32 COLORADO COLLEGE STUDIES. 



• 



sidered as coinciding with it), 1812 feet. From these ele- 

 vations we find, in the direction from A to M, a dip of 40 

 feet in 61 miles, or only about -3 of a foot to the mile; from 

 G to H, one of 312 feet in 48 miles, or 6.5 feet per mile; from 

 A to H, one of 340 feet in 67 miles, or about 5 feet per mile; 

 from M to H, one of 300 feet in 50 miles, or 6 feet per 

 mile; from G to B, one of 68 feet in 14.5 miles, or about 4.7 

 .feet per mile; from A to B, one of 96 feet in 46 miles, or 

 2.1 feet per mile; and from M to B, one of 56 feet in 22.3 

 miles, or 2.5 feet per mile, the distances, like the elevations, 

 being subject to some correction, but sufficiently exact for 

 our present purpose. 



In minor parts, the Medicine Lodge gypsum is nearly 

 pure white: in others it is suffused with leaden-gra}- or 

 dusky-brownish shades; most commonly it is greyish-white, 

 mottled with feebly defined dark spots. The latter are 

 generally the expiession of a tendency that existed in the 

 gypsum, under the original conditions of precipitation, to 

 form crystals, as is shown by the occurrence of the spots in 

 every gradation from ill-defined spot-like segregations to 

 well-formed crystals of selenite. Some of the crystals are 

 of the common rhomboidal patterns, others are of the 

 stellar type. Even the perfect crystals present the appear- 

 ance of dark spots, as transparent inclusions in an opaque 

 white matrix (comparable with cavities in such a matrix) 

 would naturally appear. Distinct crystals are far more 

 abundant in the gypsum on the Salt fork and Cimarron 

 river than on the Medicine Lodge. 



The uneven color and more or less saccharoidal tex- 

 ture of the Medicine Lodge gypsum give to its freshly ex- 

 posed surfaces, as seen in the quarries of Barber county, an 

 aspect not unlike that of marble, and the resemblance to 

 marble is further increased by the fact that the gypsum 

 takes a fine polish. Hence originated the erroneous names, 

 "Sun City marble," "Kansas onyx," etc., that have some- 

 times been applied to this gypsum. 



