A COMPARISON OF THE FEATURES OF THE EARTH AND THE MOON. 43 



CRATER VALLEYS. 



In this group may be placed a number of curious tliougli unnoted structures 

 in which one or more craters have been in some way deformed so as to make a 

 broad valley. The range of this action is great and the features to which it 

 o-ives rise rather obscure. The changes of shape, arising from this deforming 

 action, become very difficult to observe in all the vulcanoids at any distance from 

 the central field of the lunar surface, for the actual elongation is confused with 

 the apparent lengthening of the basins brought about by the obliquity of the view. 

 A fair sample of the crater-valley type is found in Hypatia, in the north- 

 central part of the fourth quadrant. (See plate xvii.) Here the crater is so far 

 deformed that its major axis, extending in a S. W.-N. E. direction, is about twice 

 as long as its minor axis ; moreover, this depression is vaguely continued as a valley 

 for some distance beyond the walls of the crater. There are other like depressions 

 in this neighborhood. Gutemberg in the same quadrant passes on the south into 

 a broad, extensive, ill-defined valley. Palitzch, near the western limb, is a yet 

 more characteristic sample, having, according to Elger, whose reckonings appear 

 always to be accurate, a length of sixty miles and a width of only twenty miles. 

 Capella also exhibits this passage into a valley, and there are, according to my notes, 

 six other like instances in this part of the field. It would be possible to collect 

 not fewer than one hundred instances of the deformation of craters into elongate 

 valleys, or their extension into broad vales, which are in some way evidently 

 connected with them. As I am not undertaking a list of lunar features I cite 

 only such as are needed for illustration of this point. 



Besides these numerous cases, in which the craters have been so far deformed 

 that they have had the character of valleys imposed upon them, there are about 

 as numerous instances in which the greater vulcanoids have been but slightly 

 deformed— so little changed, indeed, that the alteration has escaped observation. 

 In these cases, which include a large part of the pits over twenty miles in 

 diameter, the northern and southern walls show a distinct, though often slight, 

 change of form, indicating an elongation in that axis. I find that in my rough 

 notes of observations I have termed this the " spooning " of the crater in that 

 meridional direction. This feature may be best noted in the vulcanoids of the 

 central part of the lunar surface. It is distinct in Hipparchus and Albatagnius 

 which approach being crater valleys. Alphonsus and Davy show the same 

 feature, and it may be noted in perhaps one-third of the greater vulcanoids which 

 are so placed as to make it possible to discern this feature in its slightest expres- 

 sion. (See plate xvin.) Without at present undertaking to discuss the condition 

 which has brought about the evident warping of these greater vulcanoids on the 

 meridional line, it may be said that its aspect suggests that they have been 

 involved in certain movements, tending to produce considerable synclmes. I 

 have sought for, but failed to find, clear evidence of anticlinal folds correspond- 

 ing to these troughs, yet the inquiry has not been carried far enough to msure 

 that they do not exist. 



