102 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



[Maboh, 



indispensable ; and consequently there can he no possible use for a 

 main sewer Hr.,-li as the one proposed. A great objection to what 

 are called first-class sewers, too, is their great size, which renders 

 them as inefficient as they are expensive. A well matured system 

 of drainage should be properly graduated for the effectual removal 

 of all refuse matters under well calculated, mean ordinary circum- 

 stances; and for all other cases, such as those of extraordinary 

 floods, other means of removal should be provided, since no same 

 sewer can possibly be made to act with maximum efficacy under 

 the very dissimilar cases of limited or ordinary, and extraordinary 

 discharge. And surely of the two, we should give the preference 

 to efficacy under usual conditions of supply. To wish therefore 

 to build sewers large enough under any circumstances, not only 

 shows a complete ignorance of the first laws of hydraulic science, 

 but argues a want of common-sense on the part of tlie projector. 

 What — if we were to object to the human organisation, on the 

 ground that the digestive organs merely provide for the digestion 

 of the ordinary amount of food necessary for the purposes of life, 

 on the score of tlie inconvenience attending indigestion, caused by 

 no provision having been made in cases of surfeit of food — of ex- 

 traordinary " feeds" ? Our metropolitan sewers have been con- 

 structed capacious enough for all possible cases of indigestion ; 

 but, unfortunately, the gastric juice required — hydraulic pressure, 

 — has been found to lessen with the increase of their sectional 

 areas; deposits have taken place — accumulations of solid filth have 

 blocked them up — tlie whole fabric has been found not only in- 

 effective, but a public nuisance, alike dangerous to the health and 

 morals of a large portion of the population. — What the remedy ? 

 Scouring. — The consequence } A series of intermittent cesspools. 

 And is such a system still to be carried on .'' The public money 

 expended in creating a still greater number of longitudinal recep- 

 tacles for filth ? We hope not. We would lay down as a rule that 

 the minimum sufficient drain, for all ordinary purposes, whatever 

 its class, is the one that should of necessity, on the mere prin- 

 ciples of economy and common-sense, be adopted. We do not 

 presume to settle the questions wliat the sizes of minimum suffi- 

 cient drains should be under various circumstances, and for the 

 different classes of house, street, court, and main drainage ; but 

 this we wish to be understood clearly, that, until minimum suffi- 

 cient drains are adopted, maximum hydraulic pressure cannot be 

 obtained — and unless maximum hydraulic pressure be obtained, 

 maximum scouring-power and efficacy cannot possibly be realised. 



Mr. Rendel, in his address to the Board, after seconding the 

 motion made by Sir Henry Ue la Beche, said : " He had no doubt 

 that when practical engineers were put upon the Board, something 

 practical was intended should be done. He believed something 

 practical would be done from the present time, and he thought that 

 while acting so, they would have the public with them." We may 

 be allowed to observe to Mr. llendel that the putting of practical 

 engineers upon the board, was no kind of reason for at all con- 

 cluding or believing that something effectual and satisfactory, as 

 well as practical, would be done in the matter of the drainage of 

 the metropolis. Something " practical" was done, when practical 

 engineers were consulted and employed to construct the various 

 sewers now existing, — something " practical" was done when some 

 of the leading practical engineers of the day were asked to report 

 on tlie efficacy of these existing sewers — when they perambulated 

 them, where po.ssible — and expressed themselves fully satisfied ! 

 But unfortunately the " practice" in matters of drainage, which has 

 prevailed in England, up to tlie present time, is proved to have 

 been most defective and unsatisfactory. The actual state of the 

 drainage of London, after the enormous sums that have been ex- 

 pended upon it, is a sufficient warranty of the ignorance of our 

 practical engineers respecting the principles that ought to have 

 guided them in the framing of plans for actual execution. The 

 Sanitary Commissioners express themselves on this subject, in the 

 following words :— "The more the investigation advances, the more 

 it is apjiarent that the progressive improvements and proper exe- 

 cution of this class of iiublic works, together with the appliances of 

 hydraulic engineering, cannot be reasouably expected to be dealt 

 with incidentally or collaterally to (u-diiiary occupation, or even to 

 connected professional pursuits, Imt require a deyree of special study 

 vjliich not only place them lieynnd the sphere of the discussion n/' popular 

 administrative hodies, hut heijond that of ordi)iari/ professional engineer- 

 ing and architectural praetiee. In justification of this coiicliisicin, and 

 to show the evil of the perverted application of names of high general 

 professional authority, we might adduce examples of the most 

 defective works, which have received their sanction."" 



An d further, " It will be evident to any one who has followed 



, i__ " IstKepuitot llie Mtt. San. Cumin., p. 5. 



the course of the inquiries relating to Public Health works, that the 

 principles that have been established for future operations will 

 render inapplicable much of the experience that has been formed in 

 the execution of works of house, street, and land drainage, water 

 supply, and general cleansing."' 



