Joty—On the Origin of the Canals of Mars. 261 
Reasons for supposing that the lines are raised, and not depressed, upon the surface of Mars. 
It thus appears as if two very different kinds of action arising from the pre- 
sence of in-falling satellites might give rise to the double lines. In both cases we 
must infer that the canals are raised and not depressed upon the surface of Mars. 
It is necessary to say a word in support of this view based on other considerations. 
In the first place, it appears as if there was nothing in the appearance of the 
lines to lead to the belief that they are necessarily depressed and not raised. 
The fact that mountains so high as those on the Moon have not been detected on 
Mars of course leaves it an open question as to whether the lines are raised ground 
of less elevation than this or not. Many observers have maintained that they are 
low mountain ranges. Mr. Schaeberle, some four years ago, questioned the 
oceanic nature of the dark markings. The lght and shade upon these pointed, 
in his opinion, to a rough mountain country. He thought the light areas oceans, 
and the lines ridges standing up out of the water. It appears now very certain 
that neither the dark nor the light areas are at present oceanic. ‘There is, in fact, 
no appearance of sheets of water upon any portion of the surface of the planet. - 
Professor Barnard came also to the conclusion, at the opposition of 1894, that the 
dark areas were land. Mr. Lowell and his colleagues, although they question 
the existence of mountains as high as those on the Moon, frequently reported, 
during the period of their operations at Flagstaff Observatory, marks at the 
terminator which led them to think that there were mountains on the surface. 
That the shadows of mountains at sunrise or sunset might be of considerable 
extension, and still be invisible to us, may be judged from the fact, as stated by 
Lowell, that an object must possess a diameter of thirty miles in order to be 
visible to us. Again, the other mode of detecting the presence of mountains, 
that is, by their appearance as bright points within the dark edge of the ter- 
minator, will not probably be so effective in the case of Mars as in the case of 
our Moon. ‘The effects of an atmosphere will be to diminish the brightness of 
such points of light, not only by diminishing the incident light, but also by 
absorption of the reflected light. It would appear, however, that this appearance 
has been seen upon Mars. ‘The sensational “signal” seen in the dark limb of 
Mars in 1894 has been explained in this manner. It has been suggested that the 
mountain peak giving rise to the point of light was covered with snow or ice. 
From all this we see that, so far as observation goes, the idea is by no means 
precluded that they are in truth not depressed, but raised upon the surface. 
But there is another argument for supposing that the lines are low mountain 
ranges—ranges probably under 10,900 feet in height. This is involved in the 
fact that in this supposition we find a comparatively ready explanation of the 
mysterious appearance and disappearance of the lines. 
