"2 INTRODUCTION. 



throughout. The daily record begins at 1 a.m. and ends at Midnight, the hours being 

 reckoned 1, 2, 3, ... . 22, 23, Midnight. In the records of Sunshine and Rainfall 

 the amounts entered under each hour are the totals recorded in the 60 minutes ending 

 with that hour. 



The Barometer and Rainfall are recorded in inches, the Temperatures in degrees 

 Fahrenheit, and the Sunshine in hours and decimal parts of an hour. The Wind Force 

 is on a modified Beaufort Scale of to 12, the approximate values of which in 

 miles per hour will be found on page 5. The Amount of Cloud is on the to 10 Scale, 

 the symbol = denoting fog or mist. All interpolated entries are enclosed in square 

 brackets, and are included in computing the daily and hourly means. In the Barometer 

 and Temperature tables of the Ben Nevis and Fort- William Observatories the highest 

 and lowest readings of each month, and in the Rainfall and Sunshine tables the highest 

 only, are printed in bold-faced type. 



To save space the first figure of the Barometer entries is omitted. At the Ben 

 Nevis Observatory, where the pressure ranges from 26 to 23 inches, the missing figure 

 is always 2, e.g., 5*212 represents 25*212 inches and 4*753 represents 24*753 inches. 

 At Fort- William Observatory and at the Public School the whole inches range from 31 

 to 27, and therefore when the figure before the decimal point in the tables is 1 or 

 the missing figure is 3, but when it is 9, 8 or 7 the missing figure is 2, e.g., 0*376 

 represents 30*376; 9*727 represents 29*727; and 8*618 represents 28*618. 



Ben Nevis Observatory. 



The hourly values recorded in this volume at the summit of Ben Nevis are all 

 " Eye " observations, except the Sunshine, which is obtained from a Campbell- Stokes 

 Sunshine Recorder. 



The Barometer used is a Fortin Standard (No. 1385) suspended in a glazed case 

 inside the Observatory ; the case and barometer are supported by hold -fasts fixed in 

 the outer stone wall of the Observatory which do not touch the floor nor the wood 

 lining of the building. The case is only opened at the time of setting the barometer, 

 the temperature of the attached thermometer being read through the glass door before 

 opening it, and this temperature has remained between 55° and 60° by day and night with 

 few exceptions. The instrument is read at each hour, a candle being always used both 

 by day and night in setting it. The tube of the barometer hangs a few inches out 

 from the wall and the observer looking along parallel with the wall adjusts the cistern 

 and vernier while holding the candle on the opposite side of the barometer. This was 

 found to be the most satisfactory way of insuring uniformity of reading both by day 

 and night ; the reflection of the candle flame on the mercury of the cistern facilitates 



