182 W* J. Taylor on Rock Guano. 



The 0-65 of oxygen of the siilphnric acid requires 0-22 of the 

 oxygen of the lime ; the remaining lime is most likely combined 

 with carbonic acid, as nearly every specimen on treating with 

 dilute acid gave a slight effervescence (the guano rock from the 

 vertical cliff contained nearly one per cent), or possibly a rem- 

 nant of the once phosphate of lime still exists. The alumina 

 and phosphoric acid exist most likely in the form of "vvavellite, 

 which has the formula SALOa, 2PO5 +12110. It is difficult in 

 a rock which is in progress of decomposition to obtain other 

 than approximate formulse. 



This island of Centinella is now inhabited by immense num- 

 bers of water-fowl, many of which roost on the cliffs ; some of 

 these roosts have been long occupied, and judging from the 

 signs on the rocks beneath, have been much resorted to. Mr. 

 Kichards of Philadelphia, who visited the islands a short time 

 since, broke off a portion of the concretion which covers the cliffs 

 beneath a bird roost of this description ; the organic properties 

 had been mostly removed by causes which had converted the 

 inorganic constituents into a guano rock, which in composition 



3 Island and El Roque. ^ Mn 



first obtained it had quite a 



strong odor, which has now almost disappeared; it is very hard 

 and was difficult to powder. 



The analysis of the concretion is as follows : 



(VIII.) 



2-0904 grams, on ignition lost 0*23G1 gram. 11-29 p,c. 



2*2904 " 0-0248 grams. AbOa gave alumina, 1*08 " 



8470 « 0-066 " BaO, SO3 « sulphuric acid, 2'67 



0*4707 « CaO, CO2 « lime, 31-18 



« " 0-0406 " 2MgO,P05 « magnesia, 1'74 " 



0-0143 " Fe203& AI2O3 « iron and alumina, I'GO 



IS 



Eichards 



Monk 



a u 



it 



(C 



it u 



It 



u it 



0-0606 " insoluble, " silica, 5-97 



1-8570 " 1-0153 " CaO,C02 « lime, 30-68 



it 



u 



U (( 



a u 



« 0'0926 « 2MgO,P05 « magnesia, 1-79 " 



0-0340 « FeaOa AI2O3 " alumina and iron, 1-86 " 



u 



1-2520 « 2MgO, PO3 « phosphoric acid, 41-89 

 1*2142 " contained 0-0089 grams. CO2 « ' carbonic acid, 0-73 



Alumina and iron, 1-86 per cent. Oxygen ratio, 0-86 



Sulphuric acid, 2-67 " " '' ** 1-59 



Carbonic acid, 0-73 " " " " 0-54 



Lime, 31-18 " " " " 8'86 



Magnesia, 1-74 " " " " 0'69 



Phosphoric acid, 41-89 " " " " 23-25 



^ 1*59 oxygen of sulphuric acid require 0*53 of oxygen of the 

 lime ; and 0-53 of oxygen of the carbonic acid require 27 oxygen 

 of the lime ; but if there is added to this remainder the oxygen 



