70 General Notes. [Jan. 
MINERALOGY AND PETROGRAPHY.* 
Petrographical News.—Mr. G. A. J. Cole? has recently at- 
tempted to explain the occurrenct in rocks of “ hollow spheru- 
lites” like the lithophysen of Von Richthofen. The principal 
theories proposed to account for these bodies are discussed, and . 
that one is accepted which regards them as the result of the 
alteration of spherulites, in preference to the one in which a 
vesicular origin is assigned them. The present writer thinks 
that a study of the phenomena attending the alteration of spheru- 
lites will explain satisfactorily the occurrence of the hollow 
spherulites. In many of these there is often found a little patch 
of felsitic material with a radial structure, and from this Mr. Cole 
argues that the whole body was once of the same nature, and 
that the greater part of the original filling has been removed by 
decomposing agents, probably through the channels afforded by 
perlitic cracks. He then examines? many of the spherulitic rocks 
of Great Britain and some from localities in Europe and America, 
and finds that his views are on the whole confirmed. P 
fessor Milne, in a recent number of the Transactions of the Seis- 
mological Society of Japan,‘ states that the lavas of the Japanese 
volcanoes (one hundred in all, of which forty-eight are still active) 
are chiefly andesites, the hornblende varieties of which frequently 
contain quartz. Those containing olivine approximate to basalts, 
though true basalt is rare. A critical study of these rocks is 
A 
Kroustshoff® has succeeded in isolating from it small colorless 
isotropic crystals with glassy inclusions. These crystals possess 
a specific gravity greater than 3, a refractive index equal to that 
of garnet or spinel, and show, before the spectroscope, the lines 
of iron, calcium, magnesium, and aluminium. The author calls 
attention to the similarity between these crystals and those which 
he obtained in a like manner from the phonolite’ of Olbriick, and 
' 2 Edited by Dr. W. S. BAYLEY, Madison, Wisconsin. 
`a Quart. Jour. Geol. Soc., xli., No. 162, May, 1885, p. 162. 
minéral accessoire de la roche de Beucha (près de Leipzig). 
de Minéralogie, ix., No. 4, 1886; also Neues Jahrb. fiir Min., 
ee 7 Ib., ix No $- A 
