22 Colorado College Sti'dies. 



beach-deposits, and the fact that the Jurassic is represented 

 here solely by a jj^reat fresh-water lake deposit in whose 

 border-muds, near Canon City, Colorado City and Morrison 

 and elsewhere, bones of huge walking reptiles, the Dinosaurs, 

 including some, like Atlantosaurus and its allies, eighty or 

 perhaps even one hundred feet long, the most ponderous land 

 animals known ever to have trod the earth, have lain stranded 

 to the present day. 



Of all the stratified rock-systems represented at the east- 

 ern base of our front-range, the Manitou limestone, of Silurian 

 age, is nearly the oldest, only one, the underlying formation 

 of red sandstone, gravel and lime, which, from its deep-green 

 glauconitic variegations and its typical occurrence about 

 Rainbow Falls, may well be called the Rainbow formation, 

 belonging to an earlier age, the Cambrian. The extensive 

 system of caves found in the Manitou limestone, and of which 

 the Pickett cave, or Cave of the Winds, and the Grand Cav- 

 erns, besides several smaller caves, are a part, have been made 

 primarily by the solvent and secondarily by the transporting 

 action of carbonic-acid-laden waters that formerly circulated 

 through the joints and other fissures of the limestone. Sub- 

 seciuently, as happens to most caves sooner or later, those of 

 the Manitou limestone have been to a greater or less extent 

 filled with a reddish sediment, known as cave-earth, which it 

 is necessary to remove in order to display the subterranean 

 galleries and chambers in anything like their original dimen- 

 sions. Tlie cave-earth in many instances is barren, or con- 

 tains only sparingly the remains of recent animals; but in 

 others it yields the bones of extinct animals, throwmg light 

 on the history of both the cave and the surrounding region. 

 In having the cave-earth removed from a cave in this lime- 

 stone in Glen Eyrie a few years since. General Palmer saved, 

 with his usual foresight, the organic remains, consisting of a 

 number of bones, thrown out with the earth by the workmen, 

 and these he very kindly submitted to me for determination. 

 Two of the specimens were at once recognized as proximal 

 phalanges of an extinct species of Horse, whose remains occur 

 abundantly elsewhere with those of Elephants, bulky, armored 

 Ground-sloths,Llamas as large asCamels, Saber-toothed Tigers 



