ginning of the end as well. It is both the result of the evolving of definite bodies out of the agglomeration of matter-strewn space, and the cause of the higher evolution of those globes themselves. For the acquisition of heat is the necessary preface to all that follows. Heat is a body's evolutionary capital whose wise expenditure through cooling down makes all further advance to higher products possible. A body too small to have acquired it must remain forever lifeless, as dead as the meteorites themselves that enter our air as mere inert bits of stone or iron.
Curiously enough, heat both must have been and then must have been lost. Like the loss of fortune or of friends sometimes in the ennobling of character, it is through its passing away that its effects are realized. For in cooling down from a once heated condition, that train of events occurs which we most commonly particularize as evolution. So far in our survey the march of advance has been through masses of matter, a molar evolution; from this point on it passes into its minute constituents and becomes a molecular one. The one is the necessary prelude to the other. Up to this great turning-point in the history of each member of a solar system we have been busied with the acquisition of heat, though we may not have been aware of it the while. All the motions we have studied tended to that end. During these three chapters, I, II, V, we have been
