140 University Geological Survey of Kansas. 
gypsite, containing many substances foreign to the original 
gypsum rock. The very fact that there is no salt with such 
deposits, and that the more soluble magnesia salts are absent, 
would substantiate this theory of the formation of the gypsite. 
It should also be noticed, as Prof. G. P. Grimsley has already 
pointed out, that much of this deposit may be of recent date, 
and in fact the work of deposition may be going on at the pres- 
ent time in limited areas. | 
Composition of Native Gypsum. 
The symbol for gypsum being CaSO,, 2H,O, it is evident that 
the theoretical composition is: 
Calciumioxide(Ca©) eee nee ae . 32.60 per cent. 
Sulphurickan iyciriclon(SO:) penetra 46.50 se 
\Weanuer (lalfO)) ocsceoc REAR REAR nn Sere aA __ 20.90 of 
100. 
Practically, of course, there is always some impurity in the 
rock, so we have all grades of material, as the following analy- 
ses show. 
The covering of the pyramid of Cheops, as reported by Doctor 
Wallace, has the following composition : 
CEMENT USED IN THE PYRAMID OF CHEOPS. 
Exterior.| Interior. 
SHUI), Gavel TraOlkullolke: WARNRSINBWlos bods booc cous onoe sd aoccooboKo need 4.30 HBO 
AT UMMM ORIG SRA ai 5s earner) Wace cad er a Mae acal cele nD pot 3.00 2.41 
PrOMiO KIC ices RRS Beet RE Nite ee a om aac Nye RAT ce BTUNUO fe Cie A | NR 0.21 0.25 
Marnesiumi Carbonate. iV aaatswickt at ck. ee eee cise 0.79 0.59 
Caleiumicarbonate se Vise Ok eee eee ee nat: 9.80 9.47 
EHydratedicalciumitsulphatess- meee ere aoe eee eer 82.85 81.50 
Total sey eis Uae UNS aR Aone 7 le Ds EN tn 100.99 99 .52 
This is evidently a manufactured and ‘‘set’’ plaster, and cor- 
responds quite closely to many of the samples that have been 
analyzed in Kansas. The sample from the exterior would con- 
tain 65.67 per cent. of calcium sulphate. It must have been made 
from material not altogether pure, like the rock gypsum, but 
more like a recent deposit. 
58. Dictionary of Applied Chemistry, Thorpe, Vol. I, page 468. 
