J. D. Dana on the Volcanoes of the Moon. 337 
year, has published important observations on the features of the 
moon’s mountains, and traced out their voleanic character.* A 
very valuable memoir on the same topics has been presented with- 
in the current year to the Institute at Paris, by M. Rozet, in which 
the moon is shown to have been a globe in complete fusion, which 
has slowly cooled ; and its peculiarities are dwelt upon as an ex- 
hibition, in many rexpdetss of the former state of our own planet.t 
“In all the geological observations which have been hitherto 
made with regard to the moon, one important feature remains un- 
satisfactorily explained. I refer to the vast magnitude of its era- 
ters. It is not surprising that in view of their stupendous size, 
many should have been incredulous as to their crater character, 
and preferred to designate them by some non-committal term, as 
circular ridges, or ring-mountains ; nor that geologists in general 
have hardly ventured to acknowledge their belief in these lunar 
_ Imagine if possible, in place of an ordinary crater, cir- 
cular ateas 50 to 150 miles in diameter, and 10,000 to 20,000 feet 
in depth. -Such are many of the lunar craters; and they are 
crowded in great numbers over the larger part of its surface, va~ 
tying from even a more capacious magnitude, down to those that 
Measure’ but a few miles in breadth. It is not astonishing 
_ that there should be found much ‘difficulty in reconciling their 
features with those of Vesuvius and Etna, hitherto received too 
generally as the types of volcanoes and volcanic action. The 
crater of Kilauea in the Hawaiian Islands is of a wholly different 
character, and I propose to present some illustrations which it af- 
fords, appealing to such general facts regarding it as are already 
well known. If I mistake not, it will be found to give a full in- 
terpretation of whatever has been considered mysterious in these 
lunar ring-mountains. After these’ illustrations, we may return 
again to earth, and apply the knowledge which we have derived 
abroad, m exemplifying the former ese on history of our own 
a may first consider the gener features of the moon’s sur- 
“About two-thirds of hig fever betaibphiorel in view, oasis 
almost the whole of the aisstiay ball and the northeast quarter, 
RG a SNS 
_ Aran ages myth, Esq, pl 
sh Main sk oe Rend me xxii, 470. 
