354 



BEN NEVIS OBSERVATORY. — LOG-BOOK. 



[1887. 



from north-westward ; its advancing edge was then rather 

 less than 20° above horizon. A few straggling pieces of cirro- 

 cum. were here and there on sky, also moving from north- 

 westward. At m 10'',and while the advancing edge of cloud 

 stratum was still 41° 39' per stephanome, to westward or 

 north-westward of moon, a halo began to form about halfway 

 between moon and cloud. A spot in the halo brighter than 

 the rest of it was apparently a faint mock moon. To this 

 spot the radius was 23° 58' per stephanome. The following 

 notes were taken of progress of cloud, <fec. : — h 15 m , halo 

 complete. Cloud just entering western side of halo. 

 Radius per stephanome, 23° 3'. h 19 m edge of cloud at 

 zenith and at moon ; halo gone. No trace of corona on 

 cloud. Moon shining pretty strongly through. h 35 m , 

 halo faintly visible. "White beams radiating from moon, 

 some of them reaching halo. Cloud of uniform thickness ; 

 no appearance of anything to cause beams or breaks in 

 moonlight. U 46 m , a uniform pallium of stratus-like 

 cloud much lower than before h 35 m with corona, which has 

 white core, and yellowish red border ; extreme outside 

 measuring from moon, 2° 13'. All appearances of halo 

 gone. h 50 m , shadow of eastern edge of cloud now at 

 west end of Loch Laggan (unbroken moonlight to eastward 

 of that), and cloud touching (apparently) the hills at 

 Corran and Glencoe. h 55 m , lower surface of cloud just 

 at Ben (no view to westward now) and beginning to 

 brush top. Moon still visible, with corona as observed 

 already ; cloud still of uniform texture. Fog on at l h . 

 Temperature rising rapidly all forenoon ; and at 10 h the fog 

 changed to mist, and glazed frost was forming till at 21 h 

 the temperature had risen above 32°. Heavy rain falling 

 at night. 



Dec. 3. — Robinson was let loose at 22 h last night, but 

 was tied up at 4 h to-day, as it was observed that one cup- 

 arm was broken at shoulder, and was only held on by the 

 metal stay from top of instrument. Cause of breakage 

 unknown. 



Dec. 5. — At 3 h it was difficult to tell whether the cloud 

 enveloping summit was mist or fog, so " mist or fog " 

 has been entered at that hour on daily sheet. The vane 

 was frozen inside its supporting pillar all day. 



Dec. 6. — The outside part of the 3 U . observation was 3 

 minutes late, owing to lamp having been blown out. The 

 measurements of snow to-day are very doubtful, owing to 

 drift. 



Dec. 7. — St Elmo's fire was seen at l h on all points on 

 tower and on observer's hat and pencil, but not on kitchen 

 chimney ; snow and snow-hail (conical) were falling 

 heavily at the time. 



Dec. 8. — Top and sky cleared a little in forenoon. At 

 7 h a corona was seen on passing fog. At 16 h the rain- 

 gauge was buried in a snow wreath ; it was taken in, and 

 was not put out again till 20 h , owing to the heavy drift. 

 At 22' 1 30 m the thermometer box was shifted, and the fresh 

 one was put one step higher on the ladder-stand than the 

 other had been. 



Dec. 9. — Top was clear at 4 h and 5 h , and again mostly 

 all afternoon. At 15 h , 16 h , and 17 h , when the observed 

 wind direction was N.N.E., the stratus or cumulus clouds 

 immediately overhead were moving from N.N.W. 



Dec. 10. — At 22 h 5 m a large red pear-shaped meteor 

 was seen to northward about 5° above level of Ben top 

 moving westwards slowly. It was seen through thin 

 fog. 



Dec. 11. — At about 3 h 5 m a very bright meteor was seen. 

 It started from about zenith, and vanished at W. end of 

 Orion's belt. It increased rapidly, and just before bursting 

 or vanishing was at its brightest, showing blue and green 

 colour circles. It was seen for about 1-^secs. It brighted 

 up the Ben top and hills to southward ; no noise heard. 

 After 10 h the thermometer box was shifted. 



Dec. 12. — Storm all afternoon. After 20 h there was no 

 gauge out, but apparently no snow fell. 



Dec. 13. — Storm continued all morning. At 9 K it was 

 found that ozone test had been blown away. At 2 h 50 m 

 vane began to spin round at a great rate, owing to having 

 been partially sheltered by the snow on chimney and the 

 other instruments on tower. The rain-gauge was not put 

 out till 7 h , but apparently no snow fell till then. 



Dec. 14. — The snow was drifting very much in early 

 morning, consequently the amounts on sheet are rather 

 doubtful. Somewhat stormy in afternoon. 



Dec. 15.— Shifted thermometer box at l h 30 m . Sky 

 was cloudless till 6 U , fog after that till ll h , cloudy sky till 

 li\ and fog for the rest of the day. At 14 h low stratus- 

 fog on south-western and western hills clinging to hills ; 

 shortly after 14 h this fog developed into cum.-fog, and 

 came rapidly eastward enveloping Ben at 14 h 35 m . The 

 upper sky was overcast with cirro-cum., and midway 

 between upper and lower strata a few dark long detached 

 cum.-str. clouds were observed. The air temperature as 

 the fog began to pass Ben was 23° 0'. 



Dec. 16.— St Elmo's fire was seen at 20 h and 22 h , at the 

 latter hour on observer only. At 22 h and 23 h there was 

 a misty feel in the air at times, and an icy cake was 

 observed on rain-gauge, thermometer box, and other 

 exposed surfaces. 



Dec. 17. — Wind very variable and squally all forenoon, 

 and snow drifting a good deal, rendering the measurements 

 of amount obtained rather doubtful. The top was clear 

 for about an hour at mid-day, but sky was cloudy with 

 str. and cum.-str. 



Dec. 18. — The fog cleared away after ll h , and the 

 summit was clear till 19 h , after which fog came on again. 

 In afternoon the western and south-western horizon was 

 rather wild-looking with cir. and cum.-str. clouds, and there 

 was low str. -fog clinging to hills. After the 12 h observa- 

 tion the thermometer box was shifted; the fresh one was 

 put one step higher (the last step) on ladder-stand than 

 the other had been. A pink afterglow and the earth 

 shadow were seen at 16 h , both well defined. 



Dec. 20. — The wind was very squally and variable to- 

 day, and the barometer was pumping heavily mostly all 

 day. Hard icy drift blown from the cliff, and falling in 

 gauge made the measurements of snow amount worthless; 

 but as it was believed that snow was falling in early 

 morning, '060 inch has been allowed in total fall for 

 day. 



Dec. 21. — Top was clear after ll h , but fog was hanging 

 around Ben and thin stratus covered sky. In afternoon 

 it was observed that the country was snow-clad to sea- 

 level. At each observation after 20 h an aurora was seen 

 to northward; at 22 h only a small part of it could be 

 seen between clouds and horizon, but this part was very 

 bright, flashing with red, yellow, and blue colours, the 

 flashes moving from E. to W. After 20 h , the thermometer 

 box was shifted. A lunar corona was seen at 21 h and 22 h , 

 but no measurements were obtained; at 22 h the order of 



