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POPULAR SCIENCE MONTHLY. 



2. A prize of two thousand dollars for the most satisfactory 

 essay upon (a) the known properties of atmospheric air, consid- 

 ered in their relationships to research in every department of 

 natural science, and the importance of a study of the atmosphere, 

 considered in view of these relationships ; (b) the proper direction 

 of future research, in connection with the imperfections of our 

 knowledge of atmospheric air, and of the connections of that 

 knowledge with other sciences. 



3. A prize of one thousand dollars for the best popular treatise 

 upon atmospheric air, its properties and relationships (including 



those to hygiene, physical 

 and mental). This essay 

 need not exceed twenty 

 thousand words in length ; 

 it should be written in sim- 

 ple language, and be suit- 

 able for publication for 

 popular instruction. 



4. The Hodgkins medal 

 of the Smithsonian Insti- 

 tution will be awarded an- 

 nually, or biennially, for 

 important contributions to 

 our knowledge of the na- 

 ture and properties of at- 

 mospheric air, or for prac- 

 tical applications of our ex- 

 isting knowledge of them 

 to the welfare of mankind. 

 The medal will be of gold, 

 with a duplicate in silver 

 or bronze. 



The treatises may be 

 written in English, French, 

 German, or Italian, and 

 should be sent to the Secre- 

 tary of the Smithsonian 

 Institution before July 1, 



1894 ; except those in competition for the first prize, which may 

 be delayed until December 31, 1894. The time was subsequently 

 extended to December 31, 1894, for all prizes. 



Provision was made in the circular for a committee of award, 

 for extending the dates above named, and for modifying the con- 

 ditions prescribed. The circular also stated that special grants of 

 money will probably be made to specialists engaged in original 

 investigation upon atmospheric air and its properties. 



COMPARATIVE AREAS OF ZOOLOGICAL PARKS. 



