RAINFALL IF HERTFORDSHIRE. 
83 
In Table IY the mean rainfall in each district for three decades 
is given and is compared with the mean in the county. It will, 
he found, so far as can be ascertained from the material at our 
disposal, that the rainfall in the river-basin of the Ouse is 10 per 
cent, in defect of that in the county, the Cam having a defect 
of 13 per cent, and the Ivel of 7 per cent.; and that the rainfall in 
the Thames river-basin is per cent, in excess of the county 
fall, the Colne having an excess of 7 per cent., and the Lea a 
defect of 4 per cent. The differences in each district throughout 
the period agree fairly well, except in the Lower Colne, in which 
the discrepancy between the decades 1870-79 and 1880-89 is due 
to the district being represented in the first instance by Cassiobury 
where the rainfall is rather small, and in the second instance by 
Moor Park where it is very heavy. 
Tables Y and YI show that the second half of the year has 12 per 
cent, more rain than the first half, while the rain only increases 
1 per cent, from the first to the second, and 1 per cent, from the 
third to the fourth quarter; and also that the spring is the 
driest season and the autumn the wettest, winter having rather 
more rain than spring, and summer having rather less than autumn.. 
Tables YII, YIII, and IX give the mean number of wet days 
and mean rainfall per wet day in each month, quarter, and season, 
and in the year. The fourth quarter, it will be seen, has the 
greatest number of wet days, but the third has the heaviest fall 
per wet day ; spring and summer have fewer wet days than 
autumn and winter, but summer and autumn have more rain 
per wet day than have winter and spring. 
In Tables X and XI, showing the maximum and minimum 
yearly and monthly fall of rain in each decade, a departure from 
all the previous tables is made in the inclusion of other stations 
than those which have continuous records for one decade or 
more, the object being to give extremes of rainfall wherever 
they occurred, and thus to illustrate its great variability. 
Table XII.—I have here collected from every source to which 
I have access the falls of at least 2£ inches of rain which have 
occurred in 24 hours.* The remarkable character of the fall of 
the 12th of July, 1889, could not perhaps be more clearly shown 
than in this table, but some allowance should be made for increase 
in the number of rainfall observers and the probability of there 
being earlier records of heavy falls of which I have no knowledge. 
Table XIII gives particulars of all the stations for which we 
have records in our ‘ Transactions.’ Of the twenty-one stations 
with continuous records for at least one decade, from which the 
mean rainfall for the county is computed, it will be seen that 
returns are no longer received from three, viz. High Street, 
Herkhamsted; Cassiobury, Watford; and Stevenage. 
The columns in this table headed “Period” form an index 
* “ Therfield, 1879, August 2nd, 3-03,” in Mr. Harvey’s table showing falls 
of 2 inches or more ( £ Transactions,’ Yol. I, p. 158), is omitted, as the figures 
should be 2 s 03 (see p. 132 of the same volume). 
