298 Limuvan Society. 



which time the boiler was commonly in action ten hours daily, ex- 

 cept Sundays, its temperature being then at 300° Fahr. On open- 

 ing the boiler at the end of the time specified, all the pieces of 

 glass were found to have been more or less decomposed; and the 

 plate-glass in particular, which is a glass of silex and soda, was far 

 advanced in decomposition. Flat pieces, £th of an inch thick, 

 were in some parts decomposed through their whole substance ; 

 while in others a layer of unchanged glass was found in the middle, 

 covered on each side with a stratum of opaque white siliceous 

 earth, having the appearance of chalk. 



The author referred these changes to the influence of water on 

 the alkaline matter of the glass. The white earthy portions were 

 found to be entirely free from alkaline matter, which had been dis- 

 solved and removed by the water which condensed upon the glass 

 at the successive heating and cooling of the boiler, or which may 

 have been thrown upon it by splashing during ebullition. But the 

 author considered that the actual loss was not due to the extrac- 

 tion of alkaline matter only, but that the silex of the glass had in 

 some measure been dissolved along with the alkali. This was 

 proved to have been the case by the apertures of the gauze en- 

 velope being filled up at the most depending parts by a siliceous 

 incrustation, where also a stalactitic deposit of silica, about \\ inch 

 long, had formed. 



A piece of window-glass included at the same time with the 

 plate-glass, was also in a decomposing state, but in a much lower 

 degree. A piece of rock-crystal confined in the boiler at the same 

 time was wholly unchanged. 



The author adduced these facts as illustrative of the action of 

 water at high pressures on felspathic and other rocks containing 

 alkaline matters. 



LINN^lAN SOCIETY. 



April 15. — The reading was commenced of a paper containing 

 " Observations on some species of native Mammalia, Birds, and 

 Fishes, including additions to the British Fauna." By William 

 Thompson, Esq., V.P. Belfast Nat. Hist. Society. 



The author commenced by stating, that a perusal of the Rev. 

 Mr. Jenyns's paper, entitled " Some Observations on the Common 

 Bat of Pennant, with an attempt to prove its identity with the Pi- 

 pistrelle of French authors," (Linn. Trans., vol. xvi.) induced him to 

 examine specimens of the common bat of the North of Ireland, which 

 hitherto, like that of England up to the period of Mr. Jenyns's paper, 

 has been considered the Vesperlilio murium of Linnaeus, as well as 

 of recent continental authors. 



This examination led to the same conclusion as that of Mr. 

 Jenyns, the common bat of Ireland proving identical with that of 

 England, and consequently with the V. pipistrellus of the Con- 

 tinent. 



Observations on the habits, &c, of this species, when at large and 

 in captivity, were also given in detail, and were followed by some 



