PROCEEDINGS OF THE REGENTS. 107 



DEPOSITION OF JOSEPH HENRY, IN THE CASE OF 

 MORSE vs. O'REILLY, 



TAKEN AT BOSTON, SEPTEMBER, 1849. 



[From the Record of the Supreme Court of the United States '\ 



1. Please state your place of residence and your occupation ; also, 

 what attention, if any, you ha/e given to the subjects of electricity, 

 magnetism, and electro-magnetism. 



Answer. — I begin tliis deposition with the express statement that I 

 do not voluntarily give my testimony ; but that I appear on legal 

 summons, and in submission to law. I am Secretary to the Smith- 

 sonian Institution^ established in the city of Washington, where I 

 now reside. The principal direction of the Institution is confided to 

 me. As I do not expect to return to Washington until some time in 

 October, I have been called upon to give my testimony here in Boston; 

 on this account I labor under the disadvantage of being obliged to 

 testily without my notes and papers, which are now in Washington. 



I commenced the study of electro-magnetism in 1827 ; and since then 

 have, at different times, [until] within the last two and a half years, 

 when I became Secietary of the Smithsonian Institution, made original 

 investigations in this and kindred branches of physical science. I know 

 no person in our country who has paid more attention to the study of 

 the principles of electro-magnetism than myself. 



2. Please give a general account of the progress of the science of 

 electro magnetism, as connected with telegraphic communication ; and 

 of any inventions or discoveries in electro-magnetism applicable to 

 the telegraph, made by yourself. 



Ansioer. — I consider an electromagnetic telegraph as one v^^hich 

 operates by the combined influence of electricity and magnetism. Prior 

 to tUe winter of 181'J-'20, no form of the electro-magnetic telegraph 

 was possible ; the scientific principles on which it is founded were 

 then unknown. The first fact of electro-magnetism was discovered 

 by Oersted, of Copenhagen, during that winter. It is this : A wire 

 being placed close above, or below, and parallel to a magnetic needle, 

 and a galvanic current being transmitted through the wire, the needle 

 will tend to place itself at right ana:les to it. This fact was widely 

 published, and the account was everywhere received with interest. 



The second fact of importance was discovered independently, and 

 about the same time, by Arago, at Paris, and Davy, at London. It 

 is this : During the transmission of a galvanic current through a wire 

 of copper, or any other metal, the wire exhibits magnetic properties, 

 attracting iron, but not copper filings, and having the power of in- 

 ducing permanent magnetism in steel needles. The next important 

 fact was discovered by Ampere, of Paris, one of the most sagacious 

 and successful cultivators of physical science in the present century. 

 It is this : Two parallel wires through which galvanic currents are 

 passing ia. the same direction, attract each olher ; but if the currents 



