Mr J. D. Dana on (he Volcanoes of tJte Moon, 11 



and never obscured by clouds, its features are wholly open 

 to view, and the eye, aided with glasses, may wander over its 

 rugged crags, survey its craters, its Alps and its Apennines, 

 from their bases to their summits. Neither are there any 

 sedimentary deposits, soil or vegetation, — for there can be 

 none without water, — and the igneous surface, therefore, is 

 still its own naked self, exhibiting the results of igneous ac- 

 tion in their simple grandeur, unaltered and uncomplica- 

 ted by any attending operations. We may hope, therefore, 

 to find some profit in contemplating for a few moments this 

 land of the skies : and although we may not look for very 

 speedy " annexation," we may possibly gather some facts 

 and ideas which the decree of Truth will annex to the domain 

 of Science. 



The moon, as we all know, has been minutely studied in a 

 physical point of view, and already some important geological 

 conclusions have been drawn from the facts it presents. The 



eclipse, Sept. 5, 1793, observed the sharp horn of the limb of the moon, and 

 says that it seemed perfectly regular ; and that a deviation of a single second 

 by the refraction of the solar light in the moon's atmosphere would not have 

 escaped him. Phil. Trans., 1794, p. 39. — As stated in Beer and Miidler (p. 

 133), Schroter calculated the density of the supposed atmosphere to be one 

 twenty-eighth the density of our own atmosphere ; and Melanderhjelm demon- 

 strated that the moon's atmosphere, judging from that of the earth, should 

 have one thirty-sixth the density of our own atmosphere. But the above-men- 

 tioned authors say that we have yet to prove that the moon has any atmo- 

 sphere, adding, that it must be very much more rare than the rarest gas on 

 earth. They observe also, that supposing our atmosphere to extend through 

 space, its density half way to the moon, according to the Mariottian law of de- 

 crease, would be expressed by the fraction ttjtjVt)©* the denominator extending 

 to ten thousand zeros. The singular observation occasionally made, that during 

 the passage of the moon over a star, the star appears visible in front of the edge 

 of the moon, before disappearing, may possibly indicate an extremely thin at- 

 mosphere or surface vapours : but it has been attributed, with much appear- 

 ance of reason (Kep. Brit. Assoc, 1845, p. 5), to diffraction. 



The absence of any bodies of water on the moon is placed beyond doubt, both 

 by actual telescopic examination, and by inference from the absence of clouds. 

 There are no streams, lakes, or seas. An eminent astronomer has remarked, 

 that the heat of the surface exposed to the sun would occasion a transfer of 

 any water the moon might contain to its dark side, and that there may be frosts 

 in this part, and perhaps running Mater near the margin of the illuminated 

 portion. But in such a case, would not clouds appear about the margin at times 

 in telescopic views i 



