Page:The Solar System - Six Lectures - Lowell.djvu/87
(32) all the way from three to seventeen "canals " will converge upon the same spot ;
(33) the spots are perhaps a hundred miles in diameter, and their number is very great ;
(34) the dark regions are meshed by a similar network ;
(35) the points of departure of both are the same;
(36) similar centring spots show in the dark areas, darker than their background ;
(37) with the dark network "canals" others connect, running to the edge of the extreme melt- ing limits of both caps ;
(38) the lines are seasonal phenomena, develop- ing after the melting of their respective polar cap and fading out later ;
(39) those in the polar regions occupy the place of earlier rifts in the snow-field, as if the ground were there thawed by vegetation.
They are of uniform width ; that is, they waste nothing in breadth. Whatever breadth is necessary is used, and no more, and that is retained throughout. They go directly from certain conspicuously probable points to certain others. If we were obliged to connect the planet by a system of intercommunication, it is precisely those points we should ourselves select.