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BEN NEVIS OBSERVATORY. — LOG-BOOK. 



[1891. 



at the time: a mixture of soft flaky snow, and dry hard 

 snow-hail. 



March 6. — Thermometer box shifted at 14 h 10 m . 

 Box put one step higher on ladder stand. 



March 7. — Top cleared at 6 h , and remained clear for 

 the rest of the day, except for a little fog at 15 h . Air 

 mostly dry after 6 h and very dry at times, the computed 

 dew point at 10 h being — 19°'4, and the humidity 20 

 per cent. At 14 h there were two layers of cirrus, the 

 lower from S.W., the upper from W. Solar halo aud 

 mock sun seen at 17 h . Zodiacal light very bright at "20 h 

 and 21 h . Aurora seen at 23 h and midnight; pretty 

 bright at latter hour. Thermometer box shifted at 7 h 

 10 m . Height above snow not altered. 



March 8. — Very cold all day. Thin scud at 6 b ; 

 cloudy from noon till 17 h ; cloudless during the rest of 

 the day, but air saturated or nearly so. Fog on lower 

 hills most of the day, and some passing summit at times. 

 Aurora seen at l h , aud zodiacal light at 20 h . 



March 9. — Air dry most of day ; extremely so from 

 S h till noon. The mean dew point to-day is — 2° 6. 

 Aurora seen at and after 2 l h ; pretty brightly at 22 h 

 and midnight. At 22 h 20 m the highest point of aurora 

 was about 9° above horizon. Air exceedingly clear to S. 

 and S.W. in evening. Two dark objects seen on horizon 

 {through telescope) between Jura and Cantyre, which 

 were supposed to be in Ireland. 



March 10. — The aurora continued visible till 3 h , and 

 it was again seen faintly at 21 h . A spirit thermometer 

 was put out on wool on top of old box (about level with 

 surface) last night, and to-day the index stood at 0T. 

 Some fine snow crystals falling to-day, aud at 7 h some 

 of these were falling from a cloudless sky. 



March 11. — Sky overhead cloudless all day except for 

 a little scud at 9 h . Fog on the hills in forenoon, none 

 in afternoon, but a ring of small cumulus was all round 

 in distance, low near horizon. Aurora seen faintly at 2 h . 

 Zodiacal light seen at 21 h and 22 h . Minimum on cotton 

 wool, 1"9. 



March 12. — Fog on hills to E. in forenoon. Small 

 cumulus all round in afternoon at about level of summit. 

 Trace of aurora at 2 1 '. Bright aurora at and after 20''. 

 Following are notes taken of it : — 



21 h . Aurora, bright. No streamers. Two arches. 



22 h . Aurora, bright. Short streamers (15° above 

 horizon 1). 



23 h . Aurora. Bright double arch extending from W. 

 to N.E. No streamers. Height above horizon 

 of highest part 23°. 



23 1 ' 30 in . Broke up into activity. Innumerable bright 

 streamers. (Green line in spectroscope.) 



23 1 ' 45™. Began to flash. Flashes moving from N. 

 towards zenith. 



Midnight. Aurora, bright and scattered over all north- 

 ern sky up to zenith. Zodiacal light seen at 20 h . 

 Minimum on cotton wool, — 0T. 



March 13. — The aurora continued visible till 4 1 '. The 

 following are the notes taken of it : — 



l 1 '. Aurora flashing N. and S. Could hear feeble 

 fizzing on holding up pencil when standing near 

 edge of cliff when the flashes were about their 

 brightest, and coming almost close overhead. Str. 

 streaks forming and vanishing to N.W. and W. 



2 1 '. Aurora not so bright, but still flashing. 

 3 1 '. Aurora faint aud low behind stratus clouds. 

 4 h . Aurora almost gone, only a faint trace at northern 

 horizon. 



(Several times during the night some low, but 



bright short auroral streamers appeared as if they 



were the nearest to Ben, and that the greater 



part of aurora could be seen over their tops.) 



Sky cloudless almost all day, and air dry till after 22 1 '. 



Thick haze below all round. Minimum on cotton wool, 



- 1-4. 



March 14. — Thick haze below all round. At 16 h this 

 haze rose higher than Ben. It had no level top. Fog 

 on eastern hills in forenoon, and passing over summit at 

 times. A solar halo was seen at 9 h . Minimum on wool, 

 9°-2. 



March 15. — At 3 h to-day the wind rose to a gale, 

 and blew hard all day. From 7 h till noon the wind 

 force was over 10, at times 11-12. The raingauge could 

 not be worked, and till 21 h it could not be determined, 

 owing to the drift, whether snow was falling or not. 



March. 17.— Thermometer box shifted at 23 h 15 m . 

 Height not altered. 



March 18. — Summit clear except at 21 u and 22 h . 

 Sky cloudless from 2 h till 5 h , but cloudy with high cirrus 

 during the rest of the day. Haze all round below, and 

 detached cum. -fog on lower hills most of the day. Solar 

 halo seen at 15 h , and lunar halos at 20 h and midnight. 

 Between 14 h and 15 h a long band of cloud was seen 

 forming over Glen Nevis, forming rapidly at its under 

 surface and vanishing as rapidly above ; it was coloured 

 red below and blue above. Hard thin sheets of str.-cir. 

 (rare) on sky at 16 h . 



March 19.— Top clear till 18 h ; fog thereafter. Sky 

 somewhat cloudy with high clouds that (in afternoon) 

 appeared to be continually falling, thickening, and then 

 vanishing, and a higher stratum forming above. Some 

 of the cir.-c. near the sun at 15 h was variously coloured. 

 Lunar halo and " mock moon " seen at 3 h . 



March 28. — Small needle-shaped snow crystals falling 

 at 14 h . Thermometer box shifted at l h 20 m . Height 

 above snow not altered. 



March 29. — Thermometer box shifted after 7 h . Height 

 not altered. 



March 30. — Top clear all afternoon. An aurora was 

 seen at 21 h and 22 h , one arch, bright, no streamers. 

 Thermometer box shifted at 13 h . Height not altered. 



March 31. — Sky nearly cloudless most of the day. 

 An aurora was seen at 4 h , flashing faintly. Another 

 was seen at 21 u , 22 1 ', and 23 h ; following are notes : — - 

 At 21 h . Aurora bright, top half way to Pole star. 

 At 22 h . Aurora not seen so well with passing fog, but 

 in clear intervals streamers were seen, also flashes. 

 A measurement of top of aurora (badly defined) 

 gave about 29° altitude. 

 At 23 h . Aurora still bright when seen. 

 At 23 h 7 m . Clear, aurora very high, several broken 

 arches and bright flashes rising to Pole star, long 

 streamer to N.E. 

 At 23 h 12 m . Aurora broken up into very bright stream- 

 ers and flashes reaching to near zenith. When 

 flashes were brightest and rising highest, observer 

 fancied he heard a rustling noise. In the after- 



