154 COSMOS. 



Moon are in descending order at the south edge, very near the 

 Pole, Dorfel and Leibnitz, 24.297 feet ; the annular mountain 

 Neicton, where a part of the deep hollow is never lighted, 

 neither by the Sun nor the Earth's disk, 23,830 feet; Casa- 

 tus, eastward of Newton, 22,820 feet ; Calippus, in the Cau- 

 casian chain, 20,396 feet; the Apennines, between 17,903 

 and 19,182 feet. It must be remarked here, that in the en- 

 tire absence of a general niveau-line (the plane of equal dis- 

 tance from the center of a cosmical body, as is presented on 

 our planet by the level of the sea), the absolute heights are 

 not to be compared strictly with each other, since the six 

 numerical results here given properly express only the differ- 

 ences between the peaks and the immediately surrounding 

 plains or hollows.* It is. however, very remarkable that 

 Galileo likewise assigned to the loftiest lunar mountains the 

 height of about four geographical miles (24,297 feet). in- 

 circa miglia quatro," and, in accordance with the extent of 

 his hypsometric knowledge, considered them higher than any 

 of the mountains on the Earth. 



An extremely remarkable and mysterious phenomenon 

 which the surface of our satellite presents, and which is only 

 optically Connected with a reflection of light, and not hyp- 

 sometrically with a difference of elevation, consists in the nar- 

 row streaks of light which disappear when the illuminating 

 rays fall obliquely ; but in the full Moon, quite in opposition 

 to the Moon-spots, become most visible as systems of rays. 

 They are not mineral veins, cast no shadow, and run with 

 equal intensity of light from the plains to elevations of more 

 than 12,780 feet. The most extensive of these ray-systems 

 commences from Tycho, where more than a hundred streaks 

 of light may be distinguished, mostly several miles broad. 

 Similar systems which surround the Aristarchus, Kepler, Co- 

 pernicus, and the Carpathians, are almost all in connection 

 with each other. It is difficult to conjecture, by the aid of 

 induction and analogy, what special transformations of the 

 surface give rise to these luminous, ribbon-like rays, proceed- 

 ing from certain annular mountains. 



The frequently mentioned type of circular configuration, 

 almost every where preponderating upon the Moon's disk, in 

 the elevated plains which frequently surround central mount- 

 ains ; in the large annular mountains and their craters (22 

 are counted close together in Bayer, and 33 in Albatei. 



* For the six heights which exceed 19.182 feet, see Beer and MaJ- 

 ter. p. 99, 125, 234:242, 330, and 331. 



