32 THE DATA OF BIOLOGY. 



ences in molecular mobility, and probably in the rates of 

 molecular \'ibration. Each is combined with one of the others ; 

 but is capable of forming various combinations with the rest. 

 And they are severally in presence of a complex compound 

 into which they all enter, and which is ready to assimilate 

 with itself the new compound atoms that they form. Certain 

 of the ethereal waves falling on them when thus arranged, 

 there results a detachment of some of the combined atoms 

 and a union of the rest. And the conclusion suggested is, 

 that the induced vibrations among the various atoms as at 

 first arranged, are so incongruous as to produce instability ; 

 and to give collateral aflinities the power to work a re- 

 arrangement, which, though less stable under other conditions, 

 is more stable in the presence of these particular undula- 

 tions. There seems, indeed, no choice but to conceive 

 the matter thus. An atom united with one for which it has 

 a strong affinity, has to be transferred to another for which 

 it has a weaker affinity. This transfer implies motion. The 

 motion is given by the waves of a medium that is relatively 

 imponderable. No one wave of this imponderable medium 

 can give the requisite motion to this atom of ponderable 

 matter : especially as the atom is held by a positive force besides 

 its inertia. The motion required can hence be given only 

 by successive waves ; and that these may not destroy each 

 other's effects, it is needful that each shall strike the atom 

 just when it has completed that recoil produced by the impact 

 of previous ones. That is, the ethereal undulations must 

 coincide in rate with the oscillations of the atom, determined 

 by its inertia and the forces acting on it. It is also requisite 

 that the rate of oscillation of the atom to be detached, shall 

 differ from that of the atom with which it is united ; since 

 if the two oscillated in unison, the ethereal waves would not 

 tend to separate them. And, finally, the successive impacts 

 of the ethereal waves must be accumulated, until the resulting 

 oscillations have become so wide in their sweep as greatly to 

 weaken the cohesion of the united atoms, at the same time 



