96 



that they were surrounded by steam whenever the boiler was in 

 action. They were kept in this situation for four months, during 

 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 ad- 

 vanced 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 envelope 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. 



At the close of this Meeting, which terminated the Session, the 

 Society adjourned till Wednesday evening, the 5th of November. 



May 7th. — After the ordinary business of the Society had been 

 transacted, a Special General Meeting of this Society was held, when 

 the President having stated, that in compliance with a representation 

 made by His Royal Highness the President of the Royal Society, 

 the Lords Commissioners of His Majesty's Treasury had been pleased 

 to transfer to the Society additional apartments, lately in the pos- 

 session of the Royal Society, and that a sum of not less than .500^. 

 would be required to adapt the said apartments to the improvements 

 contemplated: — 



It was resolved unanimously, 



I. On the motion of Charles Denham Orlando Jephson, Esq., 

 M.P., seconded by William Henry Fitton, M.D., — That 

 the thanks of this Society be given to the Right Honour- 



