regions, we find them 

 tilted at all angles, folded, contorted (Fig. 142) overturned, broken, 



Fig. 142.— Contorted Strata. 



and slipped, so that it is difficult sometimes to determine their original 

 order of superposition. Again, in folded strata, sometimes we have the 

 most intricate crumplings of the finer lamina, such as may be seen in a 

 hand specimen (Fig. 143). Sometimes whole groups of strata are thus 



Fig. 143.— Crumpled Laminae (after Geikie). 



folded, as can be seen at one view on a sea-cliff or canon wall (Fig. 144). 

 Sometimes the whole crust of the earth, for miles in thickness and 

 many miles in extent, are thrown into great crust-waves constituting 

 mountain-ranges with their intervening valleys (Figs. 145 and 146). 