However precise and satisfactory the present state of hydrosta- 

 tical engineering (and no better proof of the satisfactory state of 

 this branch of science need be adduced than the success Mr. Ren- 

 del himself has met with, in the construction of some of the most 

 important dock-works connected with tliis country ; we may also 

 instance the lifting of the tubes of the Britannia Bridge by hydros- 

 tatic pressure), the branch to which draining essentially belongs— 

 hydrodynamical engineering — is as yet completely in its infancy, 

 and little help can be derived from the " experience" of past ages. 

 Bulky and numerous as are the writers, both English and foreign, 

 on hydraulics, little or nothing, as yet, is known of the principles 

 which regulate the How of fluids. The great Newton himself failed * 



j to grapple with this truly intricate subject. He invented the method 

 of Fluxions, which enabled him to establish a theory of lunar mo- 

 tions; but he found himself reluctantly obliged to rest satisfied 

 with a mere approximation, instead of a complete solution, respect- 



I ing the motion of three bodies mutually influencing one another; 



■ and this convinced him how hopeless was the cliance of ever accu- 



■ rately investigating the laws that regulate the motions of fluids 

 j where innumerable atoms comprise their respective influences on 

 ! each other. "Newton," says Professor Whewell, in his ' History 



of the Inductive Sciences,' "treated the subject theoretically in 

 I the ' Principia;' but we must allow, as Lagrange says, that this ia 

 I the least satisfactory passage of that great work." Formulae, to be 

 depended upon for future works of drainage, must be deduced 

 j from correct experiments. No data of value can possibly be 

 obtained, but from thoroughly checked tables of correct trials ; 

 I iind upon correct practical results only ought we to depend for the 

 framing of formula! to work with." Experiments on the flow of 

 water through tubes, have, we believe, been carried on by order of 

 the Commissioners. This is a step in the right direction. The 

 practice which will have to guide us must be founded on such e.xpe- 

 ; riments, and we have little to expect from the mere past expe- 

 rience of our practical men; indeed we should rather shun the 

 prejudices which generally accompany the constant treading in the 

 same beaten path. 

 [ We have a new field open to us, with great difficulties to con- 

 tend with, for as yet we have neither theory nor practice to guide 

 us. Our theory has to be founded on correct experiments: our 

 I practice on correct theory. Sir John Herschell expresses himself 

 with his usual clearness and simplicity on the subject: " It is a 

 j remarkable and happy fact, that the shortest and most direct of all 

 inductions should be, that which has led at once, and almost by a 

 single step, to the highest of all natui-al laws — we mean those of 

 motion and force. Nothing can be more simple, precise, and gene- 

 1 ral than the enunciation of these laws; and their application to 

 i particular facts in the descending or deductive method, is limited 

 I by nothing but the limited extent of our mathematics. It would 

 seem, then, that dynamical science were taken thenceforward out 

 j of the pale of induction, and transformed into a matter of abso- 

 lute « /)?7'oW reasoning, as much as geometry; and so it would be, 

 were our mathematics perfect and all the data known. Unhappily, 

 I the first is so far from being the case, that in many of the most 

 I interesting branches of dynamical inquiry, they leave us com- 

 \ ))letely at a loss. J)i what relates to the motions of fluids, for instance, 

 this is severely felt. We can include our problems, it is true, in 

 algebraical equations, and we can demonstrate that they contain 

 the solutions; but the equations themselves are so intractable, and 

 present such insuperable difficulties, that they often leave us quite 

 as much in the dark as before. But even were these difficulties 

 overcome, recourse to e.xperience must still be had to establish the 

 data on whicli particular applications are to depend; and although 

 mathematical analysis affords very powerful means of representing 

 in general terms the data of any proposed case, and afterwards, 

 by comparison of its results with fact, determining what those 

 data must be to explain the observed phenomena, still, in any mode 

 of considering the matters, an appeal to experience in every par- 

 ticular instance of application is unavoidable, even when the gene- 

 ral principles are regarded as sufficiently established without it. 

 2Vow, in all s^lch cases o/ difficulty, we must j-ecur to our inductive 



' Circulnr Letter to Candidates fur Inspectorships, p. 2, 



8 Pi-incipia. Book 2. Prop. 37. 1st Kdit., 16s7, and the 2nd Edition of 1714. which con- 

 tains Neutun's alteied tieatinent ot tlie snbjict. 



O *■ The scien<'e of the motions of fluids, nnlilfe ail other jirirnnry departments of me- 

 chRnics, is a siiliject on which we Ktili need experinieuts to point out the luadamental 

 principles." — Whewell. 



