92 Influence of Gravity on the 
Art. IX.—On the Influence of Gravity on the Physical 
Condition of the Moon’s Surface. By BALFOUR STEWART, 
Esq. 
THE great irregularities of the surface of our satillite, are 
discernible almost without the aid of a telescope, but, by 
means of this instrument they have been accurately measured ; 
and their stupendous character impressed upon the mind, 
which is thus enabled to compare them with the irregularities 
of the Earth’s surface. The appearance presented by the 
moon’s disc, is thus described by the Rey. Josiah Crampton, 
in his work entitled Zhe Lunar World; its Scenery, 
Motions, &c. 
“Not only,” he remarks, ‘‘are her mountains more numerous in 
proportion to her size than those of the earth, but they are much larger, 
rising to a much loftier elevation, composed apparently of a stibstance 
of a much harder texture than any thing terrestrial, and exhibiting _ 
bolder and sharper outlines, and more tremendous precipices, some of 
which project and overhang each other in such a manner as to lead 
many to suppose that the rocks composing them are of a harder and 
more solid nature than wrought iron.” 
And the Dublin University Magazine, for February, 1854, 
remarks on the same subject. 
‘Some important diversity must prevail, no doubt, for it cannot be 
by chance, that inthe lesser body sheer cliffs of thousands of feet des- 
cend from mountain tops into the valleys or chasms, while in the larger, 
no search has yet succeeded in discovering a perpendicular descent of 
five hundred feet anywhere. The moon’s craters cling to the sides of 
cliffs, cut into, encompass, and over-leap each other. In dimensions 
some of them measure one hundred miles.” 
With regard to the cause of this diversity I would venture 
an explanation. I do not look for it in any difference of 
material; for I am neither inclined to imagine with some that 
the moon’s surface has more tenacity than wrought iron, nor 
with others that it resembles cork. I would rather look for 
its chief cause in the difference between terrestrial and lunar 
gravitation. A long rod of iron will bend, and a sufficiently 
long rod of any brittle substance will break by its own 
weight; but if these be placed in circumstances where they 
retain their tenacity and all their other qualities unchanged, 
with the exception of their gravity, which is lessened, the 
rod of iron will not bend so much, and it will require a greater 
length of the brittle substance in order to break it. Now 
the weight of the same body is much less on the moon’s 
surface than on the earth’s. For the attraction of a sphere 
of matter on any point, without its force and distance, is the 
