384 FKOM NEBULA TO NEBULA 



LUNAR "VALLEYS". A veritable "Valley of the Moon" is the 

 Rheita Valley. This is a shallow groove of varying width with 

 a shorter off-shoot on the south end. It runs from the eastern 

 edge of the crater Rheita south westward more than 185 miles 

 to Rheita d; its breadth varies from n to 25 miles, with a maxi- 

 mum depth, according to Beer and Madler, of about 11,000 feet. 

 A long, narrow cleft resembling a rill, starts from near Picco- 

 lomini and trends southwestward more than 450 miles to near 

 Metius, which temporarily interrupts it ; but it continues its course 

 beyond that crater and to the right of the Rheita Valley. 



However, the Alps Valley, a straight defile traversing the 

 lunar Alps range, is the most interesting of them all, betraying 

 an exceptional character which demands for its origin an excep- 

 tional explanation. A trough-like flat-bottomed groove trending 

 east-north-east by west-south-west clean across the Alps range; 

 it is 83 miles long by from three and one-half to six miles in 

 width, and from its positioning bespeaks kinship to the Imbrian 

 deluge, thus uniting the furrow group of the western district 

 with the eastern sculpture system. 



BRIGHT RAYS. The system of brilliant rays which radiate 

 from the crater Tycho down the lunar disk, like luminous par- 

 allels of longitude, and also the wavy streaks converging upon 

 Copernicus; the lesser systems of Proclus, Kepler and Snellius, 

 are the most enigmatic phenomena of the moon's surface. Those 

 emanating from Tycho extend for vast distances across the lunar 

 disk; in one instance that of the one crossing the Mare Ser- 

 enitatis near 18,000 miles. Straight as the famed canals of the 

 desert planet Mars, they seem not to mind obstructing craters or 

 elevations in their predetermined path. As a contrast, those ra- 

 diating from Copernicus are branched and wavy and much shorter 

 than the Tychonic phenomenon. * * * 



Most conspicuous at full moon, under the vertical solar il- 

 lumination, they seem to be superficial colour-streaks only, and 

 one can be seen on the inner floor of Saussure, near Tycho, and 

 may even be traced up its inner cliffs, like a vein of volcanic trap 

 piercing sedimentary rock-strata on our own planet. This is a 

 treacherous analogy, however, as Mr. R. S. Tozer has pointed 

 out. "The lowest visible stratum on the moon is dark, the con- 

 figuration of the edges of the light coloured portion showing 

 plainly that the darker portions extend underneath. * * * Whence, 

 then, the light coloured lava? 



These brilliant rays cannot be inner material extruded from 

 beneath a crust rent by tidal stresses, since an exact restoration 

 of level which would not cast shadows at sunrise or sunset along 

 hundreds of miles would be practically impossible. But the sug- 

 gestion advanced by Mr. William Wurdemann of Washington, 

 D. C., seems more plausible; viz., that "a meteorite, striking the 



