is in an apt condition for that action which may he considered as equivalent to a lateral vibration; whereas a uniform medium, like the ether, does not appear apt, or more apt than air or water.
The occurrence of a change at one end of a line of force easily suggests a consequent change at the other. The propagation of light, and therefore probably of all radiant action, occupies time; and, that a vibration of the line of force should account for the phenomena of radiation, it is necessary that such vibration should occupy time also. I am not aware whether there are any data by which it has been, or could be ascertained, whether such a power as gravitation acts without occupying time, or whether lines of force being already in existence, such a lateral disturbance of them at one end as I have suggested above, would require time, or must of necessity be felt instantly at the other end.
As to that condition of the lines of force which represents the assumed high elasticity of the ether, it cannot in this respect be deficient: the question here seems rather to be, whether the lines are sluggish enough in their action to render them equivalent to the ether in respect of the time known experimentally to be occupied in the transmission of radiant force.
The ether is assumed as pervading all bodies as well as space: in the view now set forth, it is the forces of the atomic centres which pervade (and make) all bodies, and also penetrate all space. As regards space, the difference is, that the ether presents successive parts or centres of action, and the present supposition only lines of action; as regards matter, the difference is, that the ether lies between the particles, and so carries on the vibrations; whilst as respects the supposition, it is by the lines of force between the centres of the particles that the vibration is continued. As to the difference in intensity of action within matter under the two views, I suppose it will be very difficult to draw any conclusion; for when we take the simplest state of common matter and that which most nearly causes it to approximate to the condition of the ether, namely the state of rare gas, how soon do we find in its elasticity and the mutual repulsion of its particles, a departure from the law, that the action is inversely as the square of the distance!
And now, my dear Phillips, I must conclude. I do not think I should have allowed these notions to have escaped from me,
