THE MOON. 493 



Many of the annular elevations and inclosed plains (according 

 to Lohrmann the largest are more than 4,000 square miles in 

 extent) form connected series, and indeed in the direction of the 

 meridian, between 5 and 40 South Latitude. 40 The northern 

 polar region contains comparatively few of these crowded 

 mountain circles. In the western edge of the northern hemi- 

 sphere, on the contrary, they form a connected group between 

 20 and 50 North Latitude. The North Pole itself is within 

 a few degrees of the Mare Frigoris, and thus, like the whole 

 level north-eastern space, including only a few isolated annu- 

 lar mountains (Plato, Mairan, Aristarch, Copernicus, and 

 Kepler), presents a great contrast to the South Pole, entirely 

 covered with mountains. Here lofty peaks shine during 

 whole lunations in eternal light, in the strictest sense of the 

 word; they are true light islands, which become perceptible, 

 even with feeble magnifying powers. 41 



As exceptions to this type of circular and annular configu- 

 rations, so universally predominant upon the Moon, are the 

 actual mountain- chains which occur almost in the middle of 

 the northern half of the Moon (Apennines, Caucasus, and 

 Alps]. They extend from south to north in a slight curve 

 towards the west, through nearly 32 of latitude. Innumer- 

 able mountain-crests, and extraordinary sharp peaks, are here 

 thronged together. Few annular mountains, or crater-like 

 depressions, are intermingled ( Conon, Hadley, Calippus), and 

 the whole resembles more the configuration of our mountain- 

 chains upon the Earth. The lunar Alps, which are inferior 

 in height to the lunar Caucasus and Apennines, present a 

 remarkable broad transverse valley, which intersects the chain 

 from south-east to north-west. It is surrounded by mountain- 

 peaks, which exceed in height that of Teneriffe. 



40 Schumacher's Jahrbuch for 1841, p. 270. 



41 Madler, Astron. p. 166. 



