78 Chronicles of Science. [Jan., 



it is precisely there that we become sensible of a deficiency in the 

 work of the illustrious German astronomers; in some instances we 

 find these minute details laid down with less regard to accuracy of 

 position than would have been desirable ; in others we are inclined to 

 question whether they actually represented all that their instrument 

 was capable of showing them, and that they therefore might have seen, 

 especially if they had been willing to avail themselves of the labours 

 of their predecessors. A remarkable instance of this is to be found 

 in the great plain recently termed by Dr. Lee the Mare Smythii, where 

 Schroter's figure, under the name of Abraham Gotthelf Kastner, is 

 much more faithful than their own ; and another in the Sinus Aestuum, 

 where their assertion that no craters are discernible, was afterwards 

 retracted by Madler, and never, one would suppose, could have been 

 made had they consulted the design of Lohrmann. It is the unfortu- 

 nate want of confidence in our highest standards thus necessarily 

 resulting, which throws some doubt upon the evidence of change which 

 Mr. Webb adduces, and renders an appeal to the future still necessary 

 to render it conclusive. 



Eight separate instances of suspected change are now recorded by 

 Mr. Webb, some of these are certainly too doubtful to require more 

 than a passing notice, but others deserve careful scrutiny from time to 

 time and very accurate comparison with well-executed drawings, or if 

 obtainable, photographs. We will give a short notice of the most 

 noteworthy of these instances. 



On February 8, 1862, the S. and S.W. slope of the magnificent ring, 

 Copernicus, was seen to be thickly studded with very minute craters 

 not represented by Beer and Madler. The omission is chiefly remark- 

 able as they form a continuation of the extraordinary assemblage of 

 similar foci of eruption lying between Copernicus and Eratosthenes. 

 This latter wonderful district, it may be observed, by the way has 

 probably assumed its present honey-combed aspect during the present 

 century, as it is hardly conceivable that in such a situation it should 

 have escaped the persevering scrutiny of Schroter, and been left for 

 the eye of Gruithuisen in 1815. 



Another instance of probable change is afforded by the ring 

 mountain Mersenius. This is remarkable for the very unusual feature 

 of a convex interior, which was discovered and well drawn by Schroter, 

 and appears then to have had no object upon its summit. It is re- 

 presented equally smooth in the map cf Beer and Madler ; and from 

 their description, we are assured that this was no error in the drawing, 

 for they speak of several inconsiderable ridges and terraces round 

 the inner foot of the ring, and a general upheaving of the interior 

 towards the centre, so that for some hours this bubble-like convexity 

 casts a dictinct shadow to the eastward in the increasing moon, and 

 they have, though opportunities are not so frequent, seen it falling 

 in the opposite direction ; but they expressly add, that " a central 

 mountain is totally absent." No further evidence can be needed to 

 show that they had thoroughly investigated the spot. Now in the 

 year 1836, the Kev. T. W. Webb perceived, on the summit of this 

 well-known convexity, a minute crater, and several other delicate 



