V THE HENRY. 143 



it had unanimously agreed upon names and definitions for eiglit units 

 of ele(;trical measure, all that are thought to be necessary or desirable 

 at the present time, and no more arc likely to receive consideration for 

 some years to come. The chamber passed a resolution recommending 

 the otiticial and authoritative adoption of these units by the several 

 nations represented in the congress. They are all primarily derived 

 from the fundamental units of length, mass, and time of the metric 

 system, and are thus inter-related in the simplest possible manner. 



As already stated, it is not the i)urpose of this article to discuss the 

 conclusions reached by the chamber of delegates from a scientific stand- 

 point, but it will be desirable to name the units selected, and explain 

 in a general way their technical significance. In the order of their 

 adoption by the chamber they are as follows : The ohm, the ampere, the 

 volt, the coulomb, the farad, the joule, the watt, the henry. 



These names are derived from those of distinguished scientific men, 

 all worthy of a place in the front rank of modern ])hysicists, and many 

 of whom have made signal contributions to the advancement of the 

 science of electricity and electrical measurement. 



The ohm is the unit of resistance. It has been applied by common 

 consent for many years to one of the three most important characteris- 

 tics of a circuit conveying a current of electricity. Its use perpetuates 

 the fame of the author of a simple and beautiful law by which these 

 three fundamental elements are bound together. 



G. S. Olim was born in Bavaria in 17<S1, and educated at the Univer- 

 sity of Erlangen. In 181^7 he published a pami^hlet. The Galvanic 

 Circuit Investigated Mathematically, containing what has since been 

 universally known as ''Ohm's law," and which has had a most impor 

 taut and far-reaching influence on the development of the theory and 

 applications of r'lectricity. Guided by Fourier's classic investigation 

 of the How of heat in conductors, Ohm, from purely theoretical consid- 

 erations, arrived at the conclusion that in any circuit through which 

 an electric current was made to pass the strength of the current — that 

 is, the quantity of electricity passing a given section of a conductor in 

 one second of time — was directly ])roportional to the elec^tro-motive 

 force (often called the "electrical pressure"), and inversely proportional 

 to its resistance. The imi)ortance of Ohm's investigations was not 

 recognized at the time of their publication. Had the full meaning of his 

 conclusions been understood by those who shortly afterwards engaged 

 in the develoi^ment of the electro-magnetic telegraph, they would have 

 been guided to results which were reached oidy after nuich loss of time 

 and money and many vexatious and discouraging disappointments. 

 In ISliS Barlow, in England, had declared the imi)ossibility of the 

 telegraph, owing to the difticulty of sending electric currents through 

 long wires. It was noted that the strength of the current diminished 

 greatly when the length of the conductor was increased, and this was 

 properly assumed to be due to the greater resistance offered to the 



