our powers ever to conceive of the ultimate nature of matter. Of the structure of matter this is not the case. Various hypotheses have been offered regarding the structure of matter—all, save one, have been charged with some fatal objection and have broken down. This one, the suggestion of that powerful mind. Lord Kelvin's, is known as the vortex-ring theory. We can not give it here in any detail, but the gist of it is that the ether is universal and for the most part formless, but that some parts are differentiated from the remainder by being in motion in the shape of vortex rings. These parts in such rotational motion are matter in the ordinary forms. A remarkable thing about it, and one which exhibits the very spirit of modern physics, is that those properties of ordinary matter which emphasize its stability of form and position, especially inertia, elasticity, and rigidity, can be a result of motion. Yet Lord Kelvin has shown that with ordinary matter a limp system of bodies could be made a rigid system by merely putting them into gyroscopic rotation, and also that elasticity itself might properly be regarded as a mode of motion. The vortex-ring theory is as yet only a speculation, but when its adaptability to occult as well as to plainer properties of matter are considered, we need not wonder that it has been thought so beautiful that "it deserves to be true." At any rate it stands in such an attitude toward modern views concerning the structure of matter that "it is either that theory or nothing. There is no other one that has any degree of probability at all" (Dolbear). We can see how such a theory might reconcile conflicting views such as those above given concerning matter and ether separately.
Without waiting for a decisive answer as to the nature of ether or the structure of matter, attention is being concentrated on the relations of one to the other, the extent to which and the manner in which any change in either substance affects the other; and this examination may throw light upon the greater question regarding the nature of the substances. Do material bodies moving in the ether of space—for example, the earth and its atmosphere—move through the ether, or carry with them the ether that is distributed throughout the matter that is moving? Experiments of extraordinary precision by Prof. Michelson have led him to conclude that most probably the earth carries with it all the ether in its immediate neighborhood; that certainly the relative motion of the earth and the ether in it is exceedingly small. If he can repeat his experiments and get a different result on the top of a mountain, that conclusion may be considered established. Those conclusions were drawn from experiments in which the earth's velocity in its orbit is involved. Prof. Lodge has experimented for effects due to slower motion of bodies upon
