MAGNETIC OBSERVATIONS AT FALMOUTH. 33 



grant of GO/. The reasons for this request are in the main the same 

 as last year. It has not yet been found possible to establish the new 

 magnetic observatory and to remove the recording instruments from Kew, 

 though the Committee are informed that progress has been made in the 

 arrangements for this ; at the same time electric traction has increased 

 greatly in the neighbourhood of Kew, and the records are in consequence 

 very seriously disturbed. Thus the Falmouth records are of special im- 

 portance to science just now. 



Experiments for improving the Oonstrudion of Practical Standards for 

 Electrical Measurements. — Report of the Committee, consisting 

 of Lord Rayleigh (Ghcoirman), Dr. R. T. Glazebrook (Secretary), 

 Lord Kelvin, Professors W. E. Ayrton, J. Perry, W. G. 

 Adams, and G. Carey Foster, Sir Oliver J. Lodge, Dr. A. 

 MuiRHEAD, Sir W. H. Preece, Professors J. D. Everett, A. 

 Schuster, J. A. Fleming, and J. J. Thomson, Dr. W. N. Shaw, 

 Dr. J. T. Bottomley, Rev. T. C. Fitzpatrick, Dr. G. Johnstone 

 Stoney, Professor S. P. Thompson, Mr. J. Rennie, Dr. E. H. 

 Griffiths, Sir A. W. Rucker, Professor H. L. Callendar, 

 and Mr. George Matthey. 



APPENDICES PAOa 



I. On the Values of tlio Resistance of certain. Standard Coils of the Bntisli 

 Association. By F. E. Smith. (Fror?i the National Physical Labora- 

 tory) 38 



II. On some new Mercury Standards of Resistance. ^^ F. E. Smith. {From 



the National Physical Laboratory) 44 



III. On the Platinum, Thermometers of the British Association. By J. A. 



'Ukrk.^b., D.Sc. {From the National Physical Laboratory) . . .45 



IV. Table of the Resistance found for Piire Annealed Coiiper .... 51 



During the year a very complete comparison of the resistance standards 

 Ijelonging to the Association has been carried out, and the standards have 

 been compared with those of the Reichsanstalt and of the Board of Trade. 



The various units discussed in the report are : (1) The ' ohm,' 

 10' C.G.S. units of resistance ; (2) the international ohm — viz., the resist- 

 ance at 0° C. of a column of mercury of uniform section 106 -3 cm. in length 

 and 14-4521 grammes in mass; (3) the original B.A. unit; (4) the 

 Board of Trade unit, supposed to represent the international ohm, but 

 constructed in 1891 so as to be equal to 1-01358 B.A. units ; (5) the 

 N.P.L. unit defined as No. 4, as deduced from the wire standards of the 

 Association ; (6) the E,eichsanstalt unit, constructed at the Reichsanstalt 

 to represent the international ohm ; (7) the mercury tubes, constructed 

 at the National Physical Laboratory to represent the international ohm. 



A full account of this comparison is given in Appendix I. to the report, 

 by Mr. F. E. Smith, of the National Physical Laboratory. It appears 

 from this that changes have shown themselves in all the original platinum- 

 silver coils. The relative values of these coils are discussed in the Reports 

 of the Committee for 1888, 1890, and 1892. The 1888 report contains a 

 very complete comparison of all the coils, not merely those of platinpm- 

 silver ; and it is there shown that they then agreed with the values 



1903. D 



