262 



EDISON, THOMAS A. 



the Boston office. Here he fitted up a small 

 shop and continued his experiments. In 1870 

 he went to Kochester, N. Y., to test between 

 that city and Boston the practicability of his 

 invention of the duplex telegraph ; but the ex- 

 periment did not prove successful. He next 

 entered the service of the Gold Indicator Com- 

 pany in New York, of which he was soon 

 made superintendent. Here he introduced 

 improved apparatus, and invented the gold 

 printer and other devices. About this time 

 he established in Newark, N. J., a factory for 

 the purpose of making the machines and appa- 

 ratus which he had invented. About three 

 hundred men were employed in this establish- 

 ment, but the demands made on his time by 

 the business left him so little opportunity for 

 pursuing his experiments and making inven- 

 tions that he abandoned the enterprise, and in 

 1876 established a shop for experimenting at 

 Menlo Park, a small station on the Pennsyl- 

 vania Railroad, about twenty-four miles from 

 New York. This shop is a two-story white 

 frame building, 100 by 25 feet, situated on the 

 crown of a knoll. It is well equipped with 

 machinery, apparatus, etc., and has telegraphic 

 communication with the wires of the Asso- 

 ciated Press. 



Although Mr. Edison is still a very young 

 man, his inventions are exceedingly numerous. 

 He has taken out upward of 150 patents, but 

 few of which, however, are of real value. The 

 most wonderful, as well as the most famous, of 

 his inventions are the carbon telephone and 

 the phonograph, which were described in the 

 "Annual Cyclopaedia" for 1877. Among his 

 other important telephonic and acoustic inven- 

 tions are the microphone, the micro-tasimeter, 

 the aerophone, the megaphone, and the pho- 

 nometer. By the micro-tasimeter, or measurer 

 of infinitesimal pressure, small variations of 

 temperature may be detected, and the relative 

 expansion of substances due to a rise of tem- 

 perature may be ascertained. It was success- 

 fully used during the total eclipse of the sun 

 in July, 1878, to demonstrate the existence of 

 heat in the corona. The aerophone, which has 

 not yet been perfected, is a contrivance for 

 amplifying sound. Its purpose is to increase 

 the loudness of words spoken without impair- 

 ing the distinctness of the articulation. The 

 megaphone is as remarkable for its simplicity 

 as for what may be accomplished by it. With 

 no other apparatus than a few paper funnels, 

 a conversation may be carried on through a 

 distance of from one and a half to two miles. 

 Mr. Edison is now experimenting with a view 

 of producing an apparatus on this principle for 

 the benefit of the deaf. The phonometer is an 

 instrument for measuring the mechanical force 

 of sound-waves produced by the human voice. 

 Mr. Edison has obtained a patent for an elec- 

 tric light, and is still making experiments which 

 are expected to lead to important results. It. 

 has been reported that he has discovered a 

 means for subdividing the electric current in- 



definitely, so as to make the electric light prac- 

 ticable for small areas. He has also invented 

 an harmonic engine, with which he proposes to 

 use compressed air as a motor for propelling 

 sewing-machines and other light machinery. 

 It is said to be in advance of other electric en- 

 gines, and that through its agency electricity 

 may yet be utilized as a motive power. Among 

 his other important inventions are the electric 

 pen for multiplying copies of letters or draw- 

 ings, and the quadruplex system of telegraphy, 

 by means of which four communications may 

 be sent in opposite directions over one wire at 

 the same time. This is extensively used by the 

 Western Union Telegraph Company and other 

 lines. 



In a work on "The Speaking Telephone, 

 Electric Light, and other recent Electrical In- 

 ventions," just published by D. Appleton & Co., 

 the author, Mr. George B. Prescott, gives the 

 following interesting analysis of Mr. Edison's 

 genius : 



The great number and variety of subjects to which 

 Mr: Edison has given his attention is scarcely less 

 surprising than the marked success with which his la- 

 bors have been crowned. Electricity alone, although 

 receiving the most attention, has furnished but a 

 single field for the display of his versatile powers. 

 His path has been through extended portions of 

 physics and chemistry, and is clearly marked by 

 characteristic inventions in these vast domains. Not 

 less remarkable, too, is the originality of his ideas. 

 Many of his inventions, to be sure, are but improve- 

 ments upon the methods of previous investigators, 

 but many others have been produced while pursuing 

 a line quite outside of that followed by these earlier 

 pioneers, and in some instances^ also, without any 

 knowledge whatever that the subjects had been con- 

 sidered by them. As illustrations of this faculty for 

 original research, we have only to mention his chem- 

 ical system of telegraphy, the electro-motograph, the 

 system of double transmission in the same direction, 

 the quadruplex telegraph, and the carbon telephone, 

 in all of which this faculty is conspicuously displayed. 

 Stark, it is true, invented a method of simultaneous 

 transmission in the same direction in 1855, find at 

 that time had the idea of quadruplex telegraphy in 

 mind. Kramer shortly afterward improved upon 

 this method, and subsequently the idea was also 

 taken up by Bernstein, Schroder, Wartman, and oth- 

 ers. But all, with only slight modifications, followed 

 a similar line of investigations, and in the end only 

 succeeded in working imperfectly upon lines of very 

 short length. Mr. Edison, however, instead of em- 

 ploying relays or their equivalent for accomplishing 

 this object, as his predecessors had done, confined 

 himself solely to two, one for receiving each transmis- 

 sion. He also avoided, without employing previous- 

 ly used methods, but using^ one quite original with 

 himself, the mutilation of signals which a change in 

 the polarity of the battery current produced ; and by 

 the addition of a simple device, never thought of by 

 previous experimenters, and which was made direct- 

 ly operative by the line current, and independently 

 of the relays themselves, succeeded in completely 

 solving the question of multiple telegraphy for all 

 cases : making the quadruplex, in consequence, a 

 practical apparatus for the longest circuits. Similar y 

 original and beneficial results attended his labors in 

 the field of chemical telegraphy. With this system, 

 after carefully studying the problems involved, he 

 succeeded in vastly improving the speed of transmis- 

 sion for circuits of any length whatever. 



His originality is also shown to good advantage 

 in the invention of the carbon telephone. During 



