1888.] 



the Thermo-electric Properties of Bodies. 



235 



EF was 10 inches, AB and CD 7 inches each, total 24 inches. 

 Outside the rod was kept cool with water. 



In calculating the portion of the expansion due to the parts AB 

 and CD the numbers obtained in Experiment 4 are used. The 

 expansion is assumed to be regular "up to 143°, the number obtained 

 from this is used for the cooler portions AB and CD up to 98° ; 

 above that, the number found in the same experiment for the 

 expansion between 143° and 263° is used. 



One example will show what is meant. In Experiment 4, observa- 

 tion 1, we have — 



AB 



54° -> 



54-15 = 39x7 = 



273 



CD 



29 



29-15 = 14x7 = 



98 



EF 



143 



143-15 = 128x10 = 



1280 



Cold portion 



15 J 





1651 





™076 = . 0000045 . 

 1651 





Table showing the Temperature of each Portion of the Rod at each 

 Observation, the total Change in Length, and the Coefficient of 

 Expansion. 



AB. 



EF. 



CD. 



Cold 

 part. 



Total 

 expansion, 



Coefficient of expansion. 



Expt. 1. 180° 

 „ 2. 208 



3 <f 101 

 " ' 1 208 



r 54 

 Expt. 4. J H 

 194 



614° 



645 



300 



645 



143 



263 



282 



602 



263° 



263 

 89 



167 

 29 

 44 

 49 



167 



13° 

 14 

 15 

 15 

 15 

 15 

 15 

 15 



m. 

 '057083 

 -059375 

 -021041 

 -058541 

 -0075 

 -0183' 

 •0216 / 

 •0583 / 



-00000666 between 13 c 

 -0000066 

 -0000056 

 -000008 

 '0000045 

 -0000077 

 -0000140 

 -000009 



and 614° 



14 , 



, 645 



15 , 



, 300 



300 , 



, 645 



15 , 



, 143 



143 , 



, 263 



263 , 



, 282 



282 , 



, 602 



Nos. 1 and 2 give the average of the whole of No. 4, and part 1 

 of No. 3 is not far removed from the average of parts 1 and 2 of 4, 

 while part 2 of No. 3 is lower than the number obtained in No. 4. 



Specific Heat. — H. F. Weber gives the following numbers as the 

 specific heat of carbon at various temperatures ; unfortunately for 

 our purpose, no observations are recorded between 250° and 640°. 



