146 REPORT— 1859. 



sphere of great density, but of very small extent, and that the so-called seas 

 mi°"ht be covered with vegetation. This idea respecting a lunar atmosphere 

 has, I am inclined to believe, received some confirmation from a recent 

 observation of Father Secchi's, that the lunar surface polarizes light most 

 in the great lowlands and in the bottoms of the craters, and not appreciably 

 on the summits of the mountains. 



Radiating Lines in the Moon's Disc. — The mountain peak in the centre 

 of Tycho, about one mile in height, is very distinct in the photographs, 

 and under favourable circumstances the details in the interior of the crater 

 are well shown. The external slopes under all illuminations are darker in the 

 photograph than the internal walls and the bottom of the crater. Tycho 

 would appear to have been the focus of a wonderful disturbing force which 

 broke up the moon's crust nearly over the whole visible surface, for radiating 

 lines converge in that conspicuous volcano, like so many circles of longitude, 

 and cannot fail to attract attention. Several theories have been suggested to 

 account for these radiating lines ; by studying a series of photographs taken 

 under different conditions of illumination one becomes convinced that they 

 are due to furrows in the lunar surface*. They are in some cases overlaid 

 by craters which must have been formed at a subsequent period ; and in 

 other cases the furrow has dislocated the crater, which must therefore 

 have previously existed. 



One very remarkable Furrow fully fifty miles broad, extending from Tycho 

 over 45° of latitude in a north-easterly direction, is the deepest on the lunar 

 surface. The eastern ridge of this furrow skirts Mount Heinsius, and the 

 western ridge extends to Balliald and Euclides, where the furrow becomes 

 very shallow, but is traceable as far as Kepler. 



Another conspicuous furrow runs from Tycho in a north-westerly direc- 

 tion nearly up to the northern limb of the moon, and extends over 100° of 

 latitude, passing through Menelaus and Bessel in the Mare Serenitatis through 

 a crater (marked E in Beer and Madler's map) at the head of a pro- 

 montory running into the Lacus Somniorum, when it is crossed by another 

 furrow extending tangentially to the Apennines. The intersection of these 

 streaks resembles the letter X, and indicates another focus of disturbance 

 near the crater E in north latitude 35° and west longitude 24°. The main 

 furrow from Tycho continues on through the crater Plana, leaving Burg 

 untouched on the east, and terminates to the south of Strabo in north lati- 

 tude 60° and west longitude 45°. 



A furrow best seen about the full moon or a little after, extends from 

 Tycho, though not quite continuously, through the Mare Nectares, traver- 

 sing the crater A on the west of the crater Theophilus ; sweeping in a curve 

 eastward, it leaves Tarantius on the west, and crosses the bright craler 

 Proclus, forming an eastern tangent to Berzelius. Leaving Endymion 

 to the south-east, it forms the southern boundary of the Mare Humboldti- 

 anum in north latitude 70° and west longitude 90°, having traversed 110 

 degrees of latitude. 



A remarkable focus of dislocation exists in the Mare Fcecunditatis in lati- 

 tude 16° south and longitude 50° west, which also, by the crossing of the 

 lines of disturbance, looks like another letter X in the photograph. 



The radiating lines of dislocation are so numerous that it would be 

 impossible, within reasonable limits, to describe any but the principal ones ; 

 I should state, however, that they must not be confounded with the sinuous 

 lines which radiate from Copernicus and other lunar craters, and which are 

 markedly different in character and origin. 



* Monthly Notices Roy. Ast. ?oc. vol. xviii. p.lll. 



