SANJDSTONE DIKES OF UTE PASS. 139 



able. On the contrary, it postulates conditions which 

 must be realized now and then — a normal type of geo- 

 logical accident. The next step, therefore, is to test its 

 applicability to the actual conditions of the present prob- 

 lems. There are two questions especially Avhich the 

 acceptance of this explanation would require to be 

 answered in the afQrmative. First, are there, among the 

 sediments of the Manitou and Manitou Park basins, any 

 that, aside from structural features like stratification, 

 which would of course be obliterated during the filling of 

 the fissures, present a reasonably close agreement in 

 character (composition and texture) with the sandstone 

 of the dikes? Second, may we reasonably assume that 

 these sediments were, in part at least, unconsolidated, or 

 imperfectly consolidated, at the time when the fissures 

 were formed ? The only sandstone formations that need 

 be considered in this connection are the Potsdam, Car- 

 boniferous, Triassic and Dakota. The Laramie and 

 Monument Creek beds are so far removed in every sense 

 — lithologically, stratigraphically and topographically — 

 as to place them quite beyond the possible purview of the 

 problem. Of the four sandstone horizons first named, 

 the last three bear no special resemblance to the material 

 of the sandstone dikes. Cross insists upon this lack of 

 agreement for the Carboniferous or Fountain beds, which 

 are ruled out especially by their prevailing coarseness 

 and arkose character. It is almost as difficult to find 

 in the bright red Triassic sandstones an equivalent of 

 the reddish-brown and gray sandstones of the dikes ; 

 and similarly with the white or butt' Dakota sandstone, 

 weathering to bright yellow, orange and red tints. Fur- 

 thermore, the derivation of the dike rock from any of 

 these higher sandstone horizons would imply the exist- 

 ence of sandstone dikes in the lower sedimentary forma- 



