134 
ON MANURE. 
soda will produce similar effects, but ammonia is to be preferred. Persons are apt 
to conclude, that to this brown colouring matter we must ascribe the nutritive 
qualities of liquid manures; whereas, in fact, it is quite certain that not one 
particle of the colour can enter the spongioid of sound, undisturbed roots. 
Now, if manure-water be weighed, and then gradually evaporated at a gentle 
heat, to dryness, the weight of colouring matter will be found to be very trifling ; 
and yet, gardeners are in the habit of adding much water to this liquid, considering 
it too strong for plants growing in pots. Having thus, by dilution, reduced the 
tint to that of pale malt liquor, what activity can be expected from it ? Or if 
such liquid manure be of any avail at all, to what material can we refer its 
nutritive effects, since it is admitted that the particles of colour, minute as they 
must be, are still too gross to enter the pores of the roots ? 
To answer these queries by farther experiment, and thus gain a little more 
light upon the subject, — let a few grains of powdered quicklime be stirred into 
the coloured fluid and suffered to subside ; after a few minutes it will be seen that 
the colour of the liquid is lost ; that it has become quite pale ; while the sediment 
itself has acquired a dingy brown tinge, and a flocculent texture. As a converse 
of this experiment, let brown peat or black manure be worked up with one-third 
the quantity of quicklime, and diluted with hot water sufficient to allow of free 
subsidence. After stirring from time to time, the compound matter will subside, 
leaving the super natant liquor nearly devoid of colour : — and now caustic 
ammonia may be added to excess, without effecting any change of tint, the lime 
acting by more powerful affinity, and fixing the humic extractive in the form of 
an insoluble humate of lime. 
In this way it is that lime acts as the specific reclaimer of waste and barren 
peat-bogs, rendering them fertile by the abstraction and fixation of that inert and 
deleterious vegetable matter which is an antagonist to vegetation. And thus, by 
an induction from undeniable chemical facts, we begin to perceive that we have 
long been misled by crude theories and empirical practice. 
Liquid manures, therefore, act by the salts which they contain, not by the 
colouring solution of humus ; and thus, also, we may be permitted to sanction the 
cautious application of artificially prepared fluids, as for instance 66 Potter's Liquid 
Guano," " Humphreys' Inodorous Compound," and other fertilizers, which are 
neither more nor less than solutions of chemical salts ; among the safest, and most 
effectual of which, are the sulphate of ammonia, nitrate of potassa (salt-petre), 
and sulphate of soda. 
Lime is the interpreter of this new and most intelligible theory ; for, by it the 
important fact has been ascertained, that, for all the poisonous vegetable extract in 
peat-bogs, in old pastures, in gardens and soils over-glutted with manure, it 
exerts the most powerful affinity, attracting the humic acid, not only from alkaline 
solutions, but from the body of the soil itself, fixing it in a condition of absolute 
insolubility, and thereby rendering the poison quite innocuous. 
