Doubts aud Facts concerning Linne. 41 



the Sea of Serenity, to which. B. and M. assigned the lumi- 

 nosity 6. 



If, then, we compare, the actual appearance of Linne with 

 the text of Lohrmann and his successors, it is possible, a la 

 rigeur, to believe that it has undergone a certain change. 

 Linne has always been a deep crater, with elevated margins ; 

 its lustre has not changed — its total diameter has remained 

 about the same. A comparison of maps, on the contrary, 

 indicates a real alteration, for these figure a large crater 

 occupying all the space now filled by the white spot. Schmidt 

 thinks that we cannot refuse to attribute great weight to the 

 identity of the indications of these two maps. The authors of 

 the second, having the first at their disposal, it is probable 

 that if they had not found the great crater drawn by Lohrmann, 

 they would have noticed so extraordinary a fact. It is not, 

 however, without interest to compare their indications with 

 that of earlier maps. The picture drawn aud presented by 

 Lahire, which is in the library of St. Genevieve, repre- 

 sents Bessel, Sulpicius Gallus, and other little craters, 

 equal to Linne in the map of Madler ; but he does not 

 indicate Linne. He has only many white spots in this part of 

 the sea. Cassinl's map appears merely a copy of Lahire with 

 less detail. According to Schmidt's note, Schroter seems not 

 to have seen Linne,* at least not as one of the principal craters 

 in the Sea of Serenity, although he noticed others that were 

 smaller. 



If we consult the photographs of the moon, we see, in the 

 large copy of Warren De la Rue (1858), Bessel and Sulpicius 

 Gallus exhibiting an indication of an interior shadow, while 

 Linne figures as a white spot. The same is seen, though 

 clearer, in the enlarged copy of the magnificent photograph 

 obtained by Mr. Rutherford on the 4th March, 1865. 



The disappearance of the great crater of Linne, then, dates 

 as far back as 1858, if not as far back as Lahire. Apart from 

 the indications supplied by the maps of Lohrmann and Beer 

 and Madler, to which we may oppose the counter indications 

 of Lahire and Schroter, we only possess a single positive 

 document testifying that Linne has undergone any change, 

 and that is the affirmation of Schmidt that his crater and 

 drawings of 1841 represent the object differently to what is 

 now seen. 



KEMAKKS OE ELIE DE BEAUMONT. 



M. de Beaumont observed, when the paper was read to 

 the French Academy, that if observers placed in the moon 

 viewed Vesuvius or Etna before and after an eruption, they 



* See Mr. Huggins's quotation from Schroter. 



