FIG. 2. 



74 Mr. E. P. Perman. [Feb. 4, 



the higher temperatures it was surrounded by a wide tube, open 

 at the lower end, and closed by a cork at the upper end. The tube 

 was wrapped round with a thick layer of cotton wool. The arrange- 

 ment is shown in fig. 1, A. The liquid could be drawn up from the 

 bath into the wide tube by means of a small tube passing through the 



cork; the tube was then closed 

 by means of a clip on a rubber 

 tube connected with the glass 

 ' tube. The temperature of the 

 liquid in the wide tube was kept 

 sufficiently uniform by convec- 

 tion currents. This was shown 

 to be the case by emptying the 

 liquid into the bath, and quickly 

 drawing up a fresh portion, when 

 the reading of the thermometer 

 remained unaltered. In some of 

 the experiments the thermo- 

 meter was placed in a sloping 

 position (in order to get the 

 whole column into the bath) ; in 

 that case a correction for in- 

 ternal pressure was made, being 

 calculated from the coefficient 

 given in the certificate. A toluol 

 gas regulator was employed (not 

 shown in fig. 1), which usually 

 maintained the temperature con- 

 stant to 0-01; it rarely varied 

 more than this during an ex- 

 periment, and I do not believe 

 that the temperature error ex- 

 ceeds 0*02 in any single experi- 

 ment. The regulator is of a new 

 pattern, although it does not 

 involve any new principle. The 

 gas can be regulated in either 

 direction by the stop-cocks 



A, B, fig. 2. The quantity of mercury enclosed can be adjusted to 

 suit any temperature over a wide range by means of the bulb C, and 

 stop-cock beneath it, while, by means of the screw D, the temperature 

 can be regulated to 0*01, and can be easily brought to any desired 

 point.* 



* For details of the usual pattern of toluol regulator, see ' Physiko-chemisehe 

 Mi ssungen, Oslwald-Luther,' p. 88. 



