XXV. 



THE CLIMATE OF ST. ALBANS, 



DEDUCED FROM :\[ETEOROLOGICAL OBSERVATIONS TAKEN 

 DURING THE TEN YEARS 1887-1896. 



By JoHX HoPKiNsojf, F.L.S., F.G.S., F.R.Met.Soc, Assoc. Inst.C.E. 



Read at St. Albans, 6th April, 1897. 



FouK years ago I commuuicated to the Society a paper on " The 

 Climate of Watford, deduced from Meteorological Observations 

 taken during the ten years 1877-1886." This paper was published 

 in the ' Transactions ' of the Society for iS'ovember, 1893 (Vol. YII, 

 pp. 219-232). The observations, commenced at Watford in 1876, 

 have been continued at St. Albans from 1887 to the present time, 

 and the general results have been printed annually in the 

 * Transactions.' 



The present communication is an attempt to deduce the chief 

 elements of the Climate of St. Albans from these observations. In 

 the former paper it was stated that for all elements of climate but 

 the rainfall it is not likely that the mean annual value deduced 

 from any ten years' observations will differ greatly from the mean 

 for a much longer period, nor that the extremes will be greatly 

 exceeded. It is generally admitted that with an increase of 

 elevation with places similaiiy situated in other respects the mean 

 temperature will be lower. The level of the ground at my 

 thermometer-screen at St. Albans is 157 feet higher than it was at 

 Watford : the mean temperature at St. Albans for the ten years 

 1887-1896 was 0°-3 lower than it was at Watford for the previous 

 ten years. Again, with an increase of elevation the extreme 

 range of temperature is usually reduced : the extreme range at 

 St. Albans during the last ten years was 4°*4 less than it was 

 during the previous ten years at Watford. The range, however, is 

 likely to vary more from one period to another than is the mean, 

 and I do not place much reliance upon this test of the value of 

 ten years' observations. The slight difference in altitude between 

 Watford and St. Albans is not likely to affect the humidity of the 

 air or the amount of cloud : the mean of both of these for the 

 last ten years at St. Albans was exactly the same as it was for the 

 previous ten years at Watford. With regard to rainfall it was 

 stated in the previous paper that the mean rainfall of any place 

 cannot be directly ascertained, with any probability of accuracy, 

 from observations extending over a shorter period of time than 

 40 or 50 years. The true mean rainfall at St. Albans is not likely 

 to be greatly different from that at Watford, but at the higher 

 altitude there should be rather more rain : the mean annual 

 rainfall at St. Albans for the ten years 1887-96 was, however, 4-22 

 inches less than it was for the ten years 1877-86 at Watford. 

 This is because the earlier period was an exceptionally wet one in 



