74 Mr. H. H. Poole on Thermal Conductivity and Specific 



The results obtained from five series of observations are 

 plotted in rig. 5. Each curve represents one series of obser- 

 vations. The individual values are not plotted as there were 



'0 100 200 300 400c 



so many of them that they would render the figure confused. 

 The full line curves represent determinations on falling 

 temperatures and the dotted curves those on rising tempe- 

 ratures : the shorter of the two latter represents a determin- 

 ation with a constant supply of energy to the furnace, the 

 longer one in which the energy was slowly increased by 

 the clock as before explained. From these curves means 

 were taken, account being taken of the fact that at low 

 temperatures the cooling determinations were less reliable 

 owing to the slow rate of cooling and small temperature 

 differences involved. These averages lie on the curve 



S =z 0-161 + 0-405 x 10- 3 6>-0-45 x 1O" 6 2 



which represents the mean results of these experiments 

 between the temperatures 40° C. and 380° CI 



Further Experiments on the Granite ( '//Under. 



The cylinder was taken to pieces and the single couple 

 renewed. An attempt was made to prevent the wires from 

 breaking at high temperatures by coating them with rubber 

 solution before cementing them into the rock. It was hoped 

 that when the rubber burnt away it would leave a minute 

 air space, thus allowing the wire a certain amount of freedom. 

 The single couple and the leads of the multiple couple were 

 treated in this way. The multiple couple itself was not 

 removed from the groove system in the rock face. Seven 

 results were obtained which were very concordant with the- 

 exception of the first, which was slightly too high. These 

 results are given in the last three columns of Table III. and 

 are plotted in fig. 4 (larger circles). They lie very closely 

 along the line K = (4*77-0 00198 6) X 10" 3 and are thus 

 nearly 4 per cent, higher than the previous ones. 



