516 Messrs. Griffiths and Clark on the Determination of 



Thermo- 

 meter. 



Reference. 



R . 



E^/Ro- 



S. pt. 



t. 



Oallendar's. 



/ Phil. Trans. A. 1887, 1 

 1 sect. 2 & 3. ) 



5-0845 



1-3460 



1-46 



-289-04 



-27412 



Na+b. 



/ Phil. Trans. A. 1891, \ 

 1 pp. 151, 152. J 



9-8558 



1-3484 



1-638 



-287-03 



-27060 



Na. 



,; „ 



5-9865 



1-3482 



1-648 



-287-19 



-26960 



N b . 



>> >> 



3-8749 



1-3480 



1-639 



-287-34 



-270-86 



M r 



J Phil. Trans. A. 1891,1 

 1 pp. 132-136. / 



4-2267 



1-3381 



1-57 



-295-81 



-279-15 



M 2 . 



» 5> 



41732 



1-3383 



1-57 



-295-58 



-278-97 



H. 



f Phil. Trans. A. 1891, \ 

 I p. 153. } 



13-5216 



1-3463 



1-474 



-288-77 



-273-71 



*Mean -273-86 



The actual numbers used in these calculations are those 

 taken from the papers referred to in column 2. 



All the other thermometers mentioned by Griffiths (Phil. 

 Trans. A. 1891, pp. 43-72) were made with single electrodes 

 for rapid observations ; and thus every observation includes 

 their stem-resistance, which evidently cannot become zero, so 

 that the above investigation with their constants would be of 

 no use. 



The above table seems to corroborate the conclusions arrived 

 at by Profs. Dewar and Fleming, and at the same time is a 

 valuable testimony to the accuracy of the method adopted by 

 Callendar and Griffiths in the papers referred to, for it did 

 not appear probable that their formulae could bear the strain 

 of extrapolating over a range of nearly 300°; this is more 

 especially the case when it is remembered that the wires 

 used have different resistance coefficients and different values 

 for 8 ; the origin of these differences is probably to be found 

 in slight impurities in the platinum. 



We have reason to believe, from some recent experiments 

 conducted by us, that the rise in temperature of the wire, caused 

 by the current necessary to determine its resistance, is greater 

 than is usually supposed. If the difference of potential at 

 the ends of the wire is kept constant, the effect of the error 

 thus introduced is to make the absolute zero too low ; 



* Cf. with the value given by Joule and Thomson, — 273 0, 7, Proc. Roy. 

 Soc. vol. x. p. 502. 



