320 THE POPULAR SCIENCE MONTHLY. 



One of the most interesting investigations in molecular mechanics 

 was published by Helmholtz in 1858. It is a mathematical discussion 

 of what he calls ring-vortices, in a perfect, frictionless fluid. Helm- 

 holtz has demonstrated that such vortices possess a perpetuity and an 

 inviolability once thought to be realized only by the eternal atoms. 

 The ring-vortices may hustle one another, and pass through endless 

 transformations ; but they cannot be broken or stopped. Thomson 

 seized upon them as the impersonation of the indestructible but plas- 

 tic molecule which he was looking for, to satisfy the present condition 

 of physical science. The element of the new physics is not an atom 

 or a congeries of atoms, but a whirling vapor. The molecules of the 

 same substance have one invariable and unchangeable mass ; they are 

 all tuned to one standard pitch, and, when incandescent, emit the 

 same kind of light. The music of the spheres has left the heavens 

 and condescended to the rhythmic molecules. There is here no birth, 

 or death, or variation of species. If other masses than the precise 

 ones which represent the elements have been eliminated, where, asks 

 Maxwell, have they gone ? The spectroscope does not show them in 

 the stars or nebulae. The hydrogen and sodium of remotest space are 

 in unison with the hydrogen and sodium of earth. 



In the phraseology of our mechanics we define matter and force as 

 if they had an independent existence. But we have no conception of 

 inert matter or of disembodied force. All we know of matter is its 

 pressure and its motion. The old atom had only potential energy ; 

 the energy of its substitute, the molecule, is partly potential and 

 partly kinetic. If it could be shown that all the phenomena displayed 

 in the physical world were simply transmutations of the original en- 

 ergy existing in the molecules, physical science would be satisfied. 

 Where physical science ends, natural philosophy, which is not wholly 

 exploded from our vocabulary, begins. Natural philosophy can give 

 no account of energy when disconnected with an ever-present Intelli- 

 gence and Will. In Herschel's beautiful dialogue on atoms, after one 

 of the speakers had explained all the wonderftd exhibitions of Nature 

 as the work of natural forces, Hermione replies : " Wonderful, indeed ! 

 Anyhow, they must have not only good memories but astonishing 

 presence of mind, to be always ready to act, and always to act, with- 

 out mistake, according to the primary laws of their being, in every 

 complication that occurs." And elsewhere, " action, without will or 

 effort, is to us, constituted as we are, unrealizable, unknowable, incon- 

 ceivable." The monads of Leibnitz and the demons of Maxwell ex. 

 press in words the personality implied in every manifestation of force. 



In this imperfect sketch of the increased resources, and the present 

 attitude of the physical sciences, I have not aimed to speak as an ad- 

 vocate, much less to sit as a judge. The great problem of the day is, 

 how to subject all physical phenomena to dynamical laws. With all 

 the experimental devices and all the mathematical appliances of this 



