234 Reports & Proceedings—Mineralogical Society. 
shallow-water type, laid down near the coast-line of the old Swedish 
highlands, this coast-line being approximately determined by an 
ancient north-west-south-east fault-system. The middle part of 
the sandy shales always includes one or two beds containing com- 
paratively large quartz-grains and occasionally rounded pebbles of 
sandstone up to 10mm. in diameter. Pyrites, phosphorite, and 
calcareous layers are common, the two first especially in the coarser 
portions. An abnormal occurrence at Réstanga is of much interest, 
since here there is repetition of the series, the upper sequence being 
of much more shallow-water character than the lower; that is, 
a shallow-water facies has been thrust over strata of a deeper-water 
facies. This the author attributes to submarine land-slipping, which, 
he says, is a frequent cause of the occurrence of contorted layers, 
interbedded with horizontally bedded ones. He estimates that this 
process 1s possible with a slope of the sea-floor as low as 4 to 6 degrees. 
This striking conception is somewhat inadequately treated in the 
Germansummary. The full text describes the formation of a peculiar 
breccia or conglomerate due to the slipping. 
On account of the marked decrease in the depth of the water at 
the beginning of this stage, the old fauna almost completely 
disappeared, and only a few new forms came in. The presence of 
Climacograptus normalis serves to correlate the beds with British 
strata, but, on the whole, the fauna is mainly endemic. The presence 
of numerous ostracods and thin-shelled lamellibranchs suggests 
lagoon conditions. 
REPORTS AND PROCEEDINGS. 
MINERALOGICAL SOCIETY. 
March 22.—Dr. A. EH. H. Tutton, F.R.S., in the chair. 
Professor H. Hilton: ‘‘On the Vibrations of a Crystalline 
Medium.” ‘The paper attempts to give an indication of the kind of 
vibrations which the molecules of a crystal may be expected to make 
about their positions of equilibrium. The case of an orthorhombic 
erystal in the form of a rectangular parallelepiped is considered in 
detail, and the normal modes of the molecular motion completely 
determined. ‘ 
Professor R. Ohashi: “ Augite from Nishigatake, Japan.’ The 
crystals have been detached from basalt by natural weathering. 
Sp. gr. is 3°338 at 4° C. The prism angle agrees with that of diopside 
but that of the pyramid does not. Etched figures show that the 
crystal belongs to the holosymmetric class. a = 1°6859, 8 = 16917, 
y = 17105, 2v = 58° 25’. Extinction angle on (010) = 41°6°. 
The chemical composition is SiO, 51°37, A1,O, 5°24, Fe,O, 2°02, 
FeO 2:96, CaO 21°58, MgO 16°94, TiO, 0°58. Both the optical 
