Melting-points of Aluminium, Silver, Gold, Copper, §c. 41 



went off to galvanometer and key were soldered. They were 

 kept at an equal temperature by the device of enclosing them 

 in a stoppered glass tube, which was packed with hair-felt 

 into a one-inch hole in a five-inch cube of cast iron. This 

 arrangement was entirely satisfactory, but seems to possess 

 no material advantage over making the junction of the copper 

 leads with the Vt and Pt-Rh serve as the cold junction, and 

 immersing this in ice as in fig. 3, except that the latter makes 

 a rather more bulky mass to insert in the ice. 



The wires were also fused together at the hot junction 

 except when this was unnecessary on account of their being 

 immersed in metal. It may be noted here that, as a null 

 method was employed, the total resistance of the thermal 

 circuit, or any variation in it, was without effect other than a 

 corresponding change in sensitiveness. 



As the hot junction was to be immersed in vapour of sulphur 



as one of the known temperatures, the following apparatus was 



designed for this purpose. It is substantially the sulphur 



boiling-point apparatus of Griffiths, and is shown in fig. 4. 



Fio-. 8. Fio-. 4. 



V 



A glass tube, A, similar to the Victor Meyer vapour-density 

 tube, 16 inches long and with a two-inch bulb, was provided 

 with an asbestos jacket and hood, B, B, The upper few 

 inches of the tube were wound with a spiral wire spring, S, 

 which rendered this part efficient as a condenser. The topwas 

 closed with a layer of asbestos. Two overlapping diaphragms 

 of asbestos were inserted in the tube at D and E. The couple 

 passed downward through a glass tube to the asbestos tubular 



