The Lunar Apennines. 379 



THE LUNAR APENNINES.-CLUSTERS AND 

 NEBULA.— OCCULTATION. 



BY THE KEV. T. W. WEBB, A.M., F.R.A.S. 



We come now toaportion of the lunar surface remarkable for the 

 unusual combination of great altitude, and comparative free- 

 dom from that eruptive disturbance which has left its traces so 

 abundantly in other elevated regions. Thus far, it has some 

 similarity with the great mountain-chains of the earth, which 

 it also resembles in its rapid slope in one direction, contrasted 

 with the gradual declivity of the other side. The comparison, 

 however, as Schmidt was the first to point out, fails in one 

 important point here (and such indeed seems to be the case in 

 all the lunar highland districts) — the absence of long valleys, 

 such as either have been cut down by streams of water, or at 

 least are now their recipients : and there is something in the 

 structure of the N.W. edge different from the ordinary terres- 

 trial central crest with its double slope : the massive pedestals 

 of the loftiest peaks arise from it, but the peculiarity of their 

 connection and their local division would, in Schmidt's opinion, 

 scarcely find anything analogous on the earth. This district 

 received from Hevel the designation of the Ajpenni7ies J in 

 accordance with his fancied analogy between the lunar and 

 terrestial surface, and on our index-map is numbered 23. Schr. 

 has ascribed to it a length of nearly 460 miles, with a breadth 

 of 70 to more than 90 miles : B. and M. estimate its area 

 at nearly 74,000 square miles : and though surpassed in height 

 by several ranges upon the limb, it forms the most consider- 

 able mountain-mass, in the clearly- distinguishable part of the 

 visible hemisphere. On the E. it connects itself with the con- 

 spicuous crater Eratosthenes (29), by a narrow prolongation of 

 moderate height : southward it gradually declines in a great 

 number of low ridges into the (Sinus JEstuum (H), the Mare 

 Vaporum (F), and the region about Manilius (24) : on the W. 

 it borders on the already-described chain of Hamius, extending 

 N.E. from Menelaus (15), and the Mare Serenitatis (E) : on the 

 N. and N.E. it culminates in a long, lofty, steep crest, some- 

 what curved in its general direction, and much indented in 

 detail; this towers over the Mare Imbrium (I), with many insu- 

 lated hills and long low ridges attending its base, in places ris- 

 ing towards it in steps, and looking, as Schmidt observes, like 

 great masses of debris detached from the main chain during its 

 elevation ; perhaps it may be equally open to us to suppose 

 that they may in part be the result of landslips from its edge at 

 a more recent date. The earliest observers were astonished at 



