208 
THE GRAND CANON DISTRICT. 
volcanic action ; that they were ravaged by an erosion commensurate with 
the grander examples of that process which are proven to have occurred in 
much later stages of the world’s history; and that the region was again 
submerged. 
With the Carboniferous began that long era of deposition which extended 
without any real break into Tertiary time. The record of each period 
seems to be complete in the strata, and the deposition was apparently con- 
tinuous over the area of the Plateau Province taken as a whole, though 
here and there we may detect evidence of a brief interruption in some 
small areas. There are some general facts connected with this process of 
accumulation of strata which merit special notice. 
(1.) The strata of each and every age were remarkably uniform over 
very large areas, and were deposited veiy nearly horizontally^ In the in- 
terior spaces of the province we never find rapid increments or decrements 
of the strata. They do indeed vary in thickness, but they vary in the most 
gradual manner. Around the old shore lines, however, which form the 
present borders of the Plateau Country, we find the volumes of the strata 
much larger than elsewhere. But as we depart from them towards the 
heart of the province, we observe, in the course of two or three leagues, a 
considerable diminution in their thickness, and thenceforward the attenua- 
tion is so slow that we discover it only by comparing correlative sections 
many leagues apart. Very analogous is the constancy of lithological char- 
acters. As we trace the individual beds from place to place, we find their 
composition to be as persistent as their thickness. The sandstone of a given 
horizon is always and everywhei’e a sandstone, the limestone a limestone, 
the shale a shale. Even the minuter structure of the beds is similarly main- 
tained, and features which are almost abnormal are equally constant. The 
Jurassic and Triassic sandstones are everywhere cross-bedded after their 
own marvelous fashion. The singular cherty limestones at the summit of 
the Carboniferous are quite alike on the brink of the Grand Canon, at the 
junction of the Grand and Green rivers, and in the borders of the great 
Black Mesa at the south. The curious Shinarump conglomerate is the same 
in Pine Valley Mountains, in the terrace at Kanab, at the base of the Echo 
Cliffs, and in the Land of the Standing Rocks. The lower Triassic shales 
