The Lunar Clefts — Mare Vaporum. 97 



cleft coming* from the S., 16 miles long, very narrow, and 

 of inferior depth — a difficult object detected by B. and M. 

 23m. further, it strikes on the mountain Ariadceus /3, without, 

 however, perceptibly dividing it, as it had done a small ridge 

 a little previously. On the other' side of /3 it recommences in 

 the same direction, and passes through two minute craters, 

 appearing here to be very deep. 14m. further ou, it is inter- 

 rupted by the mountain Ariadceus a, till its traces are next 

 recovered in a narrow ravine among the hills, in a somewhat 

 altered direction. Henceforward it splits every elevation, 

 great and small, in its way, although a high ridge, Silberschlag 

 a, so compresses it that the separation can only be perceived 

 with difficulty. Further on, the heights on either side are 

 natter, and it terminates in a small crater S. of Boscovicli, after 

 a course, windings included, of 143 miles. Gruithuisen ob- 

 served a very minute prolongation of it, between Arago A and 

 Hitter, for a considerable distance towards the equator. This, 

 though confirmed by Kunowsky, was not made out by B. and 

 M., but has since been seen by Kinau and Schmidt. If it is 

 really a continuation of the great cleft, it may possess con- 

 siderable selenological interest, as showing how much more 

 effect the same cause has produced on a comparatively moun- 

 tainous surface than on a depressed plain. Two other very 

 minute clefts (if not three) between Sosigenes and Arago, and 

 two more S. of Sabine (which had been seen by Lohrmann) 

 belong to the M. Tranauillitatis. Schmidt has detected several 

 others along this shore. 



S.E. of Hyginus, and on the edge of the M. Vaporum, lies 

 the crater Tries -aeclcer , encompassed by a narrow equable wall, 

 14 miles in diameter, and 5400 feet high on the B. On every 

 side but the E. it is encompassed by loug clefts, forming the 

 most numerous group known to B. and M., some of which 

 had been seen by G. /3 and <y, the most distinct, form an 

 angular junction near the wall : the whole could very seldom 

 be seen at the same time. 8 is interrupted by a low ridge. 

 Between /3 and 7 is a very difficult little crater. Though the 

 connection and branching out of these clefts appeared to B. 

 and M. unique on the moon, yet the similarity to a terrestrial 

 river-system is very slight : there is no winding, or widening 

 in either direction, and the interruption by a hill must negative 

 any such idea. 



Having thus given an abstract of B. and M.'s description 

 of this curious region, we may find it worth while to compare 

 it with the results obtained by other observers. First of all, 

 the original discoverer, Schr., has given a long description, 

 and a figure of the two principal clefts, which alone he saw, 

 and two additional diagrams of the W. one. The name Hyginus 



VOL. XII. — NO. II. H 



