10 BELL SYSTEM TECHNICAL JOURNAL 



observed the effects of lightning flashes in place of sparks from a 

 Leyden jar, he found that he could get the lightning to magnetize 

 needles up to a distance as great as eight miles. This was about 

 1842. Here we have the earliest evidence of ether waves of the type 

 that the radio engineer emplo>s. But again the significance of 

 Henry's work was not recognized. This could only ha\e come after 

 much fuller investigation. Howe\er, it is instructive to reflect for a 

 moment on what might have been had Henry possessed the time and 

 facilities for carrying his work further. Needless to say, there is a 

 wide gulf between the wireless telegraph of today and its earliest 

 precursor with which Henry received an electromagnetic signal from 

 a lightning flash eight miles away, but it is wholly possible that, 

 had Henry not been called to other work, the world might have 

 possessed a wireless telegraph capable of sending messages over sub- 

 stantial distances many years before it did. 



Writing of Henry, Simon Xewcomb, the celebrated astronomer 

 said,^ "His scientific work is marked by acuteness in cross-examining 

 nature, a clear appreciation of the logic of science, and an enthusiasm 

 for truth without respect to its utilitarian results." A man of the 

 highest scientific ability, Henry spent the better part of his life as the 

 head of an institution dedicated to "the increase and diffusion of 

 knowledge among men." 



"The mantle of Franklin has fallen upon the shoulders of Henry," 

 wrote Sir David Brewster,^ the eminent English scientist, and it is 

 reported that Abraham Lincoln declared, when he became acquainted 

 with Henry after assuming the Presidency, "The Smithsonian In- 

 stitution must be a grand school if it produces such thinkers as Henry." 

 He was, in every way and in the best that the word implies, a scientist, 

 and the interest in scientific questions which dominated his life, 

 remained with him to the very end, — almost the last words to pass his 

 lips were whether the transit of the planet mercury had been suc- 

 cessfully observed. If we use the word "Dean" — so rich in academic 

 association — to stand at once for the greatest usefulness to one's 

 fellowmen as well as for the highest achievements in the field of 

 scholarship and research, for lifelong devotion to public service, for 

 breadth of view and tolerance regarding all questions, whether arising 

 in science or directly out of human relations, and as epitomizing all 

 that is best and highest in man's intellectual life, we may well call 

 Joseph Henry the Dean of American scientists. 



^ Biographical Memoir; National Acadenn- of Sciences, Apr. 21, 1880. 

 5 Biographical Memoir; prepared by Prof. Asa Gray in behalf of the Board of 

 Regents of the Smithsonian Institution. 



