42 , REPORT — 1889. 



Thus, in the five-and-a-half years between these two tests, this coil has not 

 changed relatively to the standards. 



Further steps have been taken towards the construction of an air- 

 condenser. As stated in the last report, Dr. Alexander Muirhead kindly 

 placed at the disposal of the Committee, for the purpose of experiment, 

 three such condensers which he had constructed. A series of tests of 

 these condensers was carried out by the secretary, and laid before a meeting 

 of the Committee in London on April 15th. It was then decided to adopt 

 Dr. Muirhead's form of condenser for the new instruments of the Com- 

 mittee, and two condensers, each having a capacity of about "01 microfarad, 

 have been ordered from the Cambridge Scientific Instrument Company. 

 It was hoped that these would have been completed early this summer, 

 but great difficulties have been met with in obtaining the brass tubes 

 required for their construction, and, though well advanced, they are not 

 yet finished. A detailed description of their design is therefore left to 

 the next report. 



A second subject of investigation has been the specific resistance of 

 copper. During the year Mr. T. C. Fitzpatrick has made a large series 

 of experiments to determine this, and the Committee desire to thank 

 cordially those manufacturers and others who have given him assistance 

 in this research. They would specially mention the firms of Messrs. 

 Thomas Bolton and Sons, of Cheadle, and Messrs. Frederick Smith and 

 Co., of Halifax. 



Before publishing the results of this investigation, Mr. Fitzpatrick is 

 desirous of experimenting on some copper which is being prepared for 

 him by chemical means — all which has been used hitherto has been 

 electrically deposited- — and of attempting still further to purify some of 

 the copper already in his possession. 



Two members of the Committee, Sir William Thomson and Mr. 

 Preece, were present at the recent Electrical Congress in Paris. They 

 report that the following resolutions, several of which have already been 

 agreed to by the Committee, were unanimously adopted. 



(1) L'unite pratique de travail est le joule. II est egal a 10'^ unites 

 C. G. S. de travail. C'est I'energie depensee pendant une seconde par 

 un ampere dans un ohm. 



(2) L'unite pratique de puissance est le watt. II est egal a 10^ unites 

 C. G. S. de puissance. Le watt est egal a nn joule par seconde. 



Dans la pratique industrielle, on exprimera la puissance des machines 

 en kilowatts, au lieu de I'exprimer en chevaux-vapeur. 



(3) Pour evaluer I'intensite d'ane lampe en bougies, on prendra corame 

 unite pratique, sous le nom de bougie decimale,' la vingtieme partie de 

 I'etalon absolu de lumiere defini par la Conference Internationale de 

 1884. 



(4) L'unite pratique de coefficient d'induction est le quadrant. 



1 quadrant ^ 10^ centimetres. 



(5) La periode d'un courant alternatif est la duree d'une oscillation 

 complete. 



(6) La frequence est le nombre de periodes par seconde. 



(7) L'intensite moyenne est definie par la relation 



1 P 



•moy 



4f 



••• Jo 



' La bougie dficimale, ainsi d6finie, se trouve gtre trfes sensiblement 6gale k la 

 bougie anglaise (^Candle ftandard) et au dixi&me de la Carcel. 



