The Surface of the Moon. 63 



him much, embarrassment if he merely wishes, as is usually the 

 case, to obtain a good knowledge or satisfactory drawings of 

 lunar outline or relief, but which ought, nevertheless, to be 

 clearly understood and taken into account. It would form 

 of itself a most interesting investigation, and one as to which, 

 at present, not much seems to have been done ; and it is to be 

 hoped that it may be taken up as a distinct but very important 

 branch of selenography by some out of the many amateurs 

 who are now directing telescopes of abundant competency 

 towards our satellite. We are referring to the very remarkable 

 effect of the different reflective power of different portions of 

 the lunar surface. This, of course, is perfectly developed in 

 the full moon, when, from the coincidence of the direction of 

 vision with that of illumination, all true shadows disappear, 

 and the circular disc, if homogeneous in its nature, would be 

 overspread with an unvaried brightness, instead of that strange 

 intermingling of clouds and stains and streaks and patches of 

 light and darkness which is visible in some measure to the 

 naked eye, and is so peculiarly unintelligible in the fuller 

 revelation of the telescope. 



There can be no doubt that the cause of all this variety is 

 to be sought in the local colour of the surface, whose tints, 

 however diversified, would naturally, at that distance, be so 

 blended and confused as to assume the appearance of different 

 shades of grey ; but it is not so easy to comprehend the singular 

 manner of their disposition, and it would be a curious inquiry 

 how far any terrestrial analogy would help us towards an 

 explanation. It is probable that, in some respects, our own 

 lands, if viewed from the moon, would present an aspect not 

 very dissimilar. The variegated hues of oar familiar landscapes, 

 the red tint of many soils under the plough, the green of our 

 meadows and woods, and the yellow of our ripe com, would 

 not be separately recognized from their small angular extent, 

 but would produce by their intermixture a neutral tint of vary- 

 ing degrees of intensity in different places ; and if it should be 

 objected that where the masses of colour are sufficiently 

 extensive their separate existence ought to be recognized, and 

 that we cannot suppose any difference beyond that of bright- 

 ness between the aspect of the sands of Sahara and the forests 

 of Brazil, it may be replied that some such indications of 

 widely-spread local hues have actually been traced in the moon 

 by Beer and Madler, and that Piazzi Smyth was obliged to 

 have recourse to colour to give sufficient likeness to his 

 spirited sketches, at first attempted in one uniform tint. But 

 this would still leave unexplained much that the student will 

 soon find to be very strange in the disposition of the lunar 

 lights and shades, and especially in connection with the forms 



