Reviews — Nasmyth and Carpenter on the Moon. 273 



MM. Nasmyth and Carpenter, and exhibited in their photographs, 

 are (2) plains and plateaux, superficially more or less smooth, sug- 

 gesting the idea of the consolidated surface of a sea of mud or lava, 

 upon which the innumerable cones and craters already mentioned 

 are profusely scattered. (3) Mountains, often occurring singly in 

 the centre of the crater rings, not unfrequently, however, having 

 several distinct peaks, and in some cases, but not many, rising from 

 the plains in rough wrinkles or linear ranges. None of the^e 

 eminences show any signs of craters upon their summits or sides, as 

 is generally ihQ case with the volcanic mountains of our globe. (4) 

 Bright but narrow streaks, usually radiating from some conspicuous 

 crater in all directions, and to distances of many hundred miles. 

 These streaks pass over all the other superficial features without dis- 

 turbing them, and rise so slightly above the surfaces they traverse 

 as to cast no shade on either side, however obliquely the sun's rays 

 strike them. Indeed they are only visible when the light falls 

 directly upon them. They convey the impression of having been 

 cracks in the already consolidated surface, starred by internal expan- 

 sion, from which liquid matter has exuded throughout their whole 

 length, and overflowed their edges, but without spreading laterally to 

 any distance. (5) Other evident cracks, narrow but deep, and to all 

 appearance empty, which likewise traverse large portions of the 

 lunar plains, and sometimes cut through a mountain range. 



These features are on the whole not very dissimilar from those 

 observable in volcanic districts on our earth's surface. The resem- 

 blance at least is sufficiently close to justify the general notion that 

 they have been produced by forces analogous to terrestrial vulcanicity. 

 The differences, however, suggest proportionately different conditions 

 under which volcanic action has operated on the respective surfaces 

 of the two planets. 



For example, while the volcanos of our earth are, as a rule, and 

 appear always to have been, intermittent in their activity, — intervals 

 of quiescence usually alternating with periods of eruptive violence 

 from the same vent, so as to produce in the result a conical moun- 

 tain with a crater on its summit, — not a single instance of this 

 kind, as has been already noticed, is to be met with on the moon. 

 Craters there are, as has been said, in numbers, encircled hy ram- 

 parts of varying heights, in some cases reaching 15,000 feet 

 from their base. But the area inclosed by these circular ranges 

 is too large to admit of the whole elevation bearing any re- 

 semblance to a volcanic mountain, the result of repeated erup- 

 tions, like Etna, the Peak, Cotopaxi, Chimboraso, Ai-arat, Fusiyama, 

 etc. It would seem that each of the lunar craters was the pro- 

 duct of only a single eruption, as in the case of the Phlegrgean 

 fields, the Pu^'s and crater-lakes of central France, the Eifel, etc., 

 — the craterless hills which so often rise in the centre of a lunar 

 crater having been the final product of the eruption which 

 hollowed it out, and threw up the encircling rampart, thus cor- 

 responding to the domes or bosses of trachyte sometimes found in 

 the interior of terrestrial craters, such as Astroni, liocca Monfina, the 



DECADE n. VOL. I. — NO. VI. 18 



