ADVERTISEMENT. 



The present memoir is the result of a series of investigations by 

 Doctors O. Liimmer and K. Pringsheim, of CharlottenbiU'g, Germany, 

 aided by a grant from the Hodgkins Fund of the Smithsonian In- 

 stitution. 



After a period of notable advance tiii^ kinetic theory of gases 

 seems to have fallen into teni[)orary abeyance, possibly from a funda- 

 mentally imperfect understanding of their behavior. 



Pi'ogress in knowledge of this fundamental uatui-e of gases may 

 reasonably be looked for from interpretative researches on their ther- 

 mal capacity, and the following paper may be regai'ded as a step in 

 this direction. 



Aside from its exceptional impoi'tance in thermodynamics, the 

 specific heat ratio is of intei'est as affording a clue to the character 

 of the molecule; and Messrs. Lummer and Pringsheim, using a new 

 method, apj)ear for the fii'st time to have reached coincident results on 

 the incoeicible gases examined. 



In accordance with the rule adopted l)y the Institution, the work 

 has been i-eferi-ed foi- examination to a Committee consisting of Pro- 

 fessor Doctor Friedr. Kohlrausch, President of the Physikalisch-Tech- 

 nische Reichsanstalt of Beilin, Doctor Carl Barns of Brown University, 

 Providence, R. I., and Pjofessor F. AV. Clarke of Washington City ; 

 and, havintr been recommended for publication, the orioinal memoir, 

 submitted to the Institution in Gei-man by Doctoi's Lummer and Pring- 

 sheim, is herewith presented, translated into English by Doctor Barus, 

 in the series of Contributions to Knowledge. 



S. P. LANGLEY, 



SECRET'ABY. 



Smithsonian Institution, 



Washington, June, 1898. 



