1887.] 



BEN NEVIS OBSERVATORY. — LOG-BOOK. 



351 



the wind was strongest. At midnight the summit was 

 white with snow. 



Sept. 10. — Robinson anemometer was untied at noon. 



Sept. 11. — Anemometer was tied at 16 h . 



Sept, 12. — Heavy showers of snow fell this morning. 



Sept. 14.— Anemometer untied at 8 h . 



Sept. 15. — The summit was clear till 16 h , but fog- 

 enveloped for the rest of the day. During the morning 

 hours the lights of the S.W. coast lighthouses were easily 

 seen. Robinson anemometer tied up at 20 h . 



Sept. 16. — Between 3 h and 4 h this morning the zodiacal 

 light was seen as a steel-grey glimmer extending from 

 eastern horizon through the constellations Leo and Cancer, 

 to the border of Gemini. At the same time a light, 

 supposed to have been the glare of the Carron ironworks, 

 was observed at the south-south-eastern horizon. Fog lay 

 in valleys and on surrounding hills all day, rising in after- 

 noon, and occasionally passing the summit. The anemo- 

 meter was untied at 13 h . 



Sept. 17. — Summit was clear after 6 h . The sky was 

 cloudless after 19 h except for some thin stratus at 22 h . 

 Fine pink afterglow observed from 18 h 45 m till 19 h 5 m . 

 Ice formed on top of thermometer screen at 21 h and at 

 midnight. A bright shooting-star was seen at 20 h ll m . 



Sept. 18. — At 3 h an aurora was seen low to northward 

 with short and not very bright streamers. The zodiacal 

 light was seen at 3 h 30 m . The summit was clear till 15 h , 

 but thick fog lay on lower hills all around, which gradually 

 rose, and enveloped summit after that hour. At 12 h and 

 at 14 h 30 m glories were seen from edge of cliff to northward. 

 At 1 3 h 30 m the following measurements were got :— 



38 



Red 

 glow. 



Inside 



of 

 Redl. 



Redl. 



Out- 

 side of 

 Redl. 



Blue. 



Green. 



Inside 



of 

 Red2. 



Red". 



Out- 

 side of 

 Ked». 



1° 12J' 



2° 56' 



3° 44' 

 3° 35' 



4° 5£' 

 3° 46' 



4° 23' 



4° 43' 



4" 56' 

 5° 3' 



5° 34' 



6° 24' 

 6° 29' 



A fog-bow was observed at same time, measuring 35° 16'. 



Sept. 19. — The fog cleared off summit after 17 h , leaving 

 thick fog in valleys all round and a cloudy sky. From 

 21 h till midnight the sky was cloudless. At 23 h a 

 glimmering light was seen at northern horizon, probably 

 auroral. 



Sept. 20. — At 30 h zodiacal light was seen looking as 

 bright as the milky way. Fog in valleys till 4 h , after that 

 cum. -fog on hills till about noon, and thick haze in valleys 

 all afternoon and at night. At about 1 8 h 45 m the afterglow 

 was seen faintly. 



Sept. 21. — Fog lying over and hiding all the lower hills 

 round most of the day. On this glories were seen 

 frequently. The following measurements were got at 7 h 

 10 m , colours as in fig. 16 :— Radius of red 2 , 4° 18'; 3° 15'; 

 4° 18'; 3° 54'; yellow 2 , 2° 59'; 3° 2'; 3°' 4'; 2° 39'; blue 2 , 

 2° 17'; 2° 21'; 2° 24'; 2° 12'. After 8 h the following 

 measurements were taken, some from top of tower and some 

 from edge of cliff. The glory appeared to vary in size 

 as different parts of the fog drifted past. 







Tower. 





Cliff. 



Radius of red 2 , 



3° 15' 



3° 44' 



3° 50' 



4° 6' 3° 54' 



, , yellow 2 , 



2° 37' 



2° 47' 



2° 58' 



3° 2' 2° 47' 



blue 2 , 



2° 2' 



2° 0' 



2° 13' 



2° 19' 1° 58' 



, , red 3 , 









6° 55' 



The fog occasionally rose above the level of the hill top, 

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



causing in each case a rapid and considerable fall of 

 temperature. 



Sept. 22. — The fog thinned away into haze in the fore- 

 noon, and a few hill tops showed above it at times. 



Sept. 23. — Thick haze in the valleys all day, mixed with 

 cum.-fog in the afternoon. Heavy dew on the top of 

 thermometer box, and on black bulb at 20 h , but nowhere 

 else. Aurora seen at night ; misty confused arch — no 

 streamers. 



Sept. 25. — Though the wet bulb read a few tenths lower 

 than dry for a few hours this morning, the air was 

 obviously saturated. 



Sept. 28. — At 3 h aurora seen flashing in waves to 

 northward ; no well-defined arch and no streamers. At 6 h 

 the "snowline" appeared to be between 2000 and 3000 

 feet. At 19 h a lunar aurora was observed occasionally, 

 formed on scud. 



Sept. 29. — At 23 h cumulus clouds all round at about 

 level of top of Ben Nevis. 



Sept. 30. — Dense masses of cumulus over all hills round, 

 and occasionally on Ben Nevis ; also during the day, but 

 clearing at night. The earth shadow was seen after 18 h 

 as the sun went down; it had been seen before sunrise on 

 all clear days recently. A well-marked afterglow was 

 seen at about 18 h 50 m . 



Oct. 1. — Thick haze and str.-fog in valleys and over hills 

 in early morning. Earth shadow seen at 6 h . Cum.-fog 

 formed all round in forenoon, and gradually rose till at 

 about 14 h it covered Ben Nevis. 



Oct. 4. — The fog sank below the level of Ben Nevis in 

 early morning, but continued to cover the other hills all 

 day. When clearing a double lunar corona 

 was observed. Measurements were got at White 



5 h , as noted in margin. Glories were also Yellow 



seen during the day on the fog to north- Orange 



ward. The following measurements were 2 ° 12 ^?* 

 got between ll h and 12 h : — Five rings — Blue 



radius of red 5 , too faint; red 4 , 6° 18'; red 3 , Green 



4° 37' ; red 2 , 2° 40' ; red 1 , 0° 52' (about). Yellow 



The earth shadow and the afterglow were , 2 r ^J 1 *' e 

 seen at 18 h . A lunar fog-bow was seen at 

 23 h , radius to inner edge (about) 38° 5'. 



Oct. 5. — At l h a few hill tops were showing through 

 the fog. A lunar fog-bow was seen. At 2 h the fog had 

 risen higher, and was beginning to blow across the hill top. 

 A distinct lunar fog-bow was seen, with traces of faint 

 second bow outside it. The following measurements of 

 the inner bow were got : — Badius inside of bow, 35° 4'; 

 outside of bow, 41° 0'. A similar fog-bow was seen at 3 h ; 

 there appeared to be a faint trace of red about the outer 

 edge of the inner bow. On both these occasions a faint 

 white patch of light was seen round the shadow of the 

 observer's head, which was probably a lunar glory. The 

 fog-bow was seen again, but without any glory, at 4 h and 

 5 h . The following measurements were made at 4 h : — 

 Radius to inside of inner bow, 36° 3'; outside, 

 41° 0'. 



Oct. 11. — At 2 h 10 m dry and wet were put out in small 

 box on lowest stage of ladder-stand about 49 inches above 

 ground. At and after 3 h the temperatures on the day's 

 sheet are those of the small box. 



Oct. 12. — The measurements of the amount of snow to- 

 day are very doubtful, owing to drift. 



Oct. 13. — The summit was enveloped in thin fog till 9 h ; 



4 A 



