Q52 THE JOURNAL OF GEOLOGY. 
The chemical composition of these rocks is shown by the 
first four analyses in Table IV., taken from Professor Merrill s 
paper. 
TABLE IV. CHEMICAL ANALYSES OF IGNEOUS ROCKS CORRESPOND- 
ING TO ABSAROKITE AND SHOSHONITE. 
I 2 3 4 5 6 7 
SiO, 46.90 49.13 50.82 51.65 50.03 52.33 54.15 
iO AI 42 59 55 61 .14 wee 
Al,O3 10.17 9.05 11.44 13.89 14.08 15.09 18.92 
Fe,0; 1.22 3.57 5 2.70 2.92 4.31 oe 
FeO Bait 7/ 5.05 8.94 4.80 6.11 4.03 ; 
MnO .10 15 .19 15 .08 .09 eater 
MgO 20.98 17.21 14.01 11.56 10.73 6.73 1.90 
CaO 6.20 5.68 8.14 4.07 7.46 7.06 Bel7ioe 
BaO acres 05 .06 .19 .04 .07 suet 
Na,.O 1.16 2.01 1 7/@) 2.99 1.46 3.14 5.47 
K,0 2.04 2.24 45 4.15 2.64 3.76 8.44 
P.O; 44 38 .20 Bil 42 TZ 
Gr,07 533 39 .03 80 tr. Deis peiete 
SO; arent Meer Re ave .19 nei Je Gl eae 
H.O at 110° 1.04 84 ainevets 1.30 Salers 2.68 Suetens 
Ign. 4.38 3.50 58 1.89 357/10 See INO CIEE, 
100,54 99.87 100.49 101.09 100.28 100.45 99.81 
1. Fort Ellis, 2% miles southeast of Bozeman, Montana—analyzed by T. M. 
Chatard 
Bear Creek, Madison Valley, Montana—analyzed by T. M. Chatard. 
South Boulder and Antelope Creek, Montana—analyzed by L. G. Eakins. 
Cottonwood Creek, Montana—analyzed by T. M. Chatard. 
Cottonwood Creek, « —analyzed by L. G. Eakins. 
Cottonwood Creek, « _ —analyzed by L. G. Eakins. 
Cottonwood Creek, «« —analyzed by G. P. Merrill. 
N Ov FW WN 
The variability of these rocks within certain limits is evident ; 
the greatest range being in magnesia. As a class they are char- 
acterized by low silica and alumina, high magnesia, compara- 
tively high alkalies, with much potash. The rock of the fifth 
analysis is a transitional variety, between absarokite and normal 
basalt. The sixth analysis is from a rock corresponding some- 
what to shoshonite, in alkalies, but slightly lower in alumina, 
