226 J. HOPKINSON — EEPOKT OX THE EAINFALL. 



The localities are here arranged in the same order as before, i.e. 

 grouped according to Mr. Pryor's botanical divisions* and their 

 distance from Watford. Four out of his five divisions are repre- 

 sented, — the one from which we have no return being the Brent, a 

 fragment (about four square miles) of Hertfordshire which may 

 fairly be said to be situated in Middlesex, as it is almost entirely 

 surrounded by that county. Of the sixteen minor districts we 

 have returns from twelve. Those for which we require observers 

 are the Upper Colne, the Chess, the Brent, and the Stort ; all but 

 the Upper Colne being outlying districts of very small extent. 



The accompanying table (p. 227) gives the monthly and annual 

 rainfall f at each station. It is seen by this table to have been 

 very unevenly distributed over the year ; and by breaking the year 

 into three periods of four months each the inequality is rendered 

 even more apparent. From January to April (inclusive) 9'73 inches 

 fell ; from May to August 5'45, or a little more than half the 

 previous quantity; and from September to December 15 -59, nearly 

 three times the fall of the four summer months. 



The next table gives the mean rainfall for each of the larger 

 divisions or main river-basins, and also for each of the smaller 

 districts or lesser river-basLns and their sub-divisions. With the 

 exception of the districts of the Lower Colne, the Yer, and the 

 Bulbome, all of which are comprised in the Colne division, in 

 which we are here more immediately interested, each of the districts 

 is dependent upon a single observer, whose return we are therefore 

 obliged to consider as representing the mean fall in the district. 



( Lower Colne... 29-61 



Colne. ..32-28 I Ver 33-00. 



( Bnlborne 34-23 



Thame 34-09 Thame 34-09 



f Lower Lea... 26-60 



I Upper Lea... 30o0 



Tea '>9.08<' ^li""''™ 30-27 



^^^ >.JWS<; Ash 28-85 



I Beane 28-93 



l^Rib 29-36 



Of the 22 observers 18 have taken their observations daily 

 throughout the year, and they give the number of days in each 

 month on which -01 inch or more fell. The mean of these for the 

 different months is as follows : — 



Jan 9-7 April 



Feb 19-2 Way 



March ... 18-1 June 



giving a mean for the year of 172-9, or (say) 173 days. The least 

 number of days of rain were at Ashlyns, Berkhampstcad (1-12), 

 Buntingford (1-13), and llickmansworth (H4) ; the greatest, at 

 Holly Bank, Watford (195), Hitchin (199), and Harpenden (204). 

 The numbers nearest the mean were at Eoyston (165), and at 

 Hertford (178). , . ' . 



These 1 8 returns also give the gi-eatcst amount of rain which fell 



* ' Transactions,' Vol. I. p. 67, and map, Plate I. 



t The amounts entered as rain here and throughout this report include 

 melted snow. 



