212 KEPORT— 1897. 



We thus get, as a second approximation to the value of }} — 



Now let V remain constant, and let p^, Tq and p^, Tj represent pressure 

 and temperature at the melting-point of ise and at the boiling-point of 

 water respectively ; we then get 



i'«=^[To-J^(ta-f/3To)] 



^^^=? [T.-^(ia + /3T0]. 

 By subtraction 



and 



Hence 



or, finally, if we assume 100 as the numerical value of the interval Ti— Tq 



T-To=100 P'J'"; 



whence we may conclude that, to the degree of approximation attained in 

 this calculation, the scale of the constant volume gas-thermometer is 

 identical with the absolute thermodynamic scale. 



APPENDIX II. 



■-On a Determination of the Ohm made in Testing the Lorenz Apparatus 

 of the McGill University, Montreal, hy Professor W. E. Ayrton, 

 i^.R.S., and Professor J. Viriamu Jones, F.B.S. 



This apparatus, made by Messrs. Nakler Brothers, is in general arrange- 

 ment and dimensions similar to the Cardiff apparatus described in the 

 'Philosophical Transactions of the Royal Society,' 1891, A, pp. 1-42, and 

 in the 'Electrician,' June 1895, vol. xxxv. pp. 231 and 253. 



The field coil, in pursuance of a suggestion contained in the Royal 

 Society paper, consists of a single layer of wire wound in a helical groove 

 of semicircular section, cut in the cylindrical surface of a massive marble 

 ring of about 21 inches outside diameter, 15 inches inside diameter, and 

 6 inches thick. This helical groove has 201 complete turns with a pitch 

 of 0-025 inch. Bare wire, of mean thickness 0-02136 inch, was first used. 



