Wherever several canals, that is to say, several bands of vegetation or bands of life, meet, it is reasonable to assume that an irrigated and habitable area of considerable extent will be developed, and in such places the imagination may picture the location of the chief centers of population, perhaps in the form of large cities, or perhaps in groups of smaller towns and villages. The so-called Lacus Solis is one of these localities. So, likewise, it seems but natural that along the course of a broad, well-irrigated band a number of expansions should occur, driving back the bounds of the desert, forming rounded areas of vegetation, and thus affording a footing for population. Wherever two bands cross such areas would be sure to exist, and in almost every instance of crossing the telescope actually shows them. As to the gemination or duplication of many of the lines which, at the beginning of the season, appear single, it may be suggested that, in the course of the development of the vast irrigation system of the planet parallel bands of cultivation have been established, one receiving its water supply from the canals of the other, and consequently lagging a little behind in visibility as the water slowly percolates through the soil and awakens the vegetation. Or else, the character of the vegetation itself may differ as between two such parallel bands, one being supplied with plants that spring up and mature quickly when the soil about their roots is moistened, while the plants in the twin band respond more slowly to stimulation. Objection has been made to the theory of the artificial origin of the canals of Mars on the ground, already mentioned, that the work required to construct them would be beyond the capacity of any race of creatures resembling man. The reply that has been made to this is twofold. In the first place, it should be remembered that the theory, as Mr. Lowell presents it, does not assert that the visible lines are the actual canals, but only that they are strips of territory intersected, like Holland or the center of the plain of Lombardy, by innumerable irrigation canals and ditches. To construct such works is clearly not an impossible undertaking, although it does imply great industry and concentration of effort.