524 The American Naturalist. [June, 
such alteration that it may now be regarded as crystalline. It 
consists of quartz, two micas, and a little feldspar. The con- 
stituents exhibit a slight tendency to parallelism, but show 
little evidence of squeezing. — The same writerj announces the 
discovery of a variety of picrite, known as scyelite, on the 
island of Sark in the British Channel. It is composed of ser- 
pentinized olivine, altered augite and bleached mica, some of 
which exhibits a banded twinned structure, one set of bands 
extinguishing parallel to the cleavage of the mineral, and the 
second band 1 8° to this cleavage. The rock was not found 
in place. — Joly' has discovered the presence of iolite in a feld- 
spathic substance associated with beryl in the granite of Glen- 
cullen Co., Dublin, Ireland. — Upon treating the quartz-por- 
phyry from Teplitz with hydrofluoric and sulphuric acids, von 
Foullon' obtained in the residue little grains of corundum. 
Miscellaneous.— In a little pamphlet entitled " Ueber 
das Verhalten der Silicate beim Uebergange aus dem gluth- 
fliissigen in den festen Aggregatzustand," Nies* discusses the 
occurrence of crystals of silicates in lava streams, describes 
the action of water, metals, and alloys in passing from the 
solid to the liquid state, calls attention to the contraction forms 
in eruptive rocks, and concludes that silicates probably expand 
upon their crystallization from a molten magma, and do not 
contract as has been generally stated, but that not enough 
facts are known to warrant a positive statement on either side. 
The apparent contraction is due to the fact that the specific 
gravities of crystallized and amorphous bodies have been taken 
while both were cold, and. therefore, that they can not be 
regarded as criteria upon which to base conclusions as to the 
relations of the substances in the two different conditions at a 
high temperature. Their different relations at a higher tem- 
perature are due to the more rapid expansion of crystalline 
substances than of amorphous ones. — An interesting contribu- 
tion to the study of morphotropism has recently been made 
by Dufet,' who has carefully investigated the mixed crystals 
produced upon the evaporation of a solution of zinc and mag- 
nesium sulphates. As a result of his measurements of certain 
» Geol. Magazine, March, 1889, p. 109. 
» Geological Magazine, 1888, p. 517, 
« Verb. I. k. k. geol. Reichsanst. 1888. No. 8, p ' 
* Stuttgart. 1888. Schweizerbartsche Verlagshau.l. 
"" Bull. Soc. Fran9. I Min. xii. p. 22. 
