August 22, 1878] 



NATURE 



453 



So much has been written on the engineering details of this 

 subject, by men far better qualified than I am to deal with them, 

 that I shall confine myself to the simple statement of the prin- 

 ciples which have been recognised by the chief authorities as 

 essential, and to a few suggestions, which my own experience 

 leads me to think may be of some value. Almost all the great 

 engineers of former generations, who have paid attention to this 

 question, Smeaton, Telford, Rennie, Golborne, Mylne, Walker, 

 Rendel, Stephenson, Jessop, Chapman, Beardmore, and without 

 mentioning names, many of the most eminent now living, have 

 agreed to the following general propositions : — 



That the freer the admission of the tidal water, the better 

 adapted is the river for all purposes, whether of navigation, 

 drainage, or fisheries. 



That its sectional area and inclination should be made to suit 

 the required carrying power of the river through its entire length, 

 both for the ordinary flow of the water, and for floods. 



That the downward flow of the upland water should be 

 equalised as much as possible throughout the entire year ; and 



That all abnormal contaminations shomld be removed from 

 the streams. 



In carrying out these principles, it is'perhaps superfluous to say, 

 that modifications must be introduced to suit the particular phe- 

 nomena of each river. In some watershed areas it would be 

 easy to construct reservoirs, which would to a great extent 

 equalize the flow and reduce floods. In others, it might be better 

 to control the floods by means of embankments. In others, to 

 have weirs, and sluices, delivering into side channels, parallel to 

 the main stream, with the same object. Sometimes reservoirs, 

 or receptacles, must be made for catching the debris brought 

 down by the streams. In fact, every river must be treated as a 

 separate entity. It is therefore necessary that a systematic col- 

 lection of data relating to rainfall, the geological character of 

 the gathering ground, and the volume of each separate stream, 

 should be made for each watershed area ; and this should be 

 carried on for a sufficient length of time to enable a fairly correct 

 estimate to be formed of the behaviour of the river both in time 

 of flood and in time of drought. The establishment of self- 

 acting, tide-registering gauges at several points of every outfall 

 should be insisted on. By these means the whole of the pheno- 

 mena 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 charac- 

 teristic, 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 imitated in this operation, by passing the sm^lus 

 rainfall into the permeable strata of the earth by means of wells, 

 or shafts, sunk through the impermeable strata overlying them. 

 Tills has been done in isolated cases for the drainage of lands, 

 but not for the deliberate purpose of preventing floods and 

 equalizing 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 considered 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 watertight, 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 

 u?e they make of movable weirs — barrages — of various construc- 

 tions 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 watermills are of little or no value, 

 and, in the present state of most rivers and streams, this is to a 

 very great 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 com- 

 pensation water which should be given for the use of riparian 

 proprietors when the watershed areas are dealt with for piurposes 

 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 pa-oportion 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 conveniently 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 

 running streams exist the power required for estate purposes, on 

 the majority of properties in the United Kingdom, might be 

 obtained by a proper conservation of the natural waterVesources 

 of those streams. 



The consideration I have been able to give to this subject has 

 helped to convince me that, although a vast amount of labour and 

 research has been devoted to it, it is nevertheless one in which 

 "a more systematic direction to scientific inquiry " is urgently 

 needed. 



A vast collection of scientific facts exists, but they require ar- 

 rangement and collation, and future observations should be more 

 strictly classified, so that the bearing of each one, both on the 

 others and on the subject at large, may be properly appreciated 

 with a view to a practical result. 



In France this is being done to a very large extent, and an 

 excellent map showing the phenomena of the rivers and streams 

 of that country is now in course of preparation. For many 

 years also very accurate observations of the phenomena of the 

 whole of the basin of the Seine have been taken, and have been 

 centralised (centralisJes) by that eminent engineer, whose loss all 

 who had the privilege of knowing him, either in his work or 

 in private intercourse, are deploring, M. Belgrand, late Inspector- 

 General of the Fonts et Chaussees, and by his'able coadjutor, 

 M. M. G. Lemoine. These observations have been published 

 in the form of diagrams, admirable in their simplicity of design, 

 which show at a glance the bearing of every one of those pheno- 

 mena on the general character of that river. 



In Italy also, where there exists a distinct department having 

 control of the hydraulic works of that country, the same ex- 

 haustive system of collation and record has been followed, and 

 the results have been published in a series of tables. In 

 Germany, although the same complete system is not in vogue, its 

 chief river has been the subject of most thorough investigation, 

 the results of which have been published in a beautiful map of 

 the Rhine and its regulating works. 



In our own country, as might be expected from the number 

 of engineering works which have been executed, there probably 

 exists an amount of detailed information on special and often 

 minute points which is unsurpassed, and probably unequalled in 

 the world. 



But, although as I have said before, a great number of em in ent 

 men have treated in an exhaustive manner the phenomena relating 

 to many of the principal rivers of Great Britain and Ireland, 

 yet, as far as I am aware, there has been no attempt to collect 

 and combine these most valuable, though detached fragments of 

 knowledge, so that their relation to one another might be seen, 

 and a general conclusion arrived at. This can only be done by 

 the establishment of a public department analogous to those 

 described as already existing in France and Italy. 



When it is considered that many lives are annually sacrificed, 



