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BEN NEVIS OBSERVATORY. — LOG-BOOK. 



69 



No unusual colours in sky during the day, but the earth 

 shadow was seen at 20 h 5 m and the after glow at 20 h 

 15 m . 



April 26. — Thick haze in valleys below all morning. 

 At 4 h there were streaks of fog among the hills to N., and 

 patches of cum. fog among those to S. At 8 h fog had 

 begun to pass over Ben Nevis also. 



April 27. — The snow which fell last night and to-day 

 was dense and heavy, and scarcely drifted at all. Ice 

 formed on all exposed surfaces out of the mist in the early 

 morning. The louvres of the thermometer box were badly 

 choked till after 6 h when they were cleared. 



April 28. — Icy hail, mixed with sleet, fell several times 

 in forenoon. All exposed surfaces heavily coated with 

 hard ice, including the thermometer box. 



April 29. — Conical snow-flakes or rather soft hail fall- 

 ing at 10 h . Thermometer box shifted at 12 h 30 m . Fog 

 crystals at night hard and rather icy. 



April 30.- — At 8 U a glory was seen from cliff edge — too 

 fleeting to measure. Fog crystals at night were dry and 

 brown in colour. 



May 1. — The fog crystals forming this morning were 

 again brown in colour. The snow which fell at night was 

 small and hard. Owing to the growth of fog crystals on 

 the tower chimney, anemometers, etc., the indications of the 

 crystal direction anemometer were very unsatisfactory. 



May 2. — At 14 h 30 m an earth current up the telegraph 

 cable moved the indicator of the telegraph instrument, 

 and immediately afterwards a flash of lightning was 

 seen. A heavy shower of hard hail had come on a few 

 minutes before and was then falling. The louvres of the 

 thermometer box were badly choked with fog crystals and 

 drift all afternoon and night. 



May 3. — The louvres of the thermometer box were 

 badly choked till 17 h . At 17 h 35 m thermometer box 

 shifted. Put one stage higher on ladder stand ; it is now 

 in the first stage of the upper part of the stand. 



May 4. — Fog very white and dazzling in afternoon. 

 The snow which fell to-day was large and coarse-grained 

 and did not drift much. A little hail fell about noon. 



May 5. — The snow falling at 2 h and thereafter con- 

 sisted of flakes, and was not the coarsely granular form of 

 last night. 



May 9. — Thermometer box shifted at 2 h 15 m . Put 

 one stage lower on ladder stand. A good deal of haze in 

 the valleys to-day but no fog. Hills round almost 

 clear of snow. 



May 10. — At 4 h faint upper glow seen. Sun rose at 

 4 h 9 m above fog lying on the hill tops to N. and E. The 

 earth shadow was also seen at 4 h . At 6 h faint mock suns 

 seen, with trace of halo on each side of sun. Radius of 

 red of mock sun = 21° 48V The halo was still visible 

 though very faint at 7 h . No fog in valleys all day, but 

 considerable haze with cumulus rising from it. At 21 h 

 there was cum.-fog to N.E. quite close to Ben Nevis. 

 The sky was covered with cum. or cum.-s. all afternoon 

 over the mainland, but the sun was shining on the 

 Atlantic. At 23 h pearly cirrus clouds to N. very low 

 down. 



May 11. — The earth shadow was seen at 4 h ; the sun 

 rising about 4 h 3 m . At 6 h a very faint halo was seen. 

 Slight haze and a little detached cumulus at horizon all 

 day. No unusual colours in sky all day. Horizon bright 



(•) White yellow red 

 Blue green red 

 Blue green red 

 Blue red 

 Halo red blue 



but not coloured to N. at midnight. At ll h a butterfly 

 flew across the hill top from S. to N. 



May 12. — At l h the wet bulb was found to be dry, and 

 its value for that hour was interpolated. A thermometer 

 was put out at 2 h lying freely exposed on the snow ; at 3 h 

 it read 25"6, the shade temperature being 37*8. At 4 h the 

 earth shadow was seen. At same hour str. fog was lying on 

 the hill tops to N. and W. This fog gradually gathered 

 on all the hills round, and by 13 h had risen high enough 

 to cover Ben Nevis also. Glories, accompanied at times 

 by fog-bows, were seen at 9 h , 12 h , 17 h and 18 h . Several 

 photographs were taken of them. Solar halo seen at 10 h , 

 red inside, blue outside; it was also seen at ll h . At 17 h 

 20 m a measurement of a glory with two sets of colours 

 gave 



Radius of inner red (outside edge) . 1° 3' 

 Radius of outer red (outside edge) . 3° 8' 

 Third and fourth sets of colours were seen occasionally. 

 At 19 h the Robinson anemometer was tied up. At 20 h 

 the black bulb was taken in. Hard icy fog crystals 

 formed on all exposed surfaces at night. 



May 13. — Thermometer box shifted at 15 h 15 m . 



May 14.— At ll h the fog was breaking at times 

 overhead, shining cum. and cir.-s. above. A halo was 

 seen on this cir.-s. at ll h 8 m . At 

 about ll h 13 m the halo was again 

 seen, and a cir.-c. cloud filled the 

 space between the sun and the halo 

 on the west side. This cloud was 

 coloured in the following order : — 

 These were portions of circles, but there were also red 

 and blue spots on the cloud not coinciding with any ring. 

 The successive rings of colours filled almost the whole 

 space inside the halo on the west side. If there had been 

 a 5 h red ring it would have about coincided with the red 

 of the halo. At 14 h the top was clear and there was no 

 fog in valleys. The snow falling at 18 h consisted of 

 small, round, soft pellets ; later in the evening it became 

 more flakey, but was still soft and did not drift. 



May 15. — The fog crystals forming to-day were white 

 and dry. Considerable surface drift all day. 



May 16. — In early morning the fog crystals were long 

 and white, but towards the middle of the day became slightly 

 brown in colour. Very faint solar halo seen at 10 h . Thick 

 haze all round when hill top was clear in morning. 



May 18. — All afternoon the raingauges were use- 

 less, as the strong wind blew up icy drift off the surface 

 loosened by the thaw. At 19 h the sunshine recorder, which 

 was standing on a box on office roof, was blown over 

 but not damaged. Snow thawed away rapidly in after- 

 noon, and at night the roof of kitchen and visitors' room 

 coming in sight. 



May 19. — A flash of lightning was seen at l b 8 m . 

 Sky ugly when seen all morning, with cum. -str. and cir.-str. 

 also cum. fog on hills. Thunder and lightning began at 

 about 14 h 35 m , and went on at intervals till about 18 h 40 m . 

 The thunder clouds came rapidly from the S.E. at about 

 the level of the hill top. It was found as each one came 

 that there was a current for a short time down the tele- 

 graph wire, and as they cleared off a similar current up the 

 wire, but the latter was more distinctly marked than the 

 former. At about 16 h 30 m , as one of the clouds was 

 mooring off the hill top, a sharp crack was heard in the 



