The same remark applies, with some modifications, to the dark markings which have been detected on the planet by all sorts of observers with all sorts of telescopes. There is no doubt that faint grey markings, such as those shown in Plate X., are to be seen; the observations of many skilled observers put this beyond all question. Even Denning, who says that personally he has sometimes regarded the very existence of these markings as doubtful, admits that 'the evidence affirming their reality is too weighty and too numerously attested to allow them to be set aside'; and Barnard, observing with the Lick telescope, says that he has repeatedly seen markings, but always so 'vague and ill-defined that nothing definite could be made of them.' The observations of Lowell and Douglass at Flagstaff, Arizona, record quite a different class of markings, consisting of straight, dark, well-defined lines; as yet, however, confirmation of these remarkable features is scanty, and it will be well for the beginner who, with a small telescope and in ordinary conditions of observing, imagines he has detected such markings to be rather more than less doubtful about their reality. The faint grey areas, which are real features, at least of the atmospheric envelope, if not of the actual surface, are beyond the reach of small instruments. Mr. MacEwen's drawings, which accompany this chapter, were made with a 5-inch Wray refractor, and represent very well the extreme delicacy of these markings. I have suspected their existence when observing with an 8-1/2-inch With reflector in good air, but could never satisfy myself that they were really seen.