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sulphites are converted into gypsum (sulphate of lime). Limekiln 
ashes are also desirable land amendments; they contain about one 
per cent. each potash and phosphoric acid, besides some lime. 
For the destruction of sorrel, heavy liming is recommended, 
and applications amounting up to two tons to the acre may be used 
for that purpose. 
CHALK is dug out and exposed to frost, and then spread, as 
it is constituted of minute microscopic shells, as well as fragments 
of shells of larger size; it contains a little phosphoric acid generally 
in combination with lime as phospate of lime. to the extent of 0.10 
to 1.25 per cent. (or 100lbs. of this burned lime contains 2¥4lbs. of 
phosphate of lime). 
Marts consist of carbonate of lime, generally resulting from 
the fragments of shells which have accumulated at the bottom of 
fresh water lakes, which have generally been filled up by clay or 
sand, or by the growth of peat. They contain from 1 to 2 per cent. 
of phosphate of lime, and at times small amounts of potash. 
Marling only pays where the material is close at hand and can 
be put on the land at a cost of a few shillings a ton. An applica- 
tion of two to three tons to the acre is by no means excessive. 
Gypsum, or hydrated calcium sulphate, has been much used as 
a manure, but as it occurs in superphosphate and is not charged 
for, is rarely applied to crops nowadays. It occurs in places 
erystallised, and is found very useful for leguminous plants, especi- 
ally for red clover, lucerne, ete. Applied from three to six ewts. 
per acre. Supplies lime and sulphate to the crops and acts as a 
solvent, which sets potash free from its state of dormant combina- 
tion in the soil. Appears to promote the process of nitrification. 
Is a valuable absorbent on the manure heap and in stables, cow 
sheds, and poultry yards, where it fixes the volatile ammonia into 
non-volatile sulphate of ammounia. Very useful in reclaiming alka- 
line salt patches containing carbonate of soda. 
The relative value of burnt sulphate of lime or plaster of Paris 
and of unburnt sulphate of lime or gypsum lies in the fact that 
roasting drives out the proportion of water of crystallisation; thus 
making a given weight of plaster of Paris richer in sulphate of lime 
than an equivalent weight of gypsum. 
Asues.—Supply in small quantities magnesium, potassium, 
calcium, iron, phosphorus and sulphur—all mineral matters neces- 
sary to the growth of plants, and for that reason they constitute 
a very good fertiliser. Besides their value as plant food, they also 
have on it a mechanical effect similar to that of lime. They are 
especially useful on light and sandy lands, rendering them 
moister. The value of ashes vary with the kind of wood burned, 
and with the care that has been taken of them. Limekiln ashes 
can at times be obtained at a reasonable price. They contain 
