Part 31

The compartment immediately behind the “steering chamber” contains the engines which are of the Brotherhood type, provided with _three_ single acting cylinders. The three-fold throw prevents any possibility of the engine getting on a “dead point.” Though this compartment is the shortest in the torpedo, the engines in the larger sizes are capable of indicating as much as thirty horse power. It has for simplicity been stated above that the pendulous weight and the balanced piston act by means of rods on the horizontal rudder; this was so in the early patterns of the torpedo, but it was soon found that they did not do so with sufficient steadiness and promptitude, and the force they could apply was in the larger and swifter forms quite ineffective. Nowadays the engine compartment always contains a little piece of apparatus which is an arrangement of cylinder and piston, upon which the compressed air acts in one or the other direction according to the way its slide-valve is moved. It is this slide-valve that the rods from the “steering chamber” move, and allow the force of the compressed air to turn the rudder up or down. This auxiliary apparatus has the same relation to the torpedo rudder that the steam-steering apparatus of a large vessel has to its rudder. Although it is only about a few inches long, its power and delicacy are such that the pressure of half an ounce on its slide admits to its piston a force equal to 160 lbs., and its introduction has given the torpedo the power of steadily steering itself.

Behind the engine compartment, but completely shut off from it, is another almost empty division occupying a considerable part of the length of the torpedo, and known as the “buoyancy chamber.” But it contains, attached to the bottom of it, a certain amount of ballasting, so adjusted to balance the weights of the other parts that the whole floats horizontally, and at the same time preserving the tube in one vertical position as regards its transverse diameter, _i.e._, so that the horizontal rudder is always horizontal. The shaft from the engine passes through this compartment, as also the rod from the small motor that moves the horizontal rudder. These, of course, pass through water-tight bearings.

At the tail of the torpedo, behind the rudders, are _two_ three-bladed screw propellers, of which the anterior one is mounted on a tubular shaft having a common axis with the other, but made to revolve in the opposite direction by means of a bevel wheel mounted on each independent shaft, with a third such wheel connecting them. The object of the double screw is to obviate “slip,” that is, ineffective motion of the blades through the water, and by this means the full power of the engines can be developed; while any tendency to _deviation_ to right or left, due to the rotation, is reduced to a minimum. We have spoken of one horizontal and one vertical rudder, although externally there appear to be two of each kind, right and left, above and below, on the tail of the torpedo. These pairs, however, are so connected as to be always in the same respective planes. The controlling mechanism acting in two different ways on the horizontal rudder has been already indicated, but nothing has yet been said about the vertical rudder. It is not moveable by anything within the torpedo, but is commonly fixed by clamping screws in or about the same vertical plane as the axis of the torpedo, and it performs the same function as a kind of back fin, which, in the earlier forms, extended nearly the whole length of the tube; and that is obviating any tendency of the torpedo to roll about its axis. The vertical rudder can also be fixed at a considerable inclination to the axis should occasion require, and the effect of that would be to cause the torpedo to pursue a circular course of greater or less radius, according to the less or greater degree of inclination. Very rarely, however, would this be required, and the vertical rudder may be considered as fixed in the axial plane, or having such slight inclination as may, on trial, have been found necessary to counteract any tendency to lateral deviation.

There are several different methods for discharging the Whitehead torpedoes from ships. They may be sent from a tube below the water-line, but the arrangements for that purpose are complicated and difficult to manage, while, on the other hand, the launch of the weapon is not perceived by the enemy, and it is at the same time out of the reach of any blow from a hostile missile while yet in its discharging tube. More commonly the discharging tube is arranged above the water-level. On regular torpedo boats, the tubes are sometimes mounted on pairs upon a revolving table, provided with many nice adjustments, and even the single above-water torpedo tube, as used between decks, is an apparatus having somewhat complicated appliances. The torpedo is expelled from the tube now preferably by a small charge of _cordite_. But in the Royal Navy no fewer than some twenty different patterns of torpedo tubes have been in use for the various sizes of torpedoes. In some of these, compressed air, in others gunpowder or _cordite_, in others, again, mechanical impulse propels the torpedo into its element. It would obviously be impossible within our limits to enter into details of these various constructions, or to attempt descriptions of _all_ the ingenious contrivances applied to the torpedo itself, or to give an account of the means of defence against mines and torpedoes, this last being a matter belonging to naval tactics. The adoption of the torpedo as a naval weapon has given rise to special types of boats adapted for its employment, and these again have required other boats to destroy them (“torpedo-boat destroyers” or “catchers”). Light draught and high speed were desired in these last; but in many cases the intended speed was inferior to that of the torpedo boats that were to be caught.

