X 



22 Messrs. C. W. Waidner and F. Mallory on 



which corresponds to zero resistance of the platinum thermo- 

 meter, gives for the absolute zero [by using 8 = 1*490 in 

 t - pt = 8[(t/100) 2 - //1 00}] - 274°-44. Similarly the 

 standardization of January 23 gives the absolute zero 



-274°-41.] 



Standardization of Platinum Thermometer. 



The details of the elaborate comparisons by Mr. Griffiths, 

 on which the constant, 8, of this thermometer is based, are 

 given below (Tables VIII., IX., X.). The resistance-box 

 (No. 6) used in this standardization was similar to the one 

 described in ' Nature/ Nov. 14, 1895. 



** For all purposes of comparison between the results ob- 

 tained here and in Baltimore, we only require the values of 



5- and 8, the magnitude of the unit used being of no con- 



sequence. I, however, give the observations in full, to show 

 the probable order of accuracy.'"' 



January 21, 1896. 



" On the above date a preliminary series of observations 

 was made in ice, steam, and sulphur-vapour. The observa- 

 tions, however, were hurried, the resistance-box was not 

 contained in its tank, and its temperature was about 15°'50 C. 

 Thus the temperature correction was large. I did not regard 

 the work as anything but preliminary, and will therefore only 

 give results (the resistances are corrected for temperature of 

 box, &c.) : — 



R' = 358-480 when barometer* = 771*24, 



R = 258-366, 



R a = 679 680 when barometer = 771*35. 



Hence we get 



B,- 358-075 % = 



R = 258-366 tt 



Fl= 99 709 S- 1*490 



* The barometer is in each case corrected for temperature, scale errors, 

 and for value of g to sea-level, latitude 45°. 



