OBSERVATIONS OF LUNAR OBJECTS. 73 



middle of the obscure area, stretching straight across it from one extremity 

 to the other, with much the same appearance as in winter in a closed cham- 

 ber the sun's rays admitted through a window are wont to present, or as 

 they are seen in the distance when cast through openings in the clouds, or 

 like comets' tails at night in a clear sky stretched out at length in space, as 

 we remember to have seen in the one which in the years 1680 and 1681 was 

 80 conspicuous to all Europe. This appearance, never before seen by me in 

 this or any other lunar spot, is represented in the figure which I give below. 



" 1, 2. The lunar spot named Plato, and the ruddy ray of the sun thrown 

 across its dark floor from the margin of the spot 1, white aiid turned towards 

 the sun. It was thus observed at Rome on the Palatine Mount, Aug. 16, 

 1725, at 1| hour after sunset, with the 150-palm telescope of J. Campini. 



" It is proposed to astronomers and physicists, for their consideration and 

 judgment, whether this is to be taken as an indication of an aperture piercing 

 the border of the spot which is turned towards the sun, through which opening 

 the rays are cast and appear as through a window ; or whether it is rather to be 

 thought that they are refracted rays, which are bent from the top of the border 

 towards the bottom, and appear of a ruddy tint as they are wont to do in our 

 own atmosphere at sunrise and sunset, and so give reason for admitting the ex- 

 istence of some denser fluid like an atmosphere surrounding the lunar globe." 



I have the following remarks on the above, dated June 4, 1867 : — 



" Bianchini appears to have been one of the earliest observers who noticed 

 ' detail ' more jiarticularly. Hevel, lliccioli, Cassini, and others aimed more 

 at delineating the entire surface, which of course included much detail that 

 is becoming more and more valuable every day ; still such observations as 

 Bianchini's, recorded in his ' Hesperi et Phosphori,' are of great value, espe- 

 cially as the appearances described and delineated could not find place in a 

 more general work." 



Sclirciter, in his ' Selenotopographische Fragmente,' vol. i. p. 334, §§ 256, 

 257, refers to the observation of Bianchini, and also to one of Short's in 1751, 

 April 22. It would appear that Bianchini's suggestion of an aperture or hole 

 in the W. rim of Plato was not verified by Short, who seems to have observed 



