150 Geological Society. 



(6) That in all these cases the hornblende occurs either in very 

 elongated prisms or in actual needles. 



The author brings forward a number of other instances to show 

 that this form of hornblende may be regarded as indicative of 

 dy n amometamorphism ; so that rocks where that mineral is more 

 granular in shape (cases where actinolite or tremolite appears as 

 a mere fringe being excepted) have not been subjected to this 

 process. 



3. " On a Secondary Development of Biotite and of Hornblende 

 in Crystalline Schists from the Binnenthal," By Prof. T. Gr. Bonney, 

 D.Sc, LL.D., F.R.S., V.P.G.S. 



Both the rocks described in this communication come from the 

 Binnenthal, and were obtained by Mr. J. Eccles, F.G.S., in the 

 summer of 1891. They belong to the Dark-mica schists described 

 by the author in former papers, and have been greatly affected by 

 pressure. In each a mineral above the usual size has been subse- 

 quently developed. In the rock from near Binn this mineral is 

 a biotite ; the dimensions of one crystal, irregular in outline and 

 having its basal cleavage roughly perpendicular to the lines indica- 

 tive of pressure, are about *175 X "03 inch. The other mineral, from 

 the peak of the Hohsandhorn, is a rather irregularly formed horn- 

 blende, the crystals (which lie in various directions) being sometimes 

 more than half an inch long. The exterior often is closely asso- 

 ciated with little flakes of biotite. The author discusses the bearing 

 of this fact, and the circumstances which may have favoured the 

 formation of minerals, so far as his experience goes, of an exceptional 

 size. 



Some remarks also are made on the relation of these structures 

 developed in the Alpine schists to the various movements by which 

 those rocks have been affected, and on the general question of pressure 

 as an agent of metamorphism. 



4. " Geological Notes on the Bridgewater District in Eastern 

 Ontario." By J". H. Collins, Esq., F.G.S. 



The plateau of the Bridgewater district consists chiefly of gneiss 

 and mica-schist, with subordinate beds of white marble, quartz- 

 conglomerate and quartzite, and some veins of ' giant-granite.' The 

 general dip of the gneissose series is eastward. 



The author notes the effect of frost in splitting off flakes of the 

 gneissose rocks and conglomerates, especially on the bare glaciated 

 surfaces, and suggests that many of the smaller and shallower 

 lakelets may have originated by this process. 



The conglomerates are described as gneisses and mica-schists, with 

 subordinate pebble-beds. 



The occurrence of gold in quartz-veins near Flinders and at Hadoc 

 is noted ; and amongst other economic products are the micas of the 

 granites, asbestiform actinolite, and marble. The author discusses 

 the mode of origin of the granite, marble, and actinolite-rock. 