The following particulars about the British torpedo-boat destroyer _Daring_ may be compared with those given of the cruiser _Majestic_. The _Daring_ is 185 feet long, 7 broad, and she draws only 7 feet of water. Her speed is about 28½ knots per hour, with a steam pressure in the boilers of 200 lbs. per square inch, and an air pressure in the stoke-holds equivalent to 3 inches of water (forced draught.)

The importance attached to the prospective use in war of the automobile torpedo may be shown by the fact that at the end of 1890 the number of torpedo boats built or laid down for England was 206, and for France 210, while other nations followed with numbers proportionate to their means. Forty “torpedo-boat destroyers” were in building for the British Navy towards the close of the year 1896, and now (March, 1897) it is announced that the number of torpedo boats and torpedo-boat destroyers in the French Navy is to be increased by 175.

SHIP CANALS.

Artificial canals are amongst the oldest of inventions, for, centuries ago, they have been constructed, even of very large dimensions, in various parts of the world. There is in China, for instance, a great canal, 900 miles in length and 200 feet broad, which is supposed to have been made 800 years ago. The advantages of canals did not escape the attention of the Egyptians, Greeks and Romans. We read of very early attempts to cut through isthmuses, in order to form a water communication between regions where other carriage would be long and difficult. It appears to be admitted that canals connecting the Red Sea with the Mediterranean existed some centuries before the Christian era, and to cut the Isthmus of Corinth by a waterway was a cherished project with several Roman Emperors, and now it appears that in this nineteenth century this project will shortly be realized. But as the canal-lock is but a comparatively modern invention, dating only from the fourteenth century, and first used in Holland, all the canals anterior to that period had to be designed as level cuts, a restriction which greatly increased the difficulties of the problem. Canals were in use in various parts of Europe, particularly in Holland and France, long before any were constructed in England, as, for example, the Languedoc Canal, which, by a cut of 150 miles, connects the Bay of Biscay with the Mediterranean. It is 60 feet broad, and attains, at its highest level, an elevation of 600 feet above the sea. The canal system in England was first introduced in the middle of the eighteenth century, and soon afterwards, the Duke of Bridgewater engaged the famous Brindley to construct a canal, connecting his collieries at Worsley with Manchester, about seven miles distant, and afterwards extended his scheme, so as to open up a more direct water communication between Manchester and Liverpool. Before the making of this canal, the cost of the carriage of goods between these towns had been forty shillings per ton by land, and twelve shillings by water. After that, they were conveyed with regularity for six shillings per ton. The system was soon extended, so as to connect the Trent with the Mersey, and the boldness of both the projectors and their engineer in carrying out this scheme is memorable in the history of such undertakings. Brindley was equal to the task of coping with the difficulty of carrying his canal over what had hitherto been supposed an insuperable obstacle, for he pierced Harecastle Hill with a tunnel more than a mile and a half in length—a then unheard of piece of engineering—to say nothing of several shorter tunnels, many aqueducts, and scores of locks. The Duke of Bridgewater, who at one period had been unable to raise £500 on his own bond for the prosecution of his scheme, died in 1803, in receipt of a princely income from the profits of his useful undertaking. For its creation, he had, however, denied himself the present enjoyments of his patrimonial revenue, by reducing his expenses at one period to the modest sum of £400 per annum. Before his death, the Duke, for taxation purposes, estimated his income at £110,000 per annum. Before the railway system was fully established a network of canals had united the most populous places in England, the total length of the waterways being not much less than two thousand miles. With the rise of railways the importance of canals as channels for the conveyance of merchandise declined. But, nevertheless, in consequence of the continued increase of traffic and the great cheapness with which goods can be carried by water, canals are often able to compete with railways in the carriage of bulky or heavy goods when speed of transit is not an object. The English canals have, therefore, never been disused or abandoned, notwithstanding the ubiquitous ramifications of the railway lines. Nay, the value of the Bridgewater Canal system, about to be superseded so far as concerns the communication between Liverpool and Manchester by the greater scheme we have presently to describe, is such that £1,710,000 is now required for its purchase; and that is the value in spite of four lines of railway connecting those great towns, and all competing for the carriage of goods. In these canals, designed for inland communication only, the navigation is confined to boats or barges of very insignificant dimensions compared with the sea-going ships that some great modern canals are constructed to receive.

