278 REPORT— 1872. 



The light portion of the floor Mr. Pratt described as extending from the west 

 border as far as the streak g and Webb's elbow, as shown on the tinted 

 plate in ' Student,' April 1870, p. 161. 



1870, March 12. — Mr. GledhiU records the floor as " light, Uke the sur- 

 face of the Mare Prigoris, * medium.' " I have registered it as 0-42. He 

 says, " all streaks seen except X, which runs west from the spot No. 3." Of 

 streak jj he says, " ri does not reach up to No. 4 ; it is a brush of light near 

 the inner border just to the N. of HE''' 2." [This certainly does not accord 

 with -q, but is much nearer the position of Pratt's I. There appears to be 

 good evidence that the streaks sliglitly vary in extent and position. — W. R. B.] 



1871, January 1. — Mr. Elger described the markings as " aU faint," but 

 did not specify them, except p, of which he says, " the new marking on the 

 south side of the floor could be traced to the east of spot No. 5 (to about half- 

 way between 5 and 17)." In his sketch December 4, 1870, Mr. Elger places 

 spot No. 5 on the luest edge of ^. 



1870, August 6. — Mr. Gledhill recorded the floor as medium, =0-50, and 

 the streaks as faint and scarcely distinguishable from the floor. On the 

 same evening Mr. Elger says, " Sector seen, but its borders were very badly 

 defined." He also described the west portion of the floor as of an even light 

 colour. This observation is greatly in accordance with Mr. Pratt's of May 10, 

 1870 (see ante, p. 277) ; the increase of light in both cases most probably 

 depended upon the same agency. 



1869, December 13.— Mr. GledhiU recorded the tint of floor as light, =0-33, 

 the N. and N.W. portions being the brightest. The sector was well seen, 

 extending as far as spot No. 3, with a bright base resting on the border ; 

 a and its vicinity, both to the south and up to the north border, bright and 

 difficult to separate. It [this brightness] extends up to I [and consequently 

 includes k and c] ; c widens as it approaches the border of Plato. [Does 

 Mr. GledhiU mean that the light surface extended from the western arm of 

 the trident on the N.W. and N. as far as spot No. 3? If so, the great 

 northern streak would, in conse(]uence of -the sector and c being connected 

 by the extension of the sector to spot No. 3, have nearly the same contour 

 as given by Mr. Pratt on August 17, 1869, see ante, fig. 5, p. 252.] e and ^ 

 were well seen. Neither y nor /3 were strong nor broad ; -q was the faintest 

 streak on the floor. 



Mr. GledhiU speaks of streak I widening as it approached the border. This 

 widening is by no means an uncommon occurrence ; the sector is a familiar 

 example, also the streak »j has presented this phenomenon : both the sector 

 and rj ju'oceed from spot No. 4, which of aU the spots is characterized by the 

 most remarkable appearances. Now this widening is closely in accordance 

 with ejecta spreading from an orifice as it descends a surface slightly incUned. 



Mr. Elger has shown (Report Brit. Assoc. 1871, p. 71) that the surface 

 between spots Nos. 1 and 4 is depressed. Mr. Gledhill says : " I have never 

 noticed that portion of the trident east of the spot No. 1 ; I am looking for 

 it. I always see that portion of the trident in which spot No. 22 is situated 

 as nearly in a line with spot No. 1 and II E '^ ^." 



1870, October 4. — Mr. Elger saw the sector only; it was in strong contrast 

 with the floor. He also exhibits the light border skirting the west side of 

 the floor. Mr. Gledhill says: — " The west portion of the floor is the brightest ; 

 the line of separation runs through a point midway between sjrot No. 1 and 

 the west Ijorder, and both ways to the north and south borders. This space 

 includes Webb's elbow, c, the west end of ^, and S.W. end of e." Similar 

 observations of this light portion are recorded under May 9 and 10, the 



