30 Lunar Details. 



across a wide extent of grey level, lies Maskelyne (14), a crater 

 about 18 miles across, 4500 feet deep from the E. side of its 

 irregular ring, and 3000 from the outer level. L. assigns to it 

 a central hill, neither figured nor described by B. and M. Less 

 than half way from this crater to Taruntius (91), we find a con- 

 siderable grey ring in the plain, and a little N. of it another 

 somewhat smaller, whose E. sides, about 300 feet high, are lost 

 to sight 16h. after the terminator has past them, so that the 

 opposite portions alone remain visible, like isolated curved 

 hills, as in fact they are figured by L. — B. and M. observe that 

 " many lunations may pass without even the most attentive 

 observer's perceiving anything of them ; this evening they are 

 not yet, to-morrow morning they are, perhaps, no longer to be 

 seen." The preceding details have been introduced for the 

 sake of this valuable remark, whose application is of a more 

 extended nature. 



Mount Hwmus. — By this name, introduced by themselves, 

 our authorities designate the S. boundary of the M. Serenitatis 

 (E), from the neighbourhood of Plinius (13), to Menelaus 

 (15), and about as much further again, to a small luminous 

 crater, Sulpicius G alius. No region, they observe, excepting 

 that adjoining Vitruvius, exhibits within so small an area so 

 many contrasts of ' ' light-tone," visible even on the dark side 

 of the moon, and producing a charming effect in the eclipse of 

 December 26, 1833, when even the minutest objects were 

 perfectly distinguishable. Some parts of the range attain 

 8° or 9° of reflective power in the Full Moon, and a multitude 

 of bright specks lie scattered about the vicinity. In proceed- 

 ing eastward from Plinius, we pass a beautiful chain of 

 " islands," the highest not attaining 800 feet, before reaching 

 the Promontorium Acherusia.* The headland so called rises to 

 4800 feet, with an aspect which may, as B. and M. remark, 

 resemble " Cornwallis and Alaksa" (Cornwall and Alaska ?), 

 seen from the moon. The mountains rise and spread, forming 

 the coasts of two different seas, the M. Tranquillitatis and 

 Serenitatis. Following the shore of the latter, we soon reach — 



Menelaus (15), a fine crater ; according to Schr. 16m. broad : 

 L. makes it 21m. B. and M. have given no measure. They 

 describe it as having a broad ring, the interior of which reflects 

 the light at different times from one or the other side, almost 

 like a concave mirror, whence its great brightness of 8° and 9°. 

 Its steepness conveys at first the impression of a greater 

 depth than it possesses; it is actually, however, very con- 



* Spelt Archer usia by Hevel and Schr., and in the great map. The text, 

 however, seems to be right. It is the ancient name of a headland in Bithynia, 

 near Byzantium, the appellation given by Hevel to the crater now called 

 Menelaus. 



