determining the Thermal Conductibility of Bodies. 139 



From the values of/ and A/3 those of « and a are readily 

 obtained according to the formulae 



300 



/= e a andA/3— =«'; 



and these values substituted in (8), in which case in the pre- 

 ceding example T = 24 and /=10, gives finally 



k = c. 8. 64-0 at 50° C. 



§5. 



After having exemplified in this manner, not only the agree- 

 ment of theory with practice, but also the manner in which the 

 value of k is obtained, I collate in the following Table III. all 

 the values of m, A, and {3 calculated from Table I. and Table II., 

 as these are the only values which require to be known in the 

 calculation of k. 



Table III. 



No. 



Thermo- 

 meter. 



No. 



m. 



A. 



15. 



A/3. 



Length of 

 Period. 



Distance 

 between 

 Thermo- 

 meters. 



1 



{? 



80-39 



88-89 



31-747 

 33010 



134° 62 

 109 2-7 



O 1 



25 3-5 



m. 



24 m.t 



millims. 



100 



2 



U 



74-57 



82-93 



25-203 



23-885 



142 21-2 

 117 47-2 



24 340 



24 m.t 



100 



3(a) 



3(b) 



< h. 



{ iv. 



58-60 

 62-82 

 76-36 



10-710 

 6-251 

 3-559 



146 51 

 121 2-7 



111 8-3 



25 2-4 

 24 54-4 



24 *.t 

 24 *.t 



100 

 100 



4 



U 



77-02 



86-80 



17-467 

 14-345 



123 26-5 

 86 4-3 



37 22-2 



\2m.t 



150 



5 



{k 



75-38 

 76-61 



18-780 



7-728 



129 51-5 

 83 50-5 



46 10 



16 *.* 



150 



6 



{ l t 



87-18 

 91-32 



6-999 

 4-290 



294 42-3 

 263 44-2 



30 581 



16 #.t 



100 



7 



U 



70-42 

 75-83 



3-713 

 1-770 



275 37-4 

 239 9-3 



36 28-1 



16m. t 



50 



8 



u 



69 24 

 74-56 



3-891 

 1-852 



275 41-6 

 238 32-2 



37 9-4 



16m. t 



50 







If k be calculated from the values of A and A/5, collated in 

 the foregoing Table, in which formula (10) is used to find/, the 

 following results are obtained if the mean temperature of the bar 

 is expressed on the Centigrade scale, and the centimetre is taken 

 as the unit of length. 



