390 



KNOWLEDGE ♦ 



[June 29, 18(>3. 



THE MOON IX A THRKE-INCH 

 TELESCOPE. 



By a Fellow of the Royal Astronomical Society. 



rpO tlie north-west of Cassini (described on p. 32G) lie the 

 JL Lunar Alps (SO in our map), a range of mountains 

 possessing a much more terrestrial character than the ma- 

 jority of objects visible on the moon's surface. They start 

 from the neighbourliood of Cassini, and extend with a very 

 remarkiiblc interruption, iuiiiK'diately to be spoken of, 

 nearly, if not quite, to Plato. The interruption of which 

 we have just spoken takes the form of an enormous 

 wedge-shaped valley, between eighty and ninety miles 

 long, and varying in width from three and a-half to six 

 miles. Our sketch represents this region as it appears 

 with a power of 120, the age of the moon being 7 58 days. 



full Moon. South of Plato stands that absolutely 

 isolated peak, Pico (131), in the dark grey Sea of 

 Showers. As it is some 8,000 feet in height, it 

 ca.sts a tremendously long shadow under the ollique 

 illumination either of sunrise or sunset, and forms 

 a most conspicuous object. Timocharis (121) is worth 

 looking at for its terraced wall. The glorious mountain 

 Chain of the Apennines (M.5, 87, 02, in our map) pre- 

 sents, like the Alps of which we have spoken above, a 

 very decidedly more terrestrial character than the vast 

 majority of lunar objects. We may regard this superb 

 range as starting in the north from Cape Hadley (87), 

 which rises more than 15,000 feet from the plain at its 

 base, although they will be seen to tend in a south- 

 westerly direction from it. Following them, however, in 

 their eastern course round the Sea of Showers, we come to 

 Bradley (89), a mountain 13,600 feet in height, and to 

 Huyghens (90), the loftiest of their peaks, attaining an 

 altitude of some 20,000 feet. The spectacle presented by 

 this range of mountains — for the observation of which a 

 power of IGO may be employed on a tine night — with their 

 glittering and corrugated highlands, and the serrated 

 shadows cast by their peaks on the plain beneath, is & 

 wonderfully beautiful one, and will repay the most earnest 

 attention the student can give to it. The projection oS 

 this noble ridge beyond the illuminated part of the moor., 

 about the time of first quarter, is easily discernible with 

 the naked eye by moderately sharp-sighted people. It may 

 be held to terminate with Eratosthenes (110), the descrip- 

 tion of which, however, we must reserve for our next 

 paper. 



The Valley of the Alps, and Suiiriee on Plato, 

 iloon's Age 7'o8 days. 



The eastern side of the valley is the steeper of the two. 

 The highest of the mountain masses lie to the west of the 

 huge cleft, the eastern range, however, increasing in 

 magnitude as it approaches Plato (132). The sun was just 

 rising on this last-named superb formation at the time our 

 drawing was made ; and its interior, as will be seen, was 

 plunged in the blackness of night. While scrutinising this 

 part of the moon's surface, the student may direct his at- 

 tention to the two interesting ring-plains to the North — 

 Archytas (46) and Timajus (170). Plato itself, and its 

 vicinity, present a most interesting region for examination 

 during the seventh, eighth, ninth, and tenth days of the 

 moon's age ; as they do (though at a most inconvenient 

 hour) when she is twenty-one or twenty-two days 

 old. This great walled plain measures sixty miles 

 across, and is notable, when fully illuminated, for 

 its steel-grey tint. Its surrounding wall is broken 

 in places, and exhibits very little of that series of descents 

 in terraces which we shall find by and by in Eratosthenes, 

 Copernicus, etc. A variety of streaks and spots have been 

 detected upon the very level floor by the aid of large and 

 powerful telescopes ; but by far the larger proportion of 

 these details are hopelessly beyond the reach of the ob- 

 server with such an instrument as that whose use is pre- 

 supposed in these papers. Under suitable illumination, 

 the shadows of three huge peaks on the western wall will 

 be seen cast upon the floor ; as will that of an even higher 

 one from the eastern wall out on to the very broken surface 

 of the Mare beyond. It is, so far, an inexplicable fact, 

 that, as the Sun rises on the interior plain of Plato, it 

 follows the usual law of getting brighter until the Sun has 

 attained an altitude of 20°, or thereabouts ; after which it 

 darkens very notably and perceptiVily until shortly after 



SUN-A^IEWS OF GREAT BEITAIN. 



\TTE give this week what may be called Sun-Views of 

 \\ Great Britain, showing how the aspect of Great 

 Britain and Ireland, Norway, Denmark, France, Spain, 

 ifcc, varies, as supposed to be seen from the sun. 



or autuiiii). 



