On the Manufacture of Glass. 115 
to the original cost of window glass. Could we substitute 
or discover, some substance, that, together with the other 
essential properties of clay, was not liable to fracture, it 
would supply what is now a great desideratum. 
various works of masonry necessary for the manufac- 
ture of siareton glass, are the following. 
1 cining ovens for preparing the materials. 
2. A reverberatory furnace, for fusing them. 
3. A flattening oven, for flattening and “gS Pad the glass. 
4. Drying ovens or wood kilns, for drying the w 
5. A tempering oven, for burning pots and chk stone 
generally. 
In the description which follows, of the various steps 
which the materials are made to pass through, in converting 
them into window glass, these several structures: wil 
y described. 
The vitrifiable materials and the éropertiohs: in. ‘which 
they are used, are the following. 
Verona sand;100. Sand, 100... Sand, 100, 
Potash, 34. Kelp, 65... Sul. Potash, 45. 
Salt, 16. Lime, 8... Lime,, ES. 
Lime, 5. Chip glass, 30... House; Sen ‘15. 
House ashes, 15. House s,(25.:, Sawdust, 2. 
Chip glass, ... 30. aaant pes Chip glass, Pe’ 
Sand, 100. Sand, i 08. Tie ne aie 
Sul. Soda,* 60. ies 5s. ; ony > have 
a ett 5, elp, sere 2 gente d vend: 
Ashes," ~ ~*~ 20. Like: 5. ed, and on several 
Saw dust, -2. House ashes, 15. accounts ‘it is per- 
Chip glass, 20. —- «Chip glass, © 25. haps preferable. 
The sand is thrown into. the calcining oven and igo 
five or six hours. The house ashes are. su 
same:treatment. The object is the same in hao burn 
away sb vegetable matter, drive off the water, and expel 
the carbonic acid, which the materials may contain. . When 
this is cectaabelahed. the materials are taken from the oven, 
ative to cool, and sifted through a mesh pee inch in 
ameter, 
* Tf thi it i z pat oS 3 éh water ra Lee vey ; 140 parts should 
cm. ; * ‘i ; 
