Physics 537 



Interference Methods to Spectroscopic Measurements," pub- 

 lished in 1892, an investigation which had been aided by a 

 grant from the Institution. In this work Professor Michel- 

 son made use of his well-known interference method, which 

 proved to be very powerful in attacking problems usually 

 given to the grating and prism. He found it "easy to sepa- 

 rate lines whose distance apart is only a thousandth of that 

 between D x D 2 , and even to determine the distribution of light 

 in the separate components," and whenever the width of the 

 lines themselves is less than their distance apart there is no 

 limit to their resolvability. 



The Smithsonian Report for 1893 includes a short, but 

 thoughtful, paper on the " Luminiferous Ether," by Sir 

 George G. Stokes, in which the difficulties of the problem 

 are well put and some hints given as to their possible 

 solution. 



No account of the relation of the Smithsonian Institution to 

 the increase and diffusion of our knowledge of radiant energy 

 would be approximately complete without reference to the 

 splendid investigations of the present Secretary, Doctor S. P. 

 Langley. Begun originally by him in the Allegheny Ob- 

 servatory, he has not allowed the burden of administrative 

 duties to prevent their being continued in the new Astro- 

 physical Observatory, where they are still in progress. The 

 remarkable results of his use of the bolometer in the study of 

 the infra-red end of the solar spectrum have revolutionized 

 our ideas of the radiations from the sun. A more complete 

 account of this work will be found elsewhere in this volume. 



SOUND 



ALTHOUGH the number of papers published on acoustics is 

 not large, some of them represent extremely important work. 



35 



