THE FLORISSANT LAKE BASIN. 19 



easterly direction (perhaps from Pike's Peak), the lake, or series of lakes, 

 was drained dry by emptying at tlie northwestern extremit}^ The drainage 

 of the valley now flowed into a brook which followed the deeper part of its 

 former floor, and the waters of the region have since emptied into the Platte 

 and not the Arkansas, passing in their conrse between Topaz Butte and 

 Castello's Mountain. 



The promontories projecting into the lake on either side are formed of 

 trachyte or other volcanic lavas, apparently occurring in fissures directly 

 athwart the general course of the northwestern or upper series of lakes, 

 and masses of the same occur at many different points along the ancient 

 shore, such as the western corner where the waters of the lake were finally 

 discharged; in the neighborhood of the village; along the eastern wall of 

 the lowermost of the chain of upper lakes, near where the present road 

 divides; and at points along both eastern and western walls of the lower 

 southern lake. In general the trachytic flows seem to be confined to the 

 edges of the lacustrine basin, but some, if not all, of the mesas or ancient 

 islands of the southern lake have trachytic flows over them ; and toward 

 the southern extremity of the lake what was once a larger island now forms 

 a rounded hill with steep northern walls, crowned by heavy beds of dark 

 trachyte, and its slopes covered with quantities of vesicular scorife. The 

 rough and . craggy knoll immediately overlooking the present village of 

 Florissant, the reputed scene of Indian combats,^ is witness of hotter times 

 than those; vertical cylindrical holes, with smooth walls, in which a man 

 could hide from sight, funnels scored by heat, mark, perhaps, the presence 

 of former geysers; the basaltic rocks themselves are deeply fissured by the 

 breaking up of the planes of divisions between the cohunns, affording the 

 best protection to the Ute and Arapahoe warriors. But the very shales of 

 the lake itself, in which the myriad plants and insects are entombed, are 

 wholly composed of volcanic sand and ash; 15 meters or more thick they 

 lie, in alternating layers of coarser and finer material. About half of this, 

 now lying beneath the general surface of the ground, consists of heavily- 

 bedd.ed drab shales, with a conchoidal fracture, and is totally destitute of 

 fossils. The upper half has been eroded and carried away, leaving, how- 

 ever, the fragmentary remains of this great ash deposit clinging to the bor- 

 ders of the basin and surrounding the islands ; a more convenient arrange- 



' Their rude fortifications still crown the summit. 



