occurred more than once; they may possibly have occurred several times throughout the ages of time past. Nor is it likely that the last phenomena of this kind have yet arrived.
The sun, after the lapse of countless years, will lose all its heat and pass into a dark mass. In that form it may endure for a period so protracted that the spell during which it has acted as the luminary to our system will appear but a moment in comparison with the dark ages which succeed the solar splendour. But we can conceive that the darkness, which is the doom of our system, need not necessarily be eternal so far as its materials are concerned; it may be that again in the course of its wanderings through space, the tide of chance may at length bring the dark and tremendous globe so near some other orb that another collision should take place with appalling vehemence. The solid materials may again become transformed into a stupendous glowing nebula, and then, in the course of the tedious contraction of this nebula, another protracted period of brilliance will diversify the career of this great body, and may last long enough for the evolution of planets and of whole races of highly organized creatures.
The essential point for our present consideration must not be misunderstood. A little reflection will show that any periods of brilliance must be regarded as exceptional periods in the history of each body. Think, for instance, of all the iron on the surface of the earth. There is the iron in the ore; there are the great stores of pig-iron lying ready for use; there are the vast bridges which span our rivers and straits; there are the thousands of miles of railway lines; there are the
