Miss Agnes M. Clerke, an astronomical writer of great merit, who has written a most lucid and comprehensive "History of Astronomy in the Nineteenth Century," says: "The canals of Mars are an existent and permanent phenomenon." Mr. Thomas Lindsay, of Toronto, read some notes before the Astronomical Society of that city in regard to the phenomenon of the so-called doubling of the canals and the explanation advanced that it was due to errors in focusing. "It had been stated by several English observers that, by racking the eyepiece within or without the focus, all the phenomena might be produced." In the case of Mars, however, he asks: "How is it possible that all the observers had their telescopes unadjusted, and, if any one had, would he not be immediately aware of it?" Mr. Lindsay thought that the theory was too obviously opposed to the simplest kind of common sense to merit a moment's consideration. Mr. John A. Patterson, in his Presidential address before the Astronomical Society of Toronto, in speaking of Mars, said the discoveries rest on the bed rock of scientific evidence; and, after speaking of the supposed spectroscopic evidence that there was no atmosphere in Mars, refers to the polar snow caps, their melting, and the lines of vegetation that are supposed to mark the margin of the canals, and he asks: "Is it possible that all these may be consistent with no vapor floating above the surface? Is it sound philosophy to conclude that the condition of things on our own little world gauges the possibilities and relations that exist in our sister world? Dame Nature does not turn out all her products in one pattern." Mr. Denning, in the "Astronomische Nachrichten," No. 3926, gives the result of his observations on Mars in 1903. He says the canals, without doubt, are objective features; changes in the appearance of these markings he attributes to vaporous condensations. One rotation period of the planet satisfies the observation of all the markings, thus proving them to be definite features of the planet's surface rather than drifting vapors such as are seen when observing Jupiter and Saturn. In spite of these admissions Mr. Denning, in 1905, while repeating his convictions as to the objectivity of the canals, denied their sharp outline. Of the ten canals he drew, eight were discovered by Schiaparelli, and two were discovered by Lowell. Denning observed these lines with a ten inch reflector. Schiaparelli compared them in sharpness to lines of a steel engraving. It rests with the reader to judge who is most likely to be correct in his description of the character of the lines--Mr. Denning with a ten inch reflector, in a poor atmosphere, or Schiaparelli and Lowell, with a twenty-six and a twenty-four inch refractor, respectively, in a far superior atmosphere.