166 



line portion, demonslraled the interesting fact, that this mineral 

 is a double sulphate of ammonia and potash, a compound hitherto 

 unknown as occurring naturally. 

 100 parts afforded ; — 

 Moisture 

 Sulphate of Potash 



'* " Ammonia . 

 " " Lime . 

 Phosphate Magnesia 

 Soap of Lime and Carbonate of Lime 

 Ferruginous Sand 



99.66 



The atomic proportion of sulphate of ammonia for 51.66 sul- 

 phate of potash, is 40.84, and when we dissolve this mineral in 

 water, and allow the impurities to subside, the clear fluid affords 

 crystals in groups, which have this composition. 



Other parts of the mass contain more sulphate of potash, even 

 so much as 70 per cent., being obviously a mixture. 



The lustre, and perhaps the plumose form of these crystals, is 

 due to the presence of the other compounds at the moment of 

 their formation. It was found that pure crystals, dissolved in 

 water containing guano, presented the same peculiarity as they 

 assumed the solid form. There are, in this connection, some 

 points which need further elucidation, and for this purpose a 

 portion of the specimen has been retained. 



The occurrence of salts of potash, instead of soda salts, in the 

 guano of the rainless climates, has been alluded to by chemists, 

 but I have nowhere met with the fact stated, that these guanos, 

 however ammoniacal, and, in consequence, apparently alkaline, 

 are truly always acid in their reactions. 



Regarding this mineral as affording a beautiful illustration of 

 the withdrawal of a definite compound of soluble salts, from a 

 putrefying mass, through which they were distributed unequally, 

 it becomes connected with the more permanent and perfect forms 

 having earthy constituents. In any system of mineralogy, it 

 will take a place with potash salts, as a double sulphate of potash 

 and ammonia bases. 



