THE 

 LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[FIFTH SERIES.] 



NOVEMBER 1885. 



XLVII. The Luminiferous JEther. By De Volson Wood, 

 C.E., M.A.j Professor of Mechanical Engineering in Stevens 

 Institute of Technology, Hoboken, N.J* 



HHWO properties of the luminiferous aether appear to be 

 JL known and measurable with a high degree of accuracy. 

 One is its ability to transmit light at the rate of 186,300 miles 

 per second f, and the other its ability to transmit from the 

 sun to the earth a definite amount of heat-energy. 



In regard to the latter, Herschel found, from a series of 

 experiments, that the direct heat of the sun, received on a 

 body at the earth capable of absorbing and retaining it, is 

 competent to melt an inch in thickness of ice every two hours 

 and thirteen minutes J. This is equivalent to nearly 71 foot- 

 pounds of energy per second. 



In 1838 M. Pouillet found that the heat- energy transmitted 

 from the sun to the earth would, if none were absorbed by 

 our atmosphere, raise 1*76 gramme of water 1° C. in one 

 minute on each square centimetre of the earth normally 

 exposed to the rays of the sun§. 



This is equivalent to 83*5 foot-pounds of energy per second, 



* Communicated by the Author. 



t Professor Michelson found the velocity of light to be 289,740 metres 

 per second in air, and 299,828 metres in a vacuum, giving- an index of 

 refraction of 1,000,265. Journ. of Arts and Science, 1879, vol. xviii. 

 p. 390. 



X ' Familiar Lectures on Scientific Subjects,' by Sir John Herschel, 

 p. 65. 



§ Comptes JRendus, 1838, torn. vii. pp. 24-26. 



Phil. Mag. S. 5. Vol. 20. No. 126. Nov. 1885. 2 F 



