Part 4

The Holt steam line to China was commenced in 1865, and was the only one _viâ_ the Cape of Good Hope which proved at once successful. Built and engined by the Scotts, the early Holt liners, starting from Liverpool, never stopped till they reached Mauritius, a distance of 8500 miles, being under steam the whole way, a feat until then considered impossible.[47] Thence the vessels proceeded to Penang, Singapore, Hong Kong, and Shanghai. Unaided by any Government grants, they performed this long voyage with great regularity.

The three vessels which inaugurated the very successful Holt line were named _Agamemnon_, _Ajax_, and _Achilles_, and were built of iron by the Scotts in 1865-6. They were each 309 ft. in length between perpendiculars, 38 ft. 6 in. beam, and 29 ft. 8 in. in depth, with a gross tonnage of 2347 tons--dimensions which were then deemed too great for the China trade, but which experience soon proved to be most satisfactory. Sails were fitted to the vessels, as shown in the engraving on the Plate facing page 40.

Alfred Holt was the first to apply the compound engine to long voyages, and his vessels were the earliest of the type built for the merchant service by the Scotts. It is true the Pacific Company had compound engines fitted to one or two ships prior to this, but these were only used in the coasting trade. The engines of these Holt liners are therefore of historical interest, and general drawings are reproduced on the next page and on Plate XII. A feature in these liners was that the propeller was abaft the rudder, which worked in an aperture in the deadwood corresponding to that for the propeller in single-screw modern ships.

A detailed description from the specification of the machinery may be reproduced, as it indicates the practice of the Scotts for a considerable time. Indeed, this type of compound engine, with slight modifications, was the standard engine for Holt liners until the advent of the triple-expansion engine. The details follow:--

The cylinders were: high-pressure, 30 in. in diameter; low-pressure, 62 in. in diameter, with 4 ft. 4 in. stroke, arranged vertically in tandem fashion, with the low-pressure cylinder on the top. There were two connecting-rods, but a common crosshead for the tandem cylinders, and a common crankpin.

The crankshaft was 13-1/2 in. in diameter, with a bearing 30 in. long at the aft end of the bedplate, which took the propeller thrust. The propeller was three-bladed, 17 ft. in diameter, with 26 ft. 6 in. pitch; with 46 revolutions per minute the piston speed was 400 ft. per minute. To ensure smooth working with the single crank, a heavy flywheel was fitted, and the pump levers carried a massive weight to help to balance the weight of pistons and rods.

The condenser had 420 tubes 1-1/2 in. in diameter, giving a cooling surface of 1375 square feet. The tubes were arranged in three nests, the water circulating through the top one first and the bottom one last. The circulating pump, instead of forcing water through the tubes, as was usual in such case, sucked from the condenser and discharged directly overboard. There were: one air pump, 24 in. in diameter; one circulating pump, 24 in. in diameter; two feed pumps, 4-3/4 in. in diameter; and one bilge pump 7 in. in diameter: all the pumps were single-acting, with 17 in. stroke. The diameters of the principal pipes were: main steam, 7-1/2 in.; to low-pressure cylinder, 12 in.; circulating inlet, 10 in.; discharge, 12 in.; air-pump discharge, 10 in.; main feed, 3-3/4 in.; and waste steam, two at 6 in. in diameter.

The two boilers were double-ended, of the locomotive type, with wet-bottomed furnaces. The centre was cylindrical, but the ends were rectangular with semi-cylindrical tops, the total weight, without water, being 78 tons. Each boiler had a long receiver passing through the uptake to dry the steam. On the receiver was a deadweight safety-valve 6-1/4 in. in diameter, to suit a working pressure of 60 lb. per square inch. The grate surface was 112 square feet, and the total heating surface 4506 square feet, there being 328 iron tubes 4 in. in diameter.

The three pioneer ships of the Holt line--the _Agamemnon_, _Ajax_, and _Achilles_--proved most economical. The _Achilles_ came home from China in fifty-seven days eighteen hours, net steaming time, or, including the stoppages at ports, sixty-one days three hours. She travelled during this period a distance of 12,352 miles, on a consumption of coal which did not exceed 20 tons per day for all purposes,[48] equal to 2-1/4 lb. per unit of power per hour, which for those early days, with comparatively low steam pressures, must be regarded as a highly satisfactory result.

The non-stop voyage between Liverpool and Mauritius was made as early as 1866 in thirty-seven days, equal to 10 knots, with a number of passengers and a fair cargo. The higher economy established for the compound engine on long voyages resulted in the ultimate supersession of the sailing ship.[49] Thus the Scotts, while still enjoying the credit of the splendid performance of the _Lord of the Isles_ in the early 'sixties, produced at their foundry the Holt compound engine, which sounded the death-knell of the clipper. The compound system had at once an influence on the size of ships. Up till 1862 no ship of over 4000 tons had been constructed, with the exception of the _Great Eastern_; by 1870 there were fifteen; by 1880, thirty-seven.[50]

The Scotts, aided by Holt, continued their research towards higher economy, and a large fleet of steamers was built, with engines having flywheels which, it was found by experience, considerably improved the economy up to a certain stage, although with increased pressure the proportion of saving was not commensurate with the weight of the wheel, and the three-cylinder three-crank engine was ultimately adopted.

The Scotts throughout the century continued to have a close association with the China trade, constructing a long series of successful steamers for the Holt company and for other lines, with services from Britain to the Far East, and carried out very extensive work in the building up of the coasting trade of Asia and Oceania. For the Holt line alone there have been constructed by the Scotts forty-eight steamers, aggregating 148,353 tons; while the propelling machinery of these represents 19,500 nominal horse-power. For the India and China services there have, in the past fifty years, been completed over one hundred and thirty steamers.

The China Navigation Company, Limited, was formed in 1873 by Messrs. John Swire and Sons, of London, for trading in China, and the first steamers built for them by the Scotts were two vessels of 1200 tons gross, completed in 1876.

Since then the Scotts' yard has practically never been without a vessel for one or other branch of the Eastern trade, and particularly for the China Navigation Company, which runs steamers from China as far south as Australia, as far west as the Straits, and as far north as Vladivostock and the Amur river. They also have ships trading up the Yangtsze Kiang to Ichang, 1000 miles from the sea, where the rapids prevent navigation farther into the interior. For this service the twin-screw steamer was adopted in 1878, much earlier than in many other trades, largely owing to the strong advocacy of the late John Scott, C.B. Up to that time most of the Yangtsze steamers were propelled by paddle-wheels driven by walking-beam engines. The first of the twin-screw steamers was built in 1878--a vessel of 3051 tons gross--and there has been constructed since then a long succession of very serviceable steamers. For this line alone, sixty-four vessels have been constructed by the Scotts, the aggregate tonnage being 115,600 tons, while the nominal horse-power of the propelling machinery fitted to these vessels is 15,000 horse-power.

But having in our brief historical sketch come to times within the recollection of the reader, it may be more satisfactory to depart from the purely chronological review of the company's operations, and to offer rather an analysis of the progress made, deferring a description of typical modern steamers for a separate Chapter.

The direct-acting vertical engine, with inverted cylinders, almost as we know it to-day, and as illustrated in connection with the work of the twentieth century, was introduced in the late 'fifties. The compound engