The Lunar Arctic Begion. 55 



Gruitlmisen would fully confirm the idea from his own obser- 

 vations, in which they held a prominent place. But whatever 

 may be our opinion as to these points, which, if demonstrable 

 at all, certainly require more rigorous demonstration, there 

 can be no question that the phenomenon described by Schroter 

 was deserving 1 of attention. It was quite safe from neglect in his 

 hands ; he measured the depth of the little crater on two occa- 

 sions, and made it 3774 and 3504 feet, the correspondence 

 showing clearly that there could be no very material error, 

 with a height of 2070 feet for the ring above the external 

 level ; a relative amount agreeing well with the usual propor- 

 tion on the moon, and showing that there is no improbability 

 in the supposition that the rings are the result of actual 

 eruption. He found also on another occasion (1791, Dec. 30) 

 the interior shadow much too trifling in proportion to its dis- 

 tance from the terminator, so as to give the appearance of 

 great shallowness ; but in no subsequent observation with any 

 of his telescopes was the greyness which at first struck him to 

 be found again. Lohrmann takes no notice of Schroter' s state- 

 ment, which is given in great detail : B. and M., as an excep- 

 tional case, have cited some part of it, and are disposed to 

 admit its correctness ; but they have added so much in the 

 way of disparaging remark that it is obvious what was their 

 real estimate of their predecessor's labours. It must be ad- 

 mitted that to a certain extent they were right, and that many 

 of Schroter' s supposed changes may be otherwise explained ; 

 but we shall hereafter find sufficient evidence that they would 

 have better consulted their own reputation if they had abstained 

 from censuring his prejudices till they had at least in some 

 places equalled the general faithfulness of his comparatively 

 rude delineations. Schroter has recorded many other minute 

 variations in the aspect of the interior level and the wall, which 

 need not be referred to further than as indicating the desirable- 

 ness of a more accurate study of similar details, for which this 

 great ring seems conveniently situated. I regret to add that 

 1 have given but little attention to it, partly perhaps in conse- 

 quence of its comparative want of elevation, which renders it a 

 less conspicuous object than might have been expected at a 

 moderate distance from the terminator. There are, however, 

 two unusually deep craters on the N.W. side of the ring, whose 

 shadows, if they were of greater breadth, would catch the eye 

 strongly. The larger, or exterior one, which is marked h by 

 Schroter, was twice measured by him at 9223 and 10,358 feet 

 — a sufficient evidence, at any rate, of its enormous depth ; 

 the corresponding measures of his i, which is the smaller, are 

 9543 and 10,976 feet; fully justifying his remark, "What an 

 extraordinary romantic prospect would not these two craters 



