1890 - 91 .] Dr Buchan on the Influence of High Winds. 89 
will, in the great majority of cases, show a higher reading than 
that of the free atmosphere. Bor these reasons, these barometric 
depressions are too large. Since 1852 meteorologists have taken 
no action on the results of Sir Henry James’s inquiry in discussions 
on barometric readings and wind-velocities ; and practically no 
advance has been made in this branch of meteorology. Various 
arrangements have been proposed, but none of them can be regarded 
as satisfactory, to arrive at the knowledge of the actual pressure of 
the free atmosphere during high winds. The difficulty consists in 
finding a perfectly unscreened position for the barometer, and 
securing at the same time that the wind, brushing past the small 
openings connecting the mercury of the cistern with the air outside, 
will not partially lower the pressure on the mercury in the cistern, 
and so render the instrument no longer indicative of the true 
pressure of the free atmosphere. The same remark applies to 
aneroids. 
In carrying out, during the past five months, the instructions of 
the directors of the Ben Nevis Observatory to discuss the observa- 
tions made at the High and Low Level Observatories, it quickly 
became apparent that the influence of high winds on the barometer 
was the first inquiry calling for serious attention. The depression 
of the barometer during high winds was plainly so serious as to 
render the examination of many questions all but a hopeless task, 
until some approximation was made to the values of these depres- 
sions for different wind velocities. 
Now, since the horizontal distance of the High and Low Level 
Observatories is only about four miles, it follows that the two may 
virtually be treated as one as regards the geographical distribution 
of pressure. But the Observatory at the top of the mountain is 
peculiarly exposed to high winds, which are occasionally so violent 
that the observers must be roped together on going outside to make 
the observations ; and it not unfrequently occurs that very strong 
winds prevail, while over the surrounding low country calms and 
light winds only prevail. On the other hand, the Low Level 
Observatory at Fort- William is in a sheltered position, and high 
winds are of comparatively rare occurrence. Thus, then, these two 
Observatories present the conditions which are essential to this 
inquiry, viz., one of the barometers is in a building exposed to 
