in Conceptions regarding the Constitution of Matter. 457 



such a case the intensity of the force, in the space external to 

 any body, is inversely as the square of the distance from the 

 centre of convergence of these lines of force. As the stone 

 recedes from the earth, its vis viva is transferred to space and 

 exists there as gravity. When the stone approaches to the 

 earth, the force existing in space is transferred back to the 

 body and appears again as vis viva. 



" The integral gravitation," says Mr. Waterston, " is a 



function of space Each element of radial distance has 



associated with it a fixed element of mechanical force, to be 

 given or taken from all bodies traversing it." 



Matter. 



Commonly associated with the hypothesis that the atoms of 

 matter attract each other at a distance is another hypothesis, in 

 regard to the physical nature of the atoms themselves. 



The common conception of matter, which however is now 

 beginning to be abandoned by many of our leading physicists 

 and chemists, is that all matter consists of atoms essentially 

 solid, indivisible, impenetrable, and infinitely hard. The con- 

 ception is, that matter is solidity occupying space. It is almost 

 needless to say that this conception is wholly hypothetical. It 

 is not a simple representation of our experience of matter, but 

 rather a hypothetical attempt at an explanation of the cause of 

 that experience. What we experience is resistance. Matter 

 offers resistance to the touch, and we say that it is hard. An 

 atom or particle of matter will maintain length, breadth, and 

 thickness against any pressure, however great, applied to de- 

 prive it of volume. Nothing can deprive the atom of the pos- 

 session of a certain amount of space ; hence it is asserted that it 

 must be infinitely hard — in short, a part of space filled abso- 

 lutely solid. This hypothesis also assumes the resistance thus 

 offered by the atom to be purely static or passive resistance. 



That this hypothesis is not necessary to account for our ex- 

 perience of matter will appear obvious from the following con- 

 siderations :— Were a cubic inch of space to become, by some 

 means or other, impenetrable (that is, were it to resist the ap- 

 proach of all bodies into it), even although it were completely void, 

 this cubic inch of empty space would appear to the senses in 

 every respect to be solid. And were a cube of what is considered 

 solid matter of the same size placed beside it, we could not by any 

 known means determine which of the two was the solid one. 



All that is necessarily implied in matter, so far as what is 

 called hardness or solidity is concerned, is that it is either a 

 power of resistance in space, or a substance which manifests resist- 

 ance as a property. If we consider this resistance to be an effect, 



Phil Mag. S. 4. Vol. 34. No. 232. Bee. 1867. 2 H 



