Page:Mars - Lowell.djvu/247

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183
SPOTS IN THE LIGHT REGIONS

there has been no symptom of cloud or other obscuration, before or after, over the place where they eventually appear,—we are led to the conclusion that, like the canals, they grow.

Indeed, in the history of their development the two features seem quite similar. Both grow, and both follow the same order and method in their growth. Both are affected by one progressive change that sweeps over the face of the planet from the pole to the equator, and then from the equator toward the other pole. In the case of the southern hemisphere, it is, as we have just seen, the most southern spots, like the most southern canals, that appear first after the melting of the polar snows. Then gradually others begin to show farther and farther north. The quickening of the spots, like the quickening of the canals, is a seasonal affair. But there is more in it than this. It takes place in a manner to imply that something more immediate than the change in the seasons is concerned in it; immediate not in time, but in relation to the result. A comparison of the behavior of three spots—the Phoenix Lake, Ceraunius, the spot at the junction of the Iris and the Gigas, and the Cyane Fons, a spot where the Steropes, a newly found canal, and the Nilus meet—will serve to point out what this something is. The Phoenix Lake lies in lat. 17° S., Ceraunius in lat 12° N., and