80 



Mr. H. S. Eaton, 



Observatory, sometimes exceeds by several degrees that observed 

 anywhere else in the neighbourhood. 



The mean temperature at the Kew Observatory agrees closely 

 with that of the Croydon stations, allowance being made for 

 difference of elevation, but the daily range of temperature is 

 smaller, partly from the sluggishness of the thermograph used in 

 the first two years, partly from the construction and exposure of 

 the screen, and partly perhaps from the modifying influence of 

 the Thames. 



Of the Croydon stations, the mean temperature at Beddington 

 is 48°'84, then follows Waddon with a temperature of 49°-00, at 

 Addiscombe it is iG'-Sl, at South Norwood 49-°40, and at Park 

 Hill 49°-41. Park Hill, the highest station, is thus 0-56° warmer 

 than Beddington, the lowest station. 



The annexed table shows briefly the main features of the 

 annual temperature at Croydon. (See also Fig. 1, page 79). 



This subversion of the general rule, that the temperature 

 diminishes with greater elevation, might possibly be attributed 

 to sensible heat being abstracted from the lower ground in 

 raising vapour from the water-meadows of the Irrigation Farm. 

 But if that were the case the diminution of temperature at 

 Beddington would be greatest by day, when the air is dry and 

 evaporation active. On the contrary, the daily maximum 

 temperature is highest at Beddington, 56°-58, and diminishes in 

 a regular manner, with increasing elevation, to 56°- 10 at Park 

 Hill ; while at night the temperature declines from 42^-72 at 

 Park Hill to 41°-12 at Beddington. The phenomenon, however, 

 may be due to the different positions of the stations referred to, 

 Beddington and Waddon being on the floor of the Waudle basin, 

 and South Norwood, Addiscombe and Park Hill on higher 

 ground on the boundary between the valleys of the Wandle and 

 the Eavensbourne. It has been shown on a former occasion,^ 



•^ ' Transactions,' 1881, p. 91. 



