Heordshire | Page 5

here be given.
Royston (London Road): lat. 52° 2´ 34´´ N.; long. 0° 1´ 8´´ W.; alt. 301
feet; observer, the late Hale Wortham, F.R.Met.Soc.
Berkhampstead (Rosebank): lat. 51° 45´ 40´´ N.; long. 0° 33´ 30´´ W.;
alt. 400 feet; observer, Edward Mawley, F.R.Met.Soc.
St. Albans (The Grange): lat. 51° 45´ 9´´ N.; long. 0° 20´ 7´´ W.; alt.
380 feet; observer, John Hopkinson, Assoc.Inst.C.E.
Bennington (Bennington House): lat. 51° 53´ 45´´ N.; long. 0° 20´ 7´´
W.; alt. 407 feet; observer, Rev. Dr. Parker, F.R.Met.Soc.
New Barnet (Gas Works): lat. 51° 38´ 5´´ N.; long. 0° 10´ 15´´ W.; alt.
212 feet; observer, T. H. Martin, M.Inst.C.E.
1. Temperature.--The mean temperature of Hertfordshire, as deduced
from the above observations, is 48.3°. It has varied from 47.0° in 1887
to 50.2° in 1898. The mean daily range is 15.9°. It was the least (14.2°)
in 1888, and the greatest (18.1°) in 1893. The mean temperature of the
seasons is as follows: spring 46.6°, summer 60.2°, autumn 49.2°,
winter 37.2°. The warmest month is July, with a mean temperature of
61.0°; the coldest is January, with a mean of 36.1°. August is very little
colder than July. In these two months only has the temperature never
been below freezing-point (32°). In December and January only has it
never exceeded 62°. It increases most rapidly during the month of May,
and decreases most rapidly during September and October.
2. Humidity.--The relative humidity of the air, that is the amount of
moisture it contains short of complete saturation which is represented
by 100, is, at 9 A.M., 82. It has varied from 78 in 1893 to 85 in 1888
and 1889. The air is much drier in spring and summer (78 and 75) than
it is in autumn and winter (86 and 89). There is the least amount of
moisture in the air from April to August (74 to 78), and the greatest
from November to January (90).

3. Cloud.--The mean amount of cloud at 9 A.M., from 0 (clear sky) to
10 (completely overcast), is 6.7. It has varied from 6.0 in 1893 to 7.4 in
1888. Spring, summer, and autumn are about equally cloudy (6.5 to
6.6), and winter is considerably more so (7.2). The sky at 9 A.M. is
brightest in September (6.0) and most cloudy in November and January
(7.5).
4. Sunshine.--At Berkhampstead only have records of bright sunshine
been taken for the whole of the twelve years. Throughout the year the
sun shines brightly there for nearly four hours a day (3.9). The average
duration in spring is 5.0, in summer 5.8, in autumn 3.2, and in winter
1.6. The duration is least in December and greatest in May; the sun
shining for rather more than an hour a day in December and nearly six
hours and a half in May. An apparent discrepancy between this and the
preceding section is due to a bright day often following a cloudy
morning and vice versâ.
5. Wind.--The prevailing direction of the wind, as recorded at
Berkhampstead, St. Albans and Bennington, is from S.W. (sixty-one
days in the year) to W. (sixty-two days), and the next most frequent
winds are N. to N.E. and S. (each about thirty-seven days). The least
frequent are S.E. (twenty-five days). About forty-four days in the year
are recorded as calm.
6. Rainfall.--Twelve years is much too short a period to give a
trustworthy mean for such a variable element of climate as rainfall, and
five stations are much too few to deduce an average from for
Hertfordshire. The average rainfall at a varying number of stations for
the sixty years 1840 to 1899 (from one station in the first decade of this
period to twenty stations in the last decade) was 26.15 inches. In the
driest year (1854) 17.67 inches fell, and in the wettest (1852) 37.57
inches. Spring has 5.40 inches, summer 6.97, autumn 7.87, and winter
5.91. The driest months are February and March, each with a mean of
1.65 inch; April is but very little wetter, having 1.69. The wettest
month is October, with 2.96 inches, and the next is November with
2.56. The mean number of days of rain in the year, that is of days on
which at least 0.01 inch fell, for the thirty years 1870-99, was 167.

Autumn and winter have each about six more wet days than spring and
summer. The rainfall is greatly affected by the form of the ground, the
southern and western hills attracting the rain, which chiefly comes from
the S.W., so greatly that with a mean annual fall of about 26 inches
there is a difference of 3½ inches between that of the river-basin of the
Colne on the W. and that of the river-basin of the Lea on the E., the
former