42 Messrs. Holman, Lawrence, and Barr on the 



hood, Oj which served as an umbrella to shed the dripping 

 cooler sulphur, and as a radiation-screen. The hood, how- 

 ever, had openings top and bottom for the free circulation of 

 the vapour. An asbestos diaphragm, H, upon which the bulb 

 rested, reduced the chances of superheating. 



For the melting metals, after trial of several devices, the 

 one shown in fig. 5 (of exactly half size) was settled upon as 



Fis*. 5. 



proving very satisfactory. The crucible, C (usually of fire- 

 clay), is supported by clay blocks in the double-walled fire- 

 clay furnace, F. A carbon block, E, channelled to fit the 

 crucible, forms its cover, and a carbon diaphragm, D, inside 

 the crucible serves to support some powdered carbon shown 

 by the dotted mass. The object of these carbon parts was to 

 prevent oxidation of molten metals, and they proved very 

 effective in the cnse of aluminium, silver, and copper. G G was 

 an asbestos diaphragm supporting a non-conducting layer of 

 fibrous asbestos, A A. The temperature was controlled by 

 the blast-lamp B. The clay crucible was one inch in diameter 

 outside, and the amount of metal employed ranged from 11 

 grams (gold) to 35 grams (copper). Larger amounts might 

 be advantageous, but with 30 to 35 grams it was easily 

 possible to obtain a constant indication for five minutes during 

 the melting or solidifying of copper. .No difficulty whatever 



