Liquid Manure. 
139 
experiment with the same results, and find in all instances in 
which I operated with liquid manure upon soils rich in oxide of 
iron and organic matters, that oxide of iron is dissolved. In 
other cases no oxide of iron passed into the liquid manure. 
May not the oxide of iron, dissolved in considerable quantities 
from some soils through the agency of liquid manure, be injurious 
to vegetation, and partly account for the failure that is expe- 
rienced with liquid manure on some soils? 
5. Lime, it will be noticed, was rendered soluble by the liquid 
manure left in contact with soil. An imperial gallon contained 
nearly 11 grains more after than before filtration. Most of the 
lime occurred originally in the manure as bi-carbonate, and some 
only as sulphate. In the same states of combination, no doubt, 
the greater part of the lime occurs also in the filtered liquid. 
Combining the sulphuric acid with lime, and the rest of the 
lime with carbonic acid, we have in thi§ liquid manure, before 
- and after filtration through soil : — 
Before After 
Filtration. Filtration. 
Sulphate of lime 6-69 4 b9 
Bi-carbonate of lime 22-45 50-24 
Whilst thus the proportion of sulphate of lime in the filtered 
liquid is but little diminished, that of bi-carbonate of lime is 
very much greater than in the original liquid manure. 
6. The small proportion of potash left in the manure after 
contact with soil is particularly interesting, inasmucli as it shows 
that the soil not only possessed the power of absorbing ammonia, 
but also potash — a constituent which in an agricultural point of 
view is of the greatest importance. It appears that potash is 
retained by the soil even with greater avidity than ammonia. 
Besides the potash, which for the greater part exists in the 
liquid before and after filtration as carbonate of potash, the soil 
absorbed the whole of the chloride of potassium, 2-74 of 
chloride of potassium correspond to 1"73 of potash, which 
quantity added to the 16 92 grains of potash, present chiefly as 
carbonate of potash, gives 18 65 grains of potash in the gallon, 
or, expressed as carbonate of potash, 27 25 grains. After contact 
with soil, the gallon contained 3 40 grains of potash, or 4-99 of 
carbonate of potash. 
15 25 grains of potash, or 22-76 of carbonate of potash, Avere 
thus absorbed by 20,000 jjrains of soil. 
1000 grains absorbed '763 of potash, or 1-138 of carbonate of 
potash. 
7. In a much minor degree than potash the soil absorbed 
chloride of sodium. By far the larger proportion of common salt 
remained in the liquid. This result agrees perfectly with previous 
observations, and with all the experiments noticed in this paper. 
