of the "grossness" or "bruteness" of tangible matter,--a notion which has survived in Christian theology, and which educated men of the present day have by no means universally outgrown. Save for some such old associations as these, why should it be supposed that matter becomes "spriritualized" as it diminishes in apparent substantiality? Why should matter be pronounced respectable in the inverse ratio of its density or ponderability? Why is a diamond any more chargeable with "grossness" than a cubic centimetre of hydrogen? Obviously such fancies are purely of mythologic parentage. Now the luminiferous ether, upon which our authors make such extensive demands, may be physically "ethereal" enough, in spite of the enormous elasticity which leads Professor Jevons to characterize it as "adamantine"; but most assuredly we have not the slightest reason for speaking of it as "immaterial" or "spiritual." Though we are unable to weigh it in the balance, we at least know it as a transmitter of undulatory movements, the size and shape of which we can accurately measure. Its force-relations with ponderable matter are not only universally and incessantly maintained, but they have that precisely quantitative character which implies an essential identity between the innermost natures of the two substances. We have seen reason for thinking it probable that ether and ordinary matter are alike composed of vortex-rings in a quasi-frictionless fluid; but whatever be the fate of this subtle hypothesis, we may be sure that no theory will ever be entertained in which the analysis of ether shall require different symbols from that of ordinary matter. In our authors' theory, therefore, the putting on of immortality is in no wise the passage from a material to a spiritual state. It is the passage from one kind of materially conditioned state to another. The theory thus appeals directly to our experiences of the behaviour of matter; and in deriving so little support as it does from these experiences, it remains an essentially weak speculation, whatever we may think of its ingenuity. For so long as we are asked to accept conclusions drawn from our experiences of the material world, we are justified in demanding something more than mere unconditioned possibility. We require some positive evidence, be it ever so little in amount; and no theory which cannot furnish such positive evidence is likely to carry to our minds much practical conviction.