liylPROVED MUFFLES. 27^ 



th^m, of such a size that the diameter thereof may be about Description of 

 three fourths of an inch less than the diameter of the concave making the 

 piece before stated ; these, being soldered to each end of the muffles, 

 first- mentioned piece, will form a stand for the hollow part of 

 the mould, and the thickness of the muffle moulded in this 

 will be exactly determined by the edge at each end. A piece 

 of hollow tin, b b, may be soldered along the top edge of the 

 mould, to form a better resistance to the great pressure with- 

 in. The next part of this mould is a flat piece of tin, fig. 2, 

 cut exactly to fit the inside of the mould,^ the use of which is, 

 to form a solid back to the muffles used for chemical pur- 

 poses. 



The second tool for this purpose is a piece of sheet brass, 

 fig. 3, about six inches long and one broad, which, being bent 

 in a semicircular form, and screwed to a piece of wood ex- 

 tending beyond its breadth about an inch, is used for cutting 

 the small airholes c (fig. 11), in the aforesaid muffles. 



The third is the tool or frame, fig. 4, for preventing the 

 contraction of the muffles in drying, which is made of fonr 

 pieces of beech, about three quarters of an inch broad, and 

 half an inch thick ; the length must be adjusted to the mould 

 of the muffle; two of these being laid parallel within the in- 

 side of the mould, and being joined across by the other two, 

 the ends of which should extend so far beyond the outer edges 

 of the other two, that they may rest upon the edges of th» 

 muffle mould, and thereby prevent its falling into the mould. 



The fourth is the tool for spreading the composition into 

 the moulds, which is formed of iron or steel, (fig. 5), about 

 thirteen inches in length, one inch apd a half broad, and 

 about one eighth of an inch thick ; its face under h being 

 rounded in such a manner, that its curve may exactly fit the 

 inner curve of the muffle mould, (fig. 6, is a section of it). 

 This should likewise have a point or tongue, extending frorpi 

 each end, long enough to be bent in the form of a bricklayer's 

 trowel, and by the wooden handles which must be put on, 

 hanging down, it will be found, that, as it is moved either 

 backwards or forwards, it will always present an edge to smooth 

 the composition, and condense it in the mould. 



The fifth is a frame {d of), fig. 15, of which-the bottom and 

 T 2 farttieit 



