THE TELEPHONOGRAPH. a 



By William J. Hammer. b 



The telephonograph, or, :is it is sometimes called, the "tele- 

 graphone," the "microphonograph," and the ""magnetophonograph," 

 is the invention of a Danish electrical engineer, Mr. Waldemar Poul- 

 sen, of Copenhagen, Denmark. This beautiful and ingenious instru- 

 ment was considered by all those who had the opportunity of seeing 

 and testing it at the recent Paris Exposition to be the most interesting 

 scientific novelty there exhibited. In principle it is so simple it seems 

 remarkable that with all our familiarity with electricity and magnet- 

 ism such an invention should not have been made long ago. The 

 apparatus, which is indicated in figure 1 (PL I), consists of a drum of 

 brass about 1H inches in length by 5£ inches in diameter. On this 

 drum, which is revolved by means of an electric motor, is wound 225 

 turns of steel piano wire, of a diameter of about 1 mm. Sup- 

 ported above this wire, and in contact therewith, is a tiny magnet, 

 such as are shown in figure 2, letters A and C, which are almost nat- 

 ural size. This magnet is attached to a brass support, mounted 

 on a shaft, so that as the drum or cylinder carrying the steel wire 

 revolves, the magnet is caused to move from right to left across the 

 drum, being guided by a grooved finger resting upon the steel wire 

 on the drum, each turn in the steel wire passing consecutively before 

 the poles of the tiny magnet. On reaching the end of the cylinder, 



a Washington, D. C. , December 6, 1901. 

 My Dear Sir: I have been much interested in the Poulsen telegraphone, which I 

 spoke of to yon in Paris, and 1 do not know of anything in the work of recent years 

 in electricity more worthy of being presented to the readers of the Smithsonian 

 report. Mr. Hammer's article, which you show me, seems to be a very satisfactory 

 popular exposition of it. 

 Very truly yours, 



Alexander Graham Bell. 

 Mr. S. P. Langley, 



Secretary of the Smithsonian Institution, 



Washington, D. C. 



h Presented at the 151st meeting of the American Institute of Electrical Engineers, 

 New York, February 28th, 1901. Reprinted, by permission, from Vol. XVIII of the 

 Transactions of the Institute. 



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