53 6 The Smithsonian Institution 



Little of moment in reference to light or heat appeared 

 in the publications of the Institution for more than a decade 

 after this date, but in 1889 the great advance made during 

 that time found expression in a reprint of Oliver Lodge's 

 excellent lecture on the " Modern Theory of Light," which is 

 a clear and forcible exposition of the electro-magnetic theory 

 of Clerk Maxwell, and of its beautiful verification by the bril- 

 liant experiments of Hertz. It is here distinctly recognized 

 that light is only a specially-restricted group out of a great 

 variety of waves emitted by the sun ; the importance of devis- 

 ing some means for selective production is emphasized, and 

 it is plainly intimated that the direction along which the next 

 advance is to be made is likely to be " to beat about for some 

 mode of exciting and maintaining an electrical vibration of any 

 required degree of rapidity." A fit accompaniment of Lodge's 

 essay is an address of Professor Joseph Lovering before the 

 American Academy of Arts and Sciences at its meeting of 

 April 10, 1889, on the occasion of the presentation of the 

 Rumford medals to Professor A. A. Michelson. Naturally, 

 the address is a summary of Michelson's principal researches 

 in optics, beginning with his first determination of the veloc- 

 ity of light, by his modified Foucault method, at the Naval 

 Academy about 1878. Professor Lovering's address is not 

 only an account of Michelson's work (up to the date of its 

 delivery), but a very careful examination and presentation 

 of the most important experiments looking to the determina- 

 tion of light-velocity, either in a vacuum or in some transpar- 

 ent medium, together with a statement of the principal results, 

 especially as affecting the solar parallax, and with some refer- 

 ence to theories of light. It is a most admirable and useful 

 contribution. 



The first part of Volume xxix of the " Smithsonian Con- 

 tributions" is a memoir by Michelson " On the Application of 



