31 
in reply to the Chairman’s objections, that the consideration of “ the force of 
gravity, as due to the ether, is a step beyond measuring its action experi- 
mentally,” and that the pushing of the ultimate parts of bodies by the action 
of the ethereal waves is a “ result deduced from the application of mathe- 
matics to the ether [and atoms] as defined.” 
It only remains for me to take notice of the Chairman’s concluding 
remarks, which seem to have been made under the misapprehension that the 
proposed theory of the cause of gravity involves the supposition of “ molecules 
impinging in countless multitudes and with immense velocity upon the 
particles of matter.” I have never in any of my writings given the least 
countenance to this hypothesis, which, on the contrary, I look upon as having 
no foundation in reason, and as having been gratuitously made for the pur- 
pose of evading the consideration in physics of such pressure as is commonly 
understood from sensation and experience. I am quite in accord with 
Mr. Brooke in his opposition to this way of accounting for gravity, and, 
adopting his words, can say that “ I do not see why the molecules should 
impinge on one side of the particles more than another, and, if they impinge 
on all sides alike, how they should have any effect ; nor do I see how the 
supposed impact of molecules should tend to bring particles together.” In 
short, I cannot but regard this arbitrary hypothesis as a retrograde step in 
physical philosophy, fit only to be classed with Descartes’ vortices, and far 
less excusable, inasmuch as Descartes had not, as we now have, mathematical 
and physical knowledge adequate to the treatment of such a question as the 
modus operandi of gravity. I have, in fact, for a long time maintained that 
the character arid laws of all the physical forces, as ascertained experi- 
mentally, admit of being accounted for by the application of modern analytics 
to the Newtonian principles of natural philosophy, and, in particular, by 
means of mathematical reasoning so applied, I have been led to a con- 
clusion which, in page 468 of my work on the “ Principles of Mathematics 
and Physics ” (published in 1869), is expressed in these terms : — “ There are 
no circumstances under which the forces of nature can act differentially on two 
neighbouring atoms to such a degree as to overcome their mutual repulsion ; 
and, consequently, the collision of atoms is an impossibility.” It is to be 
understood that this repulsion is caused by pressure on the surface of each 
atom due to ethereal waves propagated from the other, and, as varying in 
some inverse ratio of the distance between their centres, is enormously in- 
creased by approach of the atoms towards each other. I think that I need 
not say more to show how utterly opposed my view of the cause of gravi- 
tation is to this hypothesis of “ swarms ” of impinging molecules. 
In response to the Rev. Dr. Fisher’s desire for a fuller statement of my 
reasons for regarding the proof of the creation of matter as involving the 
proof of its destructibility, I am prepared to give the following explanations, 
which, I admit, were not uncalled for. In the Epistle of St. Paul to the 
Galatians (ii. 18) there occurs the following remarkable passage : “ If I build 
again the things which I destroyed I make myself a transgressor.” These 
words, in which the first person is employed impersonally, signify that any 
