NITRA TES IN CA VE EARTHS 



243 



may be noted that Mr. Hess' claim that nitrates are uniformly 

 distributed in the dry chambers of caves is not substantiated by 

 the analyses of cave earths of Wyandotte Cave made for the 

 Indiana Geological Survey. 1 Besides the analysis of niter earth, 

 there is given one of the magnesian earth which is abundant in 

 the dry portions of Wyandotte Cave. The analysis of this earth 

 shows no nitrates. An interesting variation between the distri- 

 bution of nitrates and of other nitrogen compounds throws 

 much light upon the problem, and has been investigated by 

 Miintz and Maracano for some Venezuelan caves. 2 "There is 

 thus a gradual change in the character of the nitrogenous com- 

 bination from the interior to the exterior portions of the cave, 

 as shown in the following analyses : 



If the transformation of organic nitrogen through ammonia 

 and nitrites to nitrates by the action of bacteria occurs only at 

 the surface, there should be no uniform variation in the propor- 

 tions of these components in the cave earths, but such a variation 

 as has been found might occur from the mouth of the cave 

 inward if the bacteria are acting in the cave itself. Mr. Hess 

 has doubtless performed a service in pointing out a method by 

 which cavern deposits of nitrates may be formed, and it is not 

 improbable that such deposits may be discovered. Deposits 

 thus formed, however, will have several easily recognized 

 features not found in the cavern earths now known. 



Henry W. Nichols. 

 Field Columbian Museum, 

 March 2, 1901. 



'Indiana Geol. Surv., 1878, p. 162. 



2 Merrill : Rocks, Rock Weathering, and Soils, p. 372. 



