CHAPTER XXXI.

SPEED OF TRANSPORT. All other things being equal, the system of transport that is able to afford the greatest average speed will be certain to command the lion’s share of business. There are, however, both natural and economical limits to speed, alike on water and on land. The natural limit up to the present time may be put at 50 miles an hour for railway travelling, 20 knots per hour for sea transport, and four or five miles an hour for canal navigation. The economical limits are, however, very different. A goods train cannot be worked economically at a greater speed than 20 to 25 miles an hour, and many railway companies decline to work their mineral traffic at a higher speed than 15 miles. At sea, the ordinary rate for a cargo-carrying steamer will vary from 10 to 14 knots, but seldom exceeds the latter figure. On an artificial waterway it is not possible, even in the absence of locks or other obstructions, to maintain a higher rate of speed than 4 or 5 miles without doing serious injury to the banks. A very excellent paper on the rate of speed which it is possible or usual to attain in canal navigation, under varying conditions of towage, locks, depth, and other elements that influence the question, was submitted to the Institution of Civil Engineers some years ago by the late Mr. Conder, who devoted much attention to the subject.[285] On the Belgian canals, where human labour is employed for towage, the rate of speed does not exceed 1 to 1⅓ mile per hour, against 2⅔ miles on the same canals with steam towage. On the Grand Junction Canal the speed varies from 3 to 3½ miles, and on the Rotterdam Canal it is 5 miles per hour. The limiting speed on the Suez Canal is about 5¾ miles per hour, but there is a loss of speed on that waterway, due to the trapezoidal form of section, which is estimated at about half a mile per hour. The average retardation of speed on English canals, due to locks, has been calculated at between 1·75 and 1·95 minute per mile. The greatest difficulty that lies in the way of extending canal navigation is the uneven character of the country that has usually to be traversed, and the consequent necessity of overcoming elevations and depressions by locks, lifts, inclines, or other costly mechanical devices. In crossing England, between the Thames and the Severn, a height of 358 feet has to be overcome on the 204 miles of the Wilts and Berks route; a height of 474 feet on the 180 miles of the Kennett and Avon route; and a height of 392 feet on the 206 miles of the Thames and Severn Canal route. The average difference of level on these routes, counting ascent and descent, is 4·14 feet per mile, or a little more than one-fourth of the ruling gradient laid down by Mr. Robert Stephenson for the London and Birmingham Railway. Canal lifts would overcome these differences better than locks, but then they are much more costly, and perhaps not, on the whole, so convenient. Tunnelling or cutting, as in the case of a railway, is in a large number of cases out of the question. There is, therefore, only the alternative of making locks, which involve tedious delays, and add largely to the cost of transport. In the year 1825, the same year that saw the opening of the first passenger railway, Charles Maclaren undertook to prove that for all velocities above 4 miles an hour, a railway was much more economical than a canal. At 6 miles an hour he calculated that nearly three times as much power would be required to move an equal mass on a canal, while at 20 miles an hour he computed that twenty-four times as much power would be required. At 8 miles per hour the same writer estimated that the resistance in water increased so much that two horses on a road would do as much as one on a canal, although at 2 miles an hour the same amount of horse power that is required to drag one ton on a good road would drag 30 tons on a canal. It is not a little amusing, in the light of our present experience, to find this author gravely stating that “the tenor of the evidence given before the Parliamentary Committee (on steam navigation) renders it extremely doubtful whether any vessel could be constructed that would bear an engine (with fuel) capable of impelling her at the rate of 12 miles an hour without the help of wind or tide;” while as for railway speed, he asserted that, “in speaking of 20 miles an hour it is not meant that this velocity will be found practicable at first, or even that it should be attempted.” Canal engineers have found that where they can concentrate the rise of level on a canal by the use of lifts, or inclined planes, they can usually obtain a considerable increase of speed. Thus, on the river Weaver, a height of 51 feet is cleared by the Anderton lift in about eight minutes. On the incline of the Morris Canal, again, a height of 51 feet is overcome in three and a half minutes; while on the Forth and Clyde Canal the Blackhill incline enables a height of 96 feet to be overcome in ten minutes. This averages about three times the speed that could be attained in overcoming the same rise or fall by means of locks. We have already seen it computed that there are in Great Britain one lock to every 1·37 mile of canal.