ELECTRICAL CONFERENCE AT PHILADELPHIA 629 



With a practical standard of electromotive force, such as a Clark's 

 standard cell or a thermo-electric battery, this difficulty partially van- 

 ishes. Better, perhaps, we might make simple electro-dynamometers 

 with constants determined by comparisons with a more costly instru- 

 ment. 



But where shall these standards be kept? Evidently the Govern- 

 ment, which decides on our standards of weights and measures, should 

 take in charge the electrical standards, and possibly also the thermo- 

 metric standards. The formation of such a Bureau of Physical Stand- 

 ards will be brought to the attention of this Conference. 



Having given certain standards then, the measurement of currents 

 and current energy becomes easy. The amount of heat generated in a 

 wire of known resistance by a known current is also easily found from 

 the absolute system of electrical measurement. 



Besides the two so-called absolute systems of measurement of elec- 

 tricity and electric currents, we have also one based on the chemical 

 action of the current whose laws were discovered by Faraday. Know- 

 ing the electro-chemical equivalent of some substance, we are able to 

 measure the time integral of the current or the total quantity of the 

 current which has passed. 



The absolute measurement of magnetism is equally simple with that 

 of electricity, and it is a common observation to find the earth's magnetic 

 force. But Faraday has put in our hands a very simple method of meas- 

 uring a magnetic field, and to-day all are familiar with his beautiful 

 laws with respect to magnetic lines of force. We know the laws of 

 electro-magnetism, and just how many lines of force (better induction) 

 can pass through a piece of iron of given cross-section, and what is their 

 relative resistance when passing through air or iron. In fact, we have 

 all that is necessary for a complete theory of the dynamo-electric ma- 

 chine, and consequently we find that the latter agrees perfectly with 

 theory, and no fact has been observed with reference to it which could 

 not have been foreseen from theory by a person of proper intelligence. 



This part of electrical science, the measurement of electrical and mag- 

 netic quantities, is thus in a very forward state, based, as it is, on the 

 mathematical theory of the subject. But, in reality, this forms but a 

 very small portion of our science. Shall we be contented with a simple 

 measurement of that of which we know nothing? I think nobody would 

 care to stop at this point, although he might be forced to do so. The 

 mind of man is of a nobler cast, and seeks knowledge for itself alone. 

 We are not so base as to be honest because " Honesty is the best policy," 



