212 EXPLORATION OF THE CANONS OF THE COLORADO. 
thousand five hundred feet in thickness, and beneath them we have a thou 
sand feet of conformable rocks of undetermined age. This gives us 4,500 
feet, from the summit of the plateau down to the non- conformable beds. 
Still beneath these we have 1,500 feet, so that we have more than one thou 
sand five hundred feet of other rocks exposed in the depths of the Grand 
Gallon. Standing on some rock, which has fallen from the wall into the 
river a rock so large that its top lies above the water and looking over 
head, we see a thousand feet of crystalline schists, with dikes of greenstone, 
and dikes and beds of granite. Heretofore we have given the general name 
granite to this group of rocks; still, above them we oan see beds of hard, 
vitreous sandstone of many colors, but chiefly dark red. This group of 
rocks adds but little more than five hundred feet to the height of the walls, 
and yet the beds are 10,000 feet in thickness. How can this be? The beds 
themselves are non-conformable with the overlying Carboniferous rocks ; that 
is, the Carboniferous rocks are spread over their upturned edges. 
In Illustration 79 we have a section of the rocks of the Grand Canon. 
A, A represents the granite; a, a, dikes and eruptive beds; B, B, these non- 
conformable rocks. It will be seen that the beds incline to the right. The 
horizontal beds above, (7, C are rocks of Carboniferous Age, with under 
lying conformable beds. The distance along the wall marked by the line 
x, y, is the only part of its height represented by these rocks, but the beds 
are inclined, and their thickness must be measured by determining the thick 
ness of each bed. This is done by measuring the several beds along lines 
normal to the planes of stratification; and, in this manner, we find them to 
be 10,000 feet in thickness. 
Doubtless, at some time before the Carboniferous rocks C, C were formed, 
the beds B, B extended off to the left, but between the periods of depo 
sition of the two series, B, B and (7, C there was a period of erosion. The 
beds, themselves, are records of the invasion of the sea; the line of separa 
tion, the record of a long time when the region was dry land. The events 
in the history of this intervening time, the period of dry land, one might 
suppose were all lost. What plants lived here, we cannot learn ; what ani 
mals roamed over the hills, we know not; and yet there is a history which 
is not lost, for we find that after these beds were formed as sediments beneath 
the sea, and still after they had been folded, and the sea had left them, and 
