Composition and Practical Value of Native Guano. 423 
6. That the analysis published by the Native Guano Company 
represents the manure as having a much greater fertilising 
value than any of the five samples which were sent to me for 
examination. 
The intrinsic fertilising value of artificial manures of the 
nature of sewage deposits is mainly regulated by the amount of 
phosphate of lime and of nitrogen which they contain. 
The manure prepared at Leamington contains no appreciable 
amount of ready formed ammonia ; its nitrogenous constituents, 
however, when applied to the land, soon enter into decomposition 
and readily yield ammonia. 
Phosphate of lime in the shape of bone can at present be bought 
at about 10/. a ton ; and animal matters, which readily yield 
ammonia on decomposition, can be purchased by paying 601. 
for each ton of ammonia, which they are capable of producing. 
Allowing thus 101. per ton for phosphate of lime, and 60/, for 
ammonia, the samples of Native guano, according to the pre- 
ceding analytical data would have the following value : — 
£. s. d. 
No. 1 would be worth 0 18 6 jrer ton, 
, No. 2 „ „ 1 13 6 „ 
No. 3 „ „ 0 14 0 „ 
No. 4 „ „ 0 18 G „ 
No. 5 „ „ 0 14 G „ 
At these prices all the really valuable fertilizing constituents 
in a ton of this manure may be purchased in a concentrated 
form, and be easily carried by a lad on the field in a very small bag. 
Thus a few pounds of bone-dust and dried blood will embody 
the whole of the intrinsically valuable fertilizing constituents of 
a ton of Native guano. The bulk of this manure, in fact, con- 
sists of matters which occur in abundance in almost all soils, 
and for this reason are practically without value, or, rather, have 
a negative value, inasmuch as carriage has to be paid for them, 
and the application of bulky manures necessarily is more expen- 
sive than that of concentrated manures, such as guano or super- 
phosphate. It is, therefore, manifestly practically wrong to 
estimate the money value of such bulky and poor manures by 
the same standard of prices at which the commercial value of 
guano, superphosphate, bone-dust, and similar concentrated arti- 
ficial manures is ascertained. The value of such sewage ma- 
nures may probably be determined more correctly by comparing 
them with the intrinsic fertilizing value of common dung, and 
the price which is paid for the latter. 
Ordinary farmyard manure, composed of mixed horse, cow, 
and pig dung, and plenty of straw used as litter, according to 
my analyses, on an average yields about | to -pV per cent, of 
