273 



REPORT — 1872. 



IV. 



Observers' Notes. 



Interval 12 to 24 hours. 



State of floor at sunrise (fig. 10). — For observations at sunrise, see Report 

 1871, pp.67 to 76, also p. 96, where the reader will find Mr. Pratt's observations 



Fig. 10. 



State of floor at sunrise, 1870, Nov. 1, G'' to C' 40'". 



of sunrise. In reference to the dip of the floor to the margin there men- 

 tioned, which is well established, I may remark that on the 20 th of Novem- 

 ber, 1871, I noticed the streaks of sunlight at sunrise terminated on the east 

 at some distance from the border, indicating a considerable dip of the floor, 

 if the sunlight were reflected from the true floor. (See lloport 1871, p. 68, 

 Jan. 10, 3 hours.) In reference to the streak between spots Nos. 4 and 3, I 

 would observe that the continiious observations of the streaks rj and /3 by 

 Messrs. Gledhill and Elger strongly indicate that they are connected with 

 spots Nos. 4 and 3 ; the narrow shading between these spots, as shown by 

 Mr. Pratt, is most likely a shallow depression between the streaks if Mr. 

 Pratt's suggestion of their being spurs be correct (?). — W.U. B. Fig. ] shows 

 the dip of the floor to the E. border. Tint of floor 0-33. 



The difficulty experienced on the night of Nov. 20, 1871, in obtaining a good 

 view of sunrise on Plato (if inexplicable on the fact of different apertures 

 having been employed, 7^ in. on the 10th of Jan. 1870, and 2| on Nov. 20, 

 1871) may have been produced by an absorptive medium within the enclosure 

 of Plato : the appearance mentioned in Eeport 1871, p. 68, was more intensi- 

 fied than I had previously witnessed, and the western portion of Plato, that 



