1892.] 



BEN NEVIS OBSERVATORY. — LOG-BOOK. 



417 



Nov. 11. — The thermometer box was changed after 

 1 l h . Height above snow not changed. 



Nov. 17.— Summit clear of fog from 6 h till 10 h , but 

 sky was cloudy then and fog and haze lay below. 

 Thick fog depositing brown fog crystals all afternoon. 

 Glories seen at 8 L on fog in second gorge. Thermometer 

 box changed after 8 h . Height not altered. 



Nov. 18. — Mist or fog till 21 h , when top cleared and 

 sky became rapidly cloudless. 



Nov. 19. — Cloudless or almost so and air dry till 

 7 h , but fog and haze below. Thick fog depositing brown 

 fog crystals during the rest of the day. 



Nov. 20. — Fog all day ; with some snow in early 

 morning. Brown fog crystals forming most of the day. 



Nov. 21. — Fog and E.S.E. wind all day. Brown 

 fog crystals forming nearly all day. 



Nov. 22. — Except for a short clear interval at 5 h 

 there was thin fog on summit till 20 h . After that it 

 cleared off and sky was cloudless, the air dry and warm 

 (the temperature rising quickly) till midnight. Aurora 

 seen at 5 h and at and after 21 h . At 21 h 30 m the 

 thermometer box was changed. Height above snow not 

 altered. 



Nov. 23. — Summit clear, sky almost cloudless, and 

 air dry and warm all day. Fog on hills to S. and S.E. 

 all day, and haze to N. and W. Aurora seen all 

 morning and again at 22 h . When the summit cleared 

 last night there was a heavy coating of fog crystals on 

 S.E. side of everything, but owing to the dryness and 

 warmth of air to-day, by midnight they had almost all 

 evaporated. 



Nov. 24. — The high temperature (34° to 40°) ; the 

 low humidity (37 to 56) and the clear sky continued 

 till 18 h , but there was fog to 3000 feet all round below. 

 Till 18 1 ' there was hardly any wind, but at 19 h a S.E. breeze 

 begau to blow, the fog rose and enveloped summit, and 

 the temperature fell 11°. A very faint aurora was seen 

 at 5 h and again at 18 h and 19 h . At 9 h 45 m a glory was 

 seen on the fog low down to N., and measurements, per 

 stephanome, made of red of the inner of two sets of 

 coloured rings. The mean of 6 measurements gave 

 as radius of this red 2° 54'. — The colour of the rings, it 

 was noted, was dispersed and irregular owing to the 

 irregularity in density of the cloud. In early morning 

 3 h to 6 h a great many meteors were seen, some very 

 bright. At 3' 1 as many as 20 in 4 or 5 minutes could 

 be counted. At 13 h observation the wet bulb looked 

 rather dry (the readings being Dry 37°T, Wet 31°'2), 

 another reading was made at 13 h 23 m (Dry 37° - 2, Wet 

 28° -4). The latter is entered, without time correction, 

 for 13 h on daily sheet. 



Nov. 30. — Thermometer box changed at h m . 



Dec. 1. — -Top clear except in early morning and after 

 •21 h . Sky nearly cloudless most of the time. Tempera- 

 ture low and air saturated all day. At ll h a double glory 

 and a triple fog-bow were seen to N., the order of colours 

 was : — 



Sun Blue Red Blue Red 



Red Blue Red Blue Blue Red 



Glories. Fog-bows. 



Lunar coronse were seen in evening. 

 Dec. 2.— Fog at l h and 2 h and at and after 17 h . Clear 

 and almost cloudless between those times, but detached 

 ROY. SOC. TRANS. EDIN. — VOL. XLII. 



fog and haze below, which thickened and rose in after- 

 noon. A lunar corona was seen at 4 h , a meteor at 6 h , and 

 the earth shadow at 8 h . 



Dec. 3. — About 10 b 30 m the telegraph instrument 

 indicated several flashes of lightning, the last of which 

 short-circuited the line by breaking through the protector 

 in Post-Office. Communication was restored after 16 h . 

 St Elmo's Fire was seen at 21 h . 



Dec. 7. — Summit clear from 2 h till 7 h , and air dry 

 from 3 h till 8 b — lowest humidity 36 per cent, at 4 h . Fog 

 and showers of snow from ll h till 20 h , clearing thereafter. 

 Lunar corona seen at night. Thermometer box was 

 changed at 2 h 15 m . 



Dec. 9.— Fog on or passing over summit till 18 h , when 

 it cleared off ; but sky remained cloudy and air saturated 

 (except at 23 h ). 



Dec. 12. — Thermometer box was changed at 12 u 20 m . 

 Height not altered. 



Dec. 13. — Fog clearing at times in forenoon, and 

 summit clear from 15 h till 20 h , but air saturated except at 

 18 h . Aurora seen at l h , and a fog-bow and glory at 12 h . 



Dec. 22.— Fog till ll h . Thereafter the top cleared, 

 and after 14 !l the air became gradually drier, the humidity 

 at midnight being 71 per cent. After 19 h the sky was 

 cloudless, but fog and haze filled valleys below all round. 

 Aurora seen at midnight. Box shifted at 13 u 10 m . 

 Same height as last. 



Dec. 23. — Air dry till 5 h , but saturated at and after 

 6 h . Sky clear in morning and again at night, but fog on 

 summit during the day from which brown fog crystals 

 were forming. Bright aurora seen till 5 b having very 

 active streamers, and flashing a good deal. Seen again 

 at night — pretty bright, with two well defined arches but 

 no streamers. 



Dec. 24. — Air very dry all day. From 4 h till mid- 

 night, the computed humidity ranged from 7 to 15 per 

 cent. For several hours it was below 10 per cent. Sky 

 cloudless except for a little cirrus between 10 u and 16 h 

 and again after 22 h , but thick haze in valleys, and also 

 some fog in forenoon. Faint indistinct aurora seen in 

 morning and again at night. The air was so very dry 

 to-day that after the wet bulb had been moistened, it 

 became dry in a few minutes, so that most of the readings 

 were made between the usual time and 7 minutes past 

 the hour. Since the dry bulb was on the whole steady, 

 no correction was applied to readings of wet bulb for 

 being late, nor were readings of the barometer etc. made 

 except at the usual times. At 5 h , 6 h , 7 h , and 8 h , the dry 

 bulb readings at the hour were 24°-4, 25°-3, 25°'2, and 24° - 7 

 respectively — the readings entered on daily sheet being 

 made at 5 h 16 m , 5 h 32 m , and 7 h 20 m . There was no read- 

 ing made near enough 8 h so the wet bulb was inter- 

 polated from readings made at 7 h 34 m and 8 h 49 m . At 

 19 h the entered reading was made at 19 h ll m — the dry 

 bulb at the hour being 29°*3. At 20 h the wet bulb was 

 dry, though it had been wetted at 19 h 50 m — the entered 

 readings were made at 20 h 6 m , and at 22 h the bulb was 

 almost dry (after having been nearly wetted) before the 

 mercury stopped falling. About 1 hour of sunshine was 

 lost this morning, owing to focus being off the card. 

 (Perhaps some was lost in same way yesterday?) The 

 lowest computed dew point to-day was, — 28° 9 at 16 h , and 

 the mean for the whole day — 18°*5. 



3 H 



