536 THE POPULAR SCIENCE MONTHLY 



tion of what had seemed inexplicable or untrue. Our several results 

 check one another. For, in conclusion, we may note how full of signifi- 

 cance 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 corrobora- 

 tion of the markings' own forthright showing, would hardly have been 

 supposed. Or that the ashen light of the dark side should find inter- 

 pretation in the same axial rotation through a long chain of concate- 

 nated 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 Yenusian 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 forbid- 

 ding — 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 ob- 

 tained ; for it has been acquired by research along very different lines, 

 and then by reasoning upon the results of that research to their neces- 

 sary conclusions. That these conclusions lead to a consistent concep- 

 tion 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 ex- 

 tract 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 interest 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 contem- 

 plated 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 death- 

 lessness is Venus's statuesque lot. 



