ON SOME VOLCANIC FORMATIONS OF THE MOON. 467 



grees, long extending toward the Sun, and a fainter tail three and a half degrees 

 in length turned away from the Sun, 



University of Kansas, Nov. 6, 1882. 



ON SOME VOLCANIC FORMATIONS IN THE MOONi. 



HERMAN J. KLEIN. 



The numerous circular formations of the Moon enclosing a hollow, in the 

 middle of which a group of hills generally rises, are, as is known, designated 

 Craters or Ring-mountains, By this, however, it is by no means intended that 

 these formations are to be viewed as analogues of our terrestrial volcanoes ; on 

 the contrafy, there are not only distinctions in magnitude, but fundamental dif- 

 ferences in the entire structural type, which forbid comparison with the volcanoes 

 of our world. The true volcanic formations of the Moon, those forms which 

 possess the greatest similarity to our terrestrial volcanoes, were not, generally 

 speaking, known at all to the earlier selenographers, Schroter, Lohrmann, and 

 Madler. 



Neison, in his new work 'The Moon,' remarks that the real representatives 

 on the Moon of our terrestrial volcanoes are what he terms "crater-cones.'' 

 They are those steep or conical hills which vary in size from one-half to two or 

 three English miles in diameter, with a precipitous funnel-shaped central hollow 

 scarcely half the breadth of the hills themselves. When the Sun stands at a 

 great height above them, they are visible through powerful telescopes as very 

 minute white spots ; and under a moderate elevation of the Sun, the central chasm 

 that forms the crater can sometimes be perceived in their middle. But for this, 

 a calm clear atmosphere is necessary and a very powerful telescope. Sometimes 

 they appear on the summit of a mountain, not rarely also on the plain enclosed 

 by a ring-mountain or on a walled plain, as in Plato and Fracastorius. To this 

 kind of forms belongs also the small hill containing a crater which at present 

 rises within the at one time large crater Linne, and which can only be seen for a 

 short on the terminator. In the time of Lohrmann and Madler, Linne was six 

 or seven English miles in diameter, and was at least 1000 feet deep. The filling 

 up of this large old crater was remarked by Schmidt in October, 1866; and on 

 the 26th day of December of that year he saw for the first time that alow "crater- 

 cone " had risen on the new plain, having a central chasm of perhaps 300 metres 

 in diameter. I regard this crater, which I have also seen, as a real representa- 

 tive on the Moon of our terrestrial volcanoes. Similar forms can be made out in 

 great number in the interior of the flat ring-mountain Stadius. 



Madler previously noticed here several tiny little crater-cavities ; and Neison 

 mentions thirteen crater-pits on the enclosed plain of Stadius, while Schmidt 

 counts fifty of them. None of these observers, however, mention that these tiny 



1 From Peterman's ' Mittheilungen/ 1882, Heft. vi. (Translation). 



