Winter and summer visit in succession its northern and southern hemispheres just as occurs on the planet that we inhabit, and the torrid, temperate, and frigid zones on its surface have nearly the same angular width as on the earth.

Two principal colors exist on the disk of Mars--dark, bluish gray or greenish gray, characterizing areas which have generally been regarded as seas, and light yellowish red, overspreading broad regions looked upon as continents.

The second reason is that Mars being smaller and less massive than the earth has run through its developments a cooling globe more rapidly. The bearing of these things upon the problems of life on Mars will be considered hereafter.

It should not be inferred from the fact that Schiaparelli's discovery in 1877 excited so much surprise and incredulity that no glimpse of the peculiar canal-like markings on Mars had been obtained earlier than that.

Wherever two or more canals meet, or cross, a rounded dark spot from a hundred miles, or less, to three hundred miles in diameter, is seen. An astonishing number of these appear on Mr. Lowell's charts.