OF FREQUENCY OF THE BAROMETRIC HEIGHT AT DIYERS STATION’S. 425 
Accordingly, in order to test this theory of barometric frequency, series of 
observations have been reduced and the frequency distributions for divers localities 
fitted with generalised probability curves. On the basis of these curves the attempt 
has been made to answer the following questions :— 
[a.) Is there any one type of curve especially characteristic of barometric 
frequency 1 
(5.) If so, what are the constants by which the distribution of this frequency 
can best be described ? 
(c.) Does there appear to be any numerical or geographical relation between 
these constants ? and 
[cl.) Does a knowledge of their values for a variety of localities enable us to 
make any statement with regard to the physics of atmospheric pressure ? 
2. Data of Observation, 
Our data were taken from the annual ‘ Meteorological Observations at Stations of 
the Second Order,’ kindly placed at our disposal by Mr. D. H. Scott, F.D.S., 
Secretary to the Meteorological Council. The heights dealt with are 9 o’clock 
morning heights. Twenty stations were selected, sixteen in England and Scotland 
and four in Ireland. The stations selected are given on the accompanying map 
(page 424) of the British Isles. In their choice we were guided by (i.) the desire for 
a fairly uniform distribution and if possible a coast distribution, (ii.) the extent of 
data available, and (iii.) its continuity. The minimum number of years of continuous 
observation is five, the maximum thirteen. At one or two suitable places there 
were gaps in the record ; at others less than five years were available. In all cases 
the records were only dealt with for whole years, to remove any irregularity which 
might arise from an annual periodicity in frequency. It is hoped that the fraction of 
a monthly periodicity—if there be a lunar influence on the frequency—will not be 
very sensible, wdien the records deal with 65 to 170 lunar periods. Any long period, 
such as a 19-year period, would of course render less general a frequency distribution 
based on five to thirteen years of observation only. The possibility of such a 
periodicity would render it very desirable to recalculate the frequency distributions 
for the same localities after, say, another ten years of observations. 
Observations at the selected stations, when unreduced, were reduced by formulre 
kindly provided by the Meteorological Office. 
The following is what we shall hereafter term the geographical order of selected 
stations, with the years of observation and dates :— 
3 I 
YOL. CXC.—A. 
