t 



f 



f 



W. J. Taylor on Rock Guano. 181 



2-8426 grammes treated with distilled water gave: 



" " 0-0076 grams. Ag gave clilorine, 009 p. c. 



" " 0-0347 " 2MgO,P05 " phosphoric acid, 0-78 " 



" " 0-1099 " BaO,S03 « sulphuric acid, 1-33 " 



Lime, 1-27 per cent. Oxygen ratio, 0-36 



Phosphoric acid, 0-81 " " " " 0-45 



Sulphuric acid, 1-49 " « ' " , « 0-89 



Guaiio rock has been brought from another group of islands 

 called Centiuelkj consisting of peaks, which sometimes attain a 

 height of 800 feet. The rock is described as consisting of two 



layers, the upper of which is a dark-brown compact rock, vary- 

 ing slightly from the lower layer. This so-called lower layer 

 has certainly a surface exposed, as the specimen which I have 

 examined, has been much weathered ; the outer portion is par- 

 tially reniform, and in places it shows a slight enamel, though 

 not near as distinctly as the specimens from Monk's and El 

 Eoque islands. It has evidently been formed in layers, which 

 when broken across show a slightly banded appearance not un- 

 like that already described as characteristic of portions of the 

 rock from Monk's Island- the color varies from a buff to an 

 ochreous brown ; it is hard, brittle, and much more readily pul- 

 verized than the Monk's Island guano rock. An opinion may 



seem premature, but I am inclined to the belief that this has once 

 been in the same condition as the guano rock from Monk's Island, 

 which has undergone changes from causes not yet fully studied ; 

 this seems probable from the fact that small quantities of phos- 

 f phate of alumina have been found in the Monk's Island rock. ^ 



The whitest portion of the rock was selected for an analysis, 

 which gave the following results : 



(VII.) 



1'5165 grams, ignited gave '3469 grams, 22-87 p.c. 



" 0'2000 grams, insoluble matter, silica, 13-18 " 



a 



a 



it 



it 



" 0»04'74 " BaO,S03 gave sulphuric acid, 1-07 

 ** 0-6921 " 2MgO,P05 ** phosphoric acid, 29-23 

 « 0-0720 " CaO, COs " lime, 2-66 



ii 



u 



u 



1-3048 ** 0-2 1 20 " AlaOs " alumina, 1 6-24 '^ 



** " 0-1628 ^ Fe203 " sesquiox. of iron, 12-41 



" ** 0*6438 " 2MgO,P05 " phosphoric acid, 31-60 



** 0*0660 " CaO,C03 « lime, 2*83 



u 



u 



a 



" " 0-0057 " 2Al203,3P05? " phosph.of alumina,0-43 " 



Water? 22*87 per cent. Oxygen ratio, 21-54 



Silica, 13-18 " " " « 6-84 



Sulphuric acid, 1-07 " " u H 0-65 



Phosphoric acid, 31-60 « " « « 20-24 



Lime, 2-66 " " « u o-75 



Alumina, 16-24 " " " " 7-59 



Sesquioxyd of iron, 12-41 " " « '' 3-61 



