298 



REPORT 1872. 



Interval to 12 hours. 



(Near the summer solstice.) 



In the Report for 1871 (see Report Brit. Assoc. 1871, pp. 94, 95) a de- 

 scription of sunset, as observed by Mr. Pratt, is inserted. Mr. Pratt's 

 letter was accompanied by a drawing, a copy of which is given below. 



Fig. 20. 



1870, Oct. 17, 11" to 12''. Sunset observed by Mr. Pratt. 



APPENDIX. 



Although the epochs of the following observations are not within the 

 period embraced in the foregoing discussion, they bear so intimately upon 

 the results that a notice of them may not be inappropriate. 



On November 20, 1871, I observed sunrise on Plato with the Royal 

 Astronomical Society's Sheepshank's No. 5 telescope, aperture 2-75 inches, 

 power 100. At 5.50, Greenwich mean time, I made the following record : — 

 " The appearance of Plato, examined at intervals of a few minutes since 4.35, 

 has been very curious to-night. I have been unable to divest myself of the 

 impression that a kind of sparkling or agitation played over the dark floor 

 deep in shadow. This appearance has latterly greatly increased, and now 

 there are two well-marked regions (but by no means distinct streaks of sun- 



