Lunar Details. 373 



20° at furthest from the terminator this crater-swarm becomes 

 invisible, and the surface is then almost exactly similar in 

 aspect to the Sinus Mstuum itself. 



The discovery of this very singular region is due to Grui- 

 thuisen, 1815. He has well described its aspect, and speaks 

 of the rows of craters as forming in places hollow ways, or 

 being connected by a large longitudinal furrow, while the 

 separate craters had outlets E. and W., which, however, are 

 not visible if the illumination is precisely in that direction. 

 And then he goes on, in his own way, to refer to the especial 

 fertility indicated by the darkness of the soil ; and considers 

 them, if not volcanos, the artificial dwellings of living beings ; 

 in another place indicating his own choice between the alterna- 

 tives by asserting that there is not a trace of a volcano, ancient 

 or modern, upon the Moon ! all its cavities having been formed 

 by the impact of masses falling from space — of which portions 

 still protrude as central hills ! They are mentioned again by 

 Kunowsky, 1821, who says that he often distinctly recognized, 

 in clefts, rows of crater- like eruptions. Lohrmann's Sections 

 and letterpress unfortunately do not include this region : his 

 General Map indicates broad, low ridges, pierced with a mo- 

 derate number of craters ; but, though the first impression is 

 not that of similarity to the Map of B. & M., a closer inspec- 

 tion shows that the objects represented must have been nearly 

 the same. A corresponding view with that of Kunowsky is 

 taken by Schmidt, who remarks that " everywhere a keen and 

 unprejudiced course of observation will indicate that rills 

 (clefts) are only crater-rows in a particular modification, as the 

 innumerable transition-forms prove, and as Madler first (?) 

 pointed out/-' Little craters, he tells us, often lie in long lines, 

 as if they had broken out of a crack, and he enumerates 

 about 300 visible in the region now under discussion, many of 

 which are contiguous, and frequently so confluent as to form 

 ravines like regular clefts : their external height being, he 

 thinks, very insignificant — somewhere between 150 and 600 

 feet. 



Why these crater-chains were unnoticed by Schr. is a 

 question which, thoug'h it seems to have been never asked, is 

 deserving of an attempt at a reply. It so happens, indeed, 

 that Eratosthenes and Copernicus were examined by him at 

 different times, and represented in separate views; and 

 that these miniature volcanos soon disappear after sunrise ; 

 and it may be admitted that he overlooked many small objects 

 in various places. But, on the other hand, it must be borne 

 in mind that his attention was evidently frequently directed to 

 Copernicus ; that the object, though fugitive, is in a very re- 

 markable and conspicuous place, and is by no means colloct- 



