"Dr. A.R. Wallace rather favours the idea of natural cracks or faults in the surface of the planet; and suggests that the outer crust of Mars may be a crystalline or similar formation which would lend itself to the production of numerous cracks in the surface. He points to a few cracks and faults in the earth's surface, all of small size, as confirming this idea; but the cases he adduces only seem to prove that there is on our earth absolutely no natural formation which can in any way properly be compared with the lines seen on Mars. Moreover, there seems to me no ground whatever, beyond the needs of the theory, for supposing that the crust of Mars is of a crystalline nature, or such as would predispose to the formation of cracks. On the contrary, all the evidence is against it--the existence of vegetation in some parts, the general appearance of the red portion, and the large clouds of sand which have been observed, all being indicative of a sandy formation, in the red portion at least. "The theory also fails to take into consideration the most important point of all, viz. that every canal runs direct from one definite point to another, perhaps over two thousand miles distant. In very many cases numerous lines connect with one small area, or even with one point. The Lucus Ascræus has no less than seventeen of these canals connecting with it, and appears to be a kind of Martian Clapham Junction. "The deserts on Mars serve the same purpose as our seas, as lines of communication may be established anywhere across them. A map of Mars, showing the canals converging towards some one part, bears a great resemblance to our maps showing the courses taken by vessels from different parts all converging upon one seaport. "Much has also been said about the widths of the canals as rendering them impossible of construction, so let us consider how wide they are. "The lines seen vary from two or three miles up to nearly thirty miles in width; but there are only one or two of the latter, and the majority are five to ten miles wide. Notwithstanding Professor Lowell's repeated statements that they represent bands of vegetation, these widths are often referred to as the widths of his canals. I have frequently seen them described as 'fifty miles,' a 'hundred miles,' and even as 'hundreds of miles' wide. These exaggerations usually appear in newspapers and journals, and evidently arise from insufficient knowledge on the part of the writers.