Apbil 22, 1910] 



SCIENCE 



609 



other countries have followed the Chicago 

 Congress, whereas other countries have fol- 

 lowed Germany, and hence there have been 

 two diiferent values for the volt in use. 



In course of time, the method of preparation 

 of the Clark cell was improved so that the 

 cell became more reliable, but at the same 

 time its electromotive force was slightly al- 

 tered. At the Bureau of Standards, an allow- 

 ance was made for the change in the E.M.F. 

 of the Clark cell, so as to preserve the unit of 

 electromotive force unaltered. In England, 

 however, the original numerical value was re- 

 tained in spite of the fact that the new cells 

 had slightly different values from the old. 

 The result was that a discrepancy arose be- 

 tween the values in use in England and 

 America. Hence, there were and still are 

 three different volts in use in different coun- 

 tries. The Weston normal cell, officially 

 adopted at the London Conference in place of 

 the Clark cell, has the following values : In 

 America, 1.0189 at 25°, equivalent to 1.019125 

 volts at 20° ; in Germany, 1.0186 volts at 20° ; 

 in England, 1.0184 volts at 20°. Some of the 

 other countries have the same value as Amer- 

 ica, others the same as Germany. England 

 adopted the last-named value only one year 

 ago, and no other country, as far as knovra, 

 has followed its example. 



The London Conference of 1908 adopted the 

 ohm as represented by the resistance of a 

 specified column of mercury, and the ampere 

 as represented by a certain mass of silver de- 

 posited in a silver voltameter, as the two in- 

 dependent fundamental electrical units, and 

 declared that the value of the volt should be 

 derived from these two. The electrochemical 

 equivalent of silver adopted at London was 

 1.11800 milligrams of silver per second per 

 ampere of current. It was known that differ- 

 ent investigators had obtained different values 

 for the electrochemical equivalent of silver, 

 according to the kind of voltameter used and 

 the methods of preparing the silver nitrate, so 

 that the international committee found itself 

 confronted with the problem of preparing 

 specifications for the voltameter, when there 

 was a great difference of opinion as to the 

 proper procedure and as to the true value of 



the electrochemical equivalent of silver, which 

 had, however, been definitely fixed by the con- 

 ference. 



The International Committee on Electrical 

 Units and Standards is authorized by the 

 London Conference to complete the work of 

 the conference and to carry on intercompari- 

 sons of standards among different countries, 

 and to promote investigations upon the sub- 

 ject of electrical units and standards, to the 

 end of securing international uniformity with 

 the highest obtainable accuracy. This com- 

 mittee represents eleven different countries, 

 there being two members each from America, 

 England, France and Germany, and one mem- 

 ber each from Austria, Italy, Russia, Switzer- 

 land, Holland, Belgium and Japan. The 

 president of the committee is Professor Dr. E. 

 Warburg, president of the Eeichsanstalt, 

 Berlin; vice-president. Dr. R. T. Glazebrook, 

 director of the National Physical Laboratory, 

 London; treasurer, Professor S. W. Stratton, 

 director of the Bureau of Standards; secre- 

 tary. Professor E. B. Eosa, physicist of the 

 Bureau of Standards. The other eleven mem- 

 bers of the committee are as follows: Dr. 

 Osuke Asano, Department of Communica- 

 tions, Tokyo, Japan; M. Rene Benoit, Bureau 

 International, Sevres, Prance; Dr. N. Egeroff, 

 director. General Chamber of Weights and 

 Measures, St. Petersburg, Russia; Professor 

 Eric Gerard, Liege, Belgium; Professor H. 

 Haga, Groningen, Holland; Dr. Ludwig Kus- 

 minsky. Commission of Weights and Meas- 

 ures, Vienna, Austria; Dr. Stephen Lindeck, 

 Physikalisch-Technische Eeichsanstalt, Ber- 

 lin, Germany; Professor Gabriel Lippmann, 

 The Sorbonne, Paris; Professor Antonio 

 Roiti, Florence, Italy; Mr. A. P. Trotter, 

 Electrical Standards Laboratory, Whitehall, 

 London; Professor H. F. Weber, Ziirich, 

 Switzerland. 



In addition to the fifteen members ap- 

 pointed by the International Electrical Con- 

 ference, the committee was authorized to 

 elect associate members to assist in carrying 

 on its work, and at its first meeting in Lon- 

 don, following the conference, five associate 

 members were elected as follows : Dr. W. 

 Jaeger, of Berlin; Mr. F. E. Smith, of Lon- 



