Jantauy 4, 189").] 



SCIENCE. 



13 



applicjition of the detinitions of the ainpere and tlic 

 volt hi'reiiibrfore given, and such six-ellications shall 

 he the standard specitU^itions herein mentioned. 

 Approved July 1"J, 1-"JI. 



It mil be desii-ahlo to add some remarks 

 upon the steps which have been taken in 

 the same direction by the English Govern- 

 ment since the adjoiirnmeut of the Inter- 

 national Congress. All who are familiar 

 with the legislation in the United States on 

 the subject of "Weights and ^Measures will 

 recognize the passage of the Act given 

 above as the first general legislation estab- 

 lishing units of measure for the whole coun- 

 try, on the part of the American Congress. 



Although the Constitution provides that 

 Congress shall have the power to establish 

 systems of weights and measures, it is well 

 known that Congress has never exercised 

 this power except in the Act of 1S66, which 

 involves the semi-establishment of such a 

 system Ijy making the use of the Metric 

 System permissive throughout the Uuited 

 States. Aside from this, systems of weights 

 and measures in this counti\y have been 

 uniformly and universally the result of 

 State legislation until the passage of the 

 above Act defining units of electrical 

 measure. 



In England a committee has for some 

 time been in existence whose object was 

 the recommendation of suitable units of 

 electrical measure, that they might be le- 

 galized, as is the practice in (ireat Britain, 

 by means of an • Order in Council ' signed 

 by the Queen. Among the members of this 

 committee are such well known names as 

 Lord Kelvin. PreeccGlazebrook and AjTton. 

 This connnittee made a report on the 2d 

 of August, 18it4, and this report was ap- 

 proved by the Queen on the 2.3d of the 

 same month, so that in this country we 

 were a little more than a month in advance 

 of Great Britain in the legalization of units 

 of electrical measure. The P-nglish com- 

 mittee, however, did not feel prepared to 



go as far as we liave gone in tlie recom- 

 mendation foi- the adoption of the whole 

 list of eight units approved at Chicago. 

 Some members of this committee have ex- 

 plained this in personal conference by the 

 statement that the three primary units, the 

 ohm, the ampere and the volt, were found 

 to be not difficult of material representa- 

 tion, while most of the others were verj'' 

 decidedly so, and, as most of the others are 

 derived from these three, it was thought 

 best, at the present time, to restrict author- 

 itative adoption to the ohm, the ampere 

 and the volt. In defining these units the 

 English committee has also departed 

 slightly fi-om the definitions as adopted at 

 Chicago, the changes being mostly- verbal, 

 but, in one or two instances, of such a char- 

 acter as to quite alter the fundamental rela- 

 tion of the materialized unit to its theoreti- 

 cal representative. In order that this may 

 be clearly seen, it may be well to quote the 

 definitions of these three units, as found in 

 the ' Order in Council ' of August 23d. 

 The following is quoted directly from said 

 ' Order ' : 



'• And wliereas it has l)een made to ap- 

 pear to the Board of Trade that new de- 

 nominations of standards are required for 

 use in trade based upon the following units 

 of electrical measurement, viz.: 



" First. The Ohm, which has the value 

 of 10' in terms of the centimetre and the 

 second of time and is represented by the 

 resistance oflered to an unvarying electric 

 current by a column of mercury at the tem- 

 perature of melting ice 14.4.521 grammes 

 in a mass of a constant cross sectional area 

 and of a lengtli of 106.3 centimetres. 



" Second. The Ampere, which has the 

 value tV in terms of the centimetre, the 

 gramme and the second of time, and which 

 is represented by the unvarying electric 

 current which, when passed through a solu- 

 tion of nitrate of silver in water, in accord- 

 ance with tlie specification appended hereto 



