M. Chacomac on the Moon. 371 



considered analogous to the continents of the earth, is 

 clearly distinguished from the level portion by its porous 

 structure and its great reflective power, as well as by its eleva- 

 tion ; while the other is sombre and smooth, and presents, as 

 Sir J. Herschel has said, a completely alluvial character. 

 Nevertheless, there is nothing whatever to justify the ancient 

 appellation of seas, and the expression alluvial is employed 

 only in default of a more appropriate term. In fact, there is 

 not the slightest appearance of any fluid, or body susceptible 

 of evaporation, on the lunar globe, though every portion of 

 it is exposed to the direct solar radiation during 343 con- 

 secutive hours. The surface of the continents everywhere 

 displays a character of eminently volcanic, or, at any rate, 

 igneous origin. For example, in the lunar Caucasus, Apen- 

 nines, and Alps, we find a region overspread with little hillocks 

 in very close proximity, giving the aspect of a soil violently 

 agitated by a species of ebullition followed by rapid cooling. 

 In other districts the volcanic continent appears ruined to such 

 a depth by the multiplicity of craters, that they have broken 

 out in each other's interiors. In the S. part of the disc, it is 

 not uncommon to observe three or four contiguous rings, 

 which have overthrown and defaced one another in succession ; 

 for instance, the exhausted soil of the craters Metius and 

 Fabricius. The raised portion of the continents has every- 

 where a rough, rugged, puffy character, resembling that of 

 iron dross ; the rounded hill-tops, as well as the crater-rings, 

 are perforated by a multitude of little cavities and pits, indi- 

 cating a kind of most vehement ebullition. The walls and 

 environs of Metius and Fabricius, which may be cited as types 

 of this sort of formation, are so " riddled" by these perforations, 

 that they appear, under an oblique illumination, to possess a 

 structure exactly like that of the most porous pumice-stone. 

 In some neighbourhoods the strictly volcanic character pre- 

 dominates, in others the more rounded mountainous aspect; 

 but the continental regions never offer the smooth, uniform 

 appearance of the so-called seas, whose aspect is that of har- 

 dened plaster, or, still more accurately, that of immense plains 

 of dried mud. 



From these strongly-marked physiognomical characters it 

 is possible to recognise regions to which the same origin may 

 be ascribed, even though they may be separated by a vast 

 extent of the so-called alluvial plains. 



These two kinds of surface are more intermingled than the 

 terrestrial continents and seas : in the centre of the enormous 

 levels which form more than two-thirds of the visible hemi- 

 sphere of the moon, we meet with numerous archipelagos and 

 unnumbered islets, apparently the remains of ancient continents 



