440 
PROFESSOR K. PEARSON AND MISS A. LEE ON THE DISTRIBUTION 
generalised isobar passes very close to St. Leonards, Southampton and Babbacombe, 
where in each case the fitted distribution diverges almost to the same extent from 
the standard , Plate 13, figs. x. and xii., and Plate 14, fig. xm. shows Londonderry and 
some place between Glasgow and Scaleby marking a third, while Laudale, and a 
place about midway between Dunrobin and Dundee give a fourth ; lastly, Geldeston 
and Caimaithen mark a fairly satisfactory fifth generalised isobar. These isobars are 
longhly sketched in on the map (page 424) to indicate the general grouping of stations 
with approximately identical frequency distributions. The accurate determination of 
these isobars is a pioblem for the future j it will require a knowledge of the frequency 
at a much larger number of stations and a delicate process of interpolation. 
Turning now to the diagrams on Plates 10—17, the reader will find the standard 
fiequency curve marked in strokes and dots, and the local frequency curve given by a 
broken line. Comparing these two curves, and neglecting, for the time, the irregular 
observation-polygon on which the latter is based, a continuous and regular change in 
the divergence of these two will be observed as the diagrams are taken in succession 
lound, say, the coast line of England and Scotland. There are slight local deviations 
from unifoimity, but on the whole there can be no doubt that the distribution of 
barometric frequency is a perfectly uniform and continuous phenomenon over the 
district treated. A fairly accurate distribution for any station not included among 
the twenty dealt with could be obtained by graphical interpolation from the 
generalised isobars we have roughly sketched. 
7. Oil tUQ jS'IocIgI Height of the hDcivoiyietev, 
Attention lias already been drawn by Fechner, Mazelle, H. Meyer in a series 
of papers to the importance of modal heights, which they term Scheitelwerthe* 
It seems, however, impossible to accurately determine the modal heights, even if 
the observations be grouped in very small ranges, until a theory of skew frequency 
foi the baiometer has been adopted. A glance at the diagrams for Churchstoke, 
Carmarthen, Dunrobin, &c., will sufficiently illustrate how delusive is the peak of 
the observation polygon. The true position of the mode depends, like that of the 
mean, on the ivhole series of observations, and not on the observationcol maximum 
only, which must always be largely the result of the grouping selected, and the 
elementary range taken as basis of the grouping. In Table IV., under the heading 
Mq, observed value, will be found nearly all our observation polygon by itself could 
tell us of the modal height. We should be able to determine the nearest tenth to 
* See Fechner: “ Ueber den Ausgangswertb der kleinsten Abweicliungssnmme,” Ac. ‘Abband- 
lungen der matb.-phys. Classe dei- k. Sacbsiscben Geaells. der Wissenschaften,’ toI. II, No. I, 1874; 
Mazelle: ‘Wiener Denkscbriften,’ vol. 60 , p. 433, 1893, vol. 62, p. 67, 1895; dealing’with a’ir tem¬ 
peratures; H. Meyer: ‘ Anleitung zur Bearbeitung ineteorologischer Beobachtungen,’ Berlin, 1891, 
pp. 12-27; but compare Jul. Hann : ‘ Die Klimatologie,’ 2te Ausgabe, Einleitnng. 
