OBSERVATIONS OF LUNAR OBJECTS. 295 



paling ; the darker margins of the shaded parts of the floor were still visible 

 as on the 12th and 13th, but not in such striking contrast. 



1870, October 13. — ilr. Pratt remarked that all the objects on the floor 

 appeared fainter than usual. This, which especially applies to the light- 

 streaks, which were very well defined at their edges, is remarkable when so 

 many spots are detected as on that evening. 



Summari/.— Sun's altitude 28= 54'-3 to 25° 49'-5 ; tint of floor 0-54 to 

 052. Streaks generally visible — the sector principally, the others but seldom, 

 especially the N.E. streaks. 



Intervid 84 to 72 hours. 



1869, August 26. — ilr. Gledhill recorded the sector as very faint. See 

 ante, p. 254. 



1870, September 14. — Mr. Gledhill recorded the floor as medium or light, 

 =0-42 ; streaks faint, but well seen. Mr. Neison recorded the floor as mo- 

 derately dark, =0-58, mean 0-50, or medium. 



Sammart/.— Han's altitude 25° 49'-5 to 22° 31'-3 ; tint of floor 0-52 to 

 0-49. Streaks generally visible — sector and eastern and middle arm of the 

 trident. 



Interval 72 to 60 hours. 



1869, July 28. — Mr. Gledhill recorded the sector as faint and diffuse. 



1870, August 16. — Mr. Pratt recorded the floor as medium, =0'50, and 

 much paler than on the 13th (see ante, p. 293, interval 144 to 132 hours). 

 The darker parts of the shaded portions of the floor were but just perceptible 

 with attention. 



1869, September 25. — Mr. Gledhill described the tint of the floor as " not 

 much deeper than that of the Mare Imbrium." He appears to have seen 

 streaks c [" a strong streak of light connecting the spots Nos. 16, 19, and 13, 

 which were not seen "], k [ " a diffuse streak of light runs east from spot 

 No. 3 parallel to that crater along spots 16, 19, 13 "], and the connexion of 

 K with the sector [" a streak is seen from spot No. 4 to spot No. 3, as if a 

 continuation of the sector "]. On these I have the following remark : — " c from 

 the S.W. of spot No. 13 (not seen) to II E '/' 2 on the east border made out 

 in separate streaks." The continuous direction of these streaks forming one 

 white line was seen by Mr. Pratt on August 17, 23, 26, and 28 (see pp. 252- 

 254). Mr. Gledhill desci-ibed the three arms of the trident as follows : — 

 " [e] A rectangular luminous patch stretches from the south rim of Plato to 

 spot No. 14, embracing it and passing on till nearly in a line with spot 

 No 1, at which point a luminous streak [e] shooting from the rim and em- 

 bracing spot No 22 meets it. This latter streak seemed to become a mere 

 line as it approached the streak e." The S.E. arm [^] is described as "an 

 irregular rectangular patch of light running from the south rim to spot No. 1 

 nearly." It does not appear that Mr. Gledhill observed the junction of the 

 three arms. The N.W. arm [e] is described as '* very bright, the brightest, 

 the greatest brightness being close to the rim of Plato." The central arm 

 [e] is described as " less bright," and the S.E. arm [^j as " still fainter." 

 The apex of the sector is described as beyond spot No 4, distinctly enough 

 extending to the streak /3 running from spot No. 3 to rim. The following 

 note is appended by Mr. Gledhill: — '• I could not see the limits of the three 

 arms of the trident as they approached the centre." From his sketch Mr. 

 Gledhill appears to have seen the streak " " and its continuation a, his 

 delineation being almost identical with Mr. Elger's of September 20. It is 

 not at all improbable that a change had occurred in the N.W. part of the 



