THE MOON’S FACE. 
281 
ance to an area between Metius and Vlacq. One of these 
can be traced northeastward to a point just west of the crater 
Piccolomini. Although unquestionably a unit, it is not con¬ 
tinuous, but appears here and there as though the projectile 
grazed only the higher uplands, and it is locally blotted out 
by the craters Metius and Fabricius, which are of more 
recent date. Its total length is 450 miles. Another of the 
same system appears to the northwest of the crater Furnerius. 
More conspicuous than these and more westerly in trend is 
a groove seen first at the southern tangent of Borda and 
traced for 500 miles west-southwest across the southern part 
of Snellius and past the southern margins of Haze and 
Adams. Its width is in general about 10 miles, but width 
and depth are irregular, and it leaps a number of valleys, 
including the bed of Snellius. Beer and Madler * record a 
part of it just west’of Snellius, but apparently saw no other 
part. West of the Mare Nectaris and following the eastern 
base of the Pyrenees mountains is a trough which should 
probably be classed with the furrow system, but I have not 
seen it with the illumination suitable for the determination 
of its details. In length and width it resembles the Rheita 
valley, and it trends nearly with the meridian. It is crossed 
obliquely by a narrower groove trending approximately w T ith 
the Imbrian system and intersecting the crater Capella. 
This is partly represented on Schmidt’s map. My notes 
indicate also a very old furrow trending southeastward from 
a point about 175 miles east from Clavius, but its precise 
position was not determined. The straight valley travers¬ 
ing the lunar Alps, better known than any of the others, is 
likewise exceptional in character. Its sides are no less 
irregular than those of the other furrows and are even more 
precipitous, but its bottom is smooth, so that it constitutes a 
comparatively narrow, flat-bottomed defile, traversing the 
plateau from side to side. Neison gives its length as 83 
miles and its breadth as ranging from 6 to 3J. miles, but at 
*Der Mond, page 375. 
