Page:Popular Science Monthly Volume 75.djvu/540

536 of what had seemed inexplicable or untrue. Our several results check one another. For, in conclusion, we may note how full of significance it is that the outcomes of such various investigation should fit into one another to an articulated whole. Their dove-tailing at times is indeed surprising, so diverse the character of the converging lines of research. Thus that the planet's albedo should have anything to say about the length of its day, should actually come forward in corroboration of the markings' own forthright showing, would hardly have been supposed. Or that the ashen light of the dark side should find interpretation in the same axial rotation through a long chain of concatenated circumstance was not to be anticipated. Still less would one have divined that the cycle would stand complete and that the very markings which enable us to determine the duration of the Venusian day should have had their peculiar features determined by it.

The force that such agreement to a common end imparts to the chain of argument needs no comment. It speaks for itself.

The picture of Venus thus presented to our gaze may seem forbidding—one hemisphere a torrid desert, the other deserted ice. Which side strikes us as the worse is matter of personal predilection. But the portrait has its grand features for all that; features which give us a new conception of what exists in the universe and lure our thought afield in space with all the greater insistence for being drawn not from fancy but from fact.

Not less of interest is the way in which our knowledge has been obtained; for it has been acquired by research along very different lines, and then by reasoning upon the results of that research to their necessary conclusions. That these conclusions lead to a consistent conception assures us of their truth. Two things are suggested to us by such procedure: first, the pregnancy of considering a subject from many points of view, and secondly, the importance of reasoning upon facts after they have been acquired.

The fact-gatherer has his uses, but they are not those of the highest class. It is not enough to have a thing on our plates, we must know that we have it there and interrogate it for meaning if we would extract from it the knowledge it is capable of yielding and so most truly add to the advance of our day.

In the case before us the result is of special interact because it exemplifies the eventual effects of a force in astronomical mechanics, the importance of which is only beginning to be appreciated: tidal friction. It has brought Venus as a world to the deathly pass we have contemplated together. Starting merely as a brake upon her rotation, it has ended by destroying all those physical conditions which enable our own world to be what it is. Night and day, summer and winter, heat and cold, are vital vicissitudes unknown now upon our sister orb. There nothing changes while the centuries pass. An eternity of deadly deathlessness is Venus's statuesque lot.