196 
ME. X. STOEY-MASKELYNE ON THE 
oxidation of the sulphide. When the adhering silicate and this crust have been removed, 
the mineral is readily cleaved in three directions. The mean of nearly 200 measure- 
ments of the normal angles of these cleavage-planes gave 89° 57'. That this angle is 
really 90° and the mineral cubic in its system, rendered probable by the equal facility 
of the three cleavages, is placed beyond doubt by the fact that transparent sections 
made along either plane, when examined by polarised light, afford no indications what- 
ever of double refraction. The hardness of the mineral is nearly 4; its density is 2-58. 
Boiled with water it breaks up, yielding a bright-yellow solution of calcium polysulphides 
and an insoluble residue. With acids it readily dissolves with evolution of hydrogen sul- 
phide and deposition of sulphur. 
The small amount of the mineral at command for analysis, the desirability of excluding 
as far as possible during the process all non-volatile materials from admixture with the 
constituents of the meteorite, and, as it afterwards proved, the unnecessary precaution of 
not using any reagent that might destroy or prevent the subsequent selection of the 
microscopic octahedra that have been alluded to, seemed to render a special method of 
analysis necessary. 
Experimental analyses of calcium sulphide, formed by passing first hydrogen and sub- 
sequently hydrogen sulphide over caustic lime ignited in a glass tube, led to the em- 
ployment of the following method*. 
0-4696 grm. of the mineral, dried over sulphuric acid for thirty-six hours, were placed 
in a small flask with a stoppered funnel filled with previously boiled but cold water. 
Hydrogen, purified by traversing a solution of lead acetate and aU-tube containing glass 
moistened by that liquid, was then passed by a tube through the cork into the flask, 
whence it was conducted by a delivery-tube into a solution of 3 grms. of pure silver 
nitrate, and thence, finally, by a second tube through a test-tube similarly charged. First 
a little of the boiled water and strong hydrogen chloride were introduced by the funnel 
tube, and the hydrogen sulphide formed was swept out by the hydrogen as fast as it 
was generated. The action having ceased, the flask was carefully heated for six or seven 
hours, when the hydrogen no longer discoloured lead test-paper. The silver sulphide was 
then thrown on a weighed filter, washed with ammonia and water, dried at 100°, and 
weighed. Some sulphur separated in the flask ; this, together with the undissolved 
silicates and golden-yellow crystals, was collected on a dry filter and weighed, and the 
sulphur was then removed by carbon disulphide, and its amount determined by the 
difference of weight. The yellow crystals were picked out from the undissolved residue, 
and there remained the silicates that had surrounded or been entangled with the sphe- 
rules of Oldhamite. 
The results of the first analysis are given below as No. I. ; those of a second, in which 
O' 50 61 grm. of the mineral in rather large spherules were taken, are given as No. II. 
* This calcium sulphide, in colcmr and in all but its want of cohesion and crystalline characters, resembles 
Oldhamite. Thus formed it contained 44-3 per cent, (it should contain 44-44) of sulphur. Eormed without 
the previous treatment with hydrogen it contained only 39-5 per cent. 
