286 Reports and Proceedings—Mineralogical Society. 
the head of thé Whirlpool —St. David’s buried gorge, and began to 
empty out the contents of this valley. The cutting with the full 
power of the water of the four lakes varied at times according to the 
height of the fall, and is calculated to have occupied only 3,500 years, 
for the cutting back of about 4 miles above the head of Foster’s Flats. 
Thus the entire age of the Falls is given as 39,000 years. 
II.—Mrveratocicat Soorery. 
Tuesday, March 19th.—Professor H. A. Miers, F.R.S., President, in 
the Chair. 
On the silver deposit or Sedgman lode in the Perran Mine, Cornwall, 
by F. H. Butler. The lode runs through killas in an approximately 
north and south direction. The silver ore, consisting almost solely 
of cerargyrite, occurs in compact masses, or finely disseminated in 
a gossany limonite. Splintery and ferruginous quartz, the ‘‘ cab- 
course,” is always a well-developed feature in the richest parts of 
the lode. The distribution of the cerargyrite, to the depth of 
18 fathoms to which the mine has been worked, is roughly in 
accordance with the surface contour of the land; but segregations 
have also taken place along a series of lines running from above 
downwards. The source of the chlorine, the author suggests, might 
be sea-water that has reached abyssal regions.—On the minerals of 
the Silvermines District, Co. Tipperary, by A. Russell. The mines 
extend along an east and west line of fault in which Silurian, Old 
Red Sandstone, and Carboniferous rocks are brought into juxtaposition. 
Along its course in certain places mineralisation has taken place 
resulting in contact lodes and metasomatic deposits. In the 
Ballygowan South mine is an interesting occurrence of hemimorphite, 
the only one of the kind known in the United Kingdom. The 
mineral is found in brilliant crystals lining cavities in limonite. 
The gossan also contains irregular masses of argentiferous galena, 
partially altered to cerrusite. At the Ballynoe mine copper pyrites, 
galena, and barytes form a lode between walls of Silurian and 
Carboniferous Limestone. At the Gortnadyne mine argentiferous 
tetrahedrite is found with copper pyrites and cerrusite (‘‘ cat-tooth 
ore’). An extensive series of old open workings of galena can be 
seen at the Shallee East mine.—On Baddeleyite from Ceylon, by 
G. 8. Blake and G. F. Herbert Smith. Three brilliant crystals of 
the mineral were picked out from a number of specimens of the 
heavy minerals from the gem-districts of Ceylon which were sent 
to the Imperial Institute in 1905. Of the three crystals, one 
possessing only the prism zone was used for analysis, and found to 
contain nearly 99 per cent. of zirconia. On the two other crystals, 
one of which was a twin, were observed eleven forms, including one 
new one (210).—Zinciferous Tennantite from the Binnenthal, by 
R. H. Solly and G. T. Prior. Crystals of tennantite, one of which 
was a large cube, with faces deeply striated parallel to small 
tetrahedral faces, were found on analysis to contain nearly 8 per cent. 
of zinc.—On Striiverite, a new mineral by F. Zambonini and G. T. 
Prior. This new mineral was found in detrital masses of pegmatite 
