162 Professor Secchi's Description of Lunar Volcanoes. 



Another distinct character of these volcanoes of the first 

 class is, that they are in a line, as if they burst from the 

 cracks of the solid body of the crust produced by earlier 

 formations : this is most striking in Arzahel, Purbach, Al- 

 phonsus, and many others, and they seem to follow the cracks 

 made by the soulevement which raised Tycho, the lunar Ap- 

 pennines, &c. Some of the higher chains of lunar mountains 

 are seen visibly parallel to the alignement of the craters : 

 this fact also is like that which we observe on the earth ; in- 

 deed, the large Italian volcanic chain follows the line of the 

 Apennines along this country. 



" The second class of lunar volcanoes are those which 

 have their outside edges elevated above the surrounding plain; 

 their form is generally regular, and not broken, as those of the 

 preceding class, and the ground around them is elevated in 

 a radiating disposition, as is visible around Tycho, Coper- 

 nicus, Aristotle, &c. The regularity of their forms suggests 

 that the ejected matter was not disturbed by the motion of 

 waves, and, consequently, that they were atmospherical vol- 

 canoes, like those of the Monti Laziali, Albani, and Tuscu- 

 lani, at the south-east of Rome ; the want of breach in the 

 craters seems to indicate that no lava, but only scoriae and 

 loose matters have been ejected. The disposition of the 

 soil around them suggests the opinion that they are of a 

 comparatively later epoch, and formed after the crust of the 

 satellite was pretty resistant, and was capable of being ele- 

 vated all round by a great effort. It is singular, indeed, 

 that this radiation of the soil around is found proportional 

 to the magnitude of the central crater. The effect of this 

 soulevement extended sometimes to a prodigious distance, 

 comparable to that of the Cordilleras of the Andes on the 

 earth. The greater part of the craters of both the classes 

 now described possesses an insulated rock inside, very seldom 

 appearing (at least in commonly good telescopes) perforated. 

 This bears great analogy with what we see in more than 

 one place in the ancient volcanoes of the earth, where the 

 erupting mouth has been stopped by a dome of trachytic 

 matter as by a stump. Monte Venere, near Rome, is of this 

 formation, and lies in the centre of an immense old crater. 



