44 FROM NEBULA TO NEBULA 



practicability of their conception. They tell us, with 

 every show of confidence in their words and manner, that 

 if the velocity bears to gravity a certain ratio, the result- 

 ing orbit will be a circle ; that if this velocity be exceeded, 

 the orbit will be a parabola, or hyperbola ; and that if the 

 velocity be deficient, the result will be an ellipse, broad or 

 narrow, according to the degree of such deficiency; but 

 that in no event can the circulating body fall in. To see 

 the fallacy of this representation, you need only take an 

 arc of any conic section you may choose, draw its tangent 

 and the radii vectores, and then go through the same 

 demonstration as given above. It seems to me too plain 

 for denial, that if the velocity be too slow, gravity, in the 

 first second, must inevitably pull the body within the line 

 of the conic curve, and that, the arcs of all conies being 

 shorter than their tangents, the velocity in the second sec- 

 ond will be not only slower absolutely, but, relatively to 

 the force of gravity, very much slower. To such a pro- 

 cess there could be but one sequence the body would 

 fall in short order. 



Newtonians are by no means oblivious to the in- 

 security of the ground they here occupy, so they have 

 added, by way of an alternative or makeweight, the fic- 

 tion that celestial motions are "persistent". This idea 

 they have borrowed from the so-called doctrine of con- 

 servation of energy. They have come to realize that 

 Newton was too modest in asking merely for the gift of 

 rectilinear motions by way of capital on which to run his 

 cosmic system, and so they have added, for the sake of 

 expediency, this new notion. In other words, they have 

 gratuitously substituted in the Newtonian vocabulary the 

 word persistent for inertia, its antonym. Now, our ter- 

 restrial experience offers us not a single example of 

 motion not plainly traceable to a definite physical cause ; 

 so, to mark the difference, and as a sort of honorary dis- 

 tinction, they call the one sort " celestial" mechanics and 

 the other, " terrestrial", exactly traversing, as it were, 

 Drummond's Natural Law in the Spiritual World, by 

 showing that natural law does not even rise to the height 

 of the physical heavens ! 



