October 2, 1899.] 



KNOWLEDGE. 



231 



Musical Pitch : Letters, ij'c, on the Proposal to Adopt the Low 

 Pitch. (Waterlow & Sons.) 2i. 6d. net. 



Arc/iices of the Bdntgen Rai/. Vol. III., Xo. 4, and Vol. IV., 

 No. 1. 4s. net. 



Precession Tables adapted to Ntwcomb's Value of the Precessional 

 Constant— Epoch 1910-0. B_v Dr. A. M. W. Downing. (Neill & 

 Co., Edinburgh.) 



The Studio ; an Illustrated Magazine of Fine and Applied Art. 

 ■September. Is. 



♦- 



BEN NEVIS AND ITS OBSERVATORY.-II. 



By WiLLLAM S.'Brvc'e, F.n.a.G.s., formerly in chart/e 



of tJie Observatory. 



( Illustrated by photoyraphs taken by the Author. ) 



THE staff consists of three men, two observers and 

 the cook who looks after the general comfort of 

 the establishment and keeps the rooms in order. 

 The observer in charge usually takes the night 

 watch of eight or nine hours, from 8 p.m. till 

 4 or 5 a.m., then the second man is on duty for another 

 eight or nine hours — i.e., until noon or 1 p.m. During 

 this latter time the night watchman sleeps, a fact not 

 always realized, I am afraid, in summer by early 

 visitors, who come up the mountain in the morning 

 to see the sun rise, and often make a great noise, even 

 getting on the flat roof of the Observatory and stamping 

 vigorously to keep their feet warm, a proceeding which is 

 promptly stopped by the day watchman. After dinner at 

 1 p.m., the afternoon is filled up by the shorter dog watches. 

 By this means the observers not only record, but reduce, 

 tabulate and average all the observations taken and put 

 them into form for further investigation. 



All the observations taken are eye observations, and this 

 must necessarily be so for keeping a continuous record as 

 will presently be explained. Every hour the observer goes 

 the round. First of all the barometer, which is of the 

 Fortin pattern, is read ; for the next observation, it is 



Fia. 3. — Observatory from South-East : Winter. All but Tower 

 and Stevenson Screens buried under Snow. 



necessary to go outside to some considerable distance from 

 the building in order to read the dry and wet billb 

 thermometers, which are placed in an ordinary double 

 louvred Stevenson screen. These two observations are 

 always taken so as to exactly correspond with those 



being recorded by photography and clock-work at the Low 

 Level Observatory in Fort Wilham, and the remaining 

 observations rapidly follow. The observer has carried out 

 with him an empty rain gauge. This is changed for the 

 one that has been out for the past hour, which is now 

 covered up and taken back to the Observatory. Climbing 

 up a ladder on to the roof of the Observatory, the observer 

 faces as accurately as possible the wind, notes its exact 

 direction and force (this is done with marvellous accuracy 

 by an adept), immediately after he notes the velocity 

 recorded by the anemometer, and thus his personal obser- 

 vation is checked. The clouds are next noted, whether 

 they be i'liper or Lower, and what species of upper or 

 lower, and the percentage of the sky they cover above 

 thirty degrees from the horizon. Is it raining at the 

 time of observation ? Is the sim shining clearly or 

 gleaming through a cloud, or not at all ? Are there 

 clouds (or fog, as such clouds are called at Ben Nevis) 

 below the summit, or are they passing over the summit '? 

 Are there glories, coronas, halos, fog-bows, rainbows, 

 and such like, or is the summit enveloped in a cloud ".' 

 Is that cloud in the form of mist (wet), or fog (dry) ? 

 Is it thick so that you cannot see more than five or ten 

 yards ahead, or is it so thin that you can almost see 

 the whole of the eleven acres of the summit of the Ben ? 

 Are there rifts in it, opening up a vista for a moment of 

 some of the grandest of Scottish scenery, or is it tending 

 to clear overhead, only hiding the blue sky with a thin 

 veil '? The direction in which the clouds are travelling, 

 and whether they are travelling at a quick or a slow rate 

 must be noted. Is there thunder or lightning ; or do we 

 hear the whole hill-top wildly hissing with Saint Elmo's 

 fire at every point, if it be at night, gleaming with allying 

 lurid flame ".' The tops of the chimney, anemometer, every 

 post or pole, even the observer's fingers or pencil if he 

 holds it up aloft, and perchance his hair, if he remove his 

 cap, will hiss and blaze with dancing flames. It is a time 

 when all but novices prefer to be below ! Entering the 

 tower door, and descending half-way down a ladder, 

 he now steps into a little room, where, by means of an 

 ingenious instrument invented by Mr. John Aitken, he 

 counts with great exactness the number of dust particles 

 per cubic centimetre of air — a very important branch of 

 meteorological inquiry originated by Mr. Aitken. Then 

 he descends, and enters the office, where he measures the 

 amount of rain that has been collected in the rain gauge 

 that he has just brought in with him. If there be snow 

 in the gauge, then he has to melt it first. These are the 

 regular hourly observations, but there are additional 

 observations at certain hours. The maximum and minimum 

 thermometers, which are read once a day ; the black bulb 

 thermometer in vacuo ; the depth of the snow, if any, and 

 so on. 



After every set of observations the observer has some 

 little time in the observatory before he gets ready to take 

 the same series as those just described. During this 

 time he is copying the observations he has made from 

 the hourly slip on to larger "Daily Sheets," which hold 

 all the observations taken for the whole day by the 

 superintendent and assistant, and if it be on the night 

 watch after midnight each set of the twenty-four hourly 

 observations is added up and their mean taken. The 

 maximum and minimum for the whole day of each ol 

 the twenty-four sets of observations is noted. During 

 this time also he is keeping up in a similar way the 

 " Monthly Kecord Sheets." These consist of separate 

 sheets for rainfall, sunshine, temperature, wind, etc. 

 Take barometric pressure, for instance, there are twenty- 

 four columns in this sheet, and along the top line each 



