GLASS FOR HOUSEHOLD USE AND FANCY PURPOSES. 121 



turer has, therefore, to turn his first attention to the production oi 

 quality. This is not easily attained, for two special reasons : 1st, the 

 difficulty of procuring the materials in a state of perfect purity ; and 

 2ndly, the difficulty of anticipating the exact amount of deoxidation, 

 which may take place during the fusion of the materials into glass. 

 Deoxidation alone, supposing all the materials to be perfectly pure, 

 will affect the colour of flint glass ; and if oxygen be not supplied, 

 the materials, when fused, will produce not a white, but a green tinted 

 glass. 



It is, therefore, found necessary to employ oxygen in all mixtures of 

 flint glass ; and this important agent exists most conveniently in the 

 black oxide of manganese ; which substance has a very strong affinity 

 for oxygen, parting with it so slowly, that it is only as the other ma- 

 terials in fusing become quite deoxidised that it furnishes them 

 gradually with the necessary oxygen. If too much of this material 

 is used, the glass takes a light purple tint, and is also rendered of 

 a more frangible character, in consequence of having an excess of 

 oxygen. 



With these few preliminary observations, the prominent question 

 before the Jurors is, has there been progress in the quality and mani- 

 pulation of glass, since the last International Exhibition ? Does the 

 glass exhibited in 1862 show progress, as compared with 1851 '] The 

 Jurors have great pleasute in stating, from their knowledge of the 

 goods produced for several years past in their various localities, and 

 from their recollection of the goods exhibited in 1851, that laudable 

 progress has been made in all branches of this class. 



The Jurors have had brought to their notice no improvement or 

 alteration in the constituents of flint glass. At the International Exhi- 

 bition of 1851, a Council Medal was awarded to Mons. Maes, of Clichy, 

 near Paris, for the employment of zinc in place of lead, under the im- 

 pression that this mixture would be superior to the ordinary one, 

 especially for the manufacture of glass for optical purposes ; it being 

 considered that glass of zinc would be more homogenous than glass of 

 lead. It does not now appear that any advantage has arisen from the 

 use of zinc, as far as the Jurors know, for flint glass. The want of 

 brilliancy of zinc glass is not compensated for by any special advantage 

 it was thought to possess, although Mons. Maes was fully entitled to an 

 award for his specialite. 



In comparing the manufactures of glass in England and other coun- 

 tries, consideration must be had to habits, tastes, and local advantages 

 or disadvantages. Without in the least degree depreciating the efforts 

 of foreign countries in the manufacture of glass, the Jurors would 

 submit that the- quality of the British glass* ranks so high, chiefly 



* D'Audenart states that the English preceded the French in the art of 

 making glass with the oxide of lead. " Cela vient, dit-on, de ce que le com- 



