424 PEOCEEDINGS OF THE AMERICAN ACADEMY 



Seven hundred and thirty-ninth Meeting. 



March 9, 1881. — Stated Meeting. 



The President m the chair. 



The President announced the death of Mr. George B. Em- 

 erson, the Senior Fellow of the Academy. 



The following papers were presented by title : — 



" General Properties of certain Partial Differential Equa- 

 tions similar to those of Hydrodynamics." By Thomas Craig. 



" Observations on Jupiter." By Leopold Trouvelot. 



Professor Cooke presented a bound volume of chemical 

 contributions from the laboratory of Harvard College. 



Seven hundred and fortieth Meeting. 



April 13, 1881. — Monthly Meeting. 



The President in the chair. 



The President called attention to the copies of the first 

 part of Volume XVI. of the Proceedings on the Table, which 

 were ready for distribution. 



The following papers were presented : — 



" On large Telescopes." By E. C. Pickering. 



" An Illustration of the Lines of Weakness in Cylinders." 

 By Robert H. -Richards. 



" On the Possible Causes of some Phenomena described 

 under the General Name of Zodiacal Light." By Arthur 

 Searle. 



" Studies in Metrology." First article. By William A. 

 Rogers. 



The following papers were presented by title : — 



" Photometric Measurements made at the Harvard College 

 Observatory of the Variable Stars /S Persei and DM. 81"25." 

 B}^ Edward C. Pickering. 



" On Osmyl Ditetramine." By Wolcott Gibbs. 



