124 BARUS— THE TRANSPIRATION OF AIR. [April 21, 



6.9 X lO"'^ ^. „ 



77 = -r^ „- = 366 X IO~\ 



' 67rx IO~^ ^ 



In other words the molecule moves through a liquid about twice as 

 viscous as the air itself. 



9. Conclusion. — The above data are subject to the different hypoth- 

 eses stated ; but it has been shown that the results may be obtained 

 by the method described free from ulterior assumption. It seems 

 to me that detailed investigations of the above kind carried on with 

 reference to both the chemical and the physical properties of the 

 liquid, i. e., with different liquids and different gases at different 

 temperatures and pressures, cannot but lead to results of importance 

 bearing on the molecular physics involved. Hence experiments of 

 this kind have been begun in this laboratory and I hope to report the 

 results from time to time. Obviously in a doubly closed water ma- 

 nometer (U-tube) the unequal heads of the two columns of liquid 

 must in a way similar to the above vanish in the lapse of time. This 

 method seems particularly well adapted to obviate convection. 

 Finally hydrogen shows a measurable amount of molecular tran- 

 spiration in the daily march of results already obtained, and with this 

 gas a new and direct method for obtaining the molecular diameter 

 is foreshadowed. 



Brown University, 

 Providence, R. I. 



