MARS IN HIS ICY CUIRASS 99 



stances allow. That it is fascinating in conception, 

 elaborately argued, and exquisitely presented, no lover 

 of truth or judge of literature will deny. Nevertheless 

 it has failed of convincing the profession; and, what is 

 more to the point, it is open to complete refutation. 



Prof. Lowell has made the all too common error of 

 twisting intractable facts to suit preconceived theory. 

 Unconsciously he has reasoned, not to a conclusion, but 

 to prove a conclusion previously formed. Let us see 

 now whether the facts he himself adduces will yield a 

 different and more credible interpretation. 



1. The southern snow-cap at the full covers over 

 a quarter of the planet's surface, and the northern cap 

 considerably more than a fifth. The snow must come 

 from evaporation, must it not? But Mr. Lowell denies 

 the existence of any evaporating surface save that of his 

 canals ! Were the caps a permanent feature this point 

 might be explained away; but the snow disappears every 

 summer,, and of course must be as often restored. It 

 seems to me that if Mr. Lowell had not had his theory 

 in mind, he would have reasoned that the caps could 

 not come into . existence from the evaporation of his 

 canals alone. The caps being so extensive and the solar 

 heat so feeble, there must exist an exceptionally large 

 evaporating surface. He might have reasoned further 

 that the vapors from the canals wouldn't extend his 

 theory the courtesy of proceeding intact back to the 

 poles, but would, after the manner of atmospheric hu- 

 midity, spread in all directions, and come down in rain 

 or snow, most probably the latter, indiscriminately 

 over the whole surface. His snow eggs are laid without 

 the aid of the mothering ocean. 



2. What causes the caps to disappear? Surely 

 not the solar heat! For consider. Prof. Lowell him- 



