790 THE POPULAR SCIENCE MONTHLY. 



imagination ; for, as has been shown by the molecular physicists, its 

 dimensions are so inconceivably minute as to far transcend the mech- 

 anism of vision, since it would require at least twenty thousand in a 

 line to occupy a medium wave-length of light. 



But could the molecule even be magnified to visible and tangible 

 dimensions, with a new light to view it by, it could not by any means 

 be rendered visible, either in whole or in its parts, on account of its 

 incessant and marvelous activity, both interior and translatory. That 

 the gas-molecule did not get its interior motion from the heat of dis- 

 sociation is certain, for, on being allowed to recombine, it yields up 

 its translatory activity, and with it as many degrees of temperature 

 as disappeared in accomplishing the dissociation. No means of wholly 

 destroying the interior motion are known. By some savants it is re- 

 garded as primordial and ultimate. It is highly probable, for reasons 

 which Mr. Taylor has pointed out,* that the hydrogen-molecule con- 

 tains at least four pairs of revolving elements, revolving in different 

 pei'iods, and in contractile orbits, but with periods as undeviating as 

 those of the moons of Mars. It is in the revolving or vibratory con- 

 stituent of this couple that we seek the final essence of matter, though 

 perhaps not to arrive at it. We must not endow it with gratuitous 

 attributes, but it is surely an entity of some kind, having, in the first 

 place, persistent and regulated motion. Secondly, it has inertia, or 

 mass the property of conserving vis viva. Thirdly, it has some bond 

 with its fellow by which the motions of both are modified by a con- 

 stant stress according to a definite law of distance, and this, following 

 Newton, we call attraction. Fourthly, it has the complex property of 

 interchange of momenta, accompanied by that of conserving and com- 

 pounding motion by angular rebound upon an indefinitely near ap- 

 proach, which we name resilience, or repulsion. Dimension it need 

 not have, nor any other property of masses ; but nobody has ever yet 

 succeeded in getting rid of the above four. This is not universally 

 recognized, however, and the recent controversies of philosophy are 

 owing to the strenuous attempts to reduce the number, especially of 

 those called occult. Motion being in our ordinary experience a result, 

 has not been so classified, and indeed has only more recently been 

 recognized as primary. It is with causes that philosophy seeks to 

 deal, and in our experience causation is a chain. Primordial motion, 

 however, is as occult and mysterious as static force. 



One class of philosophers, recognizing the self -existent character of 

 motion, has exhausted ingenuity in the effort to deduce attraction 

 from it, of course wittingly or unwittingly bringing into co-operation 

 the occult force inertia, to obtain vis viva. Another class would de- 

 duce all motion from attraction : while in the attempt to contrive a 

 mechanism to explain resiliency the most incomprehensible of all in a 

 body without parts immensely greater complications and difficulties 



* Annual Address before the Philosophical Society of Washington, 1882, p. 24. 



