248 PROCEEDINGS OF THE AMERICAN ACADEMY 



This investigation constituted the thesis work of Mr. Gleason, and 

 the experimental work was very largely conducted by him alone. 

 The expense attending the work has been met in part by an appro- 

 priation from the Rumford Fund of the American Academy of Arts 

 and Sciences, in part by the Institute. 



Rogers Laboratory of Phtsics, 

 August, 1887. 



