264 GEOLOGY OP THE DENVER BASIN. 



and induration of the loess in its behavior where excavated, portions yield- 

 ing readily to the shovel, other portions requiring vigorous use of the pick. 

 Moreover, on vertical surfaces exposed to seolian erosion a marked hori- 

 zontal stratification may be observed. 



The loess appears to attain its greatest development on what is known 

 as the Flats, near the eastern State line, where its maximum thickness, as 

 shown by wells sunk through it to the water-bearing stratum below, is 225 

 feet. The average thickness over what is known as the rain belt of Colorado 

 may be taken at about 125 feet. In the vicinity of Denver it has nowhere 

 been found thicker than 40 feet, nor are any such great thicknesses found 

 within the Denver Basin. This may be attributed in part probably to 

 original deposition and in part to greater subsequent erosion. 



Fossils. — Neither invertebrate fossils nor plant remains have been 

 observed in the loess of the Denver Basin. It seems better adapted, 

 however, for the preservation of vertebrate remains. Bones of two species 

 of Elephas and of ancestors of the modern bison are not uncommon. 

 Portions of six skeletons of an ancient species of horse, differing but 

 slightly from the modern Equus cahallus, have been found within the 

 limits of the city of Denver; also an isolated metapodial bone bearing 

 considerable resemblance to that of a camel. 1 Skeletons of frogs, snakes, 

 and such small rodents as Cynomys, Greomys, etc., have also been found 

 near Denver, but may be foreign intrusions. 



Mr. Thomas Belt 2 has recorded the discovery by him of human 

 remains, consisting of the top of a skull and a portion of a rib, in a 

 cutting in undisturbed loess on the Colorado Central Railroad between the 

 Platte and Clear Creek, at a depth of 3 feet 9 inches from the surface. 

 His sudden death and the loss of his specimens and notes unfortunately 

 prevented a thoroughly satisfactory verification of this discovery. An 

 examination of the spot where the bones were found shows that his 

 assumption that the loess is undisturbed is probably correct, but no more 

 human remains were discovered. 



1 Professor Cragin, of the Colorado College, pronounces some bones submitted to him from both 

 river drift and loess (and possibly from the fluvial luessi, and supposed to be bison bones, to be 

 species of Auchenia, allied to llama, alpaca, and more remotely to the camel. 



2 Proc. Am. Assoc. Adv. Sei., St. Louis meeting, August, 1878, p. 298. 



