PLEISTOCENE GEOLOGY. 



263 



proportion of cementing material. The former may be explained l>v the 

 proximity of their probable source, the pink granite near Sherman, and 

 the latter may have been derived from the Tertiary limestone n hich occurs 

 in the vicinity. Among the microscopic grains arc several minerals having 

 a high angle of refraction, one of which is apparently isotropic and resem- 

 bles a diamond. 



In the following table are given the analyses of samples of loess from 

 Colorado, to which arc added, for purposes of comparison, those of loess 

 from the Mississippi and Rhine valleys: 



.1 nalyses of loess. 



Depth . 



Surface. B feel 20 1. 1 1 



Chey- 

 enne, 



\ 7 ieka 



Mm \l 



Analvist. 



Eakina Eakins, 



Riggs. 



Eigga. 







Mil, 



Al.,0, 

 1, (l 

 FeO .. 

 i aO 

 UgO - 



( '(I,... 

 I'.".-- 



K ii . 



12 661 



,944 



N:i..i > 



ll.,n i ignition) . - 



Mull. TiO„ So s , 



an.lC 



Total . 



2, 472 

 1.797 



69.27 



1.02 

 2. 29 

 1 99 



BO '.'7 

 15 67 



2. 77 



l.iiii 



;,i 63 

 10.43 



. 18 

 i 64 

 1.13 



9 



.lie 



1.29 





1.24 



J. 117 



2.08 

 1.42 



• ■ 



1.59 



1. II 



64 



2.111 

 .51 



5.41 

 ; 69 



e . 



.00 

 1.35 



12.26 



'.''.' 54 



a Sixth Ann. Kept. U.S. Geol. Survey, p. 282. i 



I iC i.u. Phys. Geologie p. G. Biscuof, B.inc 1863 Vol.1, p. 504, 



Sample I was taken from near the foothills al Golden, and shows in its higher proportion of 

 alkalis that the material is relatively little dee posed. 



Sample II is from 8 feel below the surface on the Boulevard near Ashland avenue, North 

 I lenver, and is regarded as typical of t lie I '■ nver loess. 



Sample III is from 20 feel below the surface near St. Luke's Hospital, North Denver, and is 

 regarded as an early loess, it contains grains "i eruptive rock similar to that in the Di uv< i 



Sample IV is typical eastern i <»i.n ado loess from near Wray, i lolo., in « bich cai bonates have 



increased from practically notbiug to over S per eent. 



Sample V is a loess-like earth from near the state House al Cheyenne, Wyo. 



In spite of its great homogeneity, Mr. Cannon thinks that lie has found 

 evidence, in the vicinity of Denver, of variations in degree of compactness 



