SILVER ASSAYING 



821 



Fig. 1820 represents the muffle or pot, -which is 12 inches long, 6 inches broad in- 

 side ; in the clear 6f ; in height 4 inside measure, and nearly 5 in the clear. 



Fig. 1821, the muffle-plate, which is of the same size as the bottom of the muffle. 



Fig. 1822 is a representation of the sliding-door of the mouth-plate, as shown at d, 

 In fig. 1817. 



Fig. 1823, a front view of the mouth-plate or piece, d,fig. 1817. 



Fig. 1824, a representation of the mode of the making, or shutting-up, with pieces 

 of charcoal, the mouth of the furnace. 



Fig. 1825, the teaser, for cleaning the grate. 



Fig. 1826, a larger teaser, which is introduced at the top of the furnace, for keeping 

 a complete supply of charcoal around the muffle. 



Fig. 1827, the tongs used for charging the assays into the cups. 



Fig. 1828 represents a board of wood used as a register, and is divided into 45 equal 

 compartments, upon which the assays are placed previously to their being introduced 

 into the furnace. When the operation is performed, the cupels are placed in the fur- 

 nace in situations corresponding to these assays on the board. By this means all 

 confusion is avoided, and without this regularity it would be impossible to preserve 

 the accuracy which the delicate operations of the assayer require. In the furnace 

 above described 45 assays can be made at one time. Of late years some modifications 

 and improvements have been introduced in the above furnaces in the Royal Mint and 

 other assay offices. The fuel employed is charcoal, coke, or anthracite. (See MINT.) 



We now proceed to a description of a small assay-furnace invented by Messrs. 

 Anfrye and D'Arcet, of Paris. They termed it, le petit Fourneau a Coupclle. Fig. 1829 

 represents this furnace, which is composed of a chimney or pipe of wrought iron, a, 

 and of the furnace, B. It is 17i inches high and 7 inches wide. The furnace is 

 formed of three pieces : of a dome, A ; the body of the furnace, B ; and the ash-pit, c, 

 which is used as the base of the furnace, figs. 1829 and 1830. The principal piece, or 

 body of the furnace, B, has the form of a hollow tower, or of a hollow cylinder, flat- 

 tened equally at the two opposite sides parallel to the axis, in such a manner that the 

 horizontal section is 

 elliptical. The foot 

 which supports it is 

 a hollow truncated 

 cone, flattened in like 

 manner upon the two 

 opposite sides, and 

 having consequently 

 for its basis two 

 ellipses of different 

 diameters : the small- 

 est ought to be equal 

 to that of the furnace, 

 so that the bottom of 

 the latter may exactly 

 fit it. The dome, 

 which forms an arch 

 above the furnace, has 

 also its base ellip- 

 tical ; whilst that of 

 the superior orifice, 

 by which the smoke 

 goes out, preserves 

 the cylindrical form. 

 The tube of wrought 

 iron is 18 inches 

 long, and 2^ inches 

 in diameter; having 

 one of its ends a 

 little enlarged, and 

 slightly conical, that 

 it may be exactly 

 fitted or jointed upon 

 the upper part of the 

 furnace-dome, d (fig. 

 1829). At the union 



of the conical and cylindrical parts of the tube.there is placed a small gallery of iron, 

 e, Jigs. 1820, 1830. (Sec also a plan of it. fg. 1831). This gallery is both ingenious 



