OF FREQUENCY OF THE BAROMETRIC HEIGHT AT DIVERS STATIONS. 443 
(3"-0259) as not beyond suspicion, and accordingly open to revision when a wider 
range of data is available. The great value of the “ skewness ” in the Margate dis¬ 
tribution is also unsatisfactory. 
8. On the Variability of the Barometric Height. 
The only method hitherto used by meteorologists to express briefly the variability 
of the atmospheric pressure is, so far as we are aware, the statement of the maximum 
and minimum heights reached during any given period. The fallacy of this method 
has been illustrated by one of us elsewhere.It gives no real impression whatever 
of the manner in which the hulh of the variation is distributed, yet, for most 
climatological purposes, this is precisely what we require. Judged by such a test as 
this (namely, the range from maximum to minimum height observed) Hillington has 
a more variable climate than Scarborough, and Southampton than Babbacombe, but, 
as a matter of fact, Hillington is considerably less variable than Scarborough, and 
Southampton is slightly less variable than Babbacombe. 
Another striking illustration of the defects of this method of tneasuring the 
variability has been mentioned to us by Mr. R. H. Scott, namely, that in 23 years 
of barometric observations at Valencia, the maximum was only reached in the last 
year. 
Whatever be the form of the frequency distribution, the problem of determining 
how the bulk of the variability is distributed about either mean or mode, is exactly 
similar in character to the problem of determining how the inertia of a plate is dis¬ 
tributed about any axis in its plane. One satisfactory and useful measure in both 
cases is the swing-radius, or radius of gyradion. This is the quantity which, for 
distribution about the mean, appears under the heading a the standard deviation in 
our Table IV. 
Judged by this test the following is the order of variability in barometric pressure 
at our 20 stations :— 
( 1 ) . St. Leonards [l]. (11). Scarborough [13] 
( 2 ) . Margate [ 4 ]. (l 2 ). Parsonstown [ 11 ] 
( 3 ) . Southampton [ 2 ]. (l^)- Armagh [ 12 ] 
( 4 ) . Babbacombe [3]. (14). Scaleby [15] 
( 5 ) . Geldeston [7]. (15). Dunrobin Castle [ 20 ] 
( 6 ) . Hillington [ 8 ]. (16). Glasgow [16_ 
( 7 ) . Carmarthen [ 6 ]. (17). Dundee [18] 
( 8 ) . Stony hurst [9]. (1^)- Londonderry [14] 
( 9 ) . Churchstoke [5]. (l^)- Laudale [19] 
( 10 ). Llandudno [10]. (20). Markree Castle [17] 
* In an essay on ‘‘Variation in Man and Woman; ” see ‘ Tbe Chances of Death, and other Studies 
in Evolution,’ vol. 1, p. 275. 
