Mars

The generally bluish green colour of the dark markings, taken in conjunction with seasonal changes to which they appear to be subject, has provided the suggestion that they are areas of vegeta tion, an interpretation that has been accorded warm advocacy by certain astronomers, more especially, perhaps, those whose inter est is centred in habilitating an hypothesis of close parallelism between organic phenomena on Mars and on the earth. While the present writer is, to borrow a phrase of Schiaparelli from a pas sage quoted elsewhere in this article, "very careful not to combat this supposition, which includes nothing impossible," he has recently pointed out that a high content of blue and violet light is to be expected in the image of dark surface areas, as a conse quence of the superposition upon them of the Martian sky. That the planet's sky probably influences the colour and appearance of the surface has long been recognized, but the evidence of recent photographic observations, to be referred to later, suggesting as it 'The description sent by Mr. Slipher with the photographs is as follows: "Actual photographs of the planet Mars displaying the gradual decrease of the snow at the south pole and the darkening of the planet's tropics with the advance of Martian summer. This gradual darkening of certain regions of the planet in his summer season and their subsequent fading in winter seems best explained by assuming that these dark areas are due to vegetation." The responsi bility for the interpretations rests, of course, with Mr. Slipher.

does that a very large proportion of the blue and violet light from even the brighter parts of the planet is due to the overlying atmosphere, seems to require an alteration in the apparent colour (in the spectral direction green to blue) of surface markings, as a consequence merely of their darkness; in other words, the dark areas might be expected to appear bluish green whether that is their real colour or not. The change from blue-green to yellow, found to accompany the seasonal fading of the dark areas, would, according to this view, be merely a consequence of their fading; but changes from green to chocolate-brown, observed by Lowell in 1903 and 1905, cannot be so regarded.

The Canals.

If comment were confined to what is universally agreed upon with respect to the finer markings which pass under this designation very little could be said. That such markings exist there can be no question, and A. E. Douglas's discovery of similar features on the dark areas themselves appears to have been generally confirmed. Their visibility, like that of the seas, is vari able, some appearing at one time and some at another, so that their appearance in the telescopic view is not to be inferred from the network shown on one or another chart which usually includes all that have been seen, at least in a given season, by the person drawing it. Some observers report the canals as of sensible width, others as extremely fine, hair-like lines, while still others record canals of both descriptions. Schiaparelli, whose pioneer study of them is specially valuable, described them as straight, direct and continuous, and numerous observers have confirmed this impres sion of their appearance (Lowell, Mars and its Canals, p. 29), though astronomers of at least comparable skill and experience have reported deviations from rectilinearity, and have suggested that some of the more difficult of them may be merely the conse quence of grouping by the eye of minute markings which are not separately visible, the apparent continuity being a subjective effect (Pickering, Mars, chap. xiv.; Trumpler, Publ. Astron. Soc.

Pacific, vol. 39, p. 106; Annual Rep. Mt. Wilson Obs., 1925, p. 103.) Schiaparelli reported a gemination, or doubling of certain of the canals at stated seasons, and very positive statements have been made in confirmation of this, notably by Lowell and his fol lowers. On the other hand, skilled observers, among whom may be mentioned Barnard and Pickering, have failed to observe such conditions, despite long continued and careful scrutiny of the planet. These diverse findings would seem to prove that a study of the finer structure of the canals is beyond our present means of observation.

The impression of straightness and geometrical regularity made by the canals has stimulated the imaginations of certain astrono mers to see in them the works of intelligent beings. Why this should be so is not altogether apparent. The remarkable systems of streaks which radiate from some of the craters of the Moon are not so interpreted, while the works of man which might be regarded as of sufficient magnitude to be visible to a well equipped celestial observer are not distinguished by geometrical regularity. A world-encompassing phenomenon suggests the action of geo logical forces, and Schiaparelli was among those to suggest the play of these in the formation of the canals. His reflections on the suggestion that they are the work of intelligent inhabitants of the planet are of interest, and we are indebted to a translation of one of his essays (Mars, pp. 92-94) by Prof. W. H. Pickering for the following passage : Their [the canals'] singular aspect, and their being drawn with absolute geometrical precision, as if they were the work of rule or i compass, has led some to see in them the work of intelligent beings, inhabitants of the planet. I am very careful not to combat this sup position, which includes nothing impossible. . . . Let us add further that the intervention of intelligent beings might explain the geometrical appearance of the gemination, but it is i not at all necessary for such a purpose. The geometry of nature is manifested in many other facts, from which are excluded the idea of any artificial labour whatever. The perfect spheroids of the heavenly bodies and the ring of Saturn were not constructed in a turning lathe, and not with compasses has Iris described within the clouds her beautiful and regular arch. And what shall we say of the infinite variety of those exquisite and regular poly hedrons in which the world of crystals is so rich ! In the organic world, also, is not that geometry most wonderful which presides over the dis tribution of the foliage upon certain plants, which orders the nearly symmetrical, starlike figures of the flowers of the field, as well as of the animals of the sea, and which produces in the shell such an exqui site conical spiral that excels the most beautiful masterpieces of gothic architecture? In all these objects the geometrical form is the simple and necessary consequence of the principles and laws which govern the physical and physiological world. That these principles and these laws are but an indication of a higher intelligent power, we may admit, but this has nothing to do with the present argument.