Page:Popular Science Monthly Volume 88.djvu/206

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��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.

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��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"

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