312 FROM NEBULA TO NEBULA 



4. The undertaking, he opines, was far less formi- 

 dable than a similar one would be here. First of all, the 

 flatness of the surface would obviate much grading and 

 leveling. Then, again, on account of the lesser surface 

 gravity, the efficiency of the machinery would be perhaps 

 quadrupled. If to these positive advantages be added 

 the suppositions that the Martians are gigantic, and 

 further advanced in the mechanical arts than ourselves, 

 the objection on the score of mere physical difficulty is 

 largely reduced. 



5. The surface being flat, every point within as well 

 as beyond the polar circles would be in stable equilibrium. 

 This means that the water would not descend through 

 the canals at any useful speed without artificial propul- 

 sion. Observation proves to him that the canals show 

 activity of a certain kind immediately following the in- 

 cipient thawing of the snow-cap, and that this active 

 movement travels equatorward at the rate of 51 miles a 

 day for a distance of 3300 miles. As to the nature of 

 this change we can judge only from appearance, which 

 consists in a gradual darkening and broadening of the 

 canal lines, and this is construed by him to be due to 

 stimulated vegetation along their borders. 



6. The ancient ' ' sea bottoms ' ', he infers from their 

 color, are regions of vegetation. Yet they too exhibit 

 " canals ", not only entering from the nearest pole of 

 supply, but rising again into the arid regions nearer the 

 equator. This feat of canalizing the basin of an ocean 

 and thence raising the water to the farther shore Mr. 

 Lowell cites as a striking evidence of Martian engineer- 

 ing prowess. 



7. The distance of Mars from the sun, its source of 

 heat, is not so great as absolutely to preclude the exis- 

 tence of animal life. Mars' summer is much longer than 

 ours, and planetary life is determined rather by the mild- 

 ness of summer than by the asperity of winter. Mars' 

 mean temperature he estimates at about 48 F. 



8. Unlike the snow caps of our Arctic and Antarctic 



