68 FKAGMENTS OF SCIENCE. 



Percentage of Carbonic Acid in the Human Breath. 



Chemical analysis Physical analysis 



4-66 4-56 



5-33 5-22 



It is thus proved that in the quantity of aethereal 

 motion which it is competent to take up, we have a prac- 

 tical measure of the carbonic acid of the breath, and 

 hence of the combustion going on in the human lungs. 



Still this question of period, though of the utmost 

 importance, is not competent to account for the whole 

 of the observed facts. The aether, as far as we know, 

 accepts vibrations of all periods with the same readiness. 

 To it the oscillations of an atom of free oxygen are just 

 as acceptable as those of the atoms in a molecule of 

 olefiant gas ; that the vibrating oxygen then stands so 

 far below the olefiant gas in radiant power must be re- 

 ferred not to period, but to some other peculiarity. The 

 atomic group which constitutes the molecule of olefiant 

 gas, produces many thousand times the disturbance 

 caused by the oxygen, it may be because the group is 

 able to lay a vastly more powerful hold upon the aether 

 than the single atoms can. Another, and probably very 

 potent cause of the difference may be, that the vibra- 

 tions, being those of the constituent atoms of the mole- 

 eule, 1 are generated in highly condensed aether, which 

 acts like condensed air upon sound. But whatever may 

 be the fate of these attempts to visualise the physics of 

 the process, it will still remain true, that to account for 

 the phenomena of radiation and absorption we must 

 take into consideration the shape, size, and condition of 

 the aether within the molecules, by which the external 

 aether is disturbed. 



1 See ' Physical Considerations,' Art. iv. p. 102. 



