XIII. 



METEOROLOGICAL OBSERVATIONS TAKEX AT WANSFORD 



HOUSE, WATFORD, DURING THE YEAR 1879. 



By Jonx Hopkinsox, F.L.S., F.M.S., etc., Hon. Sec. 



Mead at Watford, 2Qth April, 1880. 



No alteration having been made since the previous year in the 

 method of observation, and the instruments used being tlie same as 

 before, it will suffice to give in this report the following brief 

 summarv of the fuller information previously given :* — 



Longitude of station, 0^ 23' 40" W. ; Latitude, 51° 39' 45" N. 

 Ground-level at thermometer- stand and rain-gauge 223 feet, and 

 cistern of barometer 233;V feet, above Ordnance Datum. 



Barometer, a " Fortin." Thermometers, dry-bulb, wet-bulb, 

 " Negretti " maximum, and "Rutherford" minimum, 4 feet above 

 the ground in a "Stevenson" screen, over grass. Eain-gauge, 

 " Snowdon " pattern, 5 inches in diameter, rim 1 foot above the 

 ground. Wind-vane, about 25 feet above the ground, 4 feet above 

 ridge of roof of stable, and 105 feet distant from nearest object of 

 equal height. 



Observations taken at 9 a.m. Reading of minimum thermo- 

 meter entered to same day, of maximum thermometer and rain- 

 gauge to previous day. Readings corrected for index-errors of 

 instruments, and readings of barometer reduced to 32° and sea-level. 



The accompanying tables (pp. 122, 123) give the monthly means 

 of the daily observations, and of other results deduced from them. 

 They scarcely require any explanation. The " adopted mean 

 temperature" is the mean of the readings of the dry-bulb (9a.m.), 

 the maximum, and the minimum thermometer. It will be found, 

 as in the previous year, to diifer but slightly from either the 9 a.m. 

 or the mean of the maximum and minimum in any month. For 

 the year the adopted mean is only O^'-S lower than the 9 a.m. 

 temperature, and only 0°-l higher tlian the mean of the maximum 

 and minimum. The column headed dryness gives the difference 

 between the temperatiu'e of the air and the dew-point temperature 

 at 9 a.m. ; and that headed relative humidity, the per-centage of 

 aqueous vapour in the air to its complete saturation. With a 

 relative humidity of about 70 per cent, the air will feel very dry, 

 and when it is from 95 to 100 very damp. 



From these tables the following summary of the principal re- 

 sults for the different seasons is deduced, the means for December, 

 1878, being taken from the previous report. December to Feb- 

 ruary are here considered as Winter months; March to May, as 

 Si)ring; June to August, as Summer; and September to JS'ovember, 

 as Autumn. 



* See ' Trans. Watford Nat. Hist. Soc.,' Vol. I, p. 217, and Vol. II, p. 209. 



