450 
PROFESSOR K. PEARSON AND MISS A. LEE ON THE DISTRIBUTION 
ill fact, Sk may, by the rule of the modal third be determined from the median and the 
mean—and, thence, and e.^ by the above formulae, make this a very convenient, 
as well as scientifically accurate, method of appreciating the range and the skewness 
of the variability at any station. 
Our discussion has now led us to the following general conclusions :— 
(1.) The mode, the standard deviation, and the skewness fully define barometric 
frequency. These three constants depend, in the first place, on geographical position, 
and appear to be constant along certain lines—the generalised isobars. 
(2.) A knowledge of these three constants enables us, by means of very simple 
formulie, to describe the chief physical features of the barometric frequency at any 
station. 
(3.) By aid of the tw^enty stations dealt with in this paper, a fair appreciation 
can be obtained of the barometric frequency at any place whatever in the British 
Isles b}'' means of interpolation. 
For example :—A line from Hillington on the Wash to a point midway between 
St. Leonards and Southampton strikes the south coast between Littlehampton and 
Worthing, cuts the generalised isobars so that they make approximately equal angles 
with it, and passes very nearly at one-third and two-thirds distances through 
Cambridge and London. Thus, if the St. Leonards constants were based on a longer 
period and so somewhat more satisfactory,* we might fairly accurately predict the 
constants of the Cambridge and London frequencies from those of Hillington, 
Southampton, and St. Leonards. We find, as a matter of fact, by interpolation : 
Mean height. 
Standard deviation. 
SkeAvness. 
London . 
29-369 
// 
0-.330 
0-165 
Cambridge .... 
29-956 
0-336 
0-176 
Actual calculiition for thirteen years at these stations corresponding to the years 
used for Soutliampton and Hillington gives :— 
Mean height. 
Standard deviation. 
Skewness. 
London . 
// 
29-966 
/I 
0-329 
0-157 
Cambridge.... 
29-952 
0-33S 
0-172 
* An attemj^t Avas made to replace the St. Leonards returns by the same thu’teen years as have been 
dealt Avith for the other stations recorded at a suitable “telegra])h station.” Unfortunately, during these 
thirteen years the most suitable station, namely, that at Dover, Avas changed to Dungeness—a station 
some considerable distance off and subject to probably someAvhat different conditions. A short missing 
period between the tAVO sets of observations was most kindly supplied by Mr. R. H. Scott, by 
intei’pola.tion from the Meterological Office Records. The result of the calculations showed a con¬ 
siderable increase of variation, probably due to the combination of two stations, and it was A’ery doubtful 
Avhether the result was of greater Aveight than the six years returns from St. Leonards. 
