22 University Geological Survey of Kansas. 
hard, composed of somewhat broad particles, and of a bright crystalline lustre, 
the pholides ; 2. Those of a softer texture composed of very small particles and 
of less glittering hue. 
‘‘The genera of the second order are: 1. Those of a softer texture which are 
very bright and glittering, the timachides ; 2. Those of a softer texture which 
are dull and opague, the clasmia. All the species of this whole class burn with 
a very slight degree of fire to what is commonly called plaster (plaister) of Paris, 
but the softer requires the smaller degrees of fire, and in general the hard and 
more marbly make the better plaster. 
‘‘The common way of burning the stone into plaster is too slight to give it all 
the hardness it is capable of. It is reported by many that a great degree of heat 
renders it greatly superior in hardness, and it is said that the artificial marble, 
with which the whole palace of Munich is adorned and which the elector of 
Bavaria esteems more than marble, for which it is mistaken by all that see it, is 
made of the common gypsum, fire burnt in the ordinary way, and afterwards 
put over the fire again in a copper vessel and suffered to boil, as it will like water 
for a long time. When this boiling ceases of itself, the matter is taken out, and 
common colors, such as are used in painting, are mixed with it in various propor- 
tions; which, on the wetting it with water and working it in the common manner 
of plaster of Paris, diffuse themselves and imitate the veins of natural marble. 
‘¢Gypsum is used in Canaries by way of remedy for their wine and about Mal- 
aga a large quantity is tunned up with the juice of their grapes.”’ 
The first edition of Chambers’ Dictionary, published in 1741, 
describes alabaster or compact gypsum in the following words: 
‘¢Alabaster, a kind of stone softer than marble yet harder than plaster of Paris, 
is used for the making of figures and other ornaments of sculpture. Alabaster, 
Mr. Boyle observes, being finely powdered and thus set in a basin ( bason) over the 
fire will when hot assume the appearance of a fluid by rolling in waves yielding 
to the smallest touch and emitting vapor, all which properties it loses again on 
the departure of the heat and discovers itself a mere incoherent powder.”’ 
Varieties and Distribution of Gypsum. 
Gypsum occurs in nature in five varieties: 1. Earthy, of yel- 
low or gray color, composed of loose particles, light:in weight, 
and formed by precipitation from solution of gypsum in water ; 
2. Compact or massive, including alabaster and gypsum rock, 
very soft, with specific gravity of 2.28 to 2.51, and with typical 
composition 323 per cent. of lime, 463 per cent. of sulphuric 
acid, and 21 per cent. of water; 8. Fibrous gypsum or satin 
spar, usually found in thin layers in form of fine needles or 
prisms; 4. Foliated gypsum, in round or concretionary masses ; 
5. Spar gypsum or selenite, found in transparent plates and 
crystals. 
