148 FUNDAMENTAL UNITS OF MEASURE. 



"As ;i unit of electio-motive {orce, t\ni intern<(tio7ial volf, which is the 

 electro-iiiotivc force that, steadily ap])lied to a conductor whose 

 resistance is one international ohm, will [troduce a current of one 

 international ampere, and which is represented sufficiently well for 

 practical use by ttM o* t'le electro-motive force between the poles or 

 electrodes of the voltaic cell known as Clark's cell, at a temperature of 

 15° ('., and prepared in the manner described iu the accompauyinj^ 

 specification.* 



"As a unit of quantity, the international coulomb, which is the quau- 

 tity of electricity transferred by a current of one international ampere 

 in one second. 



"As a unit of capacity, the international farad, which is the cajtacity 

 of a condenser charged to a potential of one international volt by 

 one international coulomb of electricity. 



"As a unit of work, the joule, which is equal to 10" units of work in 

 the c. G. s. system, and which is represented sufficiently well for prac- 

 tical use by the energy expended in one second by an international 

 ampere in an international ohm. 



"As a unit of power, the n^att, which is equal to W units of power in 

 the c. Gr. s. system, and which is represented sufficiently well for prac- 

 tical use, by the work done at the rate of one joule per second. 



"As the unit of induction, the henry, which is the induction in a cir- 

 cuit when the electro-motive force induced in this circuit is one inter- 

 national volt, while the inducing current varies at the rate of one 

 ampere per second." 



Besides the fact that the Congress in which this imjtoitant and far- 

 reaching action was taken was held in the United states, our country 

 has been honored by the action of the Chamber of Delegates iu placing 

 in the list of the illustrious names which are to be perpetuated in the 

 nomcMiclature of electricity that of our countryman, Joseph Henry, whose 

 splendid contributions to science, made about sixty years ago, have 

 only in recent years met with full recognition. For these and other 

 reasons it is extremely desirable that our Government should be among 

 the first, if not the first, to adopt the recommendations of the Chamber. 

 To make the use of these units obligatory in all parts of the country 

 will re(iuire an act of Congress, but in the absence of that, it is within 

 the i)ower of the Secretary of the Treasury to approve their adoption 

 for use in all Departments of the Government. This indeed is pre- 

 cisely the course long ago followed in reference to the ordinary weights 

 and measures of commerce and trade. Congress lias never enacted a 



the tiuode sliould be wrapped louud with pure lilter paper, secured at the back with 

 •sealiug Avax. 



The li([uid shouhl consist of a neutral solution of pure silver nitrate, containing 

 about 15 parts by weight of the nitrate to 85 parts of water. 



Tlie resistance of the voltameter changes somewhat as the current glasses. To 

 prevent these changes having too great an effect on the current, some resistance 

 besides that of the voltameter should be inserted in the circuit. The total metallic 

 resistance of the circuit should not be less than 10 ohms. 



* A committee, consisting of Messrs. Helmholtz, Ayrton, andCarhart, was appointed 

 to prepare specificationa for the Clark's cell. Their report has not yet been received. 



