PROCEEDINGS OF THE POLYTECHNIC ASSOCIATION. 543 



ness, by converting carbonate into silicate of lime. Applied to 

 calcerious stones, liable to decomposition by exposure to the air, 

 it will enable them to resist disintegration. 



Applied as a paint to wood, in several coats, of which the first 

 is thin, it will prevent it from taking fire and burning with flame. 

 A building, of which the floors and wood work are thus painted, 

 is practically incombustible. 



Mr. Bartlett.— 1 understand the soluble or water glass is used 

 as a wash, but not as a mordant. 



The President. — I can state that it has been successfully used 

 in Germany for fresco painting. I can also state a use for which 

 it has been found not to answer; that is for cleaning clothes. In 

 a large establishment, near Berlin,, where there are several hun- 

 dred children, it was thoroughly tried, but was found to dissolve 

 the linen. 



Mr. Dibben. — Will Mr. Kraft state the price at which it was 

 sold? 



Mr. Kraft. — The solid at $12 per hundred pounds, the liquid 

 at $10. 



Prof. Seely. — There is one point that I should like to make 

 here, in relation to the chemistry of glass. ' Any one acquainted 

 with the laws of chemical combination, and with the composi- 

 tion of glass, would have antici])ated that the silicic acid might be 

 replaced by boracic acid ; silicon and boron being so similar in 

 their properties. It is well known that this is found to be the 

 case ; the borates, formed by the combination of boracij acid with 

 the alkalies or metallic oxides, are glasses similar in their proper- 

 ties to the silicate glasses, but somewhat different ; for instance, 

 they are more fusible. One metallic oxide may also replace ano- 

 ther in the combination. Faraday was the first to suggest that 

 the oxide of zinc might be used in the place of oxide of lead, 

 and a glass is thus produced, superior, I believe, for certain opti- 

 cal purposes, to the lead glass. Now, the point that I wish to 

 make is, that this law indicates a wide field which has not been 

 explored. For instance, the metal cadmium is analogous to zinc, 

 and it is probable that a glass in which the oxide of cadmium 

 should replace the oxide of zinc w^ould have properties sim- 

 ilar to those of the zinc glass, but still not precisely the 

 same. Let us try it. Rubidia and cassia too, the newly-discov- 

 ered alkalies, would, doubtless, make glass with peculiar proper- 

 ties ; and it is conceivable that these properties might be of suf- 



