NATURE 



THURSDAY, DECEMBER 23, 1886 



CANAL AND RIVER ENGINEERING 

 The Principles a)id Practice of Canal a}td River Engineer- 

 ing. By David Stevenson. Revised by his Sons, 

 D. A. and C. A. Stevenson. Third Edition. Pp. 

 xiv. + 406, and iS Plates. (Edinburgh : A. and C. 

 Black, 1886.) 



THE fact of this work having reached a third edition 

 shows its appreciation by the public. The title, 

 however, indicates a wider scope than that actually 

 embraced. Thus only 65 pages are given to canals, and 

 these only for navigation ; no mention is made of the 

 very large subject of irrigation-canals (surely a passing 

 notice of the reason of this omission was required). In 

 this short compass (30 pages given to barge canals, 35 pages 

 to ship canals), part of which is an historical sketch, it is 

 of course impossible to give much constructive detail. 

 Thus no details or sketches are given of most of the 

 appliances needed for canals, e.g. locks, turbines, lifts, 

 waste- weirs, &c. The two chapters on canals are otherwise 

 unsatisfactory ; e.g. 14 pages devoted to the Suez Canal 

 consist chiefly of extracts from Reports made in 1863 and 

 1870 : much of this now purely historical matter might 

 have been with advantage replaced by later information. 



The remainder of the work (331 pp.) is devoted to river 

 improvement. And this part of the work is of great value 

 and interest, especially where accounts are given of some 

 of the numerous successful instances of improvements of 

 estuaries effected by the author and the revisers them- 

 selves. The great help of a large rise and fall of tide to 

 a commercial port situate in the tidal portion of a river, 

 viz. in aiding vessels coming to and leaving the port, is 

 first explained ; the pre-eminent importance of this tidal 

 action to England is evident. As might be expected, 

 then, the greater part of the work is devoted to the im- 

 provement of the tidal portion of rivers such as those of 

 the British Isles. 



Two useful chapters (92 pp.) are given to the observa- 

 tions required for a project for such work, e.g. tidal 

 phenomena, soundings, current-velocities, discharges, 

 salinity, &c. In quoting Cunningham's instrument (twin 

 balls, sunk one to '211 and one to 7S9 of the depth) 

 for measuring mean velocity past a vertical at one opera- 

 tion, it should be stated that the two balls should be alike 

 in all respects. Fourteen pages are given to the subject 

 of "under-currents" ; one instance is quoted (p. 135) of a 

 velocity of 4 miles per hour at 50 feet depth measured 

 with a " double-float," when the surface-velocity was only 

 I '8 miles per hour. This is one of the best instances 

 (known to the reviewer) of the excellence of the " double- 

 float " (when well designed) for sub-surface velocity- 

 measurement ; several other good instances are quoted. 

 These should surely convince those who condemn the 

 " double-float " as useless for such work. The natural 

 defects of most (tidal) rivers in their tidal reaches are 

 detailed as the presence of a "bar" at the mouth, of 

 hard veins of gravel, rock, &c., obstructing the water-way, 

 of extensive mud or sand flats through which the deep 

 channel is ever shifting, &c. 

 Vol. XXXV.— No. 895 



The explanation of the cause of a "bar" at a river 

 mouth now generally accepted, viz. as being really a sub- 

 merged part of the " beach " of the outer shore-line, pro- 

 duced from the sea by the action of the waves (not from 

 the alluvium brought down by the river), appears to have 

 been first proposed by the author of this work in 1842. 

 This suggests the treatment usually found successful in 

 tidal rivers, viz. prolonging the fairway of the river, by 

 piers, seawards into the deep water beyond the reach of 

 the waves which produce the beach. And it is seen that 

 this will fail in effecting a permanent cure in deltaic 

 rivers, in which the gradual advance of the delta will 

 reproduce shoal-water outside the ever-advancing mouths, 

 in which the waves will therefore reproduce a bar. 



The ideal improvement to be aimed at in the tidal part 

 of a river is explained to consist chiefly in introducing 

 increased tidal scour by removing obstruction to it (such 

 as bars, &c.), and by confining its action under half-tide 

 to a definite channel. These changes accelerate the pro- 

 pagation of the tidal wave, and decrease the tidal current, 

 thereby giving (sometimes greatly) increased depth of 

 water, not only over the bar at the mouth, but throughout 

 the tidal reaches, and also prolong the duration of the 

 tidal effect. The benefit of these results to navigation is 

 obviously very great. 



It is shown that jetties, groynes, &c., projected from 

 the banks of a stream for confining the fairway to a 

 defined channel are very uncertain in their effects. The 

 course recommended in general is the use of low parallel 

 training walls for confining the course of the river under 

 half-tide to a single definite channel, low enough to be 

 covered at half tide. Several interesting instances are 

 given of the failure of the jetties, &c., and success of the 

 low parallel wall system, ^fter this treatment silting will 

 generally occur in places behind the training walls, 

 increasing gradually till marsh-land is produced ; after 

 which it is often possible to reclaim some of the raised 

 land : but it is stated that it seldom pays to do this in 

 British rivers until the silting has raised the land to the 

 level of ordinary spring-tides. A most useful practical 

 rule is proposed, that reclamation work should only be 

 undertaken as part of a large general scheme of improve- 

 ment of a navigation, and never be permitted to the 

 desultory self-interested efforts of private riparian pro- 

 prietors. 



A short chapter (9 pp.) is given to the eftect of bridge 

 on navigable rivers. In highly civilised countries this is 

 now a question of rapidly increasing importance. It is 

 shown that the interests of the bridge constructors, espe- 

 cially in the case of railways, are generally adverse to 

 those of the navigation. Of course the subject cannot be 

 much developed within 9 pages. But a short description 

 (with plate) of the railway swing-bridge over the Ouse 

 has been included. 



An excellent account is given (31 pp ) of the various 

 processes of dredging and excavating, with a description 

 of some of the most recent machines, and an analysis of 

 the cost of the work. 



It will be seen that on the whole this treatise is an 

 excellent account of the principles and practice of river 

 engineering, to the successful practice of which its able 

 authors have so largely contributed. 



Allan Cunningham, Major R.E. 