[286] Mr. Conder has calculated that there is, at this rate, “an average rise or fall for the system, as far as it is represented by the time returned, of 5·84 feet per mile.” On the more uneven sections a running speed of 5 knots, or 5·76 statute miles per hour, will be reduced on an ordinary English canal by the delays caused by the locks, to a speed of 4·9 miles per hour. In other words, the rate of speed should be nearly double the speed of prompt canal service at the present time. Between Gloucester and Birmingham the merchandise sent by river and canal is delivered as quickly as that despatched by railway.[287] Speed on canals is regulated by the effect of breaking waves on their banks. In narrow canals or rivers, such a wave first appears at from 3 to 3½ miles per hour, and it has been found that at 4 miles per hour it exercises an injurious effect on the banks of the canal. When the speed is increased to 5 miles an hour, the effect becomes much more marked, the waves breaking over the towing-path, and rendering navigation destructive. Mr. Conder appeared to think that a speed of 5 miles an hour, or 8·37 feet per second, which is the limit of speed fixed for the Suez Canal, may be taken as the normal speed to be sought on the canals of England; and he adds that, “on the determination of the normal speed, and of the tonnage of the boats to be accommodated, will depend not only the steam-power required, but the sections of the canals and of the dimensions of the locks.”[288] In Sweden, as well as in Holland, where the channels are narrow, the usual speed is 3½ miles per hour, but 5 miles an hour is frequently attained, the difference depending on the area of cross-section. In curves and shallows, in narrow canals or rivers, a breaking wave first appears at from 3 to 3½ miles per hour. At 4 miles an hour the effect of the wave on the banks becomes injurious. At 5 miles an hour the wave increases, breaking over the towing-path, and being followed by other waves in succession. In parts of the Clyde, from 120 to 150 feet wide, and about 10 feet deep, vessels of from 120 to 150 feet long, with from 16 to 18 feet beam, and from 5 to 6 feet draught, are propelled by engines of from 80 to 100 horse-power, at a speed of from 8 to 9 miles per hour. At this speed a surge rises at from 2 to 3 miles ahead, and a wave is caused, which measures 8 or 9 feet from the crest to the bottom of the trough.[289] A speed of 5 knots per hour, or 8·37 feet per second, corresponding to a head of 1·08 foot of water, is the limit of speed fixed for the Suez Canal. This may perhaps be taken as the normal speed to be sought on the canals of England. On the determination of the normal speed, and of the tonnage of the boats to be accommodated, will depend, not only the steam-power required, but the section of the canals and the dimension of the locks. A speed of 30 miles a day, including stoppages, is even now attainable on English canals. The rate of speed on a canal is, of course, affected by the size as well as by the number of the locks, by the depth of the waterway, and by the tonnage of the craft that navigates it. On some English canals there is a lock to be passed through about every half mile, and the rate of speed is under a mile per hour.[290] On others, however, a speed of 3 miles may be kept up pretty well. The economical rate of speed is often put at 2½ miles. At a higher rate of speed the cost of maintenance of the canal would be likely to counterbalance the saving due to quicker transit. Speed is also affected by differences of gauge, which in some cases compels cargo to be transhipped with much loss of time that might be obviated with a uniform gauge. The size of craft which can traverse a through route depends on the least navigable depth in the canal and over the sills of the locks, and the least width and length of any lock along the route. Unfortunately, very few through canal routes exist in England which are not obstructed by some narrow locks, or shallow portions of canal, rendering the comparatively good width and depth of the remainder quite unavailable for a larger craft. In France, the same want