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VI. — On Peruvian Guano and the 3Ieans of Increasing its 
Efficacy as a Manure. By Dr. Augustus Voelcker. 
Peruvian guano, like well-made farmyard-manure, lias been 
found to benefit more or less all kinds of crops grown on every 
description of land. For this reason it is considered a more 
universal fertiliser than artificial manures, which, like nitrate of 
soda, wool-refuse, horn-shavings, &c, exercise a beneficial action 
upon vegetation solely in virtue of their nitrogen, and conse- 
quently should only be used in special cases and with great dis- 
crimination, especially on soils deficient in the mineral substances * 
found in the ashes of plants. 
With the exception of a trifling quantity of sand, seldom 
exceeding 2 per cent., and 12 to 15 per cent, of moisture, 
genuine Peruvian guano contains nothing which is not of great 
utility to vegetation. 
We find, indeed, in it in a concentrated state the most valuable 
fertilising constituents, and do not meet in it with substances 
which, though necessary to a healthy growth of plants, are 
abundantly distributed throughout most soils, and therefore may 
well be dispensed with in a concentrated manure. 
But although it contains potash, soda, chloride of sodium, 
lime, magnesia, oxide of iron, phosphoric acid, sulphuric acid, 
and silica, or nearly all the ash-constituents of plants, the large 
amount of ammoniacal salts and nitrogenous organic matter 
which enter into it chiefly determine its commercial and agri- 
cultural value. 
Ammoniacal salts and nitrogenous matters possess a money- 
value which is, in a great measure, independent of the demand 
of the agriculturist for these materials. Guano, when cheap, 
may and has been used as the raw material for the manufacture 
of spirits of hartshorn, carbonate and sulphate of ammonia, as 
also for preparing Prussian-blue, murexide-purple, and other 
dyes, and such competition would disturb, and possibly might 
injure, the market for the farmer. 
In my own mind I have no doubt that Peruvian guano is 
worth more to the agriculturist and the dealer in artificial ma- 
nures than to other chemical manufacturers, because its consti- 
tution is one that gives it special value as food for plants ; as a 
source of nitrogen, it differs materially from wool-refuse (shoddy), 
(which being impregnated with oil dissolves but slowly in the 
soil, and is therefore far less valuable,) and resembles a quick 
acting because rapidly decomposing material, such as blood or 
fish-refuse. 
Genuine Peruvian guano contains from 6 to 7 per cent, of 
ready-formed ammonia, and an amount of nitrogenous organic 
constituents which on decomposition yield about 12 per cent. 
