On Gypsum as a Cane Fertiliser. 
By E. E. H. Francis, 
YPSUM is a white crystalline mineral consisting 
of calcium sulphate (or sulphate of lime) com- 
bined with about one-fourth of its weight of 
water. The latter is not present as ordinary moisture, 
but as an integral part of the mineral, forming what is 
known as water of crystallisation. One hundred parts of 
gypsum contain : — 
Calcium oxide (lime) ... ... 32.56 1 or 79.07 0/0 of 
Sulphuric anhydride ... ... 4651 J calcium sulphate. 
Water ... ... ... ... 20.93 
Several forms of hydrated calcium sulphate or gypsum 
exist, and are given different names by mineralogists. 
The boldly crystalline transparent kind is called selenite ; 
the compact finely grained variety, alabaster ; the fibrous, 
satin spar ; whilst, schaumkalk is in small scales with 
a pearly lustre. Calcium sulphate also occurs free from 
water, and is then called anhydrite. 
Gypsum is very extensively and abundantly distri- 
buted, and is not confined to any particular geological 
formation. In England, its chief source is from the new 
red sandstone — the mineral quarried from that formation 
in Derbyshire, Yorkshire and Nottinghamshire, being 
especially famed — but it also abounds in the London clay. 
Crystals of selenite are often found distributed through 
the clay, as at Alston in Cumberland, and Shotover 
Hill, Oxfordshire, and they can be split into thin plates, 
sometimes of great size, it is said, even five feet long. 
