220 PROCEEDINGS OF THE AMERICAN ACADEMY 



rings. Of these the light takes advantage for producing a symmetrical 

 effect, just as in the formation of the rainbow it selects those individual 

 drops of moisture which serve its purpose, while the remainder of the 

 drops are inoperative. A piece of very delicately ground glass accom- 

 plishes the same result. In the atmosphere, the place of the lycopodium 

 powder is filled by the particles of moisture existing in the vesicular state ; 

 and the smaller these particles the larger will be the diameters of the 

 corona? which they produce. In this way these particles are proved to 

 vary between the .001 and the .002 of one inch in diameter.* 



Corona? indicate the presence of the cumulus cloud ; but halos imply 

 the cirrus cloud, floating at great heights, and within the region of per- 

 petual congelation. For halos are seen even in the summer and in the 

 tropics. By revealing the incipient gathering of the cirrus cloud, they 

 may foretell the approach of a storm. 



Six hundred and twenty-first Meeting. 



May 24, 1870. — Annual Meeting. 



The President in the chair. 



The Corresponding Secretary communicated letters relative 

 to exchanges, and read a report from the Council proposing 

 nominations for Foreign Honorary and Associate Member- 

 ship. 



The Treasurer presented his report for the past year, and 

 read a synopsis of it. The report was received, to be entered 

 on the records. 



Professor Lovering reported from the Committee of Publica- 

 tion its expenditures for the past two years. The report was 

 accepted. 



Professor F. H. Storer reported for the Committee on the 

 Library on the condition of the Library. 



Professor Winlock reported, from the Rumford Committee, 

 the completion of Vol. I. of Count Rumford's works, and rec- 

 ommendations of this committee for appropriations from the 

 Rumford Fund. This report was accepted, and in accordance 

 with its recommendations the following votes were passed : — 



* Kaemtz's Complete Course of Meteorology, p. 111. 



