78 



BEN NEVIS OBSERVATORY. — INSTRUMENTS, ETC. 



[1888 



INSTRUMENTS, ETC., 1888. 



Barometers. — No. 1385 was used throughout ; No. 1252 

 was not used. Both have been during the year, and still 

 are, in good condition ; each has, however, a very slight 

 coating of dust or oxide on the surface of the cistern 

 mercury. 



Dry andWetBulbThermometers.—Nos. 192660, 192672, 

 192671, and 192677 have been used. The other pair, 

 Nos. 50850 and 50852, has not been used. All these have 

 been and are in good working order. 



Self-registering Thermometers. — Max. No. 117293 and 

 mins. Nos. 116918, 138545, and 138533, have been in 

 use at different times during the year. 



Raingauges. — Mr Omond's patterns of 5-inch gauge 

 have been used as on previous years. 



Self-recording Instruments. — The barograph has been 

 in use all the year, and its records have been as satis- 

 factory as on previous years. The direction anemometer 

 has been in good order all the year, and, except in un- 

 favourable weather, good records have been got from it. 

 The Robinson anemometer worked very satisfactorily 

 when the temperature was above 32°, till the 16th Nov., 

 when two of its cups were blown off, and its supports, 

 etc., otherwise seriously injured. 



The Campbell-Stokes Sunshine Recorder has been used 

 throughout the year. 



On April 13th a set of photographic apparatus (camera, 

 lens, plates, and chemicals) was added to the instruments at 

 the Observatory. Since that date it has been used in 

 photographing clouds, halos, glories, fog crystal forma- 

 tions, etc. Till June 21st the thermometers in use were 

 exposed in the small louvred screens, mounted on ladder- 

 stand No. 1 ; and after the 5th of Oct., on ladder-stand 

 No. 2. Between these dates they were exposed in the 

 ordinary-sized (Stevenson) screen (old clock-box). 



The depth of the snow was always measured at post A. 



The black bulb chiefly used was No. 186, but No 64, 



which has a Crook's radiometer attached, was occasionally 

 used, chiefly in summer. 



Hilger's Rainband Spectroscope was in use for observing 

 the rainband. From December 7th till 23rd it was under 

 repair, having had its prisms displaced. 



For measuring halos, coronas, glories, and fog-bows, the 

 stephanome was used. 



Snow crystals were observed and sketched by means of 

 a magnifying lens, specially got for that purpose. 



Except in very dry weather in summer, and during 

 thunderstorms, the working of the Observatory telegraph 

 was satisfactory. The instrument in use all the year was 

 a single (acoustic) needle instrument. In April and May 

 a set of observations was made on earth currents in the 

 cable. These were measured by means of a Thomson's 

 Mirror Galvanometer. 



The Sextant was used occasionally. 



The working of the raingauge in stormy weather has 

 been as unsatisfactory as on previous years, the indications 

 being rendered useless by drift. Otherwise the hourly 

 observations of the various instruments and elements have 

 been made without the break of a single hour during the 

 year. On a few occasions, however, the outside part of 

 the hourly observation was made from 1 to 4 minutes 

 late, chiefly owing to the lamp having been blown out 

 before reaching the thermometer box. 



The permanent staff of the Observatory are, as on previ- 

 ous years : — R. T. Omond, superintendent ; Angus Rankin, 

 1st assistant; James Miller, 2nd assistant. Till the 16th 

 April, Alexander Drysdale was interim 1st assistant, and 

 again he has been the same since 17th October. Mr C. E. 

 Gray was telegraphist at the Observatory during the 

 autumn months. Messrs A. J. Herbertson, R. Turnbull, 

 and John Duncan took the places of some of the staff at 

 various times during the year. 



