sun’s rays as due to the age of the moon. This explanation does not, however, dispose of the question whether the crater under notice suffered any actual change before the hue and cry was raised concerning it. Attention was first directed to it by Schmidt, of Athens, whose powers of observation are known to be remarkable, and whose labours upon the moon are of such extent and minuteness as to claim for his assertions the most respectful consideration.[14] He affirmed in 1866 that the crater at that date presented an appearance decidedly different from that which it had had since 1841: that whereas it had been from the earlier epoch always easily seen as a very deep crater, in October 1866 and thenceforward it presented only a white spot, with at most but a very shallow aperture, very difficult to be detected. Schmidt is one of the very few observers whose long familiarity with the moon entitles him to speak with confidence upon such a question as that before us upon the sole strength of his own experience; and this case is but an isolated one, at least it is the only one he has brought forward. He is, however, still firmly convinced that it is an instance of actual change, and not an illusion resulting from some peculiar condition of illumination of the object. It should be added also on this side of the discussion that an English observer, the Rev. T. W. Webb, while apparently indisposed to concede the supposition of any notable changes in the lunar features, has yet found from his own observations that, after all due allowance for differences of light and shade upon objects at different times, there is still a “residuum of minute variations not thus disposed of” which seem to indicate that eruptive action in the moon has not yet entirely died out, though its manifestation at present is very limited in extent. It appears to us that, if evidence of continuing volcanic action is to be sought on the moon, the place to look for it is around the circumference of the disc, where eruption from any marginal orifice would manifest itself in the form of a protruding haziness, somewhat as illustrated to an exaggerated extent in the annexed cut. [Illustration: Fig. 46.]