34G 



BEN NEVIS OBSERVATORY. — LOG-BOOK. 



[1887. 



Radii. 



2° 9' 



2° 30' 



3° 54' 



Outer Edge. Inner Edge. 



2° 27' and 2° 30' 1° 40' 



4° 43' and 4° 37' 3° 31' 



O 



White 



Bed 1 

 Dark Blue 



Green 



Red 2 

 Dark Blue 



Green 



Red 3 

 Dark Blue 



Green 



Red* 



Another solar corona seen at 12 h 10 m , colours and radii 

 (outer edge of each colour) as under: — 



6° 48' 



7° 59A' 



White 



Yellow 



Red 1 



Dark Blue 

 Green 

 Yellow 

 Red 2 



Dark Blue 

 Green 

 Red 3 

 Blue 

 Red* 



2° 39' and 2° 39' 



4° 46' 



V 55' 



9° 41' 



All the afternoon and evening very thick fog lay over the 

 hills round, not a single hill top showing through till well 

 on in the night, while the sky was cloudless, and with no 

 trace of glare round the sun or moon and no brown 

 colour under either. The sun set into the level-topped fog 

 at 18 h 2 m . The sunset colours at 18 u 10 m were red, pale 

 yellow, and pale blue. No afterglow. Earth shadow 

 distinct to east, with a red glow above it reaching to 45° 

 altitude. 



Mar. 5. — At 3 h faint brown colour under moon. At 6 h 

 15 m appearance of eastern horizon as in diagram. At 6 h 



E.N.E 



E.S.E 



20 m red and orange colours rising higher, and gaps between 

 the bright parts lengthening. At 6 h 35 m red almost gone, 

 only faint traces of gaps left, and a faint pink glow about 

 12° above horizon. At 6 h 45'" only orange and yellow 

 colours, then colourless or blue strips of sky, then pink 

 glow; no gaps. Sun rose at 7 h 2 m . Before and as it rose 

 earth shadow 2° high to west, with shadow of Ben Nevis 

 about '2\° high distinctly marked in it. Brown colour 

 under sun in morning and evening. Haze and detached 

 cum.-fog in valleys all day, but no continuous sheet of fog 

 over hills, as there was yesterday. Earth shadow seen 

 at sunset, and shadow of Ben Nevis still visible on cloud 

 or haze to eastward after it had vanished. Sun sank into 

 haze, but was seen through it down horizon. No green 

 flash seen either when disappearing into haze or below 

 horizon. Colour of sun above haze was yellow, and in 

 haze red. Single arch aurora seen at night. Highest 



point of arch 16° above horizon, breadth of arch about 4" 

 at 20 h . Streaks of cirrus and haze to south-west at 

 night. 



Mar. 6.— At G h red and yellow sunrise colours seen. 

 At 6 lv 50 m a vertical beam of light starting from 5° above 

 the horizon to east and about 5° long was seen ; it lasted 

 till the sun rose at 6 h 56 m . One minute or so after the sun 

 rose it appeared double. Solar halo seen between 9 h and 

 10 h , as sketched (see fig. 11); colours as marked. The 

 mock suns were red inside and blue outside ; they lay dis- 

 tinctly on the outer edge of the halo. The following 

 measurements were got: — 



Left Mock Sun. Right Mock Sun. 



Radius of red, . 22° 49' 23° 17' 23° 3' 



white, . 23° 44' 24° 13' 24° 13' 



blue, . 24° 28' ... 24° 58' 



Faint traces of green and yellow seen in the mock suns 

 at 10 h 10 m . The mock suns and horizontal white bar about 

 24° above horizon at 9 h . The haloes, &c, continued to be 

 visible till 13 h . As the sun rose higher the horizontal 

 bar curved upwards, and at noon the appearance of the 

 inner halo and mock suns was more as in fig. 12. The 

 bar also extended then inside halo. The following 

 measurements were got at various times of the different 

 parts : — 



Sun to western mock sun, . . 23° 46' 



„ eastern ,, . . 23° 42' 



,, white circle E, 79° 56' ) 



,, „ 2d measurement, 81° 23' J 



„ green at junction of C and D, 50° 26' 

 Red of C to red of A, . . 25° 28' and 24° 48' 



Blue of C to blue of A, . . . 25° 13' and 24° 32' 

 Green of C to green of A, . . . . 24° 20' 



At 12 h 20 m measurements were made po = 13°22' 

 of the wings between A and B. A point F QS = 24° 8' 

 on one wing was taken and its distances PS = 29° 52' 

 from Q, S, and Z (see margin) measured. py = iQoo5' 

 The wings were not arcs of same circle ; — . . , 



judging by the old ring of stephanome, their centres 

 of curvature lay about midway between the sun and the 

 mock suns on either side. Haze with some patches of fog 

 in valleys all day. Brown colour under sun in afternoon. 

 Mock sun seen again at 17 h . Radius of red, 22° 0'; of 

 yellow, 22° 36'; of blue, 23° 17'. Faint lunar halo seen 

 at 20 h . Single-arch aurora at 22 h 30 m . At 22 h 40 m it 

 broke up into a set of short vertical rays of rapidly vary- 

 ing place and brightness. At 23 h it was gone. Its colour 

 was greenish yellow. 



Mar. 7. — At 6 h sky green near horizon to eastward. At 

 7 h faint double solar corona. Fleeting coronse and glories 

 were seen all day, but no measurements were got. Dense 

 fog over the lower hills during the day, which occasionally 

 blew across the top of Ben Nevis ; but it cleared away at 

 night, remaining longest on the hills to S.E. 



Mar. 8. — Fog gathered again on the hills round in 

 morning, and gradually rose till at about 14 1 ' 30 m it covered 

 Ben Nevis. 



Mar. 9. — White dry fog crystals forming in early morn- 

 ing. At ll u thick haze with detached cum.-fog in it in 

 valleys. The snow that fell in the afternoon was hard 

 and dry. 



Mar. 10. — The snow which fell today was light and 

 dry, and drifted along the ground easily. The gauges 



