Royal Astronomical Society. 145 



raised Tycho, the lunar Apennines, &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 ; 

 indeed, the large Italian volcanic chain follows the line of the Apen- 

 nines along this country. 



"The second class of lunar volcanoes are those which have their 

 outside edges elevated above the surrounding plane ; 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, Copernicus, Aristotle, &c. The regu- 

 larity of their forms suggests that the ejected matter was not dis- 

 turbed by the motion of waves, and, consequently, that they were 

 atmospherical volcanoes, like those of the Monti Laziali, Albani, and 

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

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

 ters, 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 resistent, and 

 was capable of being elevated all round by a great effort. It is sin- 

 gular, indeed, that this radiation of the soil around is found propor- 

 tional 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 forma- 

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



" I'he third class of lunar craters is very small, and bears a great 

 likeness with those called by geologists adventitious craters, and 

 seems to be of a very late formation, the last efforts of the expiring 

 volcanic force. They are irregularly scattered through all the moon, 

 but occur more frequently at the borders or inside of the old de- 

 molished craters, although not concentric with them, and seem to 

 have been produced after the large ones were completely closed, 

 either by trachytic ejection or by becoming lakes. These small 

 craters have very seldom rocks inside, or a flat bottom ; but their 

 cavity is conical, and does not exceed in dimension our common vol- 

 canoes, which are yet active on the earth. From these facts and ob- 

 servations it appears, that volcanic action has gone on in the moon 

 through all the same stages which it has gone and is going on in the 

 earth, and is there probably completely extinguished, on account 

 of the smaller mass of the moon, which has been cooled very rapidly. 

 This rapidity of cooling, joined with the smaller gravity, may ac- 

 count for the great development of volcanism there, and compara- 

 tively fewer Plutonian formations. But extensive instances of this 

 kind are not wanting ; the lunar Alps, the Apennines, the Ripheae, 

 &c., may represent this formation, surrounding vast basins, and 



