*873-J Condition of the Moon's Surface. 39 



terrestrial. Alluvial deposits can have no existence, for 

 example, save where there are rivers and seas, as well as an 

 atmosphere within which clouds may form, whence rain 

 may be poured upon the surface of wide land regions. It 

 is not going too far to say that we have the clearest evidence 

 to show that in the moon none of these conditions are 

 fulfilled. Whether in former ages lunar oceans and seas 

 and a lunar atmosphere have existed, may be a doubtful 

 point ; but it is certain that all the evidence we have is 

 negative, save only those extremely doubtful signs of glacier 

 action recognised by Prof. Frankland. I venture to quote 

 from Guillemin's " Heavens " a statement of Frankland's 

 views, in order that the reader may see on how slender a 

 foundation hypotheses far more startling than the theory I 

 have suggested have been based by a careful reasoner and 

 able physicist. "Prof. Frankland believes," says the 

 account, "and his belief rests, on a special study of the 

 lunar surface, that our satellite has, like its primary, also 

 passed through a glacial epoch, and that several, at least, 

 of the valleys, rills, and streaks of the lunar surface are not 

 improbably due to former glacial action. Notwithstanding 

 the excellent definition of modern telescopes, it could not be 

 expected that other than the most gigantic of the character- 

 istic details of an ancient glacier-bed would be rendered 

 visible. What, then, may we expect to see ? Under 

 favourable circumstances the terminal moraine of a glacier 

 attains enormous dimensions ; and consequently of all the 

 marks of a glacier valley this would be the one most likely to 

 be first perceived. Two such terminal moraines, one of them 

 a double one, have appeared to observers to be traceable 

 upon the moon's surface. The first is situated near the 

 termination of the remarkable streak which commences near 

 the base of Tycho, and passing under the south-eastern 

 wall of Bullialdus, into the ring of which it appears to cut, 

 is gradually lost after passing Lubiniezky. Exactly opposite 

 this last, and extending nearly across the streak in question, 

 are two ridges forming the arcs of circles whose centres are 

 not coincident, and whose external curvature is towards the 

 north. Beyond the second ridge a talus slopes gradually 

 down northwards to the general level of the lunar surface, 

 the whole presenting an appearance reminding the observer 

 of the concentric moraines of the Rhone glacier. These 

 ridges are visible for the whole period during which that 

 portion of the moon's surface is illuminated ; but it is only 

 about the third day after the first quarter, and at the 

 corresponding phase of the waning moon, when the sun's 



