NATIONAL ACADEMY OF SCIENCES. 



ing effect of violet light, and came to the conclusion that there was 

 no evidence whatever to sustain the opinions of these experi- 

 menters. In 1839 he puhlished a somewhat extended paper on the 

 use of a secondary wire as a measure of the relative tension of elec- 

 tric currents, describing the construction and use of a torsion gal- 

 vanometer and discussing a method of measuring electro-motive 

 force by the fall in the deflection when a wire of high resistance 

 was included in the circuit. He also considers in this paper tin- 

 relations of electro-motive force and of resistance to the current pro- 

 duced. In 1843 a paper on the law of the conducting power of 

 wires gave the results of his measurements made to solve the prob- 

 lem of transmitting electric impulses through long lengths of a 

 conductor, a research undertaken to aid his colleague, Professor 

 Morse, in perfecting his electro-magnetic telegraph. In this paper 

 the author shows that the diminution of the strength of an electric 

 current itself diminishes rapidly with increase of length in the wire, 

 and that generally the conducting effect of wires may be represented 

 by a logarithmic curve. 



The purely chemical researches published by Dr. Draper were 

 also few in number. Among these may be mentioned his memoirs 

 on the analysis of certain ancient coins and medals (which seemed 

 to him to prove the possibility of diffusion in solids) on micro-chem- 

 istry, on the constitution of the atmosphere, on respiration, on the 

 allotropism of chlorine, on the existence and effects of allotropism 

 in the constituent elements of living beings, on a singular property 

 of gun-cotton mixture, and on a new method for the determination 

 of urea. 



In 1K44, in a volume on the forces which produce the organiza- 

 tion of plants, Dr. Draper published, as an appendix, the scientific 

 memoirs of his which had appeared dp to that time bearing on this 



question, and in 1873, in a book entitled " Scientific .Memoirs," he 

 collected together the papers which he had published upon Radiant 

 Knergv and closely allied Subjects. 



During the later years of his life Professor Draper devoted his 

 time much more largely to literary than to scientific work. Upon 

 his appointment to the chair of physiology in 1850 he turned his 

 attention once more to physiological subjects, and in 1 866 he collected 

 together the matter which he had carefully elaborated in his class 

 lectures into his " Human Physiology, Statical and Dynamical." 

 This hook marked a new departure in the science of physiology, 



