Reports and Proceedings —Mineralogical Society. 189 
bubbles or unfused mineral particles, on the few occasions when these 
exist, are eliminated. The diffusion-column is sealed in a glass tube. 
Acid rocks were found to increase 6 to 10 per cent. in yolume, 
intermediate rocks 5 to 7 per cent., and basic rocks chiefly less than 
6 per cent. Of the minerals tested, pargasite underwent the greatest 
expansion, albite gained 10 per cent., while in anorthite and leucite 
the increase was less than 4 per cent. It is pointed out that this 
expansion would be a very effective force in the case of the melting of 
rock-magmas kept solid by pressure. Experiments were also made in 
order to ascertain the melting-points of the rocks and minerals 
experimented upon: these were found to range from 1260°C. for 
rhyolite to 1070°C. for Clee Hill dolerite. The refractive indices of 
the glasses were determined in dense fluids. In determining the 
melting-points of individual minerals, the author’s results agree fairly 
closely with those of Day & Allan, but differ from those of Joly & 
Cusack. An attempt was made to find experimentally the eutectic 
proportions of quartz and felspar. It was found impossible to 
reproduce in the laboratory the conditions which, in nature, seem to 
have existed during the formation of pegmatites. On the other hand, 
a mixture of orthoclase and albite gave a melting-poit lower than 
those of either mineral taken separately. 
V.—MINERALOGICAL SOCIETY. 
Tuesday, January 29th.—Professor H. A. Miers, F.R.S., President, in 
the Chair. 
Experiments bearing on the order of crystallisation of Rock-con- 
stituents, by Professor H. A. Miers. The general results of 
experiments made by Miss F. Isaac and Professor Miers. with 
mixtures of salol and betol in all proportions were described ;. 
the experiments have established the supersolubility curves even 
beyond the points where they cross below the eutectic temperature. 
Owing to the fact that the main separation of erystals in the cooling 
mixtures takes place only when the liquids have been supercooled to. 
temperatures given by the supersolubility curves, it has been found 
(1) that in general the mixtures do not solidify as a eutectic mixture, 
(2) that according to the conditions of supercooling either substance 
could be made to crystallise before the other in mixtures approaching: 
the eutectic in composition. It was suggested that these results are. 
applicable to the solidification of many rocks and alloys.—Serpentine 
Rock from the Tarnthaler Kopfe, Tyrol, by Dr. A. P. Young. The- 
minerals found in the serpentine are diopside, tremolite, clinochlore, 
picotite, magnetite, iron pyrites, and a fibrous mineral referred to. 
antigorite. The latter mineral is regarded as holding a place between 
the micas and chlorites. On the surface of the serpentine are. 
projecting bastite pseudomorphs coated with films of silvery lustre. 
The serpentine is a non-foliated intrusive core, which on the borders is 
highly foliated and passes into tale-bearing phyllites—A simple 
tabular arrangement of the 32 crystallographic classes, by Dr. J. W. 
Eyans. The table is based on the character of the symmetry of the 
principal zone axis or zone axes. Each column contains classes with 
