116 On the Manufacture of Glass. 
The hme is changed to an hydrate and _ likewise. sifted, 
The potash is broken into pieces not larger than a walnut. 
The salt needs no preparation. 
Kelp.—This term is applied to a salt made from the 
ashes, collected from under the kettles of the salt works at 
ate or sub-carbonate of soda, in nearly equal proportions. It 
would be preferable to potash in the formation. of glass, 
could we always rely upon its composition ; but this at times 
varying, Causes occasionally serious loss. 
» The sulphates of potash and soda, when employed, should 
be finely. pulverised. . The saw dust is used as being more 
convenient than charcoal. The effect of either is to decom- 
gether, and so intimately blended, that the different articles 
circumstances will permit, it should remain three months in 
this condition. 
several articles in market, which of course varies from time 
‘time. as : i ~ ‘ f ab 
"Sometimes, in consequence of the materials. not being 
sufficiently free from vegetable impurities, the glass will as- 
tr 
ga 
all occasionally used. They all appear to act, by furnishing 
oxygen, which combining with the carbon, carries it off in 
the form of carbonic acid gas. 
_.To get these materials to the bottom of the pots, that they 
may unite. with the glass, and produce the intended effect, is 
best accomplished by wrapping them in a wet paper, and 
