300 
REVIEW. 
With respect to the subject of glass, strong as may be 
the declaration of the author, yet all must at the present 
time be prepared to accord with it, and agree that " it is 
next to certain.that the rapid development of those sciences 
which are based upon accurate observation and experi- 
ment, such as Astronomy, Natural Philosophy, Chemistry, 
and Physiology could never have taken place without the 
knowledge of glass and its applications." 
The first part of the chapter upon glass, is devoted to 
the composition of this substance, after this follow the 
properties of the article and formulae for making the dif- 
ferent varieties. Glass is not a fixed substance, as by many 
imagined, but a chemical compound varying in ingredients 
and in the proportion of them ; potassa, soda, lime, oxide of 
lead, iron, manganese, &c, as well as 'silica enter into the 
formation of the article, the properties of which must vary 
accordingly, or from the mode of treating the ingredients. 
As for pharmaceutical and chemical purposes, a glass is 
essential which will be least acted upon by the agents 
manipulated with, the importance of selecting the right 
kind, from a knowledge of the difference in varieties, be- 
comes apparent. Our author states, that "under all cir- 
cumstances, and when every precaution is taken in the 
manufacture, it is still impossible, as far as observation has 
shown, to obtain a glass which is practically incapable of 
being attacked. " 
" Pure, finely powdered glass taken from a tube or win- 
dow pane and moistened with water, has been shown by 
Faraday and Bischoff to exhibit an alkaline reaction ; sal- 
ammoniac precipitates flocculent silica from this solution, 
according to Fuchs. The same reaction occurs, according 
to Dumas, when water is boiled for some time in a glass 
vessel, and a troubled appearance arising from insoluble 
silicate of lime, is occasioned at the same time. Griffiths 
extracted 7 per cent, of potash from flint-glass powder, by 
boiling it for weeks together with water, and repeatedly 
