1850.J 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



165 



regular, there will he nevertheless, at each joint, a little annular hollow, or a 

 break of continuity, which will produce, to a certain extent, the effect of 

 projections; and which, repeated at every joint in a long conduit, cannot hut 

 give rise to a perceptilile reduction in the discharge. M. Gueymird, ingenieur 

 den mines, has rightly insisted on this cause of reduction, and has endeavoured 

 successfully to obviate its effects in the establishment of the fountains at 

 Grenoble. 



Moreover, when the conduits are sinuous in their vertical planes (as is 

 generally the case), if there are no vents at the summits of the highest 

 parts the air which the water carries with it, and which is disengaged in a 

 greater or less quantity, rises into these elevated parts, and being there col- 

 lected, produces the effect of contractions, the bad effects of which we have 

 already seen. The cleanest waters, in appearance, always carry with them 

 foreign bodies, and especially extremely fine earthy particles, which are depo- 

 sited in parts of the pipe; and in time contracting the section, again dimi- 

 nish the discharge. I do not here speak of calcareous and siliceous matter, 

 which, although held in solution in the water, become precipitated on the 

 interior of the pipes, lining them with a stony crust, and, gradually increasing 

 in thickness, would end by stopping them altogether, if not removed in time: 

 this evil is peculiar only to certain localities. It is the same with regard to 

 ferruginous deposits, which are made in a tubercular form in the conduits of 

 Grenoble, and which continually increasing in number and size, diminish the 

 discharge to such a degree that, in eight years, it has been reduced more 

 than one-half. The aerated water, running in pipes, likewise attacks the 

 material, and forms a hydrate of iron, which is deposited in long nipples 

 parallel to the direction of the current, and in greatest quantity on the lower 

 part; underneath these, the iron is as it were corroded, nearly to Jjth of an 

 inch. ('Annales des Mines,' 1834, p. 203, et. seq.) 



Setting aside these local circumstances, it often happens that in experi- 

 ments made on conduits apparently in a sound state, the discharge has been 

 found to be less by a quarter or a third than that indicated by the forraulaj: 

 it is scarcely ever equal to it. I have quoted many of these experiments in 

 my ' History of the Formation of the Fountains at Toulouse.' In consequence 

 of these ascertained facts, the hydraulic engineers of Paris, when making 

 Dse of the formula; of discharge, diminish by one-third the value of the 

 numeric coefficients. I have adopted an analogous method, by augmenting 

 by one-half the quantity of water which should determine the size of the 

 conduit. It is, in my opinion, with such latitude that an engineer charged 

 with the establishment of a plan for a large distribution of water, ought to 

 employ the formula: which we have set forth: he wdl then avoid the dis- 

 appointments which would often occur if he uniformly adhered to results 

 given by conduits made with a precision which can seldom belong to his 

 own. 



CTo lie continued J 



cross the Atlantic with certainty and despatch, did we not extend 

 the beacon lig-ht to welcome their approach to our coasts, and pro- 

 vide the means of their witlidrawirif; from the ocean billows into 

 sheltered havens, wliere their lading might be discharged, and car- 

 goes of our country's produce shipped for foreign lands? — for it 

 must be remembered that it was only when a mariner approached 

 his destined port that the many dangers caused by rocks, shoals, 

 sand-hanks, tides, and currents, beset his course; and hence the 

 necessity of employing artificial means to secure that shelter and 

 protection which his vessel required. It would at once occur to the 

 Society that works of various kinds were employed for this pur- 

 pose: one class of these works consisted in the projection of piers 

 and breakwaters at suitable situations on the coast, so as to form 

 sheltered havens and harbours of refuge; to another department 

 belonged ship canals, by means of which exposed coasting voyages 

 wei-e avoided, and vessels were brought by sheltered and direct 

 routes to their destination; while closely connected with this might 

 be mentioned the system of inland navigation, as effected by the 

 means of canals and the upper compartments of rivers; and last 

 of all, there was that v.aried class of works by which inlets of the 

 sea, and tidal compartmettts of rivers, extending from the coast 

 into the country, were opened up and rendered navigable ; and he 

 observed in passing, that these various works, connected with the 

 improvement of navigation, formed by far the most extensive and 

 intricate department of hydraulic engineering. 



On the subject of harbours formed by the projection of piers 

 and breakwaters, he did not intend to enter at present, and only 

 requested the attention of the Society while he endeavoured to 



ON THE ART OF NAVIGATION. 



An Exposition of the Art of A'ariffation, as ajjpUcnh/e to Inland 

 Tramit, and of the Works hij means of which our Communication with 

 the Ocean is improved and maintained . By David Stevenson, Esq., 

 F.R.S.E. — (Paper read before the Royal Scottish Society of Arts.) 



