Soluble vs. Insoluble Cane Manures. 343 
ture kept for 30 days, resulted in 67 per cent, of the acid 
becoming insoluble. 
Time did not admit of any further experiments being 
made before this paper was in the hands of the printer, but 
additional experiments have suggested themselves which 
will probably be carried out subsequently. Sufficient has 
been done, however, to show that comparatively large 
quantities of costly superphosphate are easily converted 
intohighlyinsoluble, and presumably worthlesscompounds 
by clay containing about 2 per cent, of oxide, or hydrated 
oxide of iron or alumina. It only remains to add 
that the cultivated soil of the colony contains from 2 to 
10 per cent, of oxide of iron (if not free alumina), which 
is ordinarily present in the hydrated condition, and there- 
fore in the form most readily a6ted upon by the super- 
phosphate. 
On proposed substitutes for sulphate of ammonia and 
superphosphate of lime : — There appears to be but 
little hope of increasing the per-centage of sugar in 
canes by means of manures, or, at all events by those 
at present employed. This is clearly evident from Mr. 
Gilzean'S experiments at Pin. Anna Regina, (Timehri, 
V. 138.) Taking the first experiment in each of the two 
tables of results furnished by him it appears that with 
$60 worth of manure (acidulated and ammoniated 
guano) per acre, the total sugar in the canes produced 
was 17.3677; with $16 worth of manure per acre, the 
total sugar was 17.50$; whilst, without manure the 
canes yielded 1 7.91 § of sugar in the first case, and 16.90$ 
in the second. The only certain way of securing in- 
creased saccharine richness therefore seems to be by 
propagating the best individuals of the best varieties ; 
