38 



REPORT — 1903. 



two resistances of gold-silver wire made by Matthiessen himself, to repre- 

 sent the resistance at 15°^5 C. of 100 inches of pure annealed copper, 

 having the weight of 100 grains. The resistances of these coils have been 

 determined by Mr. Smith, and the results are given in the following 

 table : — 



Matthiessen's value for the resistance of annealed copper at 

 (60° Fahr.) as deduced from these coils, agrees very closely with 



1 . 11 .1 CI 0. n j.T-_ i^ .- ;_ i,:~ i oca „- 



Thus 



15°^55 C. ,„. ^ , , -0-- -. ^ 



the value calculated by the Secretary from the figures in his 1860 paper. 



The Committee have had under consideration the drawings and speci- 

 fications for the ampere balance as designed by the late Principal 

 Viriamu Jones and Professor Ayrton. The electrical parts of the 

 instrument need construction under skilled supervision. Tests of various 

 kinds have to be made continually, and the Committee have come to the 

 conclusion that this supervision can best be secured by having the 

 instrument constructed in the workshop of the National Physical 

 Laboratory, under the care of Professor Ayrton and the Secretary, who, 

 as Director, will be able, with the assistance of the staff of the Laboratory, 

 to control the work in an efficient manner. 



The Committee are of opinion that further expenditure will be required 

 in completing the set of platinum thermometers, in particular in providing 

 a satisfactory resistance-box and in carrying out the researches on the 

 Clark cell. They consider that it is of great importance that these 

 researches should be brought to a satisfactory conclusion. 



For these reasons they recommend that they be reappointed, with a 

 grant of 60/., that Lord Eayleigh be Chairman, and Mr. K. T. Glazebrook 

 Secretary, 



APPENDIX I. 



071 the Valves of the Resistance of certain Standard Coils of the British 



Association. By F. E. Smith. 



{From the National Fhybical Laboratory.) 



['J"he Report covers the period 1888-1903 inclusive.] 



Changes of very considerable magnitude have taken place since 

 1892 in the old B.A. standards. The removal of the coils, first to 

 Liverpool, then to Kew, and finally to Teddington, has resulted in the 

 comparisons being incomplete in some years. In consequence the difficulty 

 of locating differences has correspondingly increased. 