Mr. Stevenson believed he was perfectly safe in affirming, that 

 nothing had occupied a more prominent part in the work of civil- 

 ising the world than the art of navigation, which had slowly but 

 steadily progressed since the commencement of the 14th century, 

 at which early period the introduction of the mariner's compass 

 opened up a new era in the history of maritime discovery, and gave 

 an entirely new character to commercial enterprise. In its more 

 extended sense, the subject of navigation had, for the last 400 

 years, formed the grand object on which the labours of Columbus, 

 and of all subsequent explorers of the world, had been expended, 

 while the researches of the philosopher, ths astronomer, the geo- 

 grapher, the mechanician, and the engineer, had all been instru- 

 mental in bringing to their present maturity and perfection the 

 varieus branches of which the vast system of navigation, as it now 

 existed, was made up. 



It is not, however, to the subject in that compreliensive sense 

 that he had the honour, at the request of the Council, to direct the 

 attention of the Society. Such an exposition would embrace too 

 wide a field, aud lead to the discussion of topics which would not 

 fall within the scope of civil engineering; and he would therefore 

 confine his observations to th,at branch of navigation which he de- 

 fined as the department which intervened between the ocean and 

 the land — a connecting link, the true importance of which could 

 be correctly estimated only when viewed in connection with the 

 vast importance of the whole system of which it formed an indi- 

 spensable part. For how, he asked, could we be benefited by those 

 mighty results of science and of art by which sailing vessels of all 

 classes were now enabled to transport their cargoes from shore to 

 shore with comparative ease and safety, aud gigantic steamers to 



to 



convey an outline of what he conceived to be the extent of our 

 knowledge with reference to the subjects of inland and tidal navi- 

 gation. 



Mr. Stevenson said, that the antiquity of navigable canals— 

 their wide-spread introduction for the transport of goods, and the 

 important place which they had so long occupied in the commercial 

 history of every country— rendered their origin and subsequent 

 progress worth)' of attentive investigation; but that only a very 

 brief notice of that class of works could be given. And on that 

 subject he remarked, that from the writings of Herodotus, Aris- 

 totle, Pliny, and other ancient historians, we leanted that canals 

 existed in Egypt before the Christian era; and at the same early 

 period there was reason to believe that artificial inland navigation 

 also existed in China. Almost nothing, however, save their exist- 

 ence, had been recorded with reference to these very early works; 

 but soon after the commencement of the Christian era, canals were 

 introduced, and gradually extended, throughout Europe, particu- 

 larly in ancient Greece, Rome, modern Italy, Spain, Russia, Swe- 

 den, Holland, and France.' 



In speaking, however, of the earliest of these works, Mr. 

 Stevenson said that it was not to be supposed that they resembled 

 the present system of inland navigation as practised and known in 

 this country. Early as canal navigation was introduced, it was 

 not until tlie invention of canal-locks, by which boats could be 

 transferred from one le^■el to another, that the system was rendered 

 generally applicable and useful; and a writer in the Quarterli) 

 lieciew remarked, " that to us living in an age of steam-engines 

 and daguerreotypes, it might appear strange that an invention so 

 simple "in itself as the canal-lock, and founded on properties of 

 fluids little recondite, should have escaped the acuteness of Egypt, 

 Greece, and Rome.'"- But not only had the invention escaped the 

 notice of the ancients, but the se'veral gradations made towards 

 the attainment of that simple but valuable improvement, appeared 

 to have been so gradual, that, like many discoveries of importance, 

 great doubts existed, not only as to the person, but even as to the 

 nation by whom canal-locks were first introduced. Otte class of 

 writers attributed the discovery to the Dutch, and Messrs. Telford 

 and Nimmo, from whose pen the article on Inland Navigation in 

 Brewster's ' Edinburgh Encyclo|)iT>dia,' was understood to have 

 emanated, adopted the conclusion that locks were used in Holland 

 nearly a century before their ajjplication in Italy; while, on the 

 other'hand, the'invention hiid been strongly, and not unreasonably 

 claimed by engineers of the modern Italian school, and in particular 

 for Leonardo" da Vinci, the celebrated engineer and painter. 

 Without, however, entering into a discussion on this subject, he 

 would simply remark, that during the Uth century the introduction 

 of locks, whether of Dutch or Italian origin, gave a new character 

 to inland navigation, and laid the basis of its rapid and successful 

 extension. And here he said that it might be proper to remark^ 



1 Fulton on Canal Navigation. London. l/'JS.—Vallancey's Treatise on Inlaml Navi- 

 gation. Dublin, iriiS.— Tuthara's Polilical Economy of Inland Navigalioc. Louoou, 

 17U9.— Inland Navigation, Brewster's Edinburgh Encyclopedia. 



2 Quarterly Revien, No. UC; p.'.'tfl. 



