S84» Lunar Mountains Tycho^ Pictet, and Saussio-e. 



terraces lying in front of it ; they also supply an elevation of 780 toises for 

 the central mountain, and 2509 toises for the eastern wall. The central 

 mountain, then, should be nearly of the same level with the terraces. Thesfc 

 terraces surround, in a series of from three to five ranges, the internal foot 

 of the zone, always leaving a considerable portion of the plain free ; and in 

 which, besides the central mountain, some hills may also be observed. As, 

 however, it is only two days after the rising of the sun, that the plain is 

 so free from shadow that this can be distinguished from the base of the 

 ceatral mountain, and as at this epoch the lower hills have long become^ 

 wholly invisible, it is not certain that the interior is quiite so plane as is 

 represented.* 



All around Tycho are to be seen hundreds of peaks, and ridges of moun- 

 tains and craters, so that it is impossible to find the smallest level space, 

 and it requires a long series of the most careful observations to determint* 

 successively all the details which are required in designing the map. lu 

 the midst of this kind of chaos, which is so irregular in appearance, we 

 may observe that the eastern and south-eastern craters, and the long rango 

 of mountains at the west, whose direction is parallel to that of the margin, 

 form the principal traits of the picture. The mountain chains on the north 

 ai-e grouped together, without being parallel to the margin of Tycho ; and 

 it is quite impossible to disentangle the greater number of those to the 

 south. At a distance of from four to six miles, the large craters and the 

 annular mountains begin to reappear ; only a small proportion of them are 

 quite circular, although all of them approximate to this figure. Very ele- 

 vated zones surround and traverse them, so as to interfere with every thing 

 like regularity. 



At no great distance to the west of Tycho, we see the annular mountain 

 Pictety which is a very irregular hollow, of between 400 and 500 toises, 

 surrounded by a zone, which is formed of ridges of mountains, high and 

 low, and of craters. The most considerable of these is situated at C, in 

 south latitude 41° 33', and in east longitude 8°. Another annular moun- 

 tain, situated to the south, and to which Messrs Beer and Miidler have given 

 the name of Pictet u, is smaller, but less irregular and more visible, and is 

 very completely seen at full moon. Its zone is considerably elevated to- 



* It may be curious to compare with these dimensions of Tycho, those of the 

 spot Aristarchus (Mons Porphyrites, H.), so remarkable for its lustre. Aristar- 

 chus is nearly a circular mountain of six German miles (ten leagues) diameter, 

 which has a central mountain in its most brilliant point. Its western edge is 

 elevated 117(» toises above the cavity, and 414 toises above its external base. 

 The eastern part of its zone connects Aristarchus with Herodotus, likewise an 

 annular mountain, and upwards of eight leagues in diameter ; it is steeper, but 

 »ot so deep, and has no central mountain. There is in the part of its zone near 

 Aristarchus two summits, a and /3, elevated about 686 toises above the cavity ; 

 this last is very obscure, although it is about 300 toises higher than that of Aris- 

 tarchus, which has a brightness of 10" over its whole extent. The margins of 

 Aristarchus have a brightness of from 9° to 6° ; the peak a of Herodotus has 7% 

 »nd /» scarcely 3\ These two mountains are situated to the north-east of the 

 moon's centre, in the most sombre portion of the oceanus proeellarum, and have 

 scarcely any connection with other mountains or bright regions. 



