1891.] 



BEN NEVIS OBSERVATORY. — LOG-BOOK. 



317 



noon ragged cum. clouds passing the sun had 

 their edges variously and brightly coloured. 



April 1. — Top clear at times throughout the day. 

 Haze all round, which at 16 h became very thick, visibility 

 only extending across Glen Nevis. Brown fog crystals 

 forming at 20 h . At 14 h showers of snow were seen 

 passing overhead gleaming in sunshine, but none falling 

 on Ben. 



April 2.— E. or E.S.E. gale all day. Thick drift, no 

 measurements of snow owing to gale and drift. Brown 

 fo^ crystals forming all day. 



April 3. — Gale still continuing; at and after 21 h it 

 was blowing force 11 — 12. Tower storm box put out 

 at 19 h 45 m , but readings continued to be made in the 

 usual box on ladder stand. Brown fog crystals forming 

 all day, not so brown as yesterdaj'. At 23 h and midnight 

 it was blowing too hard for the fog crystals to stand, and 

 the top of tower and chimney was blown clear of them. 



April 4. — Gale still continuing, mean force for to-day 

 being 10"0. Very heavy squalls between 23 h and 

 midnight. At 15 h the fog crystals on tower were 30 

 inches long ; in the early morning there had been none, 

 the gale blowing them off as they were forming. Some 

 snow fell in afternoon, but no measurements could be 

 got owing to drift. 



April 5. — Gale all day, but not so strong as yesterday, 

 mean force for to-day being 9 "4. Fog crystals forming 

 rapidly all day. 



April 6. — The gale continued till 9 h to-day, and there- 

 after gradually fell. At 15 h the fog crystals on ladder 

 stand No. 1 were measured, and found to be 100 inches 

 long. 



April 7. — Fog or overcast all forenoon. Cloudy till 

 "21 h , cloudless thereafter. At and after 22 h a faint aurora 

 was seen, low to N. Haze in distance in afternoon. 



April 8. — Top clear all day except at 2 h , and sky 

 cloudless most of the day. Air very dry at and after 

 22 h . Detached fog on hills to N., N.E., and E. in 

 forenoon. Solar corona seen on loose cum. to S.W. at 

 14 u , also clouds variously coloured ; colours mixed. 

 Aurora seen at and after 21 h . At 22 h it was pretty 

 bright and showed some streamers. A measurement by 

 Stephanome gave 19° 51' as height above horizon of 

 highest point at 22 h . At 20 h peculiar bands were seen in 

 the sunset colours in western sky — very like, as regards 

 position relative to colours and intensity, the atmospheric 

 absorption bands in the spectrum on both sides of the 

 yellow. 



April 9. — Some cir.-s. on sky at and after 6' 1 , on 

 •which, from 7' 1 till 18 h , a solar halo was visible. This 

 halo was very bright at 17 k , and at times there were 

 traces of a second large halo, concentric with the 22° one. 

 At 18 h the 22° halo was also very bright, with a faint 

 mock sun visible, but no traces of an outer bow. Last 

 night's aurora continued visible till 3 h to-day. At times 

 it was pretty bright, and showed short bright streamers. 

 Level-topped, haze all round to-day. Very thick to N.W. 

 and N., owing to a great deal of heather burning in that 

 direction. At 4 h , and again at 20 h , the bands in sky 

 noted at 20 h yesterday were seen to-day. They were 

 also seen at 21 h . Faint glimmer in northern sky at 22 h 

 and 23 h , probably auroral. 



April 10. — Spectrum colours and bands seen at 4 h ; 



not so strong as at 20 u last night. Fog gradually spread 

 over the lower hills in early morning, and at and after 

 10 h covered Ben Nevis also. Brown fog crystals forming 

 to-day. 



April 11. — Summit clear from ll u till 19 h , fog during 

 the rest of the day. The fog crystals were brown all 

 forenoon. While the top was clear the dust in the air was 

 deposited on the fog crystals, tipping them all jet black. 

 At 23 h the formation of crystals was again going on, but 

 they were then white in colour, the black part showing 

 as a line across the complete crystal. Very thick haze all 

 round all the time the top was clear. 



April 12. — Summit clear most of forenoon ; fog in 

 afternoon. At 3 h a faint aurora was seen. At 5 h and 6 h 

 glories were seen on hill top. 



April 13. — Fog all day except at 17 h and 20 h . 

 Beautiful snow crystals falling in afternoon ; not in any 

 measurable cpiantity, only a few now and again ; are 

 perfect hexagons, some in stars and some in glassy disc 

 shapes. Most had small motes of dry snow attached to 

 them, and these motes were always on one side only, 

 not on both sides. These motes arrayed themselves 

 symmetrically on the spines of the stars, and along the 

 principal axes of the discs. Very thick haze seen all 

 round when top was clear. 



April 14. — Very thick haze all round below. Lunar 

 coronas seen at night ; sometimes green at centre. 



April 16. — Fog or overcast sky till 20 h , clearing 

 thereafter. Aurora seen at 22 h and 23 h . Thermometer 

 bos shifted at 23 h 15 m . Height above snow not altered. 

 Ascending currents in northern corry at night, forming 

 scud overhead, on which, at midnight, a lunar corona, 

 yellow at centre, was seen. 



April, 17. — Haze bands and wavy lines in eastern sky 

 at 4 h . Almost cloudless all forenoon. Some cumulus 

 in afternoon, and cloudless again after 20 h . Fog below 

 to N., E., and S.E. all forenoon. Very clear all round 

 in afternoon. Aurora seen at and after 22 u . The moon- 

 light made it rather faint in appearance, but it gave a 

 strong line in spectroscope. 



April 18. — Top clear all day. Cloudless till 10 h , but 

 fog on hills to N. and E. Cumulus on sky, and no fog 

 below till 17 h . Cumulo-cirrus, a middle stratum of 

 clouds, on sky at night. Aurora seen at l h , 2 h , and a 

 trace at 3 1 ', and again at 22 h ; but this was doubtful 

 owing to the moonlight. Pink after-glow seen at 20 h . 



April 19. — Cloudless or almost so all forenoon, cloudy 

 in afternoon. Fog on hills to N. and E. in forenoon, 

 none in afternoon. Ascending fog in Glen Nevis at 10 h . 

 After-glow seen at 20 h . 



April 20. — Sky cloudless till 6 h . Cloudy or overcast 

 for the rest of the day, chiefly with heavy cum.-s. shower 

 clouds. A cum.-s. shower cloud was seen at 4 k over 

 the Monadh-lea hills, the only cloud to be seen. In the 

 afternoon showers were seen all round, and at times fell 

 on Ben Nevis also. One of these began at 14 h , and 

 lasted till 14 h 45 ni . The snow that fell was snow-hail, 

 white and conical, and during the time it lasted there 

 was a strong display of St Elmo's Fire. The observer, 

 who was out all this time, experienced a continuous and 

 strong electrical discharge from his hands, stick, hair 

 and hat, while the shower lasted. A loud hissing noise 

 was heard all the time. 



