458 
On Phosphatic Guanos. 
Composition of Starbiick Island Guano. 
Moisture II' 06 
*Organic matter 7 '25 
tPhosphoric acid 33 '61 
Lime 41-04 
Magnesia 1'16 
Sulphuric acid '88 
JCarbonic acid I'Oo 
Alkaline salts 3-43 
Silica -02 
100-00 
* Co!itaining nitrogen -39 
Equal to ammonia -47 
t Equal to tribasic phosphate of lime .- 73-67 
X Equal to carbonate of lime 2-38 
The richest crust guano ever analysed by me came from Star- 
buck Island. Two samples had the subjoined composition : — 
Composition of Two Sa^iplss of Starbxtck Island Crdst 
Guano. 
Ho.l. 
No. 2. 
S-75 
4.T-57 
40-94 
-64 1 
3-56 \ 
•47 ) 
■07 
1001 
40-12 
44-90 
4-87 
•04 
* Equal to tribasic phosphate of lime 
100 •GO 
100.00 
09-48 
COS 
87-58 
If the phosphoric acid found in No. 1 were combined with 
lime to form tribasic phosphate it would correspond to 99-48 
per cent, of that compound, but as the proportion of lime in that 
percentage amounts to 53-91 per cent., and only 40-94 jjer cent, 
of lime were actually found, and a portion of the lime moreover 
is united with sulphuric acid as sulphate of lime, it follows that 
these crusts consist of a less basic phosphate than the ordinary 
bone-phosphate. When due allowance is made for the lime 
which is combined with sulphuric acid, the calculation of the 
results of the analysis shows that nearly the whole of the lime 
found is united with phosphoric acid as bibasic phosphate ; that 
is, a compound consisting of two equivalents of lime and one 
