HOW TO SKETCH THE MOON. 
241 
once threw open such amazing gulfs, and piled up such terraces 
and towers and pyramids, and overspread such wide-extended 
areas of the globe with confusion and ruin. Some observers 
may have perhaps been precipitate in assuming the utter and 
final collapse of all those ancient and evidently long-enduring 
energies. It were safer to wait and see whether all is indeed 
so dead and cold. And, again, we must not assume, we have 
to prove — if it can be proved — the absence of atmospheric 
phenomena. This is not one of those cases where an un- 
demonstrated negative may suffice. The burden of proof — or 
rather disproof — here naturally rests upon the opponent, when 
all analogy is in favour of some kind of gaseous envelope : and 
whatever may, or rather must, be its tenuity as compared with 
our own, its total absence would be contrary to all chemical 
and mechanical probability. Nor is it a mere theoretical 
question : indications are not wanting that the inferences of 
Schroter and Grruithuisen, to whatever exception they may be 
liable in their full extent, are at any rate deserving of some 
consideration. We may be called upon to make abundant 
deductions on the score of precipitancy and prepossession, and 
yet a residuum may be found to exist, small in amount, but 
refractory in character, which cannot be disposed of by any 
summary mode of treatment. Simple negation will not suffice, 
much less contemptuous neglect of the labours of those who 
have preceded us. The first general aspect of that great world 
lying in its confusion and desolation may indeed be, to some 
eyes, that of absolute quiescence and arid sterility ; a wilderness 
of rock and sand, lifeless and even soundless, in its unclothed 
contact with the emptiness of boundless space. But the student, 
in proportion to his earnestness and perseverance, may see cause 
to be distrustful of first impressions ; he will rather be looking 
out carefully for those minute indications — and experience has 
proved that only minute ones can be expected — which may yet 
show to a well-trained eye and cautious judgment that such a 
conclusion would be too precipitate. At any rate the question 
is not yet set at rest ; and it can only be finally decided by the 
faithful carrying out, in very circumstantial detail and with 
scrupulous accuracy, that graphical representation of the surface 
which has formed the subject of the preceding remarks. 
It need scarcely be mentioned that a record of time is an 
important element in the value of any such representations, as 
a few hours would occasionally be of considerable significance 
in a subsequent comparison ; and in such comparison any 
difference of libration will have to be carefully allowed for at 
■ any material distance from the centre of the disc. Personal 
equation enters so much into all these matters, that it may 
be desirable in the first instance to institute comparisons 
VOT,. XTI. — NO. XLVIII. R 