of uniformity of gauge on the waterways has hitherto existed; but as almost all the waterways are under the control of the State, improvements and extensions have been constantly in hand; and we have already seen that in 1879 a law was passed for providing a uniform depth of 6½ feet, locks 126⅔ feet long and 17 feet wide, and a clear height of 12 feet under the bridges, throughout the principal lines of waterway in France. The works for securing this uniformity are being gradually carried out; and when they have been completed, 300-ton barges, 126⅓ feet long, 16½ feet wide, and 6 feet draught, will be able to traverse all the principal waterways of the country. The depth of English canals ranges, for the most part, from 3 feet to 5 feet; but the Severn navigation to Gloucester affords a depth of 6 feet; the Gloucester and Berkeley Canal, 15 feet; the Aire and Calder navigation, 9 feet; and the Forth and Clyde Canal, 10 feet. The locks range in size from 72 feet length, 7 feet width, and 3½ feet depth of water over the sills, up to 215 feet by 22 feet by 9 feet on the Aire and Calder navigation. It goes without saying that if the average rate of speed that can be maintained on a canal does not exceed 3 or 4 miles per hour, the canal will never compete with the railway as a quick means of transport. The use of such waterways would thereby be limited to heavy traffic, in the delivery of which time was a matter of minor importance. But more than two-thirds of all the traffic carried on British railways, and indeed on railways generally, is of this character. The question thereupon arises, Is the economy of water transport sufficient to compensate for a slower rate of speed? Sir James Allport, who, of course, held a brief for the railway interest, informed the Canal Committee of 1883 that the railway engine would accomplish ten times as much work as a canal boat, and would do in an hour what would occupy a day on a canal.[291] Mr. F. Morton, on the other hand, speaking as a railway and canal carrier of experience, declared that, in conveying minerals between North and South Staffordshire, railway waggons and canal boats averaged about the same time—seven to eight days.[292] However this may be, there can be no doubt that where canal transport is efficient it is much cheaper, and that is the main thing for the trader. Mr. Bartholomew has made an elaborate series of inquiries and experiments upon the Aire and Calder Canal, with a view to determine the cost of different systems of canal haulage, and has found the results to be as under:— With steam tugs, carrying cargoes, 1/34_d._ per ton per mile. ” ” ” not carrying cargoes, 1/7_d._ ” ” ” horse haulage, ⅕_d._ ” ” The lowest of these charges is not comparable with the lowest railway rate of which we have ever heard, while the highest is much below what railway managers usually state to be the cost of carrying their cheapest traffic. It will, however, be impossible either to greatly increase speed or to reduce rates on British canals unless the system undergoes reconstruction. The rates given above for the Aire and Calder Canal are no doubt exceptionally low, because that is one of the best managed and best equipped canals in the country. On the average of the English canals the cost of transport will be a good deal more, and it must continue to be so until they have been brought up to the level of efficiency maintained on the Aire and Calder. In the majority of the canals of England it is either impossible, or economically impracticable, to employ steam power, without which the ultimate extent of possible economy cannot be realised. Mr. F. Morton has correctly expressed the position of affairs when he stated that “the present method of employing steam on narrow canals is about comparable to a locomotive capable of taking thirty loaded waggons, having only four or five behind her.” This must remain so until steps have been taken to do in England what has been done in France and other countries—to secure a uniform gauge and a depth sufficiently great to enable boats to be navigated that carry loads of 100 to 200 tons, so that the canal boats may be the counterpart of a railway train. If the Aire and Calder system of working trains of boats, carrying 700 to 900 tons per train can be introduced, so much the better. FOOTNOTES: [285] Conder on “Speed on Canals,” ‘Minutes of Proceedings,’ vol. 76. [286] ‘Report of the Select Committee on Canals,’ p. 125. [287] ‘Minutes of Proceedings of the I. C. E.,’ vol. lxxvi. p. 171. [288] Ibid., p. 169. [289] ‘Minutes of Proceedings of the I. C. E.,’ vol. lxxvi. p. 168. [290] Ibid., p. 161. [291] Report, q. 1620-1622. [292] Ibid., 2, 2617.