324 
DR. E. H. GRIFFITHS AND MR. EZER GRIFFITHS ON THE 
a fairly high temperature, precautions had to be taken to shield the spiral, otherwise 
the insulation would have suffered. 
This protection was effected by drawing the spiral up compactly against the top 
with thin wire loops passing out through the bolt holes. The case was fixed in an 
inverted position in water with about 1 cm. projecting, the ends of the fine 
tubing being capped with rubber tubing to prevent access of water to the manganin 
wire. 
The spiral, being totally immersed, was thus effectively shielded, while the bottom 
was soldered on with an oxy-coal gas blowpipe and, when completed, the spiral was 
released from without and the nuts screwed on to the ends of the tubing. 
Filling the case with sodium was effected in vacuo , the electrically heated iron 
vessel containing the sodium being supported by a tripod, the tube from the case 
projecting up through the bottom of the iron vessel. 
After sealing, the sodium was annealed by slow cooling from the molten state. 
The block was suspended within the enclosure by two threads, the platinum 
thermometer being inserted into the central copper tube. 
Two experiments near 0° C. were performed by the method described later in this 
paper, and the resulting mean value of the specific heat, namely, 0‘2826 at — 2°‘5 C., 
agrees extremely well with the value at 0° C, for the annealed state, previously 
obtained,* namely, (P2829. 
It will be observed that in the present arrangement there were no supporting tubes 
of quartz ; the thermometer was in the centre, while the heating coil was distributed 
throughout the volume of the metal and had a resistance of about twice that of the 
coil used previously. 
The relative proportions of copper and sodium were very different, as well as the 
geometrical form of the blocks. When we consider the complete change, both of 
apparatus and of method, the close correspondence between the results affords a 
strong proof of the validity of the assumptions underlying both methods. 
(3) Measurement of Mass, Time , Electromotive Force , &c. 
Details concerning the measurement of the above quantities have already been 
givent and all the precautions there dealt with have been observed. 
The method of determining the correction for the heating effect of the current on 
the resistance of the coil was slightly different from that previously described, 
insomuch that the temperature of the block, while the electrical supply was on, was 
maintained constant by lowering the temperature of the enclosure until losses by 
radiation,^ &c., balanced the electrical supply for each rate. 
* ‘ Roy. Soc. Proc.,’ A, vol. 89, 1914, p. 567. 
f Loc. cit., p. 126. 
t To save repetition, losses by radiation, convection, and conduction will be referred to as losses by 
radiation. 
