ADVERTISEMENT. 



The present memoir is a translation of the treatise entitled "Sur 

 I'actinometrie atmospherique et sur la constitution actinique de I'atmos- 

 phere," submitted by Professor Emile Duclaux, in competition for one of 

 the Hodgkins Fund prizes offered by the Smithsonian Institution in a 

 circular dated Marct 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 

 honorable mention to Professor Duclaux and recommended his memoir 

 for publication by the Smithsonian Institution. 



The Committee was composed of the following members : the Secre- 

 tary of the Institution S. P. Langley, Chairman, ex-officio ; Doctor G. 

 Brown Goode, appointed by the Secretary of the Smithsonian Institu- 

 tion ; Assistant Surgeon-General John S. Billings, appointed by the 

 President of the National Academy of Sciences ; and Professor M. W. 

 Harrington, appointed 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 Helmboltz; and after the death of the latter. 

 Doctor W. von Bezold was added. 



S. P. LANGLEY, 



SECBETARY. 



Washington City, May, 1896. 



