Hertfordshire. Herbert W. Tompkins
Aylesbury Canal (a branch of the Grand Junction Canal) crosses the extreme western neck of the county, from S. of Puttenham to S. of Gubblecote.
GRAND JUNCTION CANAL AT TRING
The highest water level in England
The Grand Junction Canal is largely utilised by barges traversing the W. of Hertfordshire. It is conspicuous at Rickmansworth, Boxmoor, and Berkhampstead; it enters Bedfordshire near Marsworth Reservoir.
The New River was constructed by Sir Hugh Myddelton, a London goldsmith, in 1609–13, and is largely fed by springs at Chadwell near Hertford. Its course in Hertfordshire is mostly close to and parallel with that of the Lea. The New River caused the financial ruin of its projector; one of its shares is now worth a large fortune. The whole story of this undertaking is very interesting; but as the New River was cut in order to bring water to London that story belongs to a volume on Middlesex.
III. Climate
The chief elements of climate are temperature and rainfall. A general idea of the mean temperature and rainfall of Hertfordshire, both monthly and annual, may be gained from an inspection of Bartholomew’s Atlas of Meteorology (1899). From that work it appears that the mean annual temperature of the county, if reduced to sea-level (that is, the theoretical mean for its position) would be 50° or a little above it, but that the actual mean varies from 46°-48° on the Chiltern Hills to 48°-50° in the rest and much the greater part of Hertfordshire; also that the mean annual rainfall is between 25 and 30 inches, the latter amount only being approached towards the Chilterns. Thus altitude is seen to have a great effect on both these elements of climate.
Hertfordshire is hilly though not mountainous, a great extent of its surface being considerably elevated above sea-level, with a general south-easterly inclination; it has a dry soil; is well watered with numerous rivers of clear water—already enumerated—chiefly derived from springs in the Chalk; is well but not too densely wooded; and its atmosphere is not contaminated by manufacturing towns. It thus maintains the reputation for salubrity which it gained more than three centuries ago, our earliest county historian, Norden, remarking on the “salutarie” nature of the “aire”.
Observations taken at the following meteorological stations during the twelve years 1887 to 1898 have been printed annually in the Transactions of the Hertfordshire Natural History Society, and a brief summary of some of the chief results will 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 having 28 inches and the latter 24½. The small portion of the river-basin of the Great Ouse which is within our area has rather less rain than the average for the county.
IV. Flora and Fauna
In his Cybele Britannica, H. C. Watson divided Britain into eighteen botanical provinces of which the Thames and the Ouse occupy the whole of the S.E. of England. The greater part of Hertfordshire is in the Thames province and a small portion in the N. is in that of the Ouse.
In Pryor’s Flora of Hertfordshire, published by the Hertfordshire Natural History Society in 1887, which should be referred to for full information on the botany of the county, these botanical provinces are again divided into districts, the Ouse into (1) Cam, (2) Ivel; and the Thames into (3) Thame, (4) Colne, (5) Brent, (6) Lea; both the larger provinces and the smaller districts thus being founded on the natural divisions of a country, drainage areas or