OBSERVATIONS OF LUNAR OBJECTS. 



81 



important : — " Nos. 1, 3, and especially 17 (which sni-passes all in sharpness, 

 and perhaps in brightness sometimes) are fine easy objects, "vvith moderate 

 altitudes. Now Linno never a2)pears like these except when near the even- 

 ing terminator. As to y Posidonius 1 never see it sharp and crater-Hke 

 (white and bright) when the sun is up. I could not see it at all the other 

 day when the morning terminator was a degree or two from it." Of ivhite 

 spots Mr. Gledhill remarks : " I called some spots mere white spots, because 1 

 have never seen them otherwise ; by-aud-by 1 may catch them near the 

 terminator, and have reason to change the term. I fancy that when the 

 terminator is a morning one the effect on objects diflfers from that given by 



the evening terminator.'' 



Interval 120 to 132 hours. 



1871, March 4. Mr. K'eison saw spot No. 14 very indistinct, and barely 

 brighter than a longitudinal steak running in a direction from No. 13 to past 

 No. 14, which was then situated upon it. It appeared to have its origin eX 

 the point of convergence of Gledhill's d and L On the same evening, Mr. 

 Gledhill recorded d but not c. On March 4, Mr. Neison saw No. 16 (once 

 only) as a pecuhar light-marked spot on a patch of broken light trending 

 westward. Mr. Neison also recorded parts of the N.W. and S.E. portions 

 of the floor indistinct from broken light and light streaks. 



1870, June 11. Mr. Elger recorded spots Nos. 5 and 16 as seen only by 

 glimpses. 



Intei-val 132 to 144 hours. 



1870, April 14. Mr. Gledhill records Nos. 1, 3, 4, 17, 9, 11, and 30 as 

 bright round disks. Mr. Elger writes, under date of April 26, 1870, relative 

 to his observations of April 14, as follows : — " That the visibility of the spots 

 is connected with the position and brightness of the markings (as you sug- 

 gest) is, I think, most probable : it is clear that the spots at present known are 

 mainly confined to the districts occupied by the markings, and that the floor 



Eic 



of Plata is divided by the latter 

 into three nearly equal areas. A, 

 B, C, as on sketch. Areas A and C 

 are covered with markings, but 

 area B is devoid of them. If 

 we compare the number of spots 

 in area B with the number of 

 spots in areas A and C, we shall 

 find that there are only two spots 

 (23 and 11) in area B, while in 

 area A there are ten, and in area 

 C no less than twenty-three. It 

 is true that small portions of the 

 areas A and C ai'e without 

 markings ; but the spots within those areas are, without an exception, situ- 

 ated either tqmi the light streaks or close to their borders. These facts 

 seem to me very suggestive, and point to an intimate relation between the 

 spots and markings. As observations accumulate, your present behef in a 

 connexion between the phenomena will, I think, be placed beyond doubt." 

 In connexion with the above, the following quotation from a letter by Mr. 

 Pratt, dated 1870, April 22, is interesting: — "Very curious the difficulty 

 there is in observing such delicate detail ; possibly instruments and eyes will 

 show differently, independently of the mental bias and accumulation of pre- 

 1871. o 



