506 Professor W. Chandler Bdberfs-Austen [March 15, 



unfortunately, the reductions are usually very tedious, and it would 

 be impossible to actually show you much if I were to attempt to 

 reduce before you any of the rarer metals ; but as the main object is 

 to show you how the furnace is used, it may be well to boil some 

 silver at a temperature of some 2500°, and subsequently to melt 

 chromium in the furnace (Fig. 2). This furnace consists of a clay 

 receptacle A, lined with magnesia B. A current of 60 amperes and 

 100 volts is introduced by the carbon poles C, C ; an electro-magnet 

 M is provided to deflect the arc on to the metal to be melted. [By 

 means of a lens and mirror D E the imago of the arc and of the 

 molten metal was projected on to a screen. For this purpose it 



Fig. 2. 



was found convenient to make the furnace much deeper than would 

 ordinarily be the case.] 



The result is very beautiful, but can only be rendered in dull 

 tones by the accompanying illustrations (Figs. 3, 4). It may be 

 well, therefore, to state briefly what is seen when the furnace is 

 arranged for the melting of metallic chromium. Directly the current 

 is passed, the picture reflected by the mirror E, Fig. 2, shows the 

 interior of the furnace (Fig. 3) as a dark crater, the dull red poles 

 revealing the metallic lustre and grey shadows of the metal beneath 

 them. A little later these poles become tipped with dazzling white, 

 and in the course of a few minutes the temperature rises to about 

 2500° C. Such a temperature will keep chromium well melted, 

 though a thousand degrees more may readily be attained in a furnace 

 of this kind. Each pole is soon surrounded with a lambent halo of 



