THE MOOH. 
615 
the eye are the remarkable mountainous circular formations. 
Their similarity to the great volcanoes of the earth_, extinct 
or otherwise_, has often been remarked. The maps of the 
environs of Naples^ of Yesuvius_, of the volcanoes of Auvergne 
and Teneriffe_, present the same features. But those sink into 
insignificance when compared with the vast smTace of the 
lunar volcanoes^ and could scarcely be perceived if seen from 
the moon_, and the whole of those known on the earth might 
be placed within one of the lunar annular mountains. They 
are different in other respects from the earthly volcanoes^ as 
the bottoms of the craters on the mooAs surface dip below the 
general surface. The central peak^ which appears in many of 
those formations^, is also reproduced in the volcanoes of the 
earthy and is so perfect and decided that it is astonishing to 
believe that Kepler could think for a moment that they were 
artificial formations excavated by the lunar inhabitants to 
shield themselves from the rays of the sun. The perfect 
annular mountains with a concave interior (to distinguish them 
from the walled plains and craters) are the most beautiful and 
regular of this group^ and appear to have been the latest 
efforts of volcanic action. Among the most perfect speci- 
mens of this class are the well-known mountains Tycho, Ke^jlcr , ' 
and Copernicus, which are easily recognized by being sur- 
roundecl by bright rays^ and which will amply repay a minute 
examination. A mountain of this description^ situated at the 
end of the chain of the Apennines and a little to the N.W. of 
Copernicus, is a perfect model of this class of objects. The 
outer walls_, brilliantly white^ as they rise from the level plain^ 
are strikingly in contrast with the black shadows and grey 
seas which surround this volcano. Its interior walls are much 
more steep_, but^ like the outer_, gradually descend by a series 
of steppes and terraces. In general the proper concave 
annular mountains are much inferior in size to the circular 
walled plains^ and Eratosthenes, which is the name of the 
mountain just described^ is only thirty-six miles in diameter. 
The walls are not of equal height all round_, for whilst the 
eastern wall^ as measured from the plain, is 7,500 feet high, the 
western one is only one-half that quantity. If measured from 
the interior, however, the eastern wall is 16,000 feet high, and 
that of the western about 10,000. The central peak or peaks 
are a crowd of rocky fragments, and do not rise to the 
height of the surrounding wall, which will be found to be the 
case with the other central peaks. The mountains Copernicus 
and Tycho, and the surrounding parts, with their bold and 
grand scenery, present a magnificent sight, and their terraces, 
peaks, and the shadows of their rugged tops, can be seen with 
even small telescopes. We lately viewed some of those annular 
