XI. 
HALF-A-CENTURY’S RAINFALL IN HERTFORDSHIRE. 
By John Hopkunson, F.L.S., F.G.S., F.R. Met. Soc. 
Head at Wa/ford , 18 th November, 1890. 
PLATE III. 
In our ‘Transactions’ for July, 1881 (Yol. I, p. 151), there is 
a paper by the Rev. C. W. Harvey on the “ Rainfall in Hert¬ 
fordshire, 1840-79,” in which he gives the mean monthly and 
annual rainfall, extremes of rainfall, etc., for each of the four 
decades included in this period. Another decade having terminated, 
we have materials for arriving at a knowledge of the mean rainfall 
in Hertfordshire for the last half-century. 
The results in Mr. Harvey’s paper were deduced from returns 
for one station for 1840-49, two for 1850-59, seven for 1860-69, 
and twelve for 1870-79. For the decade 1880-89 we have 
complete returns for eighteen stations, showing a very satis¬ 
factory increase in continuous observations. The actual number 
of stations from which returns have been received was 27 in the 
first year of this decade and 30 in the last year, and the number 
has varied from 26 to 30. The records, and also those for the 
five years 1875-79, have been published annually in our ‘Trans¬ 
actions,’ Mr. Harvey having drawn up the reports for the seven 
years 1880-86, and those for the eight years 1875-79 and 1887-89 
having been contributed by myself. 
The accompanying map (Plate III) shows the distribution of 
33 rainfall stations, being 30 from which returns for the year 
1889 have been received, and 3 for which we have complete 
records for at least one decade but from which returns are no 
longer received ; these, and also the 18 for which we have 
continuous records for the decade 1880-89, are distinctively 
marked. In this map the County is divided into six river- 
basins, viz. the Cam and Ivel, which are in the drainage-system of 
the Great Ouse; and the Thame, Colne, Brent, and Lea, which 
are in that of the Thames. 
This paper being intended as supplementary to that by the 
Rev. C. W. Harvey to which I have alluded, I have adopted 
his method in giving the results of the investigation in a series 
of tables preceded by explanatory observations. 
Table I.—The river-basins enumerated above are here divided 
into eighteen minor districts. These are numbered 1 to 18, and 
the numbers in the first column of Tables III and IY refer to 
these district numbers. It will be seen that we have continuous 
records for one district for 50 years, for two districts for 40 years, 
for six for 30 years, for eight for 20 years, and for twelve for 10 
years, and that thirteen are now represented,—the districts still 
without observers being the Upper Ivel, the Chess, the Upper 
Colne, the Brent, and the Stort. 
VOL. VI.-PART III. 
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