the Progress of English Agriculture. %\1 = 545 
2. Ammonia is never completely removed from its solution, 
lowever weak it may be. On passing a solution of ammonia, 
whether weak or strong, through any kind of soil, a certain 
|uantity of ammonia invariably passes through. Xo soil has the 
)ower of fixing completely the ammonia with which it is brought 
nto contact. 
3. The absolute quantity of ammonia which is absorbed by a 
oil is larger when a stronger solution of ammonia is passed 
hrough it, but, relatively, weaker solutions are more thoroughly 
xhausted than stronger ones. 
4. A soil which has absorbed as much ammonia as it will from 
weak solution, takes up a fresh quantity of ammonia when it 
i brought into contact with a stronger solution. 
5. In passing solutions of salts of ammonia through soils, the 
mmonia alone is absorbed, and the acids pass through, generally 
1 combination with lime, or, when lime is deficient in the soil, 
1 combination with magnesia or other mineral bases. 
6. Soils absorb more ammonia from stronger than from weaker 
ilutions of sulphate of ammonia, as of other ammonia-salts. 
7. In no instance is the ammonia absorbed by soils from 
ilutions of free ammonia, or from salts of ammonia, so com- 
letely or permanently fixed as to prevent water from washing 
ut appreciable quantities of ammonia. 
8. The proportion of ammonia which is removed in the several 
ashings is small in proportion to that retained by the soil. 
9. The power of soils to absorb ammonia from solutions of 
ee or combined ammonia is thus greater than the power of 
ater to redissolve it. 
It follows, from these observations, that in ordinary seasons no Effect of rain 
•ar need be entertained that heavy showers of rain will remove °" top-diess- 
, ■ p • T : T • 1 11^ in£;> of amrao- 
luch ammonia irom ammoniacai top-dressings, such as sulphate uiaeal manures. 
ammonia, soot, Peruvian guano, and similar manures, which 
e much used in England for top-dressing wheat, barley, and 
its ; but in very rainy seasons, in districts which have a large 
linfall, considerable quantities of ammonia may be removed 
om land top-dressed with ammoniacai manures, even in the 
ise of stiff clay soils. Similar investigations have shown that 
itrate of soda is not absorbed by soils, but readily passes in 
)lution into the subsoil, and when it is applied in autumn 
■ winter will be lost to a great extent by passing into land 
rainage. 
The usual practice in England is to apply guano, or sulphate Best time to 
ammonia, or compound artificial manures containing salts of ^^^^J^ 
nmonia, as top-dressings for wheat, in autumn or during the 
inter months ; whilst nitrate of soda, when used for top-dressing 
heat or other cereal crops or pasture land, is almost invariably 
