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



large pretty faint nebulae, tha-t are gradually much brighter 

 at the middle, but no well defined luminous spot could be 

 distinguished. Herschel alludes also to an eruption seen by 

 him previously, in 1783. 



Such are the general facts, which call for explanation ; to 

 wit, the existence of circular pit craters, 5 to 150 miles in 

 diameter, and 5000 to 24,000 feet in depth, — the great num- 

 ber of these pit craters, and their peculiar features,— -the de- 

 pressions of a similar character of still larger area, — and the 

 various degrees of illumination of the craters. Well may 

 the Vesuvian vulcanist look with doubt upon such vast gulfs ; 

 for he finds, in his well-known volcano, nothing parallel in 

 kind or degree. The little dark hole at the top of his moun- 

 tain has scarcely a single point of resemblance to the open 

 walled areas of the moon. 



But the case is different with Kilauea, to which we now 

 direct our attention. We observe that the facts this crater 

 presents are precisely the same in kind as those of the moon. 



1. The crater is a large open pit, exceeding three miles in 

 its longer diameter, and nearly a thousand feet deep. 



2. It has clear bluff walls through a greater part of its cir- 

 cuit, with an inner ledge or plain at their base, raised 340 

 feet above the bottom. 



3. The bottom is a plain of solid lavas, entirely open to 

 day, which may be traversed with safety ; over it there are 

 pools of boiling lava in active ebullition, and one is more 

 than a thousand feet in diameter. There are also cones at 

 times from a few yards to 2G0O or 3000 feet in diameter, and 

 varying greatly in angle of inclination. The largest of these 

 cones have a circular pit or crater at summit. 



Compare these characters severally with the lunar craters, 

 and an identity will be perceived even to the ledge that sur- 



phyrites of Hevelius. Aristarchus is described as apparently in action in 1821 

 by II. Kater, in the Philosophical Transactions for 1821, p. 130 ; also by Kev. 

 M. Ward, at nearly the same time, in the Memoirs of the Royal Astronomical 

 Society, i., 167 ; also the following year by Ilev. Fearon Fallows, in the Philo- 

 sophical Transactions for 1822, p. 237. Dr Olbers observed Aristarchus at the 

 same time witli Kater in 1821, and attributed the light to the reflection of the 

 earth's light by its smooth rocks. 



