56 Light S2iots in the Lunar Night. 



from experience. I think I should hesitate in making any such 

 assertion now. 



On the last morning Schr. found two other luminous 

 specks, where he had never perceived anything whatever on 

 former occasions : one, W. of Menelaus, and very similar in 

 aspect to Manilius, falling on the site of the Promontorium 

 Acherusia (Int. Obs., viii. 30) and Taguet, (a small bright 

 adjoining crater) ; the other on the opposite side of the M. 

 Tranquillitatis, at the Mons Herculis [qu : Prom. Heracleum~\ of 

 Hevel [Censor inns, 90] : and here, he believed, as in former cases, 

 was evidence of incidental modification, as though something 

 occasionally interfered with the uniformity of reilective power 

 on the dark side of the moon. Certain localities, it might be 

 supposed, were liable to atmospheric obscuration, which could, 

 he thought, be often traced, in the non-visibility of minute 

 objects towards the lunar sunset, and which might be continued, 

 or might be more likely to occur, during the lengthened night. 

 And he mentions the curious fact, that during a very favourable 

 view, 1790, Jan. 17, he not only noticed (what has already been 

 mentioned) that the relative brightness of Manilius and Mene- 

 laus was interchanged, but that the considerable luminosity just 

 mentioned on the site of Taquet could not be perceived again, 

 excepting as a very minute point as bright as Manilius or Mene- 

 laas during the first 15m., of which afterwards nothing could be 

 seen ; that on the other side of the M. Tranquillitatis [at Censo- 

 rmus] nothing more than a very slight increase of brightness 

 could be at times perceived; and that in another direction 

 [that of Dionysius, 25] he caught, but twice only, a very 

 minute point, brighter than either Manilius or MenelaUs, which 

 he could not recover again. In all this he found, of course, the 

 confirmation of his hypothesis. Shall we accept it as such, or 

 shall we ascribe it to mere eye- weariness, and anxiety, and 

 prepossession ? — misrepresentation, no one that knows his writ- 

 ings would for a single instant impute to that honest man. We 

 would answer, that we leave it to time to discover the value 

 or the error of his observations and inferences. Some years 

 ago we might have been disposed, like B. and M. to pass them 

 by in silence ; the new course of selenological investigation 

 seems to demand a fuller treatment of a subject more difficult 

 than it might at first appear.* 



The observations of 12 subsequent years never renewed 

 again to Schr. the illumination on the E. side of Mont Blanc; but 

 the use of larger apertures — his 13 ft. reflector had about 9£ 

 inches, and his 27ft., 19^- inches English measure — fully con- 

 firmed his previously formed opinions/ and he has recorded 

 the following interesting and final addition in his second volume. 

 * See especially Int. Obs. vii. 54, 55 ; viii. ~ ( J5. 



