458 Proceedings of the Royal Society of Edinburgh. [Sess. 
the insulated copper lead E x which forms one terminal of the heating circuit. 
Leak is prevented by the steel cone arrangement C, which is surrounded by 
an ivory collar. From C the current passes through copper rods to the iron 
vessel n containing mercury, into which the lower end of the oven 0 dips. 
The upper end of the oven O is rigidly attached to the plug K 2 , through the 
centre of which, similarly, a thick copper rod passes and makes connection 
e p 
Fig. 1. — High-temperature compression-cylinder. 
with E 2 . Ej and E 2 are connected to the terminals of an alternating 
current apparatus with a transformer which gives 1200 amperes. In 
addition, after the pattern given by Amagat, four insulated copper wires e of 
2 mm. diameter (two of which are represented in the figure) are led through 
the plug K 2 . A vertical section of the oven itself is shown on a larger scale 
in fig. 2. Copper rings F 1 and F 2 , to which the current is led by means 
of the copper pieces A and B, are connected by the platinum tube H, 10 cm. 
long and about 15 mm. in diameter. Its resistance was approximately 
