According to the corpuscular theory, when a luminous particle or corpuscle is nearing the surface of a denser medium, as glass or water, it was attracted by the denser medium, with the result that the velocity of the particle in the denser medium was greater than its velocity in air. But direct experiments prove exactly the opposite, as it is found that when light passes from a rare into a denser medium, the velocity of light in the denser or more refracting medium is less than it was in the air. Here then was a test to decide the respective merits of the two theories. As the undulatory theory was able to give a satisfactory explanation of the phenomenon, the corpuscular theory was rejected, and the undulatory theory was accepted. Now the question suggests itself, as to whether it is possible to reconcile the two theories in relation to the refraction of light by our conception of an atomic and gravitative Aether. I believe it is possible. Let us look at the case for a moment. We have, according to our theory of the Aether, to conceive of all atoms and molecules, of all planets and suns and stars, being surrounded by aetherial elastic atmospheres, or envelopes, which, like the atmosphere in association with the earth, are always the densest nearest the nucleus of the atom, getting gradually less and less dense the further they recede from the central point. Further, according to our theory, with regard to the elasticity or pressure of these elastic envelopes, they exert a pressure proportionate to their density. So that the nearer the aetherial atmosphere or envelope is to the central point or nucleus of the atom, the greater will be the elasticity or pressure. Now what I wish to call the reader's special attention to is, that the pressure in each and every case of the aetherial elastic envelopes which surround the central nucleus, is always directed _away from_ the central point, and here it seems to me is the solution of the difficulty which Newton failed to solve. For when a luminous corpuscle enters any medium, assuming it to do so, it would have to overcome the pressure due to the increased elasticity of the denser aetherial envelopes, and as the two motions, viz. that of the incident ray, and the pressure due to the elasticity of the elastic envelope, would be in opposition to each other, the result would be that the luminous corpuscle, if it entered the medium at all, would be retarded and not accelerated as suggested by Newton, and such a result is perfectly in harmony with experiment. So that by our theory of an atomic and gravitating Aether, it seems to me that it now becomes possible to reconcile the two theories.