Having shown to the satisfaction of any reasonable mind that the delicate lines, known as canals, do exist, it will be interesting to examine some of the theories which have been advanced to explain these markings, as well as some of the absurd deductions drawn from their existence. The late Dr. J. Joly, Professor of Geology in the University of Dublin, in a paper on the Origin of the Canals of Mars ("Trans." Royal Soc., Dublin) came to the conclusion that meteoric bodies, revolving on or near the surface of Mars, produced these lines. In brief, he supposed that Mars at various times in the early stages of his history, when his rotation period was much shorter, attracted small bodies, which, after whirling about the planet, finally came down on the crust and caused these lines. He conceived of satellites twice the diameter of Phobos, or say, seventy-two miles in diameter, flying about Mars at a distance of sixty-three miles, which would at this distance, by its attractive force, exert a stress on the supposed thin crust of Mars of from fifteen to thirty tons per square foot, and thus rend the surface of the planet in a zone two hundred and twenty miles wide, thus forming two parallel ridges which might be visible to us as double canals. This preposterous idea takes no account of the greater attractive force of the Earth, and that it too should have had precisely the same experience, more often repeated. No trace of such behaviors, however, has ever been detected. The Moon, too, should have caught some of these heavy bodies, but while conspicuous cracks are seen on her surface, and delicate ridges are seen radiating from the larger volcanoes, not a trace of these great meteoric furrows has ever been observed. It takes no account of the chances--one in a million--that these cavorting meteors should meet at common centres, and if they did, the impossibility that they should stop abruptly and then start off in opposite directions. It takes no account of many of the lines following the arc of a great circle, or what finally became of three or four hundred of these meteors to tally with the number of the canals, unless it is supposed that some of them went whirling around the planet three or four times, changing their courses instantly and repeatedly. Indeed, the advancement of such absurd ideas shows the desperate despair of a man who tries to escape the admission that the lines in question may be artificial--and hence the result of intelligence working to a definite end--by a conception as crazy as one might possibly get in a disordered dream. To heighten the absurdity of this theory, if that were possible, Mr. J. L. E. Dryer, who signs a notice of this paper, while calling attention to the fact that this hypothesis takes no account of the correlation of changes in the canals with seasonal changes on the planet, otherwise soberly says: "It must be conceded that there is nothing in the new hypothesis contrary to observed facts."