To the present century belongs the famous “Caledonian Canal,” as the waterway is often called that extends in a straight line for more than 60 miles across Scotland, in north-east and south-west directions. The canal work here was commenced in 1802, under the direction of Telford, and though it was opened for traffic in 1822, the work as it now exists was not completed until 1847. But the length of the actual canal construction in this case did not much exceed 23 miles, for a natural waterway, navigable for ships of any burden, is formed by the series of narrow lakes that fill what is called the “Great Glen of the Highlands.” This glen has many of the characteristics of a great artificial ditch: its highest point is only 90 feet above the tide level in Loch Linnhe; a circumstance not a little remarkable in so mountainous a country. What is also remarkable is the great depth of these lakes, which in some places exceeds 900 feet. The banks also are generally very steep, and indeed at one time it was impracticable to pass along the shores of Loch Ness, the longest of the lakes. But there are now good roads along both banks. Although the ground traversed by the artificial channels of the Caledonian Canal is chiefly alluvial, the cost of the undertaking proved to be great, amounting, it is said, to about one and a quarter million pounds sterling. Indeed, had it not been for the introduction of steam navigation before the completion of the work, and the consequent increase and facility of water conveyance, it is doubtful whether the utility of this canal would have been commensurate with its cost, or its receipts have made any profit for its promoters. By the Caledonian Canal large steamers and other vessels may pass from sea to sea, and in the summer time the steamers that traverse it are crowded with tourists attracted by the magnificent scenery it presents throughout the greater part of its length.

But whatever had previously been done in canal construction was surpassed in enterprise and importance by Lesseps’ great work in Egypt.

_THE SUEZ CANAL._

As we have already seen, the idea of opening a waterway between the Red Sea and the Mediterranean is by no means a product of the present century. The ancient Egyptians do not appear to have cut directly through the Isthmus, but Herodotus describes a canal made by Necho about the year 600 B.C., from Suez through the Bitter Lakes to Lake Timsah and then westward to Bubastis on the Nile. He mentions certain water gates, and states that vessels took four days in sailing through. This canal became silted up with sand ages ago, but it was cleared out again and re-opened in the seventh century of our era by the Caliph Omar, and traces of it are still visible. According to some recent discoveries in the chief archives of Venice, as early as the end of the fifteenth century, when Vasco da Gama had discovered the Cape of Good Hope, and the Portuguese took that new route to India, hitherto the exclusive property of the Venetian and Genoese merchants, a re-cutting of the Isthmus of Suez was thought of. Plans were prepared and embassies sent to Egypt for paving the way for the accomplishment of this great enterprise, which, it is said, was only foiled by the persistent opposition of some patricians, who were probably bribed by foreign gold to prevent the execution of the plan. One of our Elizabethan poets, Christopher Marlowe, appears, in the following lines, to have anticipated M. de Lesseps:—

“Thence marched I into Egypt and Arabia, And here, not far from Alexandria, Whereat the Terrene and the Red Sea meet, Being distant less than full a hundred leagues. I meant to cut a channel to them both, That men might quickly sail to India.”

For at that period travellers going to India in the famous sailing ships, called “East Indiamen,” were obliged to sail round the Cape of Good Hope and pass from the Southern to the Indian Ocean. The reader who wishes to understand the importance of the Suez Canal should look at the map of the Eastern Hemisphere, where he will have no difficulty in finding the position of the vast continent of Africa, which is washed on the north by the Mediterranean Sea, on the west by the Atlantic, on the south by the Southern Ocean, and on the east and north-east by the Indian Ocean and the Red Sea. If he now traces the waterway round Africa, on coming to the head of the Red Sea he will find the only interruption of the oceanic continuity in the narrow neck of land called the Isthmus of Suez. But for this, ships might long ago have made complete circuits round this vast, and, even as yet, but partially explored continent. The circuit would, indeed, be a great one of some 15,000 miles; but the barrier that the Isthmus presented to inter-oceanic communication between the eastern and the western worlds was a piece of physical geography which has undoubtedly been a most important factor in determining the course of history. It has been said that had there existed at Suez a strait like that of Gibraltar or that of Messina, instead of a sandy isthmus, the achievements of Diaz, Vasco da Gama, and Columbus would have lost much of their significance; but the advantages to the world’s commerce would have been incalculable, and the progress of the race might have been more rapid.

The Emperor Napoleon I. had the idea of restoring the old canal; but it was only when steam navigation had taken its place on the seas that the scheme was looked upon as offering any chance of financial success. But General Chesney, who made some surveys for the French Government in 1830, had come to the conclusion that there was a considerable difference of level between the two seas—a difference, he calculated, of about 30 feet. The existence of such a state of things would, of course, have been very unfavourable for the undertaking; but the General’s supposition was soon proved to have been erroneous.

The suggestion of carrying out the project of constructing a ship canal through the Isthmus was seriously revived by Père Enfantin, the St. Simonian, in the year 1833. He then induced M. Ferdinand Lesseps, the French vice-consul, and Mehemet Ali, the Pasha of Egypt, to take some practical measures towards its accomplishment. Surveys were made, but owing to the breaking out of a plague, and to other causes, not much more was heard of the scheme till 1845. In 1846 _La Société d’Etude du Canal de Suez_ was formed, and among those who turned their attention to the subject was Robert Stephenson. His report was wholly unfavourable to the enterprise. He recommended the construction of a railway through Egypt, and a line was accordingly made between Alexandria and Suez. But, notwithstanding the opinion of Mr. Stephenson, M. Lesseps persevered with wonderful energy, believing, on the report of other engineers, that the scheme could be successfully carried out. It is right, however, to state that Mr. Stephenson did not say it was impossible to complete the Suez Canal—he merely gave it as his opinion that the cost of making the canal, and keeping it in a proper state for navigation, would be so great that the scheme would not pay. However, in 1854, the Viceroy of Egypt signed the concession, and in 1860 the work was actually commenced, but not on a plan that was advocated by the English engineers of making the canal 25 feet above the sea level. There were also some political and financial difficulties to be overcome. The Suez Canal Company, it was said, had expended twelve millions of money in what was considered to be chiefly shifting sands.

When the Suez Canal was projected, many prophesied evil to the undertaking, from the sand of the Desert being drifted by the wind into the canal, and others were apprehensive that where the canal was cut through the sand, the bottom would be pushed up by the pressure of the banks. They imagined that the sand would behave exactly like the ooze of a soft peat-bog, through which, when a trench has been cut, the bottom of the trench soon rises, for the soft matter has virtually the properties of a liquid: it acts, in fact, exactly like very thick treacle. Sand, however, is not possessed of liquid properties; it has a definite angle of repose, which is not the case with thin bog. This behaviour of sand is familiarly illustrated in the sand-glass, which the diagram Fig. 123, will recall to mind. It may be observed that the sand falling in a slender stream from the upper compartment is in the lower one heaped up in a little mound, the sides of which preserve a nearly constant inclination of about 30°. In this property it is distinctly different from peat-bog or such-like material, which has no definite angle of repose. It need hardly be said that all apprehensions as to the safety of the canal from the causes here alluded to have proved unfounded.

But if some English engineers appeared to oppose the project, another eminent one, Mr. Hawkshaw, certainly helped it on at a moment when the Viceroy of Egypt was losing confidence; and, had his opinion been adverse to the project reported upon, the Viceroy would certainly not have taken upon himself additional liability in connection with the undertaking, and the money expended up to that date would have been represented only by some huge mounds of sand and many shiploads of artificial stone, thrown into the bottom of the sea to make the harbour of Port Saïd. And that M. Lesseps appreciated the good offices of Mr. Hawkshaw is shown from the fact that, when he introduced that engineer to various distinguished persons, on the occasion of the opening of the canal, he said, “This is the gentleman to whom I owe the canal.” It cannot, therefore, be said of the English nation that they were jealous of the peaceful work of their French neighbours, or opposed it in any other sense but as a “non-paying” and apparently unprofitable scheme.

The Canal was opened in great state by Napoleon III.’s Empress Eugénie, in November, 1869, when a fleet of fifty vessels passed through, and the fact was thus officially announced in Paris:—“The canal has been traversed from end to end without hindrance, and the Imperial yacht, _Aigle_, after a splendid passage, now lies at her moorings in the Red Sea.

“Thus are realized the hopes which were entertained of this great undertaking—the joining of the two seas.

“The Government of the Emperor cannot but look with satisfaction upon the success of an enterprise which it has never ceased to encourage. A work like this, successfully accomplished in the face of so many obstacles, does honour to the energetic initiative of the French mind, and is a testimony to the progress of modern science.”

An Imperial decree was then issued, dated the 19th of November, appointing M. de Lesseps to the rank of Grand Cross of the Legion of Honour, in consideration of his services in piercing the Isthmus of Suez.

The Suez Canal is 88 geographical, or about 100 statute miles long: its average width is 25 yards, and the minimum depth, 26 feet. At intervals of five or six miles, the canal is widened, for a short space, to 50 yards, forming thus sidings (_gares_) where only vessels can pass each other. At these, therefore, a ship has often to wait until a file of perhaps twenty steamers, coming the other way, has passed. Occasionally a ship gets across, or “touches,” and then the canal is blocked for hours. So much inconvenience has been found from the restricted dimensions of the work, that in 1886 it was proposed to widen the canal, or, alternatively, to construct a second canal, and use the two like the lines of a railway, so that vessels would never have occasion to pass each other. The amount of traffic is very large, and has been steadily increasing. Thus, in 1874, the tonnage of the vessels passing through was 5,794,400 tons; in 1880, the tonnage was 8,183,313, and the receipts of the Company amounted to £2,309,218. In 1875, the British Government purchased, from the Khedive, £4,000,000 worth of shares.