4 88 THE POPULAR SCIENCE MONTHLY. 



seinble a semicircle of light projecting into the blackness of the still 

 unilluminated plains around it. I should advise every reader to take 

 advantage of any opportunity that may be presented to him to Bee 

 Clavius with a powerful telescope when the sun is either rising or set- 

 ting upon it. Neison has given a spirited description of the scene, as 

 follows : 



The sunrise on Chivius commences with the illumination of a few peaks on 

 the western wall, hut soon rapidly extends along the whole wall of Clavius, 

 which then presents the appearance of a great double bay of the dark night-side 

 of tbe moon penetrating so deep into the illuminated portion as to perceptibly 

 blunt the southern horn to the naked eye. Within the dark bay some small, 

 bright points soon appear the summits of the great ring- plains within followed 

 shortly by similar light points near the center, due to peaks on the walls of the 

 smaller ring-plains, these light islands gradually widening and forming delicate 

 rings of light in the dark mass of shadow still enveloping the floor of Clavius. 

 Far in the east then dimly appear a few scarcely perceptible points, rapidly 

 widening into a thin bright line, the crest of the great southeastern wall of 

 Clavius, the end being still lost far within the night-side of the moon. By the 

 period the extreme summit of the lofty wall of Clavius on the east becomes dis- 

 tinct, fine streaks of light begin to extend across the dark mass of shadow on the 

 interior of Clavius, from the light breaking through some of the passes on the 

 west wall and illuminating the interior; and these streaks widen near the center 

 and form illuminated spots on the floor, when both east and west it still lies 

 deeply immersed in shadow, strongly contrasting with the now brightly-illumi- 

 nated crest of the lofty east wall and the great circular broad rings of light 

 formed by the small ring-plains within Clavius. The illumination of the interior 

 of Clavius now proceeds rapidly, and forms a magnificent spectacle : the great 

 brightly-illuminated ring-plains on the interior, with their floors still totally 

 immersed in shadow ; the immense steep line of cliffs on the east and southeast 

 are now brilliantly illuminated, though the entire surface at their base is still 

 immersed in the shades of night ; and the great peaks on the west towering above 

 the floor are thrown strongly into relief against the dark shadow beyond them. 



Newton (12) is the deepest of the great crateriform chasms on the 

 moon. Some of the peaks on its walls rise twenty-four thousand feet 

 above the interior gulf. Its shadow, and those of its gigantic neigh- 

 bors for the moon is here crowded with colossal walls, peaks, and 

 craters may be seen breaking the line of sunlight below Clavius, in 

 our third picture. I have just spoken of these great lunar formations 

 as chasms. The word describes very well the appearance which some 

 of them present when the line separating day and night on the moon 

 falls across them, but the reader should not be led by it into an erro- 

 neous idea of their real character. Such formations as Newton, which 

 is one hundred and forty miles long by seventy broad, may more accu- 

 rately be described as vast depressed plains, generally containing peaks 

 and craters, which are surrounded by a ring of steep mountains, <>r 

 mountain-walls, that rise by successive ridges and terraces to a stu- 

 pendous height. 



The double chain of great crater-plains reaching half across the 



