Or i (J in of (Jarbo)iaceuus Shales. 361 



not i)ure enough and deep enough to prodiiee liniestoiie. So too, 

 tlic bituminous shales of the Colorado group were deposited 

 near the shore of the Cretaceous sea. In Texas, where the 

 Cretaceous series is nearly all marine limestones, we find no 

 bituminous shales ; but as we go west toward the Wasatch 

 Mountains, the permanent shore of the Cretaceous sea, over very 

 extensive areas these limestones are replaced by black shales, 

 olf-shore deposits, which are overlain by the Ltiramie group, 

 shore and terrestrial accumulations, sandstone and conglome- 

 rate with coal strata — thai is, old peat beds. 



The upper Klamath Lake, in Oregon, is a body of water of 

 considerable size, but so shallow that water-phxnts, particularly 

 a yellow water-lily {Nitphar polysepala) root on the bottom, and 

 cover a large part of the surface with their leaves. The decay of 

 these succulent plants, existing in such quantity, must foi'm 

 a carbonaceous pulpy mass at the bottom. Since however, 

 the lake is only an expansion of a river course, — as Klamath 

 Eiver enters at one end and leaves it at the other, — it is evident 

 that at times the flow of .this stream will bring in a con- 

 siderable cpiantity of transported sediment to mingle with the 

 carbonaceous I'e^idue ; and it requires no prophet to foretell, 

 that when the bottom of upper Klamath Lake shall be exposed 

 to view, it will be found to be composed of materials which, if 

 consolidated, would become bituminous shale. 



That sheets of marine vegetation mny sometimes cover large 

 water surfaces, is shown in the existence of what are known as 

 Sargasso seas. In the wider portions of the North Atlantic is 

 that through which Columbus plowed his way, greatly to the 

 alarm of his sailors ; and others are known to exist in other por- 

 tions of the great oceanic basins. Here the sea-weeds in the 

 "Horse latitudes" are undisturbed by any storm, and grow dis- 

 connected with the earth, forming sometimes a matted sheet of 

 vegetation that conceals the water. With this growth must be 

 decay, and we are compelled to imagine the accumulation be- 

 neatli these sheets of sea-weed of a carbonaceous mud formed 

 from the decomposing cellular tissue of the plants, and such 

 inorganic matter as may be contained in their tissues, or is 

 supplied by the decay of the animal organisms which inhabit 

 such regions. 



