A Comparison of Platinum and Gas Thermometers. 327 



From the researches of the late Professor H. A. Newton, and the 

 results of the investigations of Drs. Stoney and Downing on the per- 

 turbations of Adams's orbit, the most probable value of the period of 

 revolution would appear to be at present about 33*49 years, corre- 

 sponding to mean distance of 10*39. 



Any admissible variation in the length of the period, however, makes 

 but a small change in the other elements of the orbit, as is evident 

 from Table V, in which the elements in each column have been com- 

 puted with the value of the mean distance which is contained in it. 



Table V. 





I. 



II. 



III. 



Longitude of descending node v = 



33*25 yrs. 



10*34 

 64° 46' 

 16 3 

 53 2 

 58 40 



33 *49 yrs. 



10 39 

 64° 50' 

 16 3 

 53 2 

 58 40 



33 "73 yrs. 



10*44 

 64° 54' 

 16 3 

 53 2 

 58 40 



If we adopt the value 10*39 for the mean distance, as being on the 

 whole the most probable, we have the orbit in column II representing 

 the result of the observations of 1898, as far as they have been 

 published. 



" A Comparison of Platinum and Gas Thermometers, including a 

 Determination of the Boiling Point of Sulphur on the 

 Nitrogen Scale : an Account of Experiments made in the 

 Laboratory of the Bureau International des Poids et Mesures, 

 at Sevres." By Drs. J. A. Harker and P. Chappuis. Com- 

 municated by the Kew Observatory Committee. Eeceived 

 June 8 — Bead June 15, 1899. 



(Abstract.) 



In 1886, Professor Callendar drew attention to the method of 

 measuring temperature, based on the determination of the electrical 

 resistance of a platinum wire. He showed that the method was 

 capable of a very general application, and that the platinum resistance 

 thermometer was an instrument giving consistent and accurate results 

 over a very wide temperature range. 



T Callendar pointed out that if E denote the resistance of the spiral 

 of a particular platinum thermometer at 0°, and Ei its resistance at 

 100°, we may establish for the particular wire a temperature scale, 



