Let one stand on some peak of the Verd Mountains, northeast from Phoenix, Arizona, overlooking the Gila River as it follows its course across the desert, and after the river is lost to view he will notice that the foliage along its banks marks its course. If one takes this view in winter time, the uniform gray of the plains, unbroken by a single shade of color blends with the light blue of the distant Plomas and Castle Dome Mountains on the southwest horizon. In the early spring when the water is first let into the irrigating channels with their innumerable divergent ditches, a shade of green may be seen emerging from the monotonous yellow-gray of the hot and sterile plain, first conspicuous near the source of the water supply, and then following along to Phoenix, Tempe, and other regions till in full efflorescence these cities stand out like great green carpets spread upon the Earth. From this mountain top not a trace of an irrigating ditch, large or small, would be discerned, except here and there a glint of reflected sunlight, but the effects of the life-giving waters can be traced in broad bands to the remotest limits of the water channels, when they would end as abruptly as they had begun. If we examine railroad maps, the lines of which represent the road-beds utilized to convey passengers and freight to various places, we shall observe that in mountainous regions the lines run very irregularly, often paralleling mountain chains, or following rivers. On level areas such as Iowa, Texas, and other states, the railroads run for hundreds of miles in straight lines, at times converging towards large centres of population. Their occasional parallelism and radiation from centres, all present a certain _cachet_ in angles of approach and alignment that reminds one strongly of similar features in the markings of Mars. If each railroad were bordered by a wide growth of trees with sterile desert between, these broad bands as seen from Mars would be identical with the appearance of similar lines in Mars as seen from the Earth. In Mars, however, there are no high elevations since the terminator of Mars stands out clear cut and not jagged as in the Moon. The planet being devoid of hill ranges, and large oceans, the canals can run in straight lines for hundreds of miles. If it were possible to conceive by analogy a creature on Mars furnished with a telescope, he would undoubtedly correlate the irrigating regions of Arizona as similar in nature to his own canals. The irregularity of the rivers running through such regions would puzzle him quite as much as we are puzzled by the absolute straightness of the Martian canals. He would, of course, observe that in our winter the irrigating areas became invisible, to appear again as our summer advanced. His own experience of vegetation arising from irrigation alone and starting from the north when the first water from the melting snow cap animated the growth of