74 FRAGMENTS OF SCIENCE 



It is thus proved that in the quantity of ethereal mo» 

 tdon which it is competent to take up we have a practical 

 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 im- 

 portance, is not competent to account for the whole of the 

 ot)served facts. The ether, as far as we know, accepts 

 vibrations of all periods with the same readiness. To it 

 the oscillations of an atom of free oxjgen are just as ac- 

 ceptable 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 referred 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 oxy- 

 gen, it may be because the group is able to lay a vastly 

 more powerful hold upon the ether than the single atoms 

 can. Another, and probably very potent cause of the dif- 

 ference may be, that the vibrations, being those of the con- 

 stituent atoms of the molecule,* are generated in highly 

 condensed ether, which acts like condensed air upon sound. 

 But, whatever may be the fate of these attempts to visual- 

 ize 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 con- 

 dition of the ether within the molecules, by which the ex- 

 ^mal ether is disturbed. 



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



