THE PLANETS MARS AND VENUS 359 



feeble must be the solar' rays, not simply at Mars' dis- 

 tance but at his poles. Their error lies in assuming that 

 there is only one way by which snow can be dissolved, 

 namely, by heat; whereas there is this other BY FLOOD- 

 ING. Lowell, in words almost emphatic, describes Mars 

 as being remarkably smooth, or level, no roughness of 

 any sort being discoverable on his surface. We have 

 only to surmise, then, that in the frigid season the polar 

 oceans freeze solid and dry, thus supplying a resting 

 place for the snow, and that, during the warm season 

 following, this ice either disintegrates and loses itself, 

 along with its cargoes of snow, in the ocean ; or that the 

 ice fields are periodically swept over by tides from the 

 warmer equatorial zones; or that the rains wash down 

 the snow until it turns to slush and so loses its virgin 

 whiteness. Surely, there is no mystery here! 



Mars' polar caps are exceptionally extensive, and 

 for their production demand the existence of a relatively 

 large ocean surface. This requirement is rendered more 

 imperative by the sun's remoteness, and is even further 

 accentuated by the compulsory exclusion from the avail- 

 able evaporating surface of that part of it covered, for 

 the time being, by the opposite cap. 



If Mars' seas bear a similar ratio to its solid kernel 

 as ours do to the earth's, three-fifths of his surface must 

 be covered to the depth of a mile or more. This assump- 

 tion, it may be said, is sustained by my theory that the 

 earth's axial rotation is due to the sun's tidal action. 

 Mars rotates on its axis once in 24 hrs. 40 ms., a period 

 reasonably consistent with the earth's case, especially 

 when their respective masses and solar distances are 

 taken into the reckoning. 



The center of gravity of Mars (according to my ar- 

 gument regarding the earth) lies toward its north pole, 

 and conformably we can see the outcropping of land 

 there revealed by the persistent presence of 6 of north- 

 ern cap, whereas the southern cap seasonally disappears 

 completely. 



The conclusion is inevitable : The hitherto supposed 

 "lands", with the possible exception of the blue-green 



