240 REPORT—1899. 
Hzperiments for improving the Construction of Practical Standards for 
use in Electrical Measurements.—Report of the Committee, consisting 
of Lord RAYLEIGH (Chairman), Mr. R. T. GLAZEBROOK (Secretary), 
Lord Ketvin, Professors W. E. Ayrton, J. Perry, W. G. ADAMs, 
OLIVER J. LopGE, and G. Carey Foster, Dr. A. MurrHeap, Sir 
W. H. Preece, Professors J. D. Evererr and A. SCHUSTER, 
Dr. J. A. Fiemine, Professors G. F. FirzGrratp and J. J. 
THomson, Mr. W. N. SHaw, Dr. J. T. Botromuey, Rev. T. C. 
FirzpaTRick, Professor J. Viriamu Jones, Dr. G. JOHNSTONE 
Stoney, Professor S. P. Toompson, Mr. J. Rennie, Mr. E. H. 
GrirFiTHs, Professor A. W. Ricker, and Professor H. L. 
CALLENDAR. 
APPENDIX PAGE 
I. On the Mutual Induction of Coaxial Helices. By LORD RAYLEIGH . 2, 2a 
Il. Proposals for a Standard Scale of Temperature based on the Platinum 
Resistance Thermometer. By Professor H.U.CALLENDAR  . 242 
III. Comparison of Platinum and Gas Thermometers. By Dr. P. CHAPPUIS 
and Dr. J. A. HARKER. 243 
IV. Onthe Expansion of Porcelain wi ith Rise o of Temper ature. By 4k G. BEDFORD 245 
Tur Committee have been engaged during the year on the consideration 
of the details of the new ampere balance, for which a grant of 500/. was 
voted at Bristol. 
Professors Ayrton and Viriamu Jones have ere | the plans and 
specifications, and the construction of the balance has been authorised. 
An important addition to the plan proposed at Bristol consists of an 
arrangement for adjusting accurately the position of the fixed coils. Sir 
Andrew Noble has generously undertaken to have this constructed at 
Elswick free of cost, and the Committee desire to thank him for the offer, 
which they have gladly accepted. 
In consequence of the fact that the balance is not yet completed, the 
grant of 300/. made last year has not been expended, and the Committee 
apply for its renewal. 
An appendix to the Report contains a proof by Lord Rayleigh of a 
theorem due to Professor J. V. Jones, on which the mathematical theory 
of the new balance is based. 
Details of the balance are reserved until it has actually been con- 
structed. 
Professor Callendar has brought before the Committee proposals for | 
the adoption of a standard scale of temperature based on the Platinum 
Resistance Thermometer. These are printed in an appendix and formed 
the basis of a discussion in the Section. A sub-Committee has been 
formed to consider these proposals and to report to the Committee. 
The ordinary testing of standards has been interrupted by the removal 
of the Secretary to Liverpool, and still further by his proposed removal 
to Kew. With respect to this the Committee have passed the following 
resolution :— 
That Mr. R. T. Glazebrook, as Secretary of the Committee, be 
