944 THE JOURNAL OE GEOLOGY. 
The chemical composition of five of these rocks is given in 
Table II. The analyses are arranged so as to bring those most 
alike by the side of one another. The range of silica is 6 per 
cent. Alumina is moderately high. Magnesia, with a range 
TABLE II. CHEMICAL ANALYSES OF SHOSHONITES, YELLOWSTONE 
NATIONAL PARK AND VICINITY. 
I 2 3 4 5 
SiO, - - - 50.06 53-49 52.49 54.86 56.05 
WTO < - - 51 aff 3 81 .69 .98 
Al,O3. - - - 17.00 17.19 17.89 17.28 19.70 
Fe,0O; - - 2.96 4.73 5-76 4.08 3.74 
FeO - - - 5.42 3.25 2.08 2.28 2.32 
MnO - - 14 14 .09 .19 tr. 
MgO - - - 3.61 4.42 3.49 4.19 2a Slane 
CaO - - 8.14 6.34 7.01 5-42 4.34 
BaO - - - se .06 .30 37 ae 
Na,O ay ie 3.53 3-23 3.18 3-94 3.29 
K,0 Pea he So) 3.86 B78 3-96 4.44 
PO; - : .66 43 55 .48 .66 
H,O - - 4.85 Zag, 2.63 2.16 1.86 
100.28 10.002 100.01 99.90 100.14 
1. Shoshonite, lava sheet, Lamar River, south of Bison Peak; analyzed by 
L. G. Eakins. 
2. Shoshonite, lava sheet, S. E. fork of Beaverdam Creek; analyzed by L. G. 
Eakins. 
3. Leucite (?) -shoshonite, lava sheet, mountain east of Pyramid Peak; 
analyzed by L. G. Eakins. 
4. Olivine-free shoshonite, dike N. E. of Indian Peak; analyzed by L. G. 
Eakins. 
5. Shoshonite, lava sheet, Two Ocean Pass; analyzed by J. E. Whitfield. 
of less than 2 per cent., is rather low for basic rocks. Lime, 
with a range of less than 4 per cent. is moderate. Soda is almost 
constant; and potash is relatively high, with a range of only 
I per cent. The loss upon ignition is comparatively high for all 
the rocks analyzed. As already mentioned, the mineralogical 
variation is from an abundance of olivine and augite to a paucity 
of them, with inverse variation in the feldspars. This accords 
with the variations in the chemical composition. 
