137 WILLIAM H. HESS 
earth, both from Dixon’s Cave, were obtained by igniting the 
dried samples and then treating them with dilute hydrochloric 
acid. 
Bat guano Cave earth 
Loss on ignition . - - ; 2° Bo 1(6) 6.02 
Insoluble residue - = - - - 40.65 73.80 
Soluble silica, SiO, = - - - - - 1.03 trace 
Calcium oxide, CaO - - - - 10.95 7.51 
Ferric oxide, Fe,03 - - - - = G20 B27) 
Alumina, Al,O3;_~ - - : - - 5o27/ 2.41 
Magnesia, MgO - - - - hl Oneyy/ 0.30 
Sulphuric anhydride, SO; - - - 4.37 Dpy 
Phosphoric anhydride, P,O; - - - 2.62 2.10 
Alkalis and loss” - - = - - 2.38 69/2 
This sample of cave earth contained no perceptible organic 
matter. 
It seems from a comparison of these analyses that we cannot 
prove the presence of animal remains by the total content of 
phosphoric acid soluble in dilute mineral acids, since a residue 
from limestone must contain considerable calcium phosphate on 
account of the insolubility in water of this salt of calcium. 
Analyses of the water dripping from the roofs of caves were 
made, and results were obtained which do not vary markedly 
from results obtained from analyses of ordinary sub-drainage 
waters. The following is an analysis of the residue from water 
which dripped from the roof of Mammoth Cave: 
Milligrams per liter 
Silica, SiO, - - - - - - = 1923 
Sulphuric Anhydride, SO; : - > 15.81 
Phosphoric Anhydride, P.O; - - = ALLAGE 
Chlorine - - - : - - - Doli 
Ferrous Carbonate, FeCo; - - - - 1.02 
Calcium Carbonate, CaCO; - - - 53-61 
Magnesium Carbonate, MgCO;_~ - - a ely 
Alkalis, Na,O and K,O - - - 16.56 
Ammonia, NH; - - - - - SOLO! 
Nitric Acid Anhydride, N,0O, - - - 5.71 
A comparison of the soluble constituents given in this analy- 
sis with the soluble material extracted from the cave earth, as 
