536 



Prof. J. Dewar. On the 



[June 17 r 



Pressure. Position on Scale. 



Zero = +6. 



25 - 17 



50 - 36 



75 — 55 



100 - 74 



125 - 91 



150 -110 



175 -130 



200 -149 



Mean deflection for 25 atmospheres is 19 '4 divisions of the scale. 



Series IV. 



Brine was placed ronnd the junction in the bottle, the latter being- 

 afterwards packed in ice and salt, to reduce the temperature of the 

 brine to —18° C, the other junction being placed in ice and salt in a 

 beaker outside the iron bottle. The junctions were then connected up 

 with the galvanometer, and allowed to remain until the temperature 

 became equalised : — 



Zero +85. 



Atmospheres. Position on Scale. Increase. 



25 + 98 ........ 



50 +106 8 



75 +115 ....... 9 



100 +121 ^ 



125 +128 7 



150 +134 ° 



175 +138 ) 



200 +142 4 



Jn this case a heating effect was produced, which seemed, however, 

 to decrease as the pressure was increased. It represents an increase of 

 g 1 - of a degree Centigrade for the whole 200 atmospheres. 



Series V, 



The junction in the flange was frozen into a solid block of ice as in 

 Series I, and placed in the bottle, surrounded with brine at —20° C, 

 the whole apparatus packed in ice and salt. A very slight heating- 

 effect was produced, which only amounted to about divisions for 

 200 atmospheres. 



Series VI. 



These experiments were made with the junction frozen into a test- 

 tube as in Series I, with mercury surrounding the test-tube instead of 

 water. This gave exactly the same deflection of the galvanometer as 

 when water was employed, only the experiment could not be carried 



Difference. 



19 

 19 

 19 

 17 

 19 

 20 

 19 



