1891.] NEW YORK ACADEMY OF SCIENCES. 105 



To-night I wish to show you the most intense light known to 

 science, and its adaptation for purposes of projection, which is 

 only awaiting a general adoption for use in the optical lantern. 

 There is no obstacle to prevent its use, and it recommends itself 

 upon its merits to all workers in this direction. . . . 



(A brief history of the electric light follows.) The electric 

 light is the outgrowth of the experiments of Sir Humphry 

 Davy, made at the Koyal Institution, London, in 1801, when 

 he made use of 2,000 cells with which he decomposed sodic 

 and potassic hydrates and separated their metallic bases. 



These experiments were repeated and extended, and by using 

 charcoal points as terminals an intense and dazzling light was 

 produced, to which the name voltaic arc was given. 



The arc light, then produced from a battery, brilliant as it is, 

 was confined to the lecture-room or au occasional outdoor dis- 

 play. The fatal difficulty was the labor and cost of the elec- 

 trical energy, and it was not until the discovery of induced cur- 

 rents by Faraday that this obstacle was removed. The light 

 produced by the voltaic arc received no practical application 

 until 1844, at which time it was regarded as an interesting 

 lecture experiment, requiring the use of large and powerful 

 batteries, together with suffocating fumes, and labor for a 

 possible use of one or two hours. In 1844 Leon Foucault made 

 use of the Bunsen battery, and replaced the charcoal points used 

 by Davy with pieces of compact gas carbon. He also constructed 

 a lamp worked by hand, and the first use made of it was in tak- 

 ing daguerreotypes and lighting La Place de la Concorde at 

 Paris. 



It required the combined labors of ISTollet, Van Maldern, 

 Holmes, Wilde, Ladd, and Siemens to produce by mechanical 

 means, direct from motion, a supply of electrical energy that 

 would equal that produced from the battery. Even as late as 

 1870 this did not seem possible, for the best dynamos at that 

 time yielded only a small amount of electrical energy. 



In 1871 Gramme presented to the Academy of Science the 

 description of a form of magneto-electric machine possessing 

 new features, which were so remarkable as to astonish the world. 

 •Gramme conceived the idea of using a ring, and rotating this 

 between the poles of a magnet in such a way as to prevent re- 

 versals in the armature. Many ridiculed this idea. Neverthe- 

 less it produced in practice a machine that yielded large currents 

 at much less cost, and laid the foundation of our present system 

 of electric lighting. 



From whatever source the electricity is supplied, it is neces- 

 sary that it meet with some resistance to produce light, and this 



