178 



Popular Science Monthly 



Natural Ccinnonballs 



THE cannon balls illustrated are sim- 

 ply big, nearly spherical rocks 

 which are found at intervals in the soft 

 sandstone of Southern California, the 



Natural cannon balls found in the soft sandstone of 

 Southern California 



same sand formation in which the great 

 deposits of petroleum are found. Of 

 course there is no oil left in these cliffs ; 

 it has all leached out and evaporated, but 

 where the strata dip down from two 

 thousand to three thousand feet below 

 the surface, there it is saturated with oil 

 and natural gas, to constitute one of the 

 greatest oil deposits in the world. 



The Devil's Post Pile 



THE Devil's Post Pile is one of the 

 greatest wonders of America. It is 

 such a remarkable formation of volcanic 

 rocks that it has been constituted by 

 Presidential Proclamation 

 into a National Monument. 



The huge pile is composed 

 of large l)asaltic coknnns 

 about the dimensions of tel- 

 egraph or telephone poles, 

 though most of them are 

 either hexagonal or five- 

 sided. Some, however, are 

 four-sided and closely re- 

 semble hewn timbers about 

 two feet in diameter. The 

 "posts" stand in the pile at 

 all angles from vertical to 

 almost horizontal. 



The visible height of the 

 tallest post is over fifty feet, 

 although it is not known 

 how far down they extend 



— a considerable distance it is believed 

 by geologists. Each year's freezes and 

 thaws throw down portions of the outer 

 columns. From the vastness of the rock 

 pile at the base of the standing columns 

 it is evident that this process 

 of disintegration has been 

 going on for many centu- 

 ries. The posts are com- 

 posed of basalt of great 

 hardness and density, the 

 product of volcanic erup- 

 tion. Exposed portions of 

 the top of the pile show the 

 scratching of glaciers, yet 

 the pile itself and the sur- 

 rounding country is cov- 

 ered with a layer of pumice 

 dust, an evidence that the 

 "post-pile" is the product of 

 a volcanic eruption which 

 occurred after the glaciers 

 had long since retreated. 



G 



Fossil Plants Twenty MiUion 

 Years Old 



EOLOGISTS describe what is 

 known as the Denver Basis as a 

 great, low, swampy region (Denver is 

 approximately its center) which existed 

 during an early period of the earth's his- 

 tory when the Rocky Mountains were 

 just pushing their way up out of the 

 primal ocean. This great "basin" was 

 made up of shallow lagoons and low- 

 lying, sandy shores on which grew a 

 rank, tropical vegetation somewhat sim- 



A huge pile of basaltic columns which brings to mind 

 Ireland's "Giant's Causeway" 



