240 



PROCEEDINGS OF THE AMERICAN ACADEMY. 



the crucible, is a diaphragm, Z), made from a plate of battery car- 

 bon. It lias a central perforation large enough to permit the passage 

 of the clay tube carrying the thermo-couple. Upon this diaphragm is 

 placed powdered charcoal. A block, E, of battery carbon is turned to 

 fit the rim of the crucible somewhat closely to serve as a cover. G 

 is a diaphragm of asbestos board which deflects the gases, and upon 

 this at A is placed fibrous asbestos to reduce the heat conductivity. 

 The cover belonging to the furnace is not used. Simpler details 

 might serve sufficiently well, but they must effect the same result. 



namely, to produce by slow combustion an atmosphere of carbon 

 dioxide in the crucible to retard the oxidation of the copper. As 

 above arranged, the powdered charcoal does this, and the carbon plates 

 do not burn. 



The thermo-couple projects as shown into the metal, being of 

 course thrust in during the first melting. It is obviously indifferent 

 whether the wires are joined or not. The end of the wires will 

 require clipping subsequently, to remove the short section injured by 

 action of the copper. The uniformity of the wire, however, renders 

 this a source of no sensible error. 



The apparatus being arranged as shown, and the copper liquefied 



