aif 
4 
ON METEOROLOGICAL OBSERVATIONS ON BEN NEVIS. 9} 
the results of these two methods are closely congruent. This double set 
of observations supply the data for a more exact conversion of the 
estimations of wind-force, according to Beaufort’s scale, into their equiva- 
lents in miles. A large number of similar observations made on board 
the Challenger also form a valuable contribution to this inquiry. So 
far as the observations go, they appear to indicate that the equivalents in 
miles usually given for the higher numbers of Beaufort’s scale are too 
small. From 8 to 9 am. of August 9 the anemometer registered 
86 miles, and during this hour the estimated force was from 8 to 9 
of the scale. The equivalent in miles for this force, provisionally 
adopted by the Meteorological Council, is from 48 to 56 miles. What is 
the number of miles when an estimated force of 10 or 11, which has 
been not unfrequently recorded during the colder months of the year, is 
reached and maintained for some time remains to be seen. Instances 
will in all probability occur during the autumn before the ice-deposits of 
the wind practically seal up the anemometer for the winter months. 
The mean temperature for the year ending May 1885 was 30°6, or 
0°-3 below the calculated normal temperature given in last year’s Report. 
The temperatures for the same period for stations. in the more immediate 
neighbourhood were from 0°-3 to 0°4 below their normals, being thus 
identical with the deviation from the normal at the Observatory. The 
extremes of temperature for the year were 60°'1 at 2 p.m. August 9, and 
11° 1 at midnight and 1 a.m. February 16, thus giving a range of 49°-0. 
The coldest week yet experienced was the week ending February 21, the 
mean of which was 16°-2. In this week the lowest temperature for the 
year occurred, and the humidity fell to 22. Great dryness associated 
with great cold scarcely ever occurs in the weather records of the Ben, 
and in this case the exceptionally cold dry weather terminated with the 
great storm of the 21st and 22nd February already referred to. 
From the observations of the maximum and minimum thermometers 
the mean daily range of temperature is—in winter, 6°°8; spring, 6°°4; 
summer, 7°1 ; and autumn, 6°-6—there being thus little variation with 
season. From the dry bulb, there is only 0°-7 between the mean coldest 
and mean warmest hour of the day in winter, but in summer the diffe- 
rence is 3°°0. It follows that in all seasons, but particularly in winter, 
the changes of temperature which occur are only in a subordinate degree 
due to the direct influence of the sun, but are chiefly caused by the 
passage of cyclones and anti-cyclones over the Observatory. Indeed, it 
may be regarded that, in the stormy months of winter, the Ben Nevis 
observations present the cyclonic and anti-cyclonic changes of tempera- 
ture in their simple conditions, uninfluenced by the heat of the sun. 
Lower relative humidities were observed than during the previous 
year. On January 20, the mean of the twenty-four hours gave the very 
low mean humidity of 82. On the 15th of the same month, at 5 A.m., the 
dry bulb was 20°-9 and the wet 16°-2, which from Glaisher’s tables indi- 
cates a dew-point at —16°-2 and a humidity of 19, being respectively the 
_ lowest yet noted on the top of Ben Nevis. The lowest temperature ever 
observed anywhere in the British Islands was —16°-0, at Springwood 
Park, near Kelso, in December, 1879, which closely agrees with the lowest 
dew-point on Ben Nevis. As regards atmospheric pressure, it is only in 
winter that the afternoon minimum falls below the mean daily pressure ; 
in summer this daily minimum is 0-007 inch above the daily mean. On 
the top of Ben Nevis, atmospheric pressure of the three seasons, spring, 
