HOW TO OBSERVE, 



63 



horizontal position, conformably upon each other, 

 and a force should be exerted from beneath, in a 

 direction perpendicular to their strata, sufficiently 

 strong to eject the central mass T, is it not plain 

 that, as they are elevated, the broken edges of the 

 several strata will be piled up against the ejected 

 mass ! To illustrate this still farther : Suppose, for 

 example, we lay a double series of books on each 

 other in a horizontal position, thus, and then elevate 



Fig. 16. 



Fig. 17. them by a force placed be- 



neath the line of junction, the 

 edges, of course, would be 

 raised up, and book would be 

 piled against book, like the 

 gable end of a roof, thus (fig- 

 ure 17) : 



We sometimes find rocks elevated in this manner, 

 without discovering any evidence of the cause that 

 produced the change of position. The internal 

 force may not have been sufficiently powerful to 

 raise a mass of rocks to the surface, and yet suffi- 

 cient to fissure the crust and tilt the rocks into a 

 very elevated position, as in 



Fig. 18, 



