52 
Absorption of Phosphate of Lime ; and 
superphosphate soon loses its efficacy ; inasmuch as its valuable 
constituent, the soluble phosphate, is readily washed away by 
the rainfall. The soil now used was taken from an extremely sandy 
field, which apparently contained but little clay and organic 
matter, and no limestone gravel whatever. The red colour of 
this soil indicated the presence of much oxide of iron, and its 
light porous character proved it to be a ferruginous sand. On 
analysis it yielded the following results : — 
Water 1-43 
Organic matter 3"39 
Oxides of iron and alumina 12'1G 
Carbonate of lime "lo 
Alkalies and magnesia "46 
Pliosiihoric acid traces 
Insoluble siliceous matter (sand) 82"41 
•. 100-00 
The amount of lime in this soil, it will be seen, is very trifling ; 
but there is present a good deal of hydrated oxide of iron and 
some alumina, which was determined together with the oxide ol 
iron. 
5000 grains of this Soil, 11 0*40 (/rains of Superphosphate (containing 
■40-93 grains of soluble Bone-Earth), and 21,000 grains of -Distilled 
Wafer, were mixed as in the previous Experiments. 
After 24 hours, 7000 grains of the liquid being drawn off, were found to con- 
tain 6-49 grains of phosphate, so that the whole 21,000 grains 
held in solution 19-47 grains. Hence the soil had absorbed 
21-46 grains of the bone-earth. 
After 8 days (there being uow 14,000 grains of water in the bottle), 7000 
grains were drawn off, and found to contain 5-67 grains of 
bone-earth, so that the 14,000 grains held in solution 11-3-1 
gi-ains. Hence the soil had absorbed 23-10 grains of the bonc- 
earth. 
After 17 days, it was found that the 7000 grains of water now left in the bottle 
contained 3'90 grains of bone-earth, so that the soil had 
absorbed 24-87 grains of bone-earth. ^ 
Had the whole Liquid been draicn off in each case, tee would have found in the 
Solution containing 40-93 of soluble Phosphates — 
Grains. 
After 24 hours 19-47 of bone-earth. 
„ 8 days 17-01 „ 
„ 17 days 11-70 „ 
and in 5000 grains of soil, 
Grains. 
After 24 hours 21-46 of insoluble phosphate of lime. 
„ 8 days 23-92 „ 
„ 17 days 29-23 
It appears, then, that such soils, when left in contact with 
