HOW TO SKETCH THE MOON. 
235 
with regard to its successful delineation. Much attention has 
of late been given to selenography, and very deservedly ; but 
the practical results might be of more value, if operations were 
•conducted on a more systematic plan, and with a more definite 
understanding of the possible causes of misconception or illu- 
sion, such as might easily influence the judgment of an in- 
experienced, although keen-sighted and careful observer. A 
few hints, therefore, may be permitted, which may be of ad- 
vantage to the student at the commencement of his labours. 
It may be assumed that no fresh attempt will now be made 
to represent any extensive area of the lunar surface. This 
would be only (except for practice) so much trouble thrown 
away. The broader features have been already abundantly 
delineated by Schroter, Lohrmann, and Beer and JMadler. Our 
immediate object is to fill in the outline, which they have • 
given with so much general fidelity, but by no means a corre- 
sponding minuteness of detail. This, indeed, could not in 
fairness have been expected, and would naturally be left to the 
labours of the future. And now a single large walled-plain or 
crater, or insulated mountain-group, or definite portion of a 
level region, will provide sufficient occupation for many nights, 
till every detail which the telescope employed can grasp is 
identified and delineated with as much correctness as the 
present state of our knowledge may justly require. Much has 
been said of the value of photography in producing such repre- 
sentations. Nor is there the slightest intention of disparaging 
its just claims. Grreat honour is due to those eminent men 
who have carried it through such discouraging impediments : 
its results have already proved most valuable, and its peculiar 
advantages are otherwise unattainable. No eye can be so 
certain of including every visible feature ; no hand can place 
■every detail so accurately in its relative position. The supe- 
riority of the self-produced picture in each of these respects 
will be very evident to anyone who has remarked how often 
objects are unnoticed in sketching, the detection of which on 
■a subsequent occasion may prove a source of error (Schroter’s 
new crater in Hevel was probably a case in point), or how 
much drawings of the same objects by different hands differ in 
proportion and character, of which the various representations 
of the walled-plain Grassendi are an instructive example. But 
there is a sharpness and decidedness in telescopic vision, which 
we miss in photographic portraits ; and from this cause the 
camera may fail to exhibit the existence, or at any rate the 
true character, of the minutest features. And besides this, 
whatever may be the perfection of the photographic apparatus, 
the nights in which the air is sufficiently steady to admit of 
the development of its full ability are few indeed, compared 
