found in the Guano Deposits and in their Vicinity. 547 



despatched both from London and Liverpool in search of 

 those valuable substances, particularly as it was considered 

 they might be obtained upon the same terms as Ichaboe guano, 

 namely, for nothing but the labour and expense of fetching. 

 No favourable accounts however have as yet been received 

 as to the success of these undertakings. The evidence of 

 such deposits existing there at all was very unsatisfactory ; 

 the circumstance much relied upon was the existence of large 

 beds of nitrate of soda in the neighbourhood of the coast of 

 South America, and large deposits of guano similar in many 

 respects to the deposits of guano on the African coast : there 

 was certainly an abundance of animal matter and ammoniacal 

 salts to furnish the nitric acid, and a temperature high enough 

 to effect the decomposition, but the source from whence the 

 alkaline bases of potash and soda were to be derived was 

 not very evident. The principal source of saltpetre in the 

 East Indies is from numerous districts of nitrous earth found 

 on the surface of the soil, which being compounds of lime 

 and magnesia with nitric acid, they are dissolved out, and the 

 saltpetre subsequently formed by the decomposition of these 

 nitrous compounds by potash salts. The nitrate of soda salt- 

 petre beds in the Province of Tarapaca near Iquiqua on the 

 coast of South America, are the only instances known of the 

 occurrence of saltpetre ready-formed in extensive beds, but 

 even this deposit contains the salt in a state of great impurity. 



These explorations, however, on the African coast have 

 brought to light various other substances which have been 

 found there, the details of which are more particularly the ob- 

 ject of this communication. 



The substances which I shall now describe are found in the 

 guano beds, or in their vicinity, either in a crystalline state, 

 or in distinct masses. The first substance is a crystalline salt, 

 perfectly transparent, with a cleavage and brilliant faces in 

 one direction only ; it gives a yellow precipitate with nitrate 

 of silver ; gives off ammonia upon application of caustic pot- 

 ash, and when heated to redness loses about 50 per cent, of 

 water and ammonia ; I consider it therefore to be phosphate of 

 ammonia. The portion of salt I examined consisted only of a 

 few grains, and was consequently too small a quantity to ana- 

 lyse with exactness. 



The next substance was also a crystalline salt a little mixed 

 with guano in its cavities ; it possessed a cleavage with bril- 

 liant planes in two directions: upon examination with the re- 

 flecting goniometer, it gave 112° as the measurement of the 

 angle formed by the meeting of the adjacent planes. Upon 

 analysis I found it to consist of — 



