338 



BEN NEVIS OBSERVATORY. — LOG-BOOK. 



[188G. 



April 12. — Aurora described yesterday was observed 

 till 2\ At 5 1 ' dark shadow observed to westward rising 

 to about 1 4° ; and at the same time faint glow in eastern 

 sky. Brown colour round sun in forenoon, strongest 

 underneath ; none in afternoon, but only a faint glare 

 round sun. 



April 13. — Icy fog crystals forming in early morning. 

 At 20 h dense bank of cum. -fog in northern valley, rising 

 to over 4000 feet, but standing clear of the hill side. 



April 14. — At 10 h fog-bow seen to northward rather 

 broad and indistinct. At 17 h glimpses of blue sky over- 

 head. All afternoon icy fog crystals were forming. 



April 15.— Misty corona at night. 



April 16.— Thermometer box shifted at h 12 m . Misty 

 corona seen at times in early morning and at night. At 

 3 h very faint brown colour under moon. No brown haze 

 round sun all day. At 8 h bank of fog at E. end of Ben 

 Nevis, flowing down and vanishing. At 10 11 clouds over 

 Glen Nevis at about 4000 feet above top, with a rotatory 

 motion round horizontal axis, the southern or south-eastern 

 side rising and the north or north-western side sinking. 

 At 19 h haze in north-western valleys coloured yellow by 

 sun shining down on it from behind clouds. After 23 h 

 clouds opened showing blue sky above the scud that was 

 driving across the hill top. 



April 17. — Great masses of cumulus fog all round Ben 

 Nevis in forenoon. When the top cleared at 20 h the 

 southern hills were capped with dense cumulus, which 

 gradually disappeared. Fragments of lunar halo seen at 

 night, and faint brown colour under moon. 



April 18.— At 19 h the wind was E.S.E., but the fog 

 was rushing up from northern valley, and passing over- 

 head from N. to S., while above it and below it were east- 

 south-eastern currents. . 



April 19. — Icy fog crystals forming in afternoon. 



April 20. — At 19 h solar halo observed. Radius of 

 inner edge, horizontally, 23° 17' ; vertically, 22° 0'. Faint 

 brown colour under moon at night. 



April 21. — In early morning fragment of lunar halo 

 observed several times. Sunrise colours are visible at 3 h . 

 Faint solar halo observed in forenoon. Seven ravens seen 

 at 13 h . No unusual colours round sun. Faint auroral 

 arch at night. Meteor as bright as first mag. -star seen at 

 23 h 5 m . It went from Pole-star toward W.N.W. horizon, 

 and left a train about 10° long at a height of about 50°, 

 which remained visible for a second. No sounds heard. 



April 22. — Faint brown colour under moon in early 

 morning, and under sun at 7 h . At 7 h fog low down about 

 Loch Ness and Strathglass. At 14 h pale glare round sun ; 

 sky very blue. This afternoon a new flexible shaft was 

 put on the Robinson anemometer, and the instrument got 

 a general overhaul. It was set agoing at 19 h 30™. 



April 23. — Black bulb (old) was put out to-day on 

 bracket stand at post A, 58 inches above snow. Double 

 solar corona observed at 1 l h . The following measurements 



were made : — 











I. 



II. 



III. 



Radius of inner red, 



3° 46' 



3° 20' 



3° 2' 



„ outer red. 



6° 41' 



6° 18' 



6° 41' 



April 24. — At 8 h spot of light forming part of solar 

 halo was observed, coloured red, yellow, green, and blue, 

 on north side of sun. Radius of red, 24° 20'. At 9 h a 

 complete halo, red inside, blue outside. Radius of red, 

 23 30' ; 23° 3' : 23° 30'. Also double corona. Radius of 



inner red, 3° 21'; outer red, 7° 22'. At 10 h it was found 

 that the flexible shaft of the Robinson anemometer had 

 got broken, probably owing to having been frozen fast near 

 the top and twisted up. 



April 25. — At 9 h upper segment of halo seen on cirrus 

 much higher than the general amount of cirrus at the 

 time. At 17 h solar halo seen. The following measure- 

 ments were made : — Inside of red (radius), 23° 3'; 23° 3'; 

 23° 3' ; outside of red, 24° 28'. The red colour was on the 

 inside of the halo. 



April 28. — This morning the sky under and around the 

 sun was singularly clear and free from haze or glare. 



April 29. — At 16 u sun behind a cloud, but sky under- 

 neath all brown in colour. Faint auroral streamers to 

 N.N.W. at 23 h , and distinct but low auroral arch at mid- 

 night. 



April 30.— Thermometer box shifted at 23 h 15 m . 



May 1. — At 7 h brown colour under sun. At 8 h solar 

 corona on passing fog. At 14 h no brown colour or glare 

 round sun. No fog in valleys all clay, but dense haze 

 round horizon all afternoon and night. Faint auroral 

 light seen at 23 h and midnight. 



May 2. — Portion of solar halo seen at 5 h , the part 

 above sun white and ill-defined, but bright red and blue spot 

 to southward of sun ; radius of this red, 22° 49'. At 7 h 

 complete halo seen, red inside. Radius vertically, 23° 3'; 

 21° 48'; 22° 49'; horizontally, 22° 36'. Very thick dark 

 haze all round during the day. 



May 3. — Long icy fog crystals forming in early morning. 



May 5. — Dry and wet bulbs shifted at 3 h 5 m . 



May 6. — At ll h clouds passing over Ben Nevis from 

 S., and passing down the north side into the valley. 



May 7.— Solar halo in forenoon. A rough measure- 

 ment at 10 11 gave radius, 22° 36' (red inside). A better 

 set of measurements at 12 h gave — 



I. 



III. 



Radius of red («), 22° 36'. 



Radius of red (a), 21° 36'. 



(6), 22° 36'. 



(6), 21° 2'. 



(c), 22° 0'. 



IV. 



II. 



Radius of blue (a), 14° 28'. 



Radius of red (a), 22° 42J'. 



(b), 24° 28'. 



(b), 22° 36'. 



(c), 24° 13'. 



(c), 22° 36'. 





Measurements in II. and III. were taken alternately ; 

 II. being radius of red on upper side of halo, and III. on 

 lower ; red in III. not well defined. La and lY.b were 

 measurements of same portions of arc ; II.6 and IV.c were 

 measurements of same portions of arc. At 13 h measure- 

 ments got were — Radius of red upper side, 21° 48'; 

 23° 3'; 22° 12'. Shortly after the measurements were 

 made at 13 h , the cir.-str. clouds on which the halo was 

 formed changed into cir.-cum., and it disappeared, but 

 soon came into view again on some filmy cir.-str. This 

 afternoon the flexible shaft of the Robinson anemometer 

 was repaired, and the instrument set going. 



May 8. — Robinson anemometer was tied up at 7 h , but 

 set going again at 10 h . At 17 h , however, it was found 

 that the flexible shaft had broken again. 



May 9. — Snow flakes at 7 h were very large — from f 

 inch to 1 inch in diameter. 



May 10.— Thermometer box shifted at l h 12 m . At 

 9 h small bird, not a bunting, seen on roof. 



May 11. — Dense rolling cumulus all round in after- 

 noon. 



