gists now, so there were slaveholders and the anti-slavery people in my time; and even in the days of the deluge, there were the diluvians who were in favor of a flood and the antediluvians who were opposed to it." A tale which has a peculiarly scientific moral, as in science anti and ante seem often interchangeable terms.
When I began the course of lectures that resulted in this volume, I labored under the apprehension that an account of cosmic physics might prove dull. It soon threatened to prove too startling. I therefore hasten to reassure the timid by saying that we are outgrowing ice ages and probably deluges. Elevations of the Earth's crust are likely to be less and less pronounced in the future, and meanwhile such as exist are being slowly worn down. Secondly, the Sun is sure to continue of much the same efficiency for many æons to come. And lastly, the essential ingredient of both prodigies, water, is daily becoming more scarce. To this latter point we now turn, and perhaps when it is explained to him the reader may think that he has been rescued from one fate only to fall into the hands of another.
Geology is necessarily limited in its scope to what has happened; planetology is not so circumscribed in its domain. It may indulge in prognostication of the future, and find countenance for its conclusions in the physiognomy of other worlds. Thus one of the things which it foresees is the relative drying up of our abode.
