not only are they mere sensations in us, there are, moreover, no qualities in things by which they are induced. How, then, are these various sensations induced? They are induced by the quantitative differences of the atoms. For instance, the atoms which occasion the sensation of heat, the atoms which occasion the sensation of smell, the atoms which occasion the sensation of taste, of touch, the atoms which occasion the sensation of sound, the atoms which occasion the sensation of colour—all these atoms are the same in themselves, only, in consequence of their different magnitudes, and shapes, and motions, they affect our sentient organism differently, and hence arises the variety in our sensations. The atoms which induce the sensation of heat are, we may suppose, exceedingly fine, sharp, and agile; the atoms which occasion our sensations of taste are perhaps less subtle and less sharp; and so in regard to the other atoms by which our other sensations are excited. Thus a mere quantitative difference in the atoms, their sharpness or smoothness, their subtlety or comparative grossness, their slowness or velocity, is held to be sufficient to explain all our varied sensations. And thus, too, a mere quantitative difference in the atoms will explain not only the different impressions which arise in our different senses, but also the different impressions which arise in the same sense. Thus the configuration of the atoms which induce the taste of bitterness, is different from the configuration of atoms which induce the sensation of sweet-
