KERSHAW. 225 
PROGRESS IN ELECTRO-METALLURGY 
of large intensity but low pressure in the secondary coil of the appa- 
ratus. The metal is contained within an annular ring built up of 
refractory — blocks == —— 
round the primary 
coil of the furnace, 
and by varying the 
current in the pri- 
mary, the heat de- 
veloped in the sec- 
ondary can be regu- 
lated as desired. 
The advantages of 
the Kjellin furnace 
are the development 
of the heat just 
where it is wanted, spams 
i. e., entirely within 
the metal, and con- 
sequent small wear 
and tear upon the 
structure and walls 
of the furnace, and 
secondly, the ab- 
sence of impurities 
picked up from the 
electrodes used in 
all other methods 
of applying electric 
heat. The Kjellin 
process and furnace are being 
worked successfullyat Gysinge 
in Sweden, at Gurtmellan in 
Switzerland, at Krupp’s steel 
works in Germany, at Vicer’s 
steel works in Eng- 
land, and also at the 
Araya steel works 
in Spain, while 
in America a 
furnace patented by Colby 
but worked upon the same 
principle has been operated 
with successful results at Fic. 4.—Plan and elevation of Stassano revoly- 
Philadelphia. ing furnace. 
Three electric-furnace methods for the production of iron and steel 
