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Proceedings of the Royal Society 
frozen fast every now and then, it was necessary to do this from the 
hourly eye observations. The scale for wind pressure used is 
supposed to be the ordinary Beaufort Scale, running from 0 to 12, 
and in reducing the observed winds to miles per hour I used the 
numbers given by Mr Scott of the Meteorological Office, which are 
usually regarded as the standard for this purpose. Since then I 
have found that our variety of the Beaufort Scale differs from the 
standard in a rather curious manner. In the following table the 
velocities in miles per hour corresponding to each Beaufort number 
is given — first, according to Mr Scott, and second, from the averages 
of the readings of the Bobinson Anemometer when working satis- 
factorily at Ben Nevis Observatory. 
B. Scale, . 
0 . 
1 
2 
3 
4 
5 
6 
7 
8 
9 
10 
11 
12 
Scott, 
3 
8 
13 
18 
23 
28 
34 
40 
48 
56 
65 
75 
90 
B.N.O., . 
5 
12 
21 
31 
39 
50 
63 
73 
The result is shown graphically in the diagram. In this the 
abscissae are the numbers of the Beaufort Scale, and the ordinates 
miles per hour. At the top are put the numbers of the Land Scale 
used in the reports from Ben Nevis published in the daily papers; 
each number in it is just one-half of the corresponding Beaufort 
number. The red line is drawn from Mr Scott’s constants showing 
the velocity corresponding to each number. The black line gives 
the results got at Ben Nevis Observatory up to force 8. It will be 
seen that at 1 our velocity is lower than the standard, at 2 about 
the same, and at all above that higher. And what is more remark- 
able, while Mr Scott’s is a pretty regular curve, ours, making allow- 
ance for the shakiness due to the small number of observations, is 
practically a straight line. There are no observations above force 8, 
but the velocity corresponding to force 8 on Ben Nevis (force 4 in 
the newspaper reports) is very nearly equal to what is usually 
called force 11, namely, 73 miles an hour; and if the line continues 
straight at the higher values, as indicated by the dotted extension 
on the diagram, the average velocity of the wind in a first class 
Ben Nevis gale, such as was experienced in February 1885, must be 
somewhere about 1 20 miles an hour. 
By using Mr Scott’s numbers to reduce the Ben Nevis observa- 
