Apkil 2, 1915] 



SCIENCE 



491 



feet of increasing lesistance. The Physikalisohe- 

 Anstalt had not been in existence two years before 

 this valuable metal was discovered. 



Then followed this colloquy : 



Pkopessor von Helmholtz. The discovery of a 

 metal whose resistance diminished with tempera- 

 ture was made by an American engineer. 



Professor Ayrton". By an Englishman — Wes- 

 ton. 



Lord Kelvin: That serves but to intensify the 

 position I wished to take, whether the discovery 

 was made by an Anglo-American, an American- 

 Englishman, or an Englishman in America. It is 

 not gratifying to national pride to know that these 

 discoveries were not made in this country. 



The misinformation of Kelvin was due 

 to the fact that after the "Weston patents 

 had been published, his alloy was called 

 manganin in Germany, and a good deal of 

 publicity had been given to its properties 

 with scant reference to its real inventor, 

 an occurrence which, unfortunately, is not 

 infrequent not only among commercial 

 interests but in technical or scientific 

 circles as well. 



No less important was the invention of 

 the Weston cell, which in 1908, by the 

 international commission for the establish- 

 ment of standards of electrical measure- 

 ments, has become the accepted universal 

 practical standard for electromotive force. 

 Here again, this physical standard was ob- 

 tained by chemical means. 



Until Weston researches on standard 

 cells, the Clark cell had been the standby 

 of the electricians and electrochemists of 

 the world, as the standard of electromotive 

 force. It required the keen analysis of 

 a Weston to ascertain all the defects of this 

 cell and to indicate the cause of them. 

 Later, he drew from his careful chemical 

 observations, the means to construct a cell 

 which was free from the defects of its pre- 

 decessors — a cell that had no temperature- 

 coefficient and had no "lag." 



He detected that the choice of a satu- 

 rated solution of sulphate of zinc in which 



was suspended an excess of crystals of this 

 salt, was an unsuitable electrolyte and one 

 of the principal causes why the indications 

 of the Clark cell varied considerably with 

 the temperature. It is true that this could 

 be obviated by placing the cell in a bath 

 of constant temperature. But this involves 

 new difficulties due to the proper deter- 

 mination of the real temperature. Further- 

 more, there is always a "lag" in the indica- 

 tions due to the fact that at varying tem- 

 peratures it requires a certain time before 

 the solution of the salt has adjusted itself 

 to the coefficient of saturation for each 

 newly acquired temperature. By studying 

 the comparative behavior of various salts at 

 different temperatures, he came to the con- 

 clusion that cadmium-sulphate is more ap- 

 propriate and this was one of the several 

 important improvements he introduced in 

 the construction of a new standard of 

 electromotive force. 



Dr. Weston assures me that he has suc- 

 ceeded in making his alloys to show only a 

 change of one millionth for a variation of 

 one degree centigrade. The metallic alloys 

 he discovered are used practically in nearly 

 all kinds of electrical measuring instru- 

 ments throughout the world. Weston in- 

 struments and Weston methods are now 

 found in aU properly equipped laboratories 

 and electrochemical establishments of the 

 world. On a recent trip to Japan, I saw 

 them in the University of Tokio, as well as 

 in the Japanese war museum, where their 

 battered remains attested that the Russians 

 used them on their captured battleships. I 

 have worked in several laboratories in 

 Europe equipped with instruments said to 

 be "just as good" as those of Weston, but 

 in most instances, they were imitations of 

 Weston instruments and it was significant 

 that they kept at least one Weston instru- 

 ment to be used to correct and compare 

 their national product. 



