Geological Society. 



217 



observed hardly represents the full value of the insulation given 

 by the cover. The temperature of the room during the ex- 

 periments varied between 22° and 23° C. There can be little 

 doubt that if favourable conditions, that is, pure snow out- 

 side, pure water inside, &c. were obtained, and if the instru- 

 ment were more carefully insulated, the column might be kept 

 far more steady than is possible in the usual way. 



In a few words, by the use of the cover we allow the in- 

 strument to remain at its own freezing-point, instead of 

 trying to compel it to assume some temperature which may 

 be, which is sure to be, slightly different. 



XXV. Proceedings of Learned Societies. 



GEOLOGICAL SOCIETY. 



[Continued from p. 141.] 



April 6, 1887.— Prof. J. W. Judd, F.B.S., President, in the Chair. 



THE following communications were read : — 

 1. " On the Bocks of the Malvern Hills." Part II. By Frank 

 Butley, Esq., F.G.S. 



The details of the microscopic examination of the rocks constituted 

 the principal part of the present paper. The Author finds that the 

 truly eruptive rocks are more plentiful in the range than he was 

 at first led to suppose. In all 33 rock-specimens were described, and 

 in some cases Mr. Timmins's analyses were quoted. The author 

 commenced with the rocks of the North Hill and concluded with 

 those of the Baggedstone Hill. Bocks between a little south of the 

 summit of the Worcestershire Beacon on to Wind's Point, those of 

 Midsummer Hill, and those of Keys Hill were not collected. The 

 following are the general results : — 





Eruptive. 



Foliated. 



Stratified. 



North Hill 



Hornblende-gabbro. 

 Diorite. 



Gneissic Syenite. 

 Gneissic Diorite. 



Altered Tuff? 







Quartz-syenite. 







North Hill (above 



Mica-diorite. 



Biotite-gneiss. 





West Malvern). 









North Hill (The 



Mica-diorite. 







Dingle). 





v 





Worcestershire Beacon 



Grranulite? 

 Granite. 

 Diorite. 

 Epidotite ? 







Herefordshire Beacon 



Eucrite. 



Basalt. 



Devitrified Obsidian. 



Hornblendic Gneiss. 



Diabase-tuff? 



Swin yard's Hill 



Pegmatite. 

 Hornblende-pegmatite. 



Biotite-gneiss. 

 Biotite-muscovite. 











Diorite. 



Gneiss. 





Hollybush Pass 



Diabase. 







Baggedstone Hill 





Mica-schist. 



Altered Sandstone. 







Micaceous Quartzite- 



Q.uartzite. 







scbist. 





