Mr J. D. Dana on the Volcanoes of the Moon. 15 



said by Beer and M'adler to be often but one-half or one-third 

 the height above the bottom of the crater ; the outer slopes 



Fig. 2. 

 Fig. 1. — — — i 



are generally steep, so 

 that the margin appears 

 like a raised rim around 

 the pit. 



Mr Nasmyth figures 

 one which is filled to its 

 summit, and is tipped 

 with a plain 40 miles in 

 diameter;* looking, he 

 says, as if *' brim-full of 

 molten lava," having 

 cooled, probably, when 

 thus filled. 



termincd : with regard to the breadth of the craters, there can be no more 

 doubt, than with resjiect to the diameter of the moon itself. 



There are many who receive with scepticism the facts we have stated, or even 

 deny where they know nothing. It is taking a high ground, to dispute with 

 all the astronomers since Galileo, and one to which ignorance alone would pre- 

 sume. The best antidote we can propose to such presumption, is to take the 

 first opportunity which offers, to look through a good telescope at the moon's 

 surface, and examine its features for themselves. We j^redict that they will 

 soon become conscious of a growing willingness to be humble learners of such 

 men as Hcrschel and others who have made the moon their study. 



* Mem. of the Roy. Astronom. Soc, xv., 152. 



