MOON, RECENT OBSERVATIONS AND STUDY OF THE. 



587 



ing through a delta would represent very well, tion as their, size decreases their numhers in- 

 Judging from appearances, upheavals occurred crease, so that but a few ring-mountains aver- 

 in its course during the earlier period of its age over eighty miles in diameter, and they 

 flow, which turned aside its waters and left exhibit a decided smoothing down of their 



their bed unfilled. 



mountain-masses, while the smallest, percep- 



The mountain-rims of those basins do not tible in the telescope, are very numerous, with 



THE RAY ACROSS THE BASIN. 



seem to be a continuous, nnbroken ridge ; for 

 the flow evidently made its entrance and exit 

 through passes that it found in the base of the 

 range, and widened those passes by its attri- 

 tion, precipitating into the basin from the side 

 first encountered the debris it had disinte- 

 grated from the bases of the mountain-masses, 

 while upon the side of the outflow long, drift- 

 like formations appear behind separated mount- 

 ain-masses which have survived complete de- 

 pletion. There is a great ring-basin known as 

 Stafler, about 70 miles across, and a smaller 

 one by its side named Fernelius, which have 

 had their rims more than half depleted by the 

 flow from Tycho, 300 miles away. These facts 

 prove that these ring-mountains, crossed or 

 depleted by the flow from Tycho, were com- 

 posed of pliable materials; that their forma- 

 tions antedated that of Tycho; and that flow- 

 ing water upon the moon produced upon fria- 

 ble matter precisely the same effects that it 

 does upon the earth. 



Tycho is one of a few exceptions to the rule 

 that the larger these basins are the more likely 

 they are to bear the impress of age by their 

 mountain-rims giving evidence of denudation ; 

 and, though there are examples of all sizes, 

 which give evidence of various degrees of an- 

 tiquity, yet, as a rule, the smaller they are the 

 more recent appears to have been the period 

 of their formation, judging by the sharpness of 

 their outlines. It is also true that in propor- 



sharply defined rims. They are scattered with 

 about equal profusion over the level of the 

 general surface and of that of the sunken plains, 

 showing that the formation of these plains 

 must antedate that of the small basins. The 

 mountain-rims of the large ones are composed 

 of rugged masses, more or less broken and de- 

 tached ; but this character becomes gradually 

 lost as their diameter decreases, until in the 

 small ones it is entirely obliterated, and they 

 most decidedly assume the appearance of those 

 formed in the Yellowstone valley, which have 

 been constructed by the up-flow of water. It 

 would be difficult to give a better idea of the 

 small lunar basins than that of the spring 

 near Castle Geyser in the Yellowstone country. 

 If seen telescopically from the moon, it would 

 present the same appearance that they do, 

 for the telescope looking into its waters 

 could convey to the observer only the appear- 

 ance of a round, dark spot. The rim, the con- 

 tour of the surface about it, and the water- 

 marks radiating from it, are most unmistakable 

 features of lunar scenery ; and it will be re- 

 membered that those basins in the Yellowstone 

 are not all hot-water springs, for some are de- 

 scribed as cold and clear as crystal. 



It is obvious, from a consideration of the 

 preceding facts, that the forces that upheaved 

 and constructed the selnographic formations 

 underwent modifications as time went on by 

 which they gradually passed from the vast ag- 



