have been hotter when it was placed there than when you felt it. If when you had felt the temperature you found the water as cold as the air in the room, then you could not infer its original temperature. It might have been a jug of cold water to begin with, or it might have been warm, and have grown cold; you could not tell which. If, however, the water be in the slightest degree warmer than the air in the room, then the argument that it must have cooled from a higher temperature is irresistible. This is so obvious a doctrine that it may seem unnecessary to write it down. But, obvious though it be, it will yet teach us much about the past history, both of our earth and of other globes; especially will it prove instructive about those unfinished worlds of which we are now speaking.
If in a blacksmith's forge you incautiously placed your hand upon a piece of iron, and it burned your fingers, and if the blacksmith told you that the iron had lain there for half an hour, you would not doubt that it must have been much hotter when the blacksmith drew it from the fire than you found it to be. Probably it was even red hot at the time it was laid aside. The argument would still apply if the object, instead of being a lump of iron, were a block of stone; it would apply if the body were as big as a mountain or as big as the moon; neither the fire nor the material would really affect the reasoning. If you found the body to be hot you may feel perfectly certain that hours ago, or days ago, or years ago, or centuries ago, it must have been hotter still. We must apply this argument to that immense globe, 8,000 miles in diameter, on which we are standing. It has an exterior crust of rocks and stones,
C
