216 J. HOPKDTSOJf THE CLIMATE OF ST. ALBANS. 



this part of England. Any diiference, therefore, between the two 

 places in these elements of climate is traceable to known causes, 

 and the rainfall appears to be the only element affected by the 

 shortness of the periods of observation. 



]n the former paper were given the reasons for the sequence of 

 the tables which revealed the climate of Watford. As the same 

 sequence is followed here, these reasons may be repeated. "After 

 temperature and rainfall, the sequence of phenomena in relative 

 importance, as indicating the nature of the climate of any place, 

 is probably humidity, cloud, and wind. Atmospheric pressure can 

 scarcely 'be considered an element of climate, but in determining 

 the character of other meteorological phenomena it is of paramount 

 importance, and it will therefore be discussed first. For a similar 

 reason — the cause preceding the effect — humidity, cloud, and wind 

 will be discussed before rainfall." 



Some information will first be given as to the locality where the 

 observations have been made, the instruments used, and the method 

 of observation and reduction. This will be followed by a discussion 

 of the general results obtained. 



SiTUATlOIf OF StATIOIJ. 



The Granqe, St. Albans.— Latitude, 52° 45' 9" N. ; longitude, 

 0° 20' 7" W. (of Greenwich). Centre of St. Albans (the Town 

 Hall) 170 yards WSW. ; Parish Church (St. Peter's) 340 yards 

 NNE. Ground-level at thermometer- screen 380 feet above mean 

 sea-level (Ordnance Datum) and at rain-gauge 379 feet ; cistern of 

 barometer 388 feet above Ordnance Datum. 



The situation is very open and well elevated above the valley of 

 the Ver. The ground slopes downwards slightly towards the south 

 for a short distance and then much more steeply in the same 

 direction. It also falls on either side of this main gradient, so 

 that the contour is convex, being made up of a south-westerly 

 slope to the River Ver, which is half a mile distant, and of a south- 

 easterly slope to the Eiver Colne, distant about three miles. The 

 ground rises to about 410 feet half a mile to the north-east, and 

 falls to about 250 feet half a mile to the south. The distances 

 given above indicate the position of the thermometer-screen and 

 rain-gauge ; the barometer is 200 feet to the west-north-west ; 

 part of the increase in its altitude is due to the slope of the ground 

 and part to the height of the ground-floor of the house above the 

 ground-level and the height of the barometer above the floor. 

 The elevations were ascertained by levelling from a bench-mark 

 (3S4-3ft.) on the wall by one of my own gate-posts about 40 feet 

 from the barometer. 



The subsoil is gravel on chalk, and there is a considerable depth 

 of surface-soil, but this, having very little clay in its composition, 

 soon transmits the rain which falls upon it to the pervious gravel 

 underneath. The natural level of the plane of saturation in the 

 chalk is about 130 feet beneath the surface, but it is lowered by 

 pumping at the waterworks about one-third of a mile to the 



