1890 - 91 .] Dr Buchan on the Influence of High Winds. 
93 
real lowering of atmospheric pressure in these districts, but are 
only an increased depression of the barometer brought about by the 
stronger winds which prevail in those parts of the country. 
In forecasting weather it will be necessary to keep this effect of 
high winds on the barometer constantly in mind, with the view of 
arriving at a better approximation to the real geographical distribu- 
tion of pressure at the time the forecasts are being framed. 
In working out the question of the barometric gradient from 
actual observations, particularly the relations of the higher gradients 
to the wind velocities, the results hitherto arrived at cannot be said 
to he satisfactory. The reason is that, while the wind velocities were 
known with tolerable accuracy, the pressure of the free atmosphere 
could not be dealt with, because the observations did not record it ; 
what the observatories recorded was only the barometric readings, 
not reduced proportionally to the force of the wind at each observa- 
tory. For such discussions to be satisfactory, the amount of the 
depression of the barometer, owing to the force of the wind prevailing 
at the time, should be approximated to and allowed for. 
Table II., showing the mean diurnal variation of the differences 
between the two reduced barometers for the six months has been 
prepared in this way : The differences for each hour of the day 
were corrected by adding, in each case, the corrections indicated in 
Table I., according to the wind force at the time, from which the 
monthly means were calculated. The six months’ means show that 
from 7 p.m. to 9 a.m., the reduced High Level Barometer reads 
the higher, and from 10 a.m. to 6 p.m. that it reads the lower. 
In these reductions the mean temperature of the stratum of atmo- 
sphere from the bottom to the top of the mountain has been assumed 
to be the same as the mean at the two observatories. If it be sup- 
posed that the diurnal variations for the six months in Table II. are 
simply an expression of the degree to which the mean temperature 
of the two observatories falls short of, or exceeds, the mean of the 
whole intervening stratum, it follows that during the warmer hours 
of the day the temperature of the whole intervening stratum is 
about 0 o, 8 lower, and during the colder hours of the night 0°*8 higher 
than the mean of the two observatories. 
The variations of differences are of course much larger and more 
uniform in their distribution during the hours of the day. It will 
