IX THE VALLEY OF THE GADE. 161 



was tlirovrn across the mill-head as rapidly as skilled hands could 

 work ; and wlieu once it was completed all danger had ceased, 

 but before tbisluippy eonsiiraniation was attained only about a yard 

 and a half of the bank remained intact, llad this trifling barrier 

 been washed away, an inundation, attended with considerable 

 danger anil great damage to property, must certainly have ensued. 



Kespeotiug the flood, I think that I have now said sufficient ; 

 it will not soon be forgotten by those who witnessed it. Allow 

 me, in conclusion, to allude for a few moments to the causes that 

 appear to have contributed to its occurrence. 



During the year 1878, 34-27 inches of rain* had fallen over 

 the Watford district; during the first seven months of 1879, more 

 than 2.) inches of rain had also been recorded. I give below par- 

 ticulars lor this period received from a few neighbouring stations : — 



Berkhampstead 



Great Gaddesden 



Harpendeu (Rothamsted) . 



I believe that in the Midland Counties a rainfall amounting to 

 58 inches in nineteen consecutive months is without a parallel. 

 At the commencement of August, 1879, the soil of the lower 

 portions of the valley was full to saturation, and this fact con- 

 tributed, beyond doubt, an important item among the causes that 

 produced the flood. 



I think it may be considered that an area of one mile in extent, 

 on either side of the river, drains into the valleys, and it must be 

 remembered that both the Hempstead and Berkhampstead valleys 

 alike contribute towards the supply of water to the lower reaches 

 of the Gade. Accepting this estimate as about correct, a few 

 measurements on the Ordnance Map enable me to compute the area 

 of the water-shed that supplies our river as comprising about 34 

 square miles. I have stated that, during the short period of six 

 hours, an average of 2^ inches of rain, a downpour almost tropical 

 in its proportions, fell over this district. With these data before us, 

 it is easy to calculate the weight of water that actually fell within 

 the area of di-ainage on the night in question'. 



The next step in advance is surrounded with much difficulty. 

 It is, unfortunately, impossible to estimate with absolute certainty 

 the per-centage of water that would, under such circumstances, at 

 once find its way into the streams. The numerous lanes that 

 abound on both sides of the valley constitute, without doubt, the 

 principal media for the outlet of surface-drainage. They convey to 

 the valleys not only the rain that falls upon them, but they act 

 as channels both for natural and artificial drainage supplied by the 

 fields and meadows through which they pass. I am informed by 

 Mr. John Evans that there are, in the parishes of Abbot's Langley 

 and King's Langley, no less than 152 acres of these lanes. It is 

 certain that the hill-sides would absorb, during the continuance of 

 the storm, large quantities of water ; but, on the other hand, it 



* ' Trans. Watford Xat. Hist. Sue.,' Vol. II, p. 213. 



VOL. I. — PART V. 11 



