418 



JOURNAL R. A. S. (CEYLON). 



[Vol. III. 



every thing he saw, examined, and described, are generally 

 correct, even to this day. I quote from his valuable "Account 

 of the Interior of Ceylon " published in 1821, respecting 

 the Nitre Caves of Ceylon : — 



" Nitre and Nitrat of lime are of frequent occurrence. The names 

 of twenty-two places may be enumerated, in which saltpetre is 

 produced, and in which it has been manufactured ; and no doubt, 

 besides these, there are many other spots that yield this salt, 

 known to the natives, whose policy it is not to make us ac- 

 quainted with them. Judging from four nitre caves that I have 

 visited, and from the specimens of rocks of several more that 

 I have examined, I believe that they are all very similar ; 

 and that the rock in which they occur, in every instance contains 

 at least felspar and carbonate of lime ; from the decomposition of 

 the former of which, the alkaline base of the salt is generally derived, 

 and by the peculiar influence of the latter, (yet not at all understood,) 

 on the oxygen and azote of the atmosphere, the acid principal is 

 generated. In confirmation of thi* statement, it may be remarked, 

 that I have never been able to detect saltpetre, excepting superficially, 

 where air could have access ; never unaccompanied by nitrat of lime, 

 or magnesia; in no rock, not containing lime and felspar; that the 

 richness of the rock, in general, has been proportional to the abund- 

 ance and intimate mixture of these two ingredients ; and that the 

 results of experiments which I have made on a variety of specimens 

 of saltpetre-earth from Bengal, for which I am indebted to the kindness 

 of Mr. Brown of Calcutta, were similar to those just mentioned, and 

 tended to the same conclusions. 



" Besides the essential circumstances of the presence of atmospheric 

 air, lime, and an alkaline mineral, there are other circumstances 

 which, if my observations be correct, greatly aid in the operation of 

 forming the salt. I shall mention the most remarkable only, which 

 appear to me to be slight humidity and the presence of a little 

 animal matter. Perhaps, humidity is absolutely necessary ; certainly, 

 I have seen spots in a nitre cave, without any impregnation of 

 saltpetre, which, excepting their great dryness, seemed to possess 

 every requisite for the production of the salt. Animal matter, 

 by those ignorant of chemistry, is considered of itself the chief 

 source of nitre. Persuaded of this, my countrymen in Ceylon, with 

 whom I conversed on the subject, generally attributed the saltpetre 

 of the caves in question to the dung of bats, with which the caves are 

 more or less infested. It is easy to refute such a notion ; and to 



