J. norEiNsox — the ci.imatk of watford. 221 



SlTTTATrON OF STATIONS. 



Holly 7?ff«/-.— Lutitudc, 51° 40' 5" N. ; longitude, 0° 24' 10" W. 

 (of Given wk'li). Centre of Watford about a mile S.S.E. Ground- 

 level at thermometer-screen and rain-gauge 2(58 feet, and cistern 

 of barometer 272 feet, above Ordnance Datum (mean sea-level). 

 Ground in the immediate neiglibourhood nearly level, then rising 

 very slightly towards X., and falling slightly towards E. and S.E. 

 to the lliver Colne, distant about a mile. 



Wansford House.— Latitude, 51° 35' 45" N.; longitude, 0° 23' 40" 

 "W. Centre of Watford about half a mile S. Ground-level at ther- 

 mometer-screen and rain-gauge 223 feet, and cistern of barometer 

 234 feet, above Ordnance Datum. Ground immediately around 

 slightly inclined towards E., then rising slightly towards N.W., 

 and falling rather more considerably towards E. and S.E. to the 

 River Colne, distant about half a mile. 



The subsoil is gravel on chalk, the plane of saturation in which, 

 except where loAvered by pumping, rises at a very slight gradient 

 from the river, the surface of which is, at Watforcl, 180 feet above 

 mean sea-level. To pen back the water for the Watford Mill, 

 the banks of the river have been raised ; being thus rendered very 

 sluggish, it has gradually silted up its bed ; and, just above 

 Watford, its surface is now at least a foot above the alluvial 

 plain through which it flows, which is consequently often flooded 

 after heavy rain. The town of Watford is now extending over this 

 low-lying land, which it would seem to be impossible effectually 

 to drain. All other parts of Watford and the country around it 

 have a very dry subsoil, the effects of heavy rain soon disappearing. 



Instrfments, and Method of Observation and Reduction. 



Barometer, a Eortin standard with tube half an inch in internal 

 diameter. Thermometers, clry-bulb, wet-bulb, Negretti maximum, 

 and Rutherford minimum, 4 feet above the ground in a Stevenson 

 screen, over grass. Rain-gauge, Snowdon pattern, 5 inches in 

 diameter, top of rim .1 foot above the ground (grass), capacity 

 of receiver 8 inches depth of rain. Wind -vane (at Wansford 

 House only), about 25 feet above the ground, and 105 feet 

 di.stant from nearest object of equal height. 



Observations taken at 9 a.m.*" Readings of minimum ther- 

 mometer entered to day of observation, of maximum thermometer 

 and rain-gauge to previous day. Readings corrected for index- 

 errors of instruments, and barometric readings corrected to 32° in 

 accordance with the temperature shown by attached thermometer, 

 and reduced to sea-level. No corrections made for diurnal range 

 of pressure or temperatiire, the mean temperature adopted being 

 the arithmetical mean of the minimum and maximum readings. 



Reductions made in part from Guyot's ' Tables, Meteorological 

 and Physical' (3rd Ed.), and in part from tables in the Royal 

 Meteorological Society's ' Instructions for the Observation of 

 Meteorological Phenomena,' by AV. Marriott (2nd Ed.). 



* The observations taken at first at 9 p.m. also, are not here utilised. 



