14 SCIENTIFIC SURVEY OF YORK AND DISTRICT 



up on the roof of Bootham School, no suitable site being available in the 

 Philosophical Society's grounds. Records with the same instrument were 

 made continuously until 1930, when the old recorder was replaced by 

 a new instrument. We thus have available a record of sunshine dating 

 back to the original introduction of the Campbell-Stokes instrument. 

 The chimneys of buildings westward of the site cut off a little sunshine 

 near the time of sunset, but the loss from this cause is not serious. There 

 is also a slight cut-off by the Minster towers, to the south-east, from 

 November to February. 



The observing station in the Philosophical Society's grounds may be 

 regarded as thoroughly representative of the City of York, but it is rather 

 too much shut in for satisfactory obsei-vations of wind. It is proposed, 

 therefore, to restrict this article to the discussion of the climatological 

 elements other than wind. 



In Fig. I curves are given showing the annual variation of the more 

 important elements. Following the standard practice of the Meteoro- 

 logical OfKce, the averages of temperature (daily maximum, minimum 

 and mean), rainfall and sunshine refer to the period 1881 to 1915. A 

 relatively short period is sufficient to give satisfactory averages of humidity, 

 and those given in this article refer to the ten years 1921-30. Extremes 

 of temperature refer to the sixty years 1871 to 1930. 



Rainfall. . 



Referring to Table I, we see that October, with 68 mm., is normally 

 the wettest month, and February, with 38 mm., the driest. The summer 

 holiday months, July and August, are only slightly less wet than October. 

 There is a very pronounced dip in the annual rainfall curve at September, 

 a feature found in the annual curves at most British stations. The 

 number of days of rain is highest (18) in October, November and De- 

 cember, and lowest (13) in June and September. The wettest month of 

 any name was October 1903 with 177 mm., but September 1918 

 gave the highest fall reckoned as a percentage of the monthly normal. 

 It is of interest to mention that no rain actually fell in the calendar 

 month of February 1891. The 2 mm. credited to that month fell 

 in a shower at about 6 a.m. on March i. This amount, however, was 

 entered to February 28 in accordance with the convention whereby the 

 ' rainfall day ' terminates at 9 A.M. on the day of reading. 



To judge from the statistics given in the last column but one, York is 

 relatively free from heavy individual falls of rain. The highest recorded 

 fall is 58 mm., on July 25, 1886 — a relatively low figure when it is re- 

 membered that we are dealing with a period of nearly sixty years.^ In five 

 of the twelve months the highest daily fall has only slightly exceeded an 

 inch (25-4 mm.). 



With an annual fall of 618 mm. York is one of the driest spots in 

 Yorkshire. Its rainfall is, in fact, almost exactly the same as that of 

 London (Camden Square, 622 mm.). The wettest year, 1912, yielded 

 138 per cent., and the driest year, 1921, 66 per cent, of the average for 



^ This record was surpassed on May 21, 1932, when a fall of 70 mm. occurred. 



