234 



Prof, J. Phillips on some Parts of 



[Jan. 16_, 



minute puckerings, and small monticules appear and disappear in almost 

 every part. In several of the maria, minute angular cup-craters about half 

 a mile across are frequent ; and on several of the exterior slopes of the 

 crater-rings are seen pits, ridges, fissures, and rude craters, something 

 like the sloping surfaces of Etna. Copernicus is a good example of this 

 common occurrence. It appears extremely desirable that the details of 

 this magnificent mountain should be carefully reexamined on the basis 

 of Secchi's fine drawing, for the purpose, amongst others, of determining 

 exactly how many of the bosses and ridges bear cup-hillocks ; for many 

 inequalities, which in feeble telescopes have but the indistinct character of 

 being heaped up, appear distinctly crateriforra with superior optical power*. 



On the very crest of a ring-mountain it is rare to find a cup-crater ; 

 quite common to find them in the interior, especially towards the middle, 

 and, in several cases, exactly central. But it happens often that the central 

 mountain-mass of a large crater, such as Gassendi and Theophilus, is of a 

 different structure. In the former a complicated digitated mass of elevated 

 land appeared to me for a long time to be entirely devoid of any small 

 craters ; by continued scrutiny at last I see on one of the masses a distinct 

 depression. The area in Gassendi reminded me of the volcanic region of 

 Auvergne, in which, with many crater-formed mountains, occur also the 

 Puy de Dome, Puy Sarcoui, Puy Chopin, and others which are heaps of a 

 peculiar trachyte not excavated at the top, while the others are formed of 

 ashes and lava-streams and are all crateriform. The central masses of 

 Theophilus (Nos. 7, 8, and 9) are very lofty and grandly fissured from the 

 the middle outwards, with long excurrent buttresses on one side, and many 

 rival peaks separating deep hollows, and catching the light on their small 

 apparently not excavated tops. This is like the upheaved volcanic region 

 of Mont d'Or, with its radiating valleys, wide in the central part, and con- 

 tracted to gorges toward the outside of the district. 



The Yesuvian volcanic system, including the Phlegrsean fields, exhibits, 

 in all respects but magnitude, remarkable analogy with parts of the moon 

 studded with craters of all magnitudes, as those adjoining Mount Mauroly- 

 cus, engraved for comparison by Mr. Scrope in his admirable treatise on 

 Volcanos (p. 232). It is probable that many of the differences which ap- 

 pear oh comparing lunar ring-mountains may be understood as the effects 

 of long elapsed time, degrading some craters before others were set up, and 

 turning regular cones and cavities into confused luminous mounds. It 

 would much augment our confidence in the possible history of the moon 

 which these differences seem to indicate, if we could believe it to have 

 ever been under the influence of atmospheric vicissitude as well as changes 

 of interior pressure. 



That the latter cause has been in great activity at some early period 

 of the moon's history is not only evident, by the many sharply cut fis- 



* See " Comparative Eemarks ou Gassendi aud Copernicus," Koy. Soc. Proc. for 1856, 

 p. 74. 



