1887.] 



BEN NEVIS OBSERVATORY. — LOG-BOOK. 



345 



Purple. 

 1° 34' 



Green. 

 1° 49' 



Yellow. 



Red. 



2° 28' 



]) White. Red. 

 Radii, ... 1° 14' 



At 17 h misty pinkish colour to westward below level of 

 Ben. As the sun set the shadow of Ben was distinctly seen 

 above the horizon to E.N.E. for a few minutes, until lost 

 in the general earth shadow. The sun set into the sea, 

 and as it disappeared a momentary bright green flash was 

 observed. No afterglow was observed. At 21 h aurora, 

 consisting of a bright single arch without streamers, was 

 observed. Height of top of arch above horizon about 12°; 

 width of bright part of arch, 2° 15'. At 22 h the arch 

 was more irregular, being apparently made up of several 

 superimposed on each other, and a few long streamers 

 reaching nearly to the zenith were seen. The clouds 

 which formed overhead in afternoon appeared to sink 

 down as evening came on; though the sky was clear the 

 air on the hill top was nearly saturated at 20 h , and it did 

 not dry again till midnight. 



Feb. 13. — Double fog-bow seen at 12 h . Trace of red 

 outside outer, and inside inner bow. 



Feb. 15. — Bright light seen to northward through 

 breaks in fog at l h , possibly auroral. A few passing 

 glories seen at 14 h .10 m . Solar corona observed on passing 

 scud at 12 h , always double, sometimes triple; best seen 

 when scud was uniform in thickness — not fibry— and thin 

 enough to see the blue sky through. 



Radius of inner red, 

 outer red, 



35' 



28' 



3° 31' 

 5° 43' 



J3°52'\ 3° 21' ("4° 13') 

 t6°55'J \7°38'i 



The bracketed values were taken at as nearly as possible 

 the same time. At 9 h 20 m the fog crystals on the stand 

 for hygrometer were measured. Next the wood was one 

 inch deep of white badly-defined and rather powdery 

 crystals, then -| inch of brown well-defined feathery 

 crystals, then ^ inch of pure white crystals, grown in 

 last half hour. Between the f layer and the ■£$ inch 

 layer was a belt of minute black specks which had appa- 

 rently formed while the top was clear of fog. At ll h the 

 outer white layer was - 55 inch long, showing a rate of 

 growth of over -J inch per hour. 



Feb. 16.— Brown fog crystals forming in early morning. 



Feb. 17. — Ice on all exposed surfaces in morning, but 

 110 trace of dust in it. 



Feb. 18.— Thermometer box shifted at 22 h 15 m . 



Feb. 21. — Louvres of thermometer box choked with 

 fog crystals and drift all yesterday and to-day. 



Feb. 24. — The snow which fell at night was dry and 

 hard, and in rather large flakes. 



Feb. 25.— Thermometer box shifted at 19 h 20 m . The 

 measurements of amount of snow this afternoon are very 

 doubtful, owing to drift. 



Feb. 26. — Very thin film of cirrus over sky in early 

 morning ; stars showing through it. At 7 h the under 

 surface of the clouds to eastward was like sheets of flame, 

 and the sky behind of a sickly pale green colour. At 7 h 

 15 m the colours had faded. Slight brown colour under 

 sun at 13 h . Sunset colours weak ; no afterglow ob- 

 served. 



Feb. 27. — Dark haze mixed with small patches of 

 cum. -fog round horizon and in valleys all day. Snow 

 almost gone off other hills round. Dull "smoky" colours 

 at sunset. 



Feb. 28. — Haze similar to yesterday in the valleys all 

 day. Faint brown colour under sun at 16°. 



Mar. 1. — Solar corona at 13' 1 

 Three rings, red outside in each, 

 ments were got : — 



10 m on passing scud. 

 The following measure- 



Radius of first red, 

 ,, second red, 

 ,, third red, 



I. 



1° 46' 

 2° 26' 

 4° 8' 



II. 



III. 



2° 34' 2° 39' 



IV. 



1°41' 

 2° 44' 



4° 40' 



At the same time a faint red corona seen on cirrus clouds 

 when the scud cleared off ; radius about 0° 56'. Ther- 

 mometer box shifted at 15 h 12™. At 16 h faint brown 

 colour under sun. At 17 h misty red colour under sun, and 

 solar corona formed on scud. Three rings, red outside in 

 all. The following measurements were got : — 





] 



[. 



II. 



III. 



Radius of first red, 



1° 



41' 



1° 25' 



1° 19 



,, second red, 



2° 



23' 



2° 26' 



2° 30 



,, third red, . 



3° 



54' 







At night lunar corona seen occasionally ; too fleeting 

 to measure. Fog crystals at night white and icy. 



Mar. 2. — About half an inch of hard ice on all exposed 

 surfaces this morning. 



Mar. 3. — Ice forming freely on exposed surfaces all 

 morning ; no trace of dust in it. At 12 h and 13 h fog-bow 

 seen, red outside ; no other colours. Icy fog crystals 

 forming in afternoon. After 18 h the sky above was 

 apparently clear, but banks of fog higher than Ben Nevis 

 lay all round, and the hill top was often enveloped by 

 this fog drifting over. 



Mar. 4. — Glories seen on passing fog all day. At ll h 

 15 m one seen from roof of Observatory, the shadow of 

 observer falling on the snow about 10 yards away. Colours 

 in following order :— Centre, white, red 1 , blue, green, 

 red 2 , blue, red 3 . Radius of red 1 , 2° 15' and 3° 12 (inside 

 and outside of colour). Another seen from edge of cliff at 

 ll h 20 m ; no fog-bow with it. Four rings of colours in 

 order below. Measurements to outside edge of colour 

 in each case. The radii appeared to vary slightly as the 

 surface of the fog rose and fell. 



Radii. 



Colours. 



9° 28', . 



Faint Red i 





Faint Green 



6° 12' and 6° 18', . 



Red 3 



5° 14', . 



Yellow 



4° 40', . 



Green 



4° 51', . . . 



Dark Blue 



3° 35' and 3° 25', . 



Red 2 





Yellow 





White 





Bad Blue 



1° 41' and 1° l- 1 -', . 



Yellowish Red x 





Centre of Shadow 



Another glory seen at 14 h 5 m from 



edge of cliff. Four 



rings, red outside in each : — 





Radius of second red, 



3° 46' 



„ second yellow, . 



2° 40' 



„ second blue, 



1° 43' 



„ third red, 



. 10° 37' 



„ third yellow, 



6° 12' 



„ third green, 



4° 25' 



Bright glories, too fleeting to measure, were seen all 

 afternoon on the loose fog drifting across the hill top. 

 Solar corona seen at ll b 10 m ; colours as follow : — 



