Gypsum as a Cane Fertiliser. 131 
Such plates of selenite were used by the ancient Romans 
like window glass, for glazing beehives and conserva- 
tories, and the mineral was called by them lapis specu- 
laris. Gypsum exists largely in many other parts of 
Europe, the deposits in the tertiary strata of Mont- 
martre, near Paris, being of historical interest. Ex- 
tensive beds occur in several States of North America, 
especially in New York, Ohio, Illinois, Tennessee 
and Arkansas, being usually associated with brine 
springs and salt deposits. Trinidad, and probably 
other West Indian islands, possess large stores of gypsum. 
Compact gypsum, or alabaster, is used like marble 
for making ornamental articles, — statuettes, vases, &c. 
It is comparatively soft/ and can be easily worked, 
but is not readily reducible to powder. By being 
gently heated, however, it readily parts with its water 
of crystallisation, and then offers little resistance to 
grinding. If the dehydration is effected at a tempera- 
ture between ioo° and 300 C, the powdered mineral 
forms the well known " plaster of Paris," which is 
remarkable for its property of becoming solid, or " set- 
ting," in a few minutes after being mixed with water to 
a thin paste. The setting takes place in consequence of 
a chemical re-union ot the powder with the water to 
form gypsum. Anhydrite, like plaster of Paris, gradu- 
ally absorbs water and becomes gypsum, but not 
sufficiently fast to be used in place of it. 
Although the virtues of gypsum as a manure were 
known, to some extent in the early ages, yet it gained no 
particular prominence as a fertiliser until the middle of 
the eighteenth century, when MEYER, a German parson, 
finding it in use in Hanover, studied its effects, and by 
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