RECONNOISSANCE OF THE LYON NITRATE PROSPECT. 5 



2. From the exposure on the south side of the point: 



Three specimens from No. 2 of the section, 0.33, 0.95, and 1.30 per cent. 



Two specimens from No. 3 of the section, 1.01 and 1.12 per cent. 



Four specimens from No. 4 of the section, 0.67, 1.30, 1.78, and 3.20 per cent. 

 (The last two specimens showed surface efflorescence and can not he con- 

 sidered as representative of the rock.) 



Five specimens from No. 5 of the section, 0.23, 0.39, 0.78, 0.95, and 1.13 per cent. 



The average of #11 analyses is 1.16 per cent potassium nitrate. 

 Excluding the two samples which carried visible surface efflores- 

 cence, as noted above, the average is 1.04 per cent potassium nitrate. 



It is not possible to be certain as to the origin of the nitrate, but 

 it seems very probable that it is derived, either directly or througli 

 bacterial alteration from the excrement of animals (including, per- 

 haps, birds and bats), which have occupied the cavities in stratum 

 2 of the section, or the more or less sheltered holes and ledges weath- 



FIG. 5. View of hole eroded into stratum 3 at nitrate exposure ou south side of point. Also shows 

 calcite-lined cavities in stratum 2. 



ered into strata 3 and 5, as shown in figures 3 and 5. No guano is 

 visible in these cavities, but partially eaten nuts prove the presence 

 of squirrels or similar rodents. It is possible also that caves contain- 

 ing larger quantities of animal refuse may exist in the superimposed 

 limestones, and that nitrate therefrom may have leached downward 

 and impregnated the strata in which it is now found. A superficial 

 inspection failed to disclose any such caves, but no careful search 

 was made. The hypothesis of animal origin is strongly favored by 

 the fact that the nitrate is entirely of potassium rather than of 

 sodium. So far as the writer is aware, potassium nitrate has never 

 been discovered in nature otherwise than as the product of the alter- 

 ation of animal excrement and remains. 1 Furthermore, any other 



1 It should be noted that Orhsenius regards the potassium nitrate deposits of Hungary as formed by 

 reaction between organic matter and mother liquors residual from the evaporation of sea water, but this 

 theory has never gained general acceptance. 



