NITRATES IN CAVE EARTHS 



A new theory of the origin of nitrates in cave earths has been 

 recently propounded by Mr. William H. Hess (Jour. Geol., 

 Vol. VII, p. 2) who considers that they are the product of the 

 nitrifying bacteria in the soil above, and that they enter the 

 cave with the seepage through the roof and are deposited by 

 the total evaporation of the water in the dryer parts of the cave. 

 In other words the dry galleries and chambers of a cave serve 

 as a gigantic natural still, catching the seepage from the surface 

 and retaining the solids. Inasmuch as the older theory that 

 these nitrates are leached from the bat guanos formed in the 

 caves is on the face of it sufficient to account for the facts while 

 difficulties arise in the application of the new theory a compari- 

 son would seem to be in order. The first and most serious 

 objection Mr. Hess urges against the older theory is a state- 

 ment that bats never go far from the mouth of the cave, while 

 many analyses (not quoted) show that the nitrates are distrib- 

 uted through the dry chambers of the cave. This would seem 

 to be decisive if rigorously verified, for if bats never went far 

 from the entrance it would be exceedingly difficult to account 

 for the presence of derivatives of bat guano in all dry portions of 

 the cave. In reality, bats frequent in very large numbers 

 remote portions of caves. Dr. O. C. Farrington, in a recent 

 expedition through the caves of Indiana, found bats in all parts 

 of the caves visited. 1 Mr. Hess' second objection is that the 

 cave earth contains little or no organic matter. Two specimens 

 in the collections of the Field Columbian Museum, one from 

 Indiana and one from South America do contain organic matter 

 visible on casual inspection. As the niter, according to the 

 general opinion, is for the most part not a decomposed or altered 

 guano but a residual clay or sand impregnated with soluble 

 salts by seepage from bat guano, there is no reason why it should 



'Field Columbian Museum Publication 53, p. 244. 



236 



