184 Prof. Tyndall on the Absorption and 



Table IV. — Mixture of Ether Vapour and Air. 



Unit- 



measure ^th of a cubic inch. 





Absorption. 





i — ' i 



Measures. 



Observed. Calculated. 



1 



4-5 4-5 



2 



9-2 9-0 



3 



135 13-5 



4 



18-0 18-0 



5 



228 23-5 



6 



27-0 27-0 



7 



31-8 31-5 



8 



36-0 36-0 



9 



397 40-0 



10 



45-0 45-0 



20 



810 900 



21 



828 95-0 



22 



840 99-0 



23 



87-0 104-0 



24 



88-0 108-0 



25 



90-0 1130 



26 



930 117-0 



27 



94-0 1220 



28 



95-0 126-0 



29 



98-0 131-0 



30 



100-0 1350 



Up to the 10th measure we find that density and absorption 

 augment in precisely the same ratio. While the former varies 

 from 1 to 10, the latter varies from 4*5 to 45. At the 20th 

 measure, however, a deviation from proportionality is apparent, 

 and the divergence gradually augments from 20 to 30. In fact 

 20 measures tell upon the rays capable of being absorbed, — the 

 quantity destroyed becoming so considerable, that every addi- 

 tional measure encounters a smaller number of such rays, and 

 hence produces a diminished effect. 



With ether vapour alone, the results recorded in the following- 

 Table were obtained. Wishing to determine the absorption ex- 

 ercised by vapour of very low tension, the capacity of the unit- 

 measure was reduced to y^th of a cubic inch. 



