Polytechnic Association. 947 



April 26, 1872. 



Prof. S. D. Tillman, in the. chair ; Robert Weir, Esq., Secretary. 



The meeting was opened by the reading of the following paper by 

 the author : 



Apparatus foe Electric Measurement, with Rules and Directions 



for its Practical Application. 



By L. Bradley, Jersey City, N. J. 



1. It is about eight years since the writer of this paper undertook 

 the work of constructing an instrument for the measurement of resist- 

 ances, intended to be used daily in regular business, as the grocer used 

 his scale-beam. The result, though rude and imperfect, was still 

 valuable, for it enabled him approximately to determine the resist- 

 ances of all helices and electro- magnets manufactured and put upon 

 the market by him. 



The measurement of resistance was all that was then aspired to, and 

 the apparatus received the name of Anthistometer, a Greek derivative 

 signifying " a measurer of resistance." 



From that to the present time, he has endeavored by indefatigable 

 exertion and thongtht, to keep pace with the progress so rapidly mak- 

 ing in electrical science, and especially in that of electric measure- 

 ment generally. 



Instead of a rude and imperfect measure of resistance, he now pre- 

 sents an apparatus so largely improved, and so well denned in its 

 applications and capacities, that electricians in all departments find 

 every desirable means for absolute and correct measurement, put up 

 in a substantial, compact, cheap and portable form. 



By this, telegraph companies may directly measure the resistance 

 of their lines ; also their insulation resistance up to millions of ohms. 

 They may locate breaks, faults and crosses, when they occur, and they 

 may determine the resistance, strength and electro-motive force of 

 their batteries. 



Metallurgists, engaged in electrolysis, may determine the quantity 

 of metal of any kind deposed by a current in a given time with great 

 accuracy ; a desideratum to those engaged in electrotyping, gilding, 

 etc. 



Wire manufacturers may readily determine the quality of the metal 

 they are working up ; the specific resistance and conductivity of the 

 wire put upon the market, compared with that of pure copper ; a 



