4; 12 On Remarkable Solar Halos and Mock Suns. 



sions with L, rose from the true sun, passed through the ver- 

 tex of the circle A, where it cut the segment L, and stretched 

 out towards the north-east. This was inverted with respect 

 to L. 10° of a circle of large dimensions also cut the seg- 

 ment L at P. On the west horizon a few long muddy cirro- 

 strati were just visible above the fog. 



1^ 15"^. The circle A alone remained, the other portion of 

 the phaenomenon having disappeared soon after 1*^ 10°*. 



1^ 30™. More clouds ; the halo A fainter ; but another 

 feature was at this hour traceable — a ring, Q, fig. 7, whose 

 centre was a few degrees above the true sun, cut the circle A 

 at R and the circle G at T; the vertical diameter was 70° 

 and the horizontal diameter 55°. The circle A had become 

 more elliptical ; its vertical diameter was 48° and its horizontal 

 diameter 4:4!^°. 



jh 37111^ Another change took place; the circle Q vanished, 

 but there were two other segments of circles, U and W, fig. 8, 

 of apparently 140° in diameter; these crossed each other at 

 the point X, which was distant 70° from the sun. These 

 segments both went eastward ; there were again three mock 

 suns visible, viz. M, N and C; the latter was bright but 

 colourless, and had a tail of 8° in length, diminishing to a 

 point, and proceeding diametrically opposite to the true sun. 



Ih 40™. All had vanished but the circle A. 



1^ 50™. Circle A disappeared. Sky becoming clear. 

 Temperature, 44° ; hygrometer, 94 ; wind, west and calm. 



1^ 55^. Faint portion of the circle A again formed above 

 the true sun, and at this time prismatic. It finally disap- 

 peared at 2^^, and the sky became thinly and partially scat- 

 tered over with clouds of cirrocumuli. 



The width of all the circles was 1°. 



A fine night, succeeded by a foggy morning and slight 

 solar halo. On the 16th all day a prismatic solar halo, and 

 at 3^ 25"* there were two prismatic mock suns formed on the 

 horizontal level of the true sun in the halo of 45° diameter; 

 these lasted 7 minutes. 



It is well to add, that all the measurements were made 

 with an admirable and at the same time simple instrument 

 invented by Mr. Lawson for this purpose. It is hung in the 

 observatory, and is ready for use at a moment's notice. 



Observatory, Lansdown Crescent, Bath, 

 February 17th, 1849. 



