662 LOWELL—MARS ON GLACIAL EPOCHS. [Nov. 16, 
(I do not here consider temperature, which, according to some re- 
searches of my friend, Prof. Story, may possibly set superior limits 
to all planatory atmospheres. ) 
27. In consequence of this to compass a result for which a mod- 
erate ascent would suffice on earth, an immoderate one must be 
made on Mars. For gravity there being but 224 our own, nearly 
three times the rise is necessary. A Mt. Everest would stand for 
an Etna and something no less than eight miles high for a Mt. 
St. Elias. Ifsuch peaks existed, they could not fail of detection. 
Nevertheless none have been made out, nor are there any certain 
signs of even much lesser elevations. What have been most sup- 
posed to suggest them—the projections which, illuminated by slant 
lightning across the sunset or sunrise edge of the disk, stand out as 
bright points upon the terminator—do not tally with the look of hills, 
but are best explained by cloud. For they change in aspect only 
as clouds could contrive to do. Nor are other indications of pos- 
sible mountains more expressive. Indeed, from every point of view 
Mars presents itself to us as futilely flat. 
28. Dispensing, then, with earthly analogies we must look to Mars 
itself for explanation. Surveying the surface with this intent we 
presently note one trait which marks off the southern from the 
northern hemisphere—the relative absence in the latter of blue- 
green areas. It is, indeed, not a little odd how devoid the one- 
half of its globe is of what the other makes so fair a showing. The 
great mass of dark markings are to be found on that part of the 
planet which lies between the equator and the south pole. 
29. Pursuing the subject, we find further that the blue-green 
regions are widest, reaching both farther down and higher up, be- 
tween longitudes 300° and go°. Here these regions stretch away 
to or fade into the arctic circle. Now it is in the centre of these 
longitudes, half way, roughly, across the breadth of the blue-green, 
that is found the centre of the southern snow-cap. Bowed toward 
this region, it evidently acknowledges some compelling potency 
there. And the continuance of the obeisance from the cap’s be- 
ginning to its end points to a cause itself continuous. 
30. The blue-green areas are, without doubt (see 23), vast 
vegetation bottoms. ‘Though the dip is unquestionably but slight, it 
suffices to drain into them sub-erially or surface-wise such mois- 
ture as may be present in the neighborhood. Whence their cloth- 
ing of grass or forest or what does for these in Martian flora, their 
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