the assumption of a resisting medium. On the other hand, it seems exceedingly natural to suppose that some matter in a very thin state is diffused about the planetary spaces. Then we have another consideration: just as the sun and moon make tides upon the sea, so the planets make tides upon the sun. If we consider the tide which the earth makes upon the sun, instead of being a great wave lifting the mass of the sun up directly under the earth, it lags behind, the result is that the earth, instead of being attracted to the sun's centre, is attracted to a point behind the centre. That retards the earth's motion, and the effect of this upon the planet is to make its orbit larger. That planet disturbing all the other planets, the consequence is, that we have the earth gradually going away from the sun, instead of falling into it.
In any case, all we know is that the sun is going out. If we fall into the sun then we shall be fried; if we go away from the sun, or the sun goes out, then we shall be frozen. So that, so far as the earth is concerned, we have no means of determining what will be the character of the end, but we know that one of these two things must take place in time. But in regard to the whole universe, if we were to travel forward as we have traveled backward in time, consider things as falling together, we should come finally to a great central mass, all in one piece, which would send out waves of heat through a perfectly empty ether, and gradually cool itself down. As this mass got cool it would be deprived of all life or motion; it would be just a mere enormous frozen block in the middle of the ether. But that conclusion, which is like the one that we discussed about the beginning of the world, is one which we have no right whatever to rest upon. It depends upon the same assumption that the laws of geometry and mechanics are exactly and absolutely true, and that they have continued exactly and absolutely true for ever and ever. Such an assumption we have no right whatever to make. We may therefore, I think, conclude about the end of things that, so far as the earth is concerned, an end of life upon it is as probable as science can make any thing, but that in regard to the universe we have no right to draw any conclusion at all. So far we have considered simply the material existence of the earth; but of course our greatest interest lies not so much with the material things upon it, its organized things, as with another fact which goes along with that, and which is an entirely different one—the fact of the consciousness that exists upon the earth. We find very good reason indeed to believe that this consciousness in the case of any organism is itself a very complex thing, and that it corresponds part for part to the action of the nervous system, and more particularly of the brain of that organized thing. There are some whom such evidence has led to the conclusion that the destruction which we have seen reason to think probable of all organized beings upon the earth will lead also to the final destruction of the conscious-
