8 Mr. C. Barus on the Fusion 



was found satisfactory, is shown in longitudinal section 

 (scale £) in fig. 5, where B B B is the cylindrical body, and 

 AAA the dome-shaped lid (perforated at a a a) already re- 

 ferred to. The burners H H and G G, project into the 

 furnace as far as the inner surface, and their construction is 

 shown. Compressed air enters the tubes g g and hh, and the 

 gas inlets are at c and c'. Attached to the burners are the 

 rectangular slides II and KK, which pass through guides 

 L and M. The pins e e and d d further regulate the action, 

 by which the burners can be easily inserted in or withdrawn 

 from the furnace. Finally, the gas inlets, c and c', are each 

 in connexion with a graduated stopcock (half-inch clear bore), 

 by which the gas-supply, and hence the furnace temperature, 

 can be regulated at pleasure. In this way the torch of flame, 

 fully two feet in length, is reduced to a blue cone about eight 

 inches long by the blast, which may then be further reduced 

 to a mere ribbon of flame by shutting off the gascocks. 

 Burner explosions do not occur. 



The muffle proper is shown at E C F D E in fig. 5, and 

 consists of two identical halves of refractory fire-clay, each of 

 which is a hemisphere with two diametrically opposite gut- 

 tered arms ; the two halves are placed together with their 

 flat faces contiguous, but without cement, and secured by 

 surrounding the axles with appropriate collars of iron, N N 

 and N' N' (fig. 5), the outer edges of which are widely flanged. 

 These flanges, P P and P' P', are turned circularly with their 

 circumferences bevelled so as to fit the grooves of two pairs 

 of friction-rollers, Q Q and Q' Q', of which E and B/ are the 

 respective axes, four in number. Set screws, T, T ; , sink into 

 the rib of the collar and fasten it to the axle, asbestos being 

 usually interposed. 



The four friction-rollers, Q Q', are adjustable (see figure), 

 so that the muffle in its rotation never touches the walls of 

 the furnace, but revolves on the rollers. Such an arrange- 

 ment is essential, for the rolling parts must be placed at some 

 distance from the hot parts of the axle to slide smoothly ; 

 and the friction of an imperfect mechanism would, at high 

 temperatures, tend to wrench off the axles of the white-hot 

 muffle. Another essential adjustment may here be mentioned. 

 After firing, neither do the axles of the muffle coincide in 

 prolongation nor are they straight. Hence the friction 

 rollers, Q Q', rotate on cylindrical rods, RR', along which the 

 former are in some measure free to slide, their extreme 

 positions being fixed by four adjustable collars, X X'. 



The belt pully, Z Z', supplies the power. 



Finally, the figure shows the air- thermometer fhil in 



