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Rh draw the conclusion that there is but one species of men, and that the differences existing between them are only differences of race. Again I say, in reaching this conclusion, we have never gone beyond science. I repeat this declaration, because, in all that I shall say to you, I wish you distinctly to understand that I never put foot outside the domain of science, where alone the scientific man can speak with. authority.

The unity of the human species once demonstrated, many problems arise before us.

The first is that of the antiquity of man. Have men been always upon the earth? Did they appear at the same time with the other species of animals? Are they very ancient on the globe? Such are the first questions which present themselves to our minds.

Throughout all time have men lived on the earth? Many of you,

doubtless, are already able to answer me. My brother professors of geology and paleontology have probably addressed you on these questions. I shall only recall to you the general facts bearing upon the case.

You all know what is the action of heat upon certain bodies. For example, you all know that water heated to a certain degree vaporizes; that if this vapor loses a certain quantity of heat, it is liquefied; that in losing still more, it forms a solid body ice. This ice may become so solid, that in St. Petersburg they have been able to construct it into palaces, and have made cannons of ice that have been fired. You can understand that a sufficient quantity of heat will reduce all bodies to vapor, and that sufficient cold will solidify them.

Now, the facts of astronomy seem to prove that, of old, our earth,