68 REPORT 1871. 



breaks in the S. and N. borders passed throngh the western ends of the 

 earliest streaks of light thrown on the floor. This line appears to be coinci- 

 dent with the great fanlt crossing Plato. With reference to this I have the 

 following note : — " This phenomenon, the western extremities of the streaks 

 falling in a line with the breaks in the N. and S. borders, was well observed 

 in January 1870. An elevation of the gronnd in the direction of this fault 

 has been seen. It would, however, appear that diiferences in the lengths of 

 the streaks would depend not on any unevenness of the ground, but on the 

 relative depths of the gaps in the W. border." 



1870, January 10, 2'' to 8''. — From ten to sixteen hours after epoch of sun- 

 rise at the equator, E. long. 4° 6'-l , — £3 , Jan. 9, 16'', equal to l70°27'-8. 

 This was by far the finest observation of sunrise on Plato by no less than 

 seven observers, viz. Messrs. Gledhill, Pratt, Elger, Neison, Birmingham, 

 Joynson, and liirt. Mr. GledhiU's rccoi'd is so full and so interesting that 

 a reproduction of it will convey a vivid impression of the progress of iUu- 

 minatiou of a lunar formation as the sun rises upon it. 



Jan. 10, 2\ Cloudless. Terminator just on the E. border of Plato; can 

 just see the outline of the crater, which now lies in deep shadow. On the 

 E. side the lofty steep wall just jS". of a triangular formation marked II E'/'^ 

 glowed intensely in the solar rays. 



'3^. The E. waU from the great breaks in the S. and N. borders appeared 

 as a bright narrow band. The curved outline of the N.E. border was bright, 

 sharp, and narrow, but the lower slope within could not be seen. I could 

 fancy that the W. part of the floor is, if possible, deeper in shadow than the 

 E. half. [This phenomenon has often been witnessed, and has been attri- 

 buted to the reflection of the strong light of the eastern interior from the 

 dark floor. Upon attentively contemplating this degradation of shadow near 

 its eastern boundary, it will often be seen that it is not simply a reflection 

 from the floor, but apparently the illumination of a something above the 

 floor.— W. E. B.] 



gh ^5m_ ^ bright narrow broken line was seen between the two breaks on 

 the £. and N.E. The outline of II &^ is not yet visible. 



4" 18". At this moment (12 hours 18 minutes after epoch) the first streak 

 of light fell upon the floor. Within it and near its western extremity was 

 seen No. 3 as two elevated objects, very near each other, but quite distinct. 

 I could not detect shadow between them after hard gazing, although it was 

 easily seen to the N.E. of the lower object. The sti-eak was three times the 

 breadth of the two objects together where it enclosed them, and it became 

 broader near the N.E. border of Plato ; it was brightest about and to the 

 west of No. 3, and inclined a little downwards at the E. end. * * * The 

 two components of No. 3 are of the same size apparently, are equally but 

 not very bright ; they lie nearly E. and W. of each other, but the E. com- 

 ponent is a very little to the N. of the other. 



^h gQm_ rpj^g streak widens. I could not detect motion in it. I now care- 

 fully placed the wire on the great gap in the west border ; the line passed 

 along the axis of the streak. The west angle of the streak is not sharp, but 

 rounded, and lies a little beyond No. 3. The lower of the cones of No. 3 

 touches the lower edge of the streak. It now assumed a fan shape, being 

 broadest at the E. end, which is now more than halfway to the E. border. 



411 4Qni_ rpj^g streak is now much wider. I think I see a minute elevation 

 a little to the E. of No. 3 and in the streak. The two components of No. 3 

 are now bright and sharp, with shadow on the east. Another streak has 

 been barely visible or suspected for a few minutes; it lies to the S. of the 



