102 The Lunar Clefts — Mare Vaporum. 



is double, or ratter that in this space are comprised the ends 

 of two clefts not in the same line, but running parallel for a 

 short distance, as is shown in the accompanying' very rough 



sketch. The S. portion, though narrow, 

 was very evident. As I have found this 

 subsequently confirmed, I would venture 

 to propose an addition to the nomencla- 

 ture here, aud to call the E. portion 

 " the cleft of Silberschlag/ 3 as the W. is that of Ariadceus. 

 How so apparent a feature should have escaped all previous 

 observers, and even Schmidt himself, it is not easy to under- 

 stand ; but it proves how much yet remains to be done for 

 the topography of the Moon. 



This becomes still more evident with great apertures and 

 high powers, for which many peculiarities here are doubtless 

 reserved. Such was especially my conviction in the use of 

 Mr. Bird^s noble 12 in. silvered mirror, 1865, Sept. 5. The 

 illumination was then far too high, but some idea of the scene 

 may be obtained from the fact that the bottom of the first cleft 

 W. of Hyginus was distinctly seen as a grey streak bordered 

 by two parallel bright lines. This was interesting in another 

 respect. The steep banks, as less directly enlightened, should 

 have had a darker appearance, on optical grounds, than the 

 included level space ; their opposite aspect must have been due 

 to local colour. On one occasion I thought, in using my 9^- in. 

 mirror, that the Silberschlag cleft passed over, not through, a 

 considerable mountain ; but the observation was too hasty, and 

 should be repeated. 



As to the region of Triesnecker, I have noted several addi- 

 tions. The angular point of meeting, and the minute crater 

 on the slope beneath it, are both set too near the ring by B. 

 and M., and that angle is really the common junction of four 

 clefts ; one of which proceeds due S., I know not whether it 

 may be £, ill-drawn in their map, or a Hue of communication 

 with it ; another runs as a continuation of ft up to the N.W. 

 edge of the great ring : the cleft y, as Breen had previously 

 found, is double, with overlapping ends, like those of the 

 junction between Ariadceus and Silberschlag ; and possibly this 

 may be found to be a peculiarity of frequent occurrence. 7 

 appears, too, to lead directly towards the small crater near its 

 N. end : while c, or e (both which letters are affixed in the 

 map to the cleft pointing to the centre of Tricsneclcer — e has 

 been accidentally misplaced in our diagram), probably passes 

 W. of the little crater E. of Hyginus. 



We leave now this curious region with the sincere hopo 

 that some of our readers may be induced to make it an object 

 of patient research : a very little experience will show that no 



