Melting Points of Certain Metals. 



507 



rammed firmly into position by applying a force of twenty or 

 thirty tons ; this force is communicated through a small steel 

 cylinder of the same diameter, which is properly drilled or 

 grooved so as not to injure or interfere with the wire or wires. 

 In order to prevent the wires being actually squirted out 

 through the holes in the stone, two procedures may be followed. 



Fig. 3. 



Fig. 3. Electric furnace and interior of bomb, drawn to scale. JJ is the 

 furnace, .SS soapstone blocks for thermal insulation of the ends, and O and 

 H, the plugs which close the bomb. Freedom from leaks is insured by the 

 use of the rings or " washers" of sheet copper shown at LL. Thermocouple 

 wires TT are led into the bomb through the upper steel plug G. One termi- 

 nal of the heating circuit is grounded onto the bomb at I ; the other passes 

 out insulated through H. The graphite crucible with thermocouple tube 

 in place is shown suspended from the upper plug. 



The soapstone cylinder may be made in two or more parts and 

 the holes for the wires staggered ; or the internal part of the 



