[[Categoria:Pagine che usano RigaIntestazione|Scientia - Vol. VII.djvu{{padleft:14|3|0]] see, and only by such explanation does it seem possible to account for the facts.

These lines are the so-called canal of Mars. It is not supposed that what we see is the conduit itself. On the contrary, the behaviour of these lines indicates that what we are looking at is vegetation. Now, vegetation can only be induced by a water supply. What we see resembles the yearly inundation of the Nile, of which to a spectator in space the river itself might be too narrow to be seen, and only the verdured country on its banks be visible. This is what we suppose to be the case with Mars. However the water be conducted, whether in covered conduits, which seems probable, or not, science is not able to state, but the effects of it are so palpable and so exactly in accord with what such a system of irrigation would show, that we are compelled to believe that such is indeed its vera causa.

Flagstaff, Arizona Lowell Observatory.