The photographs were taken with a sixty-inch telescope, and possibly this very large aperture was not stopped down sufficiently to secure on the photographic plates such very fine detail as the canal lines; on the other hand, the atmospheric conditions at the moments of exposure of the plates may have been unfavourable for good definition. However good the photographs may be, the deductions drawn from them are erroneous. Against such purely negative evidence--which never affords good ground for argument--we must set the positive evidence of Professor Lowell's numerous photographs, which do show many of the canal lines and also confirm the drawings of observers. Professor Schiaparelli, who has been appealed to on the subject, still maintains the objectivity of the canal lines which he was the first to discover, and repudiates the suggestion that the new photographs supply any evidence against them. He remarks that during the last thirty years many other astronomers, using more perfect telescopes than his, have observed and drawn these canal lines, and have taken photographs which reproduce an identical disposition of the lines. He adds that a collective illusion on the part of so many astronomers is impossible, and that the photographs which do show the canals cannot be illusions. Professor Lowell controverts M. Antoniadi's claim to have proved that the lines are non-existent, and that the only markings are small separate shadings which are illusively seen as lines. He points out that what M. Antoniadi has seen is exactly what would be seen when using a very large telescope, and that it indicates poor seeing instead of good definition. He remarks that when using such large instruments, which are so much more affected by atmospheric conditions than smaller ones, the diffraction rings round a star (which should appear as complete concentric circles) begin to waver, then break up into fragments--a sort of mosaic--and finally end in an indiscriminate assemblance of points. In certain kinds of bad seeing the parts may seem quite steady, but the fact that the mosaic exists is proof positive of poor seeing. What happens to the rings in such circumstances must also happen to fine lines! the mosaic effect seen by M. Antoniadi is therefore "the exact theoretic effect that a large aperture should produce on continuous lines, such as the canals, and always does produce in the case of the rings in the image of a star!" It has been stated that Professor Lowell had admitted the illusory nature of the canal lines. His reply, however, is emphatic: "I have never made any retractation as to the reality and geometricism of the canals; they are marvellous beyond conception, and are only doubted by those who never observed the planet itself sufficiently well."