490 



SCIENCE 



[N. S. Vol. XLI. No. 1057 



very passage of tlie electric current, fluctu- 

 ating changes in temperature are liable to 

 occur, which would make the observations 

 totally incorrect. All this led to hesitation 

 and slowness in measurements. Weston 

 wanted to correct this defect, but he was 

 told that the very laws of physics were 

 against his attempts. Before he was 

 through with his work, he had to correct 

 some of our conceptions of the laws of phys- 

 ics ; now let us see how he did it : 



Weston knew that the favorite metal for 

 resistances was so-called German-silver. 

 Strange to say, he was the first one to point 

 out to the Germans themselves that "Ger- 

 man-silver" is a word which covers a multi- 

 tude of sins, and that the composition of 

 German-silver varies considerably accord- 

 ing to its source of supply. The result was 

 that he soon proposed a standard-copper- 

 and-nickel-and-zinc-alloy containing about 

 30 per cent, of nickel, and which had a re- 

 sistance of almost twice that of ordinary 

 German-silver and a much lower tempera- 

 ture coefficient. Not satisfied with this, he 

 took up the systematic study of a large 

 number of alloys. The first batch which 

 he undertook to study amounted to more 

 than three hundred different alloys. Since 

 that time, he has considerably increased 

 this number, and is still busy at it. Every 

 one of these alloys he made himself in his 

 laboratory, starting from pure materials, 

 and controlling the whole operation from 

 the making of the alloy to the drawing of 

 wires of determined size. By long and re- 

 peated observations, on which many years 

 have been consumed, he was able to deter- 

 mine the electrical behavior of each one of 

 these alloys at different temperatures. 

 After awhile, he began to observe remark- 

 able properties in some manganese alloys 

 he compounded. He managed to produce 

 an alloy which had sixty-five times the re- 

 sistance of copper. But getting bolder and 



bolder, he strove to obtain an aUoy which 

 had no temperature-coefficient whatever. 

 He not only succeeded in doing this, but 

 finally produced several alloys which had 

 a negative temperature-coefficient. In other 

 terms, their resistance, instead of increasing 

 with rise of temperature, decreased with 

 increasing temperature. He also showed 

 that the resistance of these alloys depended 

 not only on their composition, but on cer- 

 tain treatments which they undergo, for 

 instance, preliminary heating. And since 

 that day, the physicists have had to bury 

 their favorite definition of metals and non- 

 metals. The present generation can hardly 

 realize what this discovery meant at that 

 time. I could not better illustrate this than 

 by reminding you of the fact that in 1892, 

 at the meeting of the British Association 

 for the Advancement of Science, where it 

 was urged to found an institution similar 

 to the Deutsche Reichsanstalt, Lord Kelvin 

 said in his speech: 



The graad suecesa of the Physikalishe-Eeiehs- 

 anstalt may be judged to some extent here by the 

 record put before us by Professor von Helmholtz. 

 Such a proved success may be followed by a coun- 

 try like England with very great profit indeed. 

 One thing Professor von Helmholtz did not men- 

 tion was the discovery by the Anstalt of a metal 

 whose temperature coefficient with respect to elec- 

 trical resistance is practically nil; that is to say, a 

 metal whose electrical resistance does not change 

 with temperature. This is just the thing we have 

 been waiting for for twenty or thirty years. It is 

 of the greatest importance in scientific experi- 

 ments, and also in connection with the measuring 

 instruments of practical electric lighting, to have 

 a metal whose electrical resistance does not vary 

 with temperature; and after what has been done, 

 what is now wanted is to find a metal of good qual- 

 ity and substance whose resistance shall diminish 

 as temperature is increased. We want something 

 to produce the opposite effect to that with which 

 we are familiar. The resistance of carbon dimin- 

 ishes as temperature increases; but its behavior is 

 not very constant. Until within the last year or 

 so nothing different was known of metals from 

 the fact that elevation of temperature had the ef- 



