148 THE HENRY, 



of the horsepower, shoiihl be given to the new unit. The iratt is also 

 simply rehited to the ceutiuieter-grani-second unit of power, and is 

 defined as work done at the rate of 1 joule per second. The rate of 

 expenditure of energy in the glow lamp already quoted would be 03 

 watts. One horsepower is equal to about 74(5 watts. When Watt came 

 to (Jlasgow he was i)revented from securing work as a mathematical- 

 iustrumeut maker by the action of the trades unions of that time. For- 

 tunately, the door of the great university was opened to him, and there, 

 in the capacity of maker and repairer of instruments and apparatus, his 

 genius received its first encouragement and development. Altliough 

 by education and training rather a i)ractical than a scientific man, he 

 possessed the true scientific insight to an unusual degree, and is emi- 

 nently worthy of the associates among whom he is here placed. 



The foregoing somewhat lengthy and detailed account of the history 

 and origin of seven of the eight units of electrical measure recently 

 adopted by the international congress has been thought desirable, if 

 not necessary, to a full understanding of their relation, historically and 

 otherwise, to the eighth and last, the name of which is the title of this 

 article. 



Most Americans are more or less familiar with the name and fame of 

 Joseph Henry. To many he is known, however, only as the first Secre- 

 tary of the Smithsonian Institution. Giving a broad and liberal inter- 

 pretation to the somewhat vague language of the will of its fi)un(l(n', 

 Henry molded the institutioii, while it was yet plastic and without 

 traditions, into the form in which it has since essentially existed. He 

 directed its energies into channels very different Irom those that would 

 have been selected by one whose horizon was narrower than his, and, 

 by steadfastly adhering to his own splendid conception of its functions 

 as an instrument "for the increase and diffusion of knowledgeamong 

 men," he made of it an organization which is, and nuist i)erpetually be, a 

 benefit and a blessing to all mankind. Others, a smaller number, think 

 of him as the youthful professor of mathematics and natural philos- 

 opliy in tlie Albany Academy, where, in si)ite of the seven solid hours 

 of teaching each day required of him, he found time to begin the series 

 of researches in electro-magnetism winch in later years were to make 

 him famous. Here, and at the College of New Jersey, at I'rinceton, to 

 which he was shortly transferred, he is seen pursuing these researches 

 with that clearness of* vision which characterized his work along all 

 lines, and with an extraordinary fruitfulness which goes only with great 

 intellectual activity accompanied by unfiiuching honesty of purpose. 

 For fourteen years at Princeton, where he discharged the duties of 

 professor of natural philosophy with signal success, he continued his 

 original investigations, which, while touching many of the more impor- 

 tant branches of i)hysical science, were in general related to his favorite 

 subjects, electricity and magnetism. At the end of this period, when 

 at the very highest development of his powers, he was transferred to 



