90 REPORT—1885. 
Report of the Committee, consisting of Professor Crum Brown 
(Secretary), Mr. MitneE Home, Mr. Jonn Murray, and Mr. 
Bucwan, appointed for the purpose of co-operating with the 
Scottish Meteorological Society in making Meteorological Obser- 
vations on Ben Nevis. 
Dorinc the past twelve months the observations on Ben Nevis have 
been made every hour, by night as well as by day. This remarkable 
continuity in the observations, conducted under such great difficulties, is 
due to the enthusiasm and undaunted devotion to the work evinced by 
Mr. Omond and his assistants, and to the completion of the Observatory 
building last summer with its tower, which admits of a ready egress 
from the Observatory when the doors are blocked with rapidly accumu- 
lating snow-drifts, except during those rare occasions, of which the winter 
months of 1884-85 afforded only one example, in the great storm of 
February, when from 6 p.m. of the 21st to 8 a.m. of the 22nd no light 
could be carried in a lantern outside to the instruments. This inter- 
ruption refers only to the observations of the temperature of the air. 
During the year the most notable additions made to the observations 
refer to the rainfall and the wind. The actual precipitation—rain, sleet, 
snow, or hail—has been collected with rain-gauges specially designed for 
the purpose, and measured with the greatest care every hour since 
June 24, 1884, with, it is believed, a very close approximation to the 
truth ; and the hourly results for each month have been calculated. 
In the end of October the anemometers designed by Professor 
Chrystal for the Observatory, to register continuously the velocity and 
direction of the wind, were added to the observing instruments. Unfor- 
tunately, however, in the colder months of the year the deposition of 
ice-crystals, which Mr. Omond has described in a recent paper, renders 
all anemometers quite useless, except at rare intervals. During the 
seven months from November 1, 1884, to May 51, 1885, there was only a 
mean of thirty days in which the anemometer was in working order. 
During these days the greatest velocity was on the night of April 24-25, 
when for twelve hours the mean velocity was seventy-four miles, rising 
one hour to eighty-one miles. 
Estimations of wind-force have continued to be made every hour 
during the year, and the results show, as in the previous year, that the 
wind is above the mean daily force during the night and below it during 
the day. The maximum occurred from 2 to 3 A.M. and the minimum 
from 2 to 3 p.m., the difference between the extremes being between two 
and three miles an hour. The means of the observations made since the 
Observatory was opened sbow that the same relation holds good during 
each of the four seasons. These peculiarities in the diurnal variation in 
the velocity of the wind on Ben Nevis are of the greatest importance, 
especially in view of similar curves obtained at other high-level obser- 
vatories situated on mountain peaks, and by Mr. Archibald Douglas from 
his balloon observations and experiments, and their bearing on atmo- 
spheric movements. 
During July 1885 the anemometers have been continuously at work, 
and there are now before us a month’s complete hourly records of 
reccrded velocities and estimated wind-force. The curves drawn from 
