217 



30. — Meteoeological Obseryatio^ts taken at Holly Bank, 

 Watford, during the year ending 28th February, 1877. 



By John Hopkinson, F.L.S., F.M.S., etc., Hon. Sec. 

 [Read 12th April, 1877.] 



The meteorological observations, some of the results of which. I 

 propose to give in this communication, were in part commenced 

 in January, 1876; but, as it was not until the end of February that 

 the barometer and thermometers were obtained, to complete a year 

 the first two months of 1877 are included. 



Though it is to be regretted that the results of observations in 

 the entire year 1876 cannot be given, there is one advantage in the 

 arrangement adopted — by commencing in March we can di^-ide the 

 year into its four seasons. 



The result we wish more particularly to arrive at being a know- 

 ledge of the climate of the neighbourhood of Watford, obtained by 

 data which will enable us to compare its climate with that of other 

 places where similar observations are carried on, by dividing the 

 year into the four seasons — Spring, Summer, Autumn, and Winter 

 — and taking the means for each season, a more satisfactory com- 

 parison may be made than by taking only the means for the year, 

 and a more comprehensive and less tedious one than by comparing 

 with each other the monthly means. 



This being the first report, it will be necessary to give certain 

 particulars as to the locality, the instruments used, their position, 

 and the time and method of obseiwation. 



The locality is perhaps as suitable a one as could be chosen in 

 the immediate neighbourhood of Watford. The position as related 

 to the surrounding country is high, the ground falling sKghtly in 

 every direction, either immediately or at the distance of a few 

 hundred yards ; and, with the exception of a belt of trees forming 

 the eastern margin of Cassiobury Park, which perhaps gives some 

 slight protection against westerly winds, there is nothing to in- 

 terfere with a free current of air in every direction. 



The longitude is 0^ 24' 10" W. (of Greenwich), and the latitude 

 51° 40' 5" N. The town of Watford is about a mile to the south- 

 east. The ground-level is about 268 feet above Ordnance Datum 

 (mean sea-level), 30 feet higher than the centre of the town of 

 Watford, and 10 feet higher than the ground on which the trees 

 on the west, already mentioned, are situated. 



The instruments used are by Mr. J. J. Hicks, of Hatton Garden, 

 London, and they have been verified at the Kew Observatory. 



The barometer (IS'o. 473) is a standard on Fortin's principle. 

 The tube is half an inch in internal diameter, and the correction 

 required, according to the Kew certificate, is -f- 0-004 inch, of 

 which -}- 0-003 is due to capillarity, the error of construction or 

 "index error" being therefore only 0-001 inch. The cistern of 



VOL. I. — PT. IX. 17 



