314 Tainter and Bell—Production of Sound by Light. 
continuously upon the receiver, but the intensity of which upon 
that receiver is subject to rapid changes corresponding to the 
changes in the vibratory movement of a particle of air during 
the transmission of a sound of definite quality through the 
atmosphere. The curve that would graphically represent the 
changes of light would be similar in shape to that representing 
the movements of the air. o not know whether this con- 
ception had been clearly realized by J. F. W., of Kew, or by 
Mr. Sargent, of Philadelphia, but to Mr. A. C. Brown, of 
London is undoubtedly due the honor of having distinctlyeand 
independently formulated the conception and of having devised 
apparatus, though of a crude nature, for carrying it into execu- 
tion. ry 
It is greatly due to the genius and perseverance of my friend, 
r. Sumner Tainter, of Watertown, Mass., that the problem of 
roducing and reproducing sound by the agency of light has at 
ast been successfully solved. For many months past we have 
been devoting bashes to the solution of this problem and I 
— reat pleasure in presenting to you to-night the results of 
our labors. 
Researches of Sumner Tainter and Alexander Graham Bell. 
The first point to which we devoted our attention was the 
reduction of the resistance of crystalline selenium within man- 
ageable limits. The resistance of selenium cells, employed by 
former experimenters, was measured in millions of ohms, and 
we do not know of any record of a selenium cell measuring 
less than 250,000 ohms in the dark. 
tween the brass and selenium has contributed to the low resist- 
ance of our cells by forming an intimate bond of union be- 
tween the selenium and brass. 
We have observed that melted selenium behaves to other 
substances as water to a greasy surface, and we are inclined to 
think that when selenium is used in connection with metals 
not chemically acted upon by it, the points of contact between 
the selenium and the metal offer a considerable amount of re- 
sistance to the passage of a galvanic current, and thus serve to 
increase the apparent resistance of the selenium. 
By using brass we have been enabled to construct a large 
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