ADVERTISEMENT. 



The present memoir was submitted by Lord Rayleigh and Profes- 

 sor Ramsay, in competition for one of the Hodgkins Fund prizes offered 

 by the Smithsonian Institution in a circular dated March 31, 1893. 

 The competition closed December 31, 1894; and on August 9, 1895, 

 the Award Committee, having completed its examination of the 218 

 papers submitted by contestants, granted the tirst prize, of $10,000, for 

 a treatise embodying some new and important discovery in regard to 

 the nature or properties of atmospheric air, to Lord Rayleigh, of 

 London, and Professor William Ramsay, of the University College, 

 London, for the discovery of " ARGON," a new element of the atmos- 

 phere. 



The Committee was composed of the following members : Doctor 

 S. P. Langley, Chairman, ex-officio ; Doctor (}. Brown Goode, ap- 

 pointed by the Secretaiy of the Smithsonian Institution ; Assistant 

 Sui'geon-General John S. Billings, U. S. A., by the President of the 

 National Academy of Sciences ; and Professor M. W. Harrington, by the 

 President of the American Association for the Advancement of Science. 

 The Foreign Advisory Committee, as first constituted, was represented 

 by Monsieur J. Janssen, Professor T. H. Huxley, and Professor von 

 Helmholtz ; and after the death of the latter, Doctor W. von Bezold 

 was added. 



The memoir is here presented in the form in which it was sub- 

 mitted to the Committee. A revised version, re-edited, with additional 

 matter, was, with the consent of the Smithsonian Institution, published 

 in the Philosophical Transactions. 



S. P. LANGLEY, 



SECRETARY. 



Washington City, May, 1896. 



