ON “QUIET” DAYS DURING THE ELEVEN YEARS 1890 TO 1900, ETC. 4 - 2 \} 
§ G4. In conslderino’ results sucli as those in Talde XLYL, allowance must l^e made 
for tlie fact that in the case of such an element as rainfall tlie results fiom any 
single station for a single year, or even occasionally for a group of three years, may 
not lie fairly representative for more than a very limited area of country. But most 
of tlie other elements are much more representative in cliaractei-, and it seems 
safe to conclude that, as between the two groups of years of sun-spot maximum and 
minimum, tliere was not in the south of England generally any difference of 
meteorological character at all of the same order as tliat manifested in tlie magnetic 
elements. From this generalization I would however exclude atmosplieric electric 
potential. 
There seem, unfortunately, no data whence one can derive trustworthy information 
as to changes from year to year in the mean potential gradient in the open. An 
attempt is at present being made at Kew to fill this gap, but with what success 
remains to be seen. I think information on the point, liotli at hioh and low levels is 
much to be desired. 
§ Go. We shall now consider certain resemblances between magnetic and meteoro* 
logical phenomena in the average year, V'hich merit consideration in connection with 
theories as to the source of the magnetic diurnal variations. 
If we take the mean monthly values of temperature range and vapour pressure at 
Ivew, irsed in obtaining fable XLY I., and represent each monthly value as a 
percentage of the mean of the 12 monthly values, we get the results in Table XlAHl, 
hor comparison, this also gives the cori’esponding monthlv percentages v'hich aie the 
means found for the ranges of D and 11 emploved in the calculation of'fables XXXIII, 
and XXXIV. 
Table XLVII. 
Jan. 
Eel). 
Harcli. 
April. 
Hay. 
June. 
July. 
Aug. 
)Sept. 
Oet. 
Nov. 
1 
Dec. 
1 ) and 11 ranges . . . 
ru 
G2 
102 
128 
134 
132 
131 
1 33 
120 
9G 
95 
GG 
42 
G7 
Temperature ranges . . 
G2 
7a 
98 
117 
125 
128 
124 
IIG 
119 
7 ij 
4 apour pressure . 
72 
70 
74 
85 
99 
12G 
139 
142 
127 
102 
90 
74 
In the case of vapour pressure, we are dealing not with a diurnal range, but with 
the mean value for the 24 hours. I have introduced it princi})ally to sliow that tin' 
seasons of maximum and minimum vapour pressure are conspicuously later in the 
year than the seasons of maximum and minimum magnetic rano-e, and that the 
values of vapour pressure in March and December are much alike, whereas magnetic 
ranges in tlie former month am double those in the latter. 
It will be noticed that the annual range in temperature percentages in 
lable XLVII., viz., from G2 to 128, is less than that foi' D and 11, and that the 
