To suppose that these are all the same dead-level as the light-coloured portions are assumed to be, implies that the darkness is one of material and colour only, not of diversified contour, which again is contrary to experience, since difference of material with us always leads to differences in rate of degradation, and hence of diversified contour, as these dark spaces actually show themselves under favourable conditions to independent observers.
_Lowell on the System of Canals as a whole._ We will now see what Mr.Lowell claims to be the plain teaching of the 'canals' as a whole: "But last and all-embracing in its import is the system which the canals form.

Instead of running at hap-hazard, the canals are interconnected in a most remarkable manner.

They seek centres instead of avoiding them.
The centres are linked thus perfectly one with another, an arrangement which could not result from centres, whether of explosion or otherwise, which were themselves discrete.

Furthermore, the system covers the whole surface of the planet, dark areas and light ones alike, a world-wide distribution which exceeds the bounds of natural possibility.

Any force which could act longitudinally on such a scale must be limited latitudinally in its action, as witness the belts of Jupiter and the spots upon the sun.