684 report— 1878. 



behaviour of the river hoth in time of flood and in time of drought. The estab- 

 lishment of self-acting tide-registering gauges at several points of every outfall 

 should be insisted on. By these means the whole of the phenomena of a watershed 

 area could be ascertained and recorded, and safe and trustworthy knowledge could 

 be obtained, which would contribute towards the determination, not only of the 

 works which ought to be executed, but of the incidence of the taxation by which 

 the necessary funds should be raised. For instance, it is obvious that where the 

 geological character of a watershed is variable, one portion of it consisting of a 

 permeable stratum, such as chalk or red sandstone, and another portion of an 

 impervious stratum, such as the tertiary clays or the shales of the millstone grit, the 

 same works would not be adapted to each section of the river, nor would it be fair 

 to charge all with the expense according to the same scale of contribution. The 

 former, that is the permeable stratum, is not only, from its absorbent nature, not 

 the cause of floods, but is, by reason of that characteristic, absolutely constituted 

 by nature one of the very works which must be devised by art to mitigate the 

 effects of rainfall on the latter, or impervious stratum. 



Bearing this in mind, I have often thought that nature might be usefully imi- 

 tated in this operation, by passing the surplus rainfall into the permeable 

 strata of the earth by means of wells, or shafts, sunk through the impermeable 

 strata overlying them. This has been done in isolated cases for the drainage of 

 lands, but not for the deliberate purpose of preventing floods and equalising the 

 flow of rivers. 



I also wish to remark that artificial compensating reservoirs may be much more 

 frequently made use of than is generally supposed to be possible, when it is con- 

 sidered that, so long as the dams are constructed in situations where there is 

 no danger of their giving way, it is by no means necessary that they should be 

 water-tight, and that, therefore, they can be constructed at a very much smaller 

 outlay. In fact, the purpose would be answered by a series of open weirs, which 

 would collect the water in times of flood and discharge it gradually down the 

 stream. 



The example of our French neighbours in the more general use they make of 

 moveable weirs — barrayes — of various constructions could, I am satisfied, be 

 followed by us with very great advantage in many cases. 



The question of water power is one which I think deserves more consideration 

 than it has lately received. It has been the fashion to consider that small water- 

 mills are of little or no value, and, in the present state of most rivers and streams, 

 this is to a very prreat extent true, but only because the supply of water to work 

 them is so variable and uncertain. Sufficient attention has never yet been given to 

 the subject of the amount of compensation water which should be given for the use 

 of riparian proprietors when the watershed areas are dealt with for purposes of 

 water supply. There is a kind of empirical rule acknowledged by most of the 

 eminent water engineers, that one-third of the average flow of three consecutive 

 dry years is a fair equivalent for the abstraction of the water falling on a gathering 

 ground. I am strongly of opinion that, looking to imperial interests, advantage 

 should be taken of every opportunity of dealing with a gathering ground to provide 

 for a much larger proportion of its available water being sent down the streams, so 

 that the natural water power of the country may be properly developed. The extra 

 cost of the necessary works must, as a matter of course, be borne rateably by the 

 interests benefited. It is certain that with the progress of invention many more 

 ways of utilising this power will be discovered. At present, through the medium 

 of compressed air, of hydraulic pressure, and of electro-motors, the great disadvantage 

 of its being only available at the spot where the water runs is overcome, and the 

 power can be transmitted to any distance, and used wherever it may be most con- 

 veniently applied. 



Sir Robert Kane, in his most valuable and exhaustive work on the ' Industrial 

 Resources of Ireland,' has given an estimate of the value of the power allowed to 

 escape every year in the shape of floods, and the same calculation might be applied 

 to the sister kingdom. It is probably no exaggeration to say that where run- 

 ning streams exist the power required for estate piirposes, on the majority of 



