has refused to show them to this day, are facts that speak emphatically on the point.
The importance of atmosphere in the study of planetary detail is far from being appreciated. It is not simply question of a clear air, but of a steady one. To detect fine detail, the atmospheric strata must be as evenly disposed as possible.
Next in importance to a steady air comes attentive perception on the part of the observer. The steadiest air we can find is in a state of almost constant fluctuation. In consequence, revelations of detail come only to those who patiently watch for the few good moments among the many poor. Nor do I believe even average air to be entirely without such happy exceptions to a general blur. In these brief moments perseverance will show the canals as faint streaks. To see them as they are, however, an atmosphere possessing moments of really distinct vision is imperative. For the canals to come out in all their fineness and geometrical precision, the air must be steady enough to show the markings on the planet's disk with the clear-cut character of a steel engraving. No one who has not seen the planet thus can pass upon the character of these lines.
Although skepticism as to the existence of the so-called canals has been now pretty well dispelled by these and other observations, dis-
