W. J. Taylor on Rock Guano. 185 



0-8806 grams. 0-1158 AI2O3 gave alumina, 13-03 p. c. 



" 3P05 f ^'°^^^ " phosphate of iron, 3-61 " 



"2MgO,P05 0-2394 « pliosphoric acid, 17-41 « 



Silica, .52-07 per cent. 



Lime, 0-37 



u u 



Magnesia, 0*57 



Water, ^ ^ 12-17 " " Oxygen ratio, 10-81 



Sulphuric acid, trace 



Alumina, 13'03 " " « « 6-12 



Phosphate of iron, 3-01 " " 



Phosphoric acid, 17-41 " " " « 9-81 



The alumina and phosphoric acid seem in this to be in the 

 form of wavellite. 



The guano rock from the various groups of islands has very 

 ^ varying composition, as has been seen from the foregoing inves- 



tigations. It is found in layers, and the surface sometimes cov- 

 ered with an alluvial deposit; these layers are in places highly 

 inclined, showing that since their deposition their original posi- 

 tion has been altered. This same phenomenon is described as 

 occurring at the Chincha islands in the Peruvian guano where it 

 IS found in layers two or three yards in thickness. 



Prof. 0. U. Shepard has, with his characteristic energy, ex- 

 tended his mineralogical species to various portions of this rock. 

 He designates the so-called species generally as Pyroguanite min- 

 erals, and describes them as entirely destitute of ammonia ;* but 

 ?f examinations made of an average sample of a cargo from Monk's 



Island show one-half per cent of nitrogen. Every specimen 

 which I have examined, has on ignition given very marked evi- 

 dence of burning organic matter. How this can be retained in 

 a rock that has been subjected to tlie agency of heated trap is 

 as difficult to understand, as that minerals existing with, and 

 forming a part of, its mass, as Prof Shepard describes, contain 

 Water in their composition. Moreover, how can a rock sub- 



jected to the agency of heated trap have as its principal basis a 



salt with the formula 2CaO, HO, PO5, which is the formula as- 

 cribed to it by Ifrs. ^iggot and Beckell, of Baltimore, and which 

 seems to be the proper composition of some portions, as shown 

 \y the analysis of Monk's Island rock (Y), — though in the analy- 

 sis of the specimen from El Koque (X) there is obtained tlie 



formula 3CaO, PO5. 

 As I have already mentioned, this guano rock from Los 



Conges has been called a native super-phosphate of lime, but no 



satisfactory proofs are given as to its meriting such a name; 



phosphoric acid being found in solution after the guano is treated 



♦ Am. J. Sci. [2 J, xxii, 96. 



SECOND SERIES, VOL, XIIV, NO. 71. — SEPT., 1857. 



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