Yet even these do, I think, afford us some hints towards an interpretation of the mysterious lines.

But as our knowledge of the internal structure and past history even of our earth is still imperfect, that of the moon only conjectural, and that of Mars a perfect blank, it is not perhaps surprising that the surface-features of the latter do not correspond with those of either of the others.
_Mr.Pickering's Suggestion._ The best clue to a natural interpretation of the strange features of the surface of Mars is that suggested by the American astronomer Mr.W.H.
Pickering in _Popular Astronomy_ (1904).

Briefly it is, that both the 'canals' of Mars and the rifts as well as the luminous streaks on the moon are cracks in the volcanic crust, caused by internal stresses due to the action of the heated interior.

These cracks he considers to be symmetrically arranged with regard to small 'craterlets' (Mr.Lowell's 'oases') because they have originated from them, just as the white streaks on the moon radiate from the larger craters as centres.

He further supposes that water and carbon-dioxide issue from the interior into these fissures, and, in conjunction with sunlight, promote the growth of vegetation.