J. D. Dana on the Volcanoes of the Moon. 335 
Arr. XXX.—On the Volcanoes of the M oon ; by James D. “ong 
| Read wonee the Assoc. of Amer. Geologists and Naturalists, Sept, 1846.) 
Tae ad of the moon affords a most interesting subject for 
the study of the geologist. Though at a distance ve many thou- 
_ sand miles, the telescope exhibits to us its structure with won- 
- derful distinctness ; and already, as a learned astronomer has ob- 
served; we are better acquainted with the actual heights of its 
Mountains, than with those of our own planet.* Having an atmo- 
sphere of extreme rarity} (if any) and never obscured by clouds, 
its features are wholly open to view, and the eye aided with 
S, may wander over its rugged crags, survey its craters, its 
ie and its Apennines, from their bases to their summits. _Nei- 
ther are there any sedimentary deposits, soil, or vegetation,—for 
ome there can be none without water,—and the igneous surface 
therefore j is still its own. naked self, exhibiting the results of ig- 
| rs halal 
*M. Arago, ang des Lonptudde pour I’an 1842, 2d ed., Paris, 1842.—P. 
526, in an a n the Lunar Volcanoes, Arago says :—* I] est remarquable que 
eta 1 exactitude d’Hevelius on ait connu la hauteur des inentegnas 
de Ja Lune Sa plus tOt que la hauteur des montagnes de la Terre. 
yet to prove that the moon has any atmosphere, adding that it must be v 
Much more rare than the rarest gas on earth. They observe also that sepidaiiag 
our atmosphere to extend through space, its density h half way to the moon, ac- 
yet. to the Mariottian law of d ectease, would be er eee by ae fraction 
son (R 
‘The enn of any , bodies of ‘eats on Shei 
by Actual telescopic examination and by in _fupiinns fro 
There « are no streams, lakes or seas. ‘Aneminen 
¥ of the surface 
is placed beyond doubt, both 
m ad ewe * oe tay 
at the 
transfer of any water the 
this obi and per- 
4 a case, 
ould occasion a 
