Mesozoic and Ccenozoic Geology and Palceontology. 103 



of the substratum composed of softer-grained materials aud lime. 

 Nearer to aud aloug the base of the Colorado pinery, whose lignitic 

 hills have escaped destruction, by the upheaval of the ridge, these con- 

 glomerates, still detached from the common mass, and molded into the 

 most diversified forms by disintegration, have scattered columns, pin- 

 nacles, round towers, and cupolas over a wide area, the far-famed 

 Monument Park. 



From the mouth of Bear creek into the Platte, a few miles west of 

 Denver, the Lignitic formation abutting against the Cretaceous and 

 diversely thrown up by the upheaval of the primitive mountains, fol- 

 lows the base of these mountains in a nearly continuous belt to Che}^- 

 enne. Though generally covered b}' detritus, the basin is deeply cut 

 by all the creeks descending to the plain — Clear, Ralston, Coal, Erie, 

 Boulder, Thompson creek and others, and the strata thus exposed. 

 Golden is on the banks of Clear creek, at its outlet from a deep canon, 

 and in the middle of a narrow valley, shut up, on the west, by the 

 slopes of the primitive rocks, and on the east by a high wall, a trap- 

 dike, which here follows the same trend as that of the mountain at a 

 distance of one to one and one-half miles. As it is generally the case 

 along the eastern base of the Eocky mountains, the more recent for- 

 mations have been thrown up and forward, and their ^dges upraised to 

 a certain degree nearest to the uplift, and thus succeeding each other 

 by hog-backs facing the mountains, they pass towai'd the plains in 

 diminished degrees of dip and soon take their horizontal position. 



At Golden, the lignitic strata, compressed, as the}' are, between two 

 walls of eruptive rocks, have been forced up on the western side, in a 

 nearly perpendicular position, while on the other the}' were thrown up, 

 at the same time, b}' the basaltic dike, and thus folded or doubled 

 against their faces, in the same way, as the measures of the anthracite 

 basin of Pennsylvania have been so often compressed in multiple folds 

 between the chains of the Alleghen}- mountains. In that way the 

 lowest strata of the Lignitic, which are nearly perpendicular, overlie 

 the upper Cretaceous strata, which, following the slope of the moun- 

 tain's plunge, incline in a less degree. The line of superposition of 

 both formations is seen along a ditch "opened for a canal of 

 irrigation, about two hundred feet from the tunnels, made in a bank of 

 clay which underlies the lower lignite bed, and which is worked for 

 pottery. These upper Cretaceous strata are seen in the vsame position, 

 and exactly of the same nature as at Gehrung's; thin beds of soap- 

 stone or laminated clay, with Cretaceous fossils, and above them the 

 same kind of Ttiten-clay, a few inches thick, under the lower sand- 



