1886.] 



BEN NEVIS OBSERVATORY. — LOG-BOOK. 



339 



May 12.— Thermometer box shifted at l h 20 m . Faint 

 upper arc of halo seen at 5 h . No fog in valleys, but 

 cumulus on hills round most of the day. 



May 14.— Thermometer box shifted at 10 h 30 m . At 

 17 h the wind was easterly (2-3) ; but the sky was 

 covered with cumulus at no great height, moving from 

 N.N.W. 



May 15. — Thermometer box shifted at 14 h 15 m . 



May 16. — Double lunar corona at 2 h on low clouds, 

 too fleeting to measure. At 3 h cum.-fog on hills all round. 

 At 4 h level-topped all over western hills. On this fog the 

 shadow of Ben Nevis was clearly seen at 4 h 10 m . Fog 

 also on hills far to E. and N.E. Fragments of solar halo 

 at 5 h . The snow which fell at night was small and hard. 



May 18. — The snow that fell at night was hard and 

 icy in texture. 



May 19.— Thermometer box shifted at 22 h 20 m . At 

 midnight the northern horizon was faintly tinged with 

 red by the sun. 



May 20. — Faint brown colour under moon at 2 h . 

 Brown colour under sun at 5 h . Solar halo at 7 b ; colours 

 faint, red inside. At 10 h triple solar corona on scud; 

 too fleeting to measure. Air very clear to S.W. in early 

 morning. 



May 21. — Dark, but not thick, haze in valleys at night. 



May 22. — Faint brown colour under moon at l h . 

 Brown colour under sun at 6 h , and low fog on Loch 

 Lochy. At 7 h cloud above sun coloured red and blue in 

 patches (about 5£° above the sun). When it came nearer 

 to the sun the colours vanished. There 

 R J^ e was no trace of arrangement in the colours. 



Bl ue The cloud of the cir.-cum. type. At 8 h 3 m 



Eed a similar cloud showed the same colours, 



Yellow k u t as tliis cloud approached the sun the 



B j^ n colours formed a more regular corona, being 



Violet arranged as in margin. Another cloud 



Eed passed at 8 h 6 m , giving similar colours ; 



Yellow t h e violet and blue in this one were very 



™f bright. A third cloud passed at 8 h 10 m , 



also with bright violet, blue, and green. A 

 measurement of the inner red of this last gave for radius 

 3° 31'. At 10 h Ben Wyvis seen distinctly, and looking 

 very high. 



May 23. — At 4 h the sun was behind a thick bank of 

 haze, and its disc scarcely discernible. A faint upper glow 

 at about 45° above the sun was seen. Solar corona at 

 Red 1 2 h ; colours as in diagram. Inner and 



Red and blue outer red distinct, but space between very 



mixed mixed in colour. Radius of inner red, 



Red 3° 25'; 3° 25'; 3° 18'; 3° 35'; outer red, 



® 6° 41' ; 6° 35' ; 6° 41' ; 6° 41.' Very large 



haze all round last night and all to-day. At 16 h both 

 cir.-cum. and cir.-str. were observed. The cir.-str. was 

 distinctly below the cir.-cum., but was apparently moving 

 in the same direction, S.S.W. At 20 h the high cumulus 

 appeared to meet the haze all round, leaving no clear sky. 

 The rainfall at 21 h is filled in by interpolation. The rain 

 came on in short sharp showers, while the air was dry. 



May 24.— At 18 h 10 m dry and wet shifted. During 

 the dry fog to-day the air felt very close and warm. 



May 26. —Thermometer box shifted at 16 h 10 m . 



May 27. — At 6 h faint brown colour under sun. At 9 h 

 ascending currents from Glen Nevis forming cumulus 

 clouds. At 1 3 U bright halo seen ; red inside, then 



TRANS. ROY. SOC. EDIN. VOL. XXXIV. 



yellow and blue outside 

 were made : — 

 Radius of 



The following measurements 



of 



Red. 



Yellow. 



Blue. 



1st, 



21° 24' 



23° 44' 



24° 43' *r 



2nd, 



22° 0' 



22° 49' 



24° 43'<- 



3rd, 



22° 12' 



23° 30' 



24" 18' J 



4th, 



22° 0' 



23° 0' 



24° 43' „ 



/* 



The double arrows represent the diameters along which 

 the four measurements were made. 



May 24. — Thermometer box shifted at 4 h 12 m . Fog 

 rising from Glen Nevis in forenoon. Huge masses of 

 cumulus all round at 13 h . Snow at 14 h hard and dry. 

 Air may have been dry. 



May 21. — No colour round sun in forenoon, but at 

 15 h a faint brownish glare was observed. A very faint 

 afterglow was seen at 21 h . The door and windows were 

 a good deal blocked up with drifted snow during the last 

 week of May. They were dug out on 31st May, after 

 being closed for four days. 



June 1. — Brown colour under sun at 5 h and 6 h . Frag- 

 ment of halo, red inside, seen at 13 h . Haze to northward 

 of a curious green colour at 22 h . 



June 3. — At midnight the higher cirrus clouds to north- 

 ward were bright, apparently with sunlight; but the 

 lower ones were quite dark. 



June 4. — At 5 h 10 m halo and mock suns observed, 

 halo red inside and blue outside. Mock suns at each side 

 so bright as to be dazzling, the right hand one the brightest. 

 Radius from centre of sun to centre of mock suns, 23° 17'. 

 Vertical white segment below sun, and horizontal seg- 

 ment passing through mock sun. This horizontal segment 

 was 12° 32' above the level-topped haze. At the right 

 mock sun, the red of the halo was not broken, the white 

 mock sun being outside it. The following measurements 

 of the halo were made : — Radius of red, 22° 36' ; 22° 36': 

 yellow, 23° 3'; 23° 30'; blue, 23° 44'; 23° 44'. The mock 

 sun to the left was coloured red, yellow, and blue in 

 same order as the halo. At 8 1 ' halo seen again, rather 

 faint. Radius of inside of red, 22° 0'; outside of red, 

 23° 17'; outside of blue, 24° 43' — measured on lower 

 segment of halo. At 8 h a corona was also observed on 

 cir.-cum. Radius of inside of inner red, 2° 50'; outside of 

 inner red and inside of blue, 3° 46'; outside of blue and 

 inside outer red, 5° 52'. Corona was faintly seen again 

 at 13 h . No unusual colours round sun when clear of 

 clouds. 



June 5. — At 13 h the rain-gauge, which was buried out 

 of sight on 7th April, was found and taken in. 



June 7. — At h 10 m thermometer box shifted one 

 stage lower on ladder-stand. No glare round sun all day, 

 but brown colour at western horizon at 16 h . Halo at 8 h . 



June 8. — Fog on hills to S.E. in early morning, which 

 gradually spread over to Ben Nevis. 



June 10. — At 17 h raven heard croaking, but not seen. 

 To-day Wm. Stewart, J. Macdonald, and one horse came 

 up. The horse got right up to the Observatory, the snow 

 being hard. This the first horse up this year. 



June 11. — At midnight the dry and wet read 36°T and 

 35° "2, though the dry had a large drop of water hanging 

 from it. 



June 12. — At 14 h 10 m thermometer box shifted one 

 stage lower on ladder-stand. 



3 x 



