1886, ] Mineralogy and Petrography. - 453 
is by Mr. Woodward (agreeing with Professor Boyd Dawkins) 
considered to be identical with Æ. minutus from the caves and 
fissures of Malta. 
The Indian species are s¢valensis, iravaticus and namadicus from 
the Siwalik hills, and pa/eindicus from the Narbadas. 
MINERALOGY AND PETROGRAPHY.! 
MinerRALocicat. News.—The late Dr. Lasaulx, of Bonn, re- 
cently examined? very thoroughly the mineral corundum with 
reference to its microstructure and optical properties. The fact 
that sections of this mineral cut perpendicular to the vertical axis 
often show a biaxial interference figure in converged polarized 
light has been known for some time. Lasaulx attempts to find 
the cause of this. Sections of crystals from nine localities were 
system; (2) the anomalies in optical properties are due to irregu- 
larity in growth; (3) this irregularity in growth often gives rise 
ferent lamellæ are twinned, optical disturbances are produced ; 
finally (6) decomposition may give rise to aggregate polarization. 
~— Orthoclase has been found for the first time as a druse min- 
eral in leucite-tephrite.? In the cavities of this rock were found 
crystals of phillipsite, calcite, orthoclase (adularia), altered pyrite 
and calcite again, in a regular order of deposition. The adularia 
occurred in groups covering the phillipsite and also in perimorphs 
-of calcite, Crystals of the latter mineral were covered with a 
druse of adularia, and showed under the microscope a rim with 
aggregate polarization, as if the calcite substance were gradually 
being r eplaced by adularia. In an article on gothite,* Ed. Palla 
<Clares as a result of a series of measurements on crystals from 
Cornwall, that the mineral is either orthorhombic with the akes o ă 
‘9 :C = .9163:1:.6008, or monoclinic with £ = go? 36’ 25"" ae 
and a:b:¢ = 9164: 1:.6008. If the former view is taken the 
Side o É me P'a co P 38, 1 P e, P and PW must be con- 
sidered as vicinal ; whereas if the mineral is considered as mond 
clinic these (with the exception of the first) become o È Oe of a 
= 
ted by W. S. Bayey, Johns Hopkins University, Baltimore, Md. 
Chrift für Krystallographie, x, p. 346. 
Zepharovich. Zeitschrift für Krystallographie, x, p. 601. 
für Krystallographie, XI, p. 23- 
