128 
On the Chemical Properties of Soils. 
Ammonifv. 
Experiment. Grains. 
1st. Eemovcd by 7000 grains of water .. .. '236 
2nd. ,, .... -642 
3ni. ,, ,, .. .. -610 
4th, ,, ,, .... -622 
5th. .... -120 
6th. ., .... -193 
7th. ,, .... -228 
Total 2-651 
Thus '2651 grains of ammonia were removed by 49,000 grains 
of water from J lb. of soil. This quantity of soil absorbed 
from a strong ammoniacal solution 4"G55 gi'ains of ammonia. 
By deducting 2'651 grains of ammonia, i. e. the amount washed 
out by seven successive washings, with 7000 grains of water each, 
Ave obtain 2*004 as the quantity of ammonia which was retained 
by the soil, after all the washings with water. 
More than half the ammonia originally absorbed by the soil 
was thus again removed by washing with water. 
It appears thus distinctly that the power of soils to remove am- 
monia from solutions is very much greater than their property of 
yielding it again to tcater. 
Indeed even a very much larger quantity of water than that 
which falls annually upon our fields in the shape of rain is 
incapable of washing out of the soil such a proportion of am- 
monia, as can be of any account in relation to the quantities 
incorporated with it in the shape of natural or artificial manures. 
In the experiments before us the weight of water which Avas 
passed through the soil was twenty-eight times as large as the 
weight of the soil, and yet little more than half the quantity 
of ammonia absorbed by the latter was extracted by this 
immense amount of water. In nature such excessive washings 
by rain are not likely to occur ; we need not therefore fear that 
the ammonia absorbed by the soil we cultivate Avill be removed 
by the most heavy rain-storms to anything like the extent in 
which it was removed in my experiments. 
At the same time it is well to remember that each shoAver of rain 
renders soluble some ammonia which may have been previously 
absorbed by the soil. The best fertilizing matters, if presented 
to plants in great abundance, exercise an injurious effect upon 
their growth, or, at any rate, favour an unhealthy development 
of one part of the vegetable organism at the expense of another. 
Thus wheat or barley grown on a dung-heap becomes rank and 
attains a great size, but will hardly flower, and never produce any 
grain. This is accounted for by the fact that farm-yard manure 
contains far too much soluble manuring matters to be beneficial 
to the healthy development of the crops which we cultivate. 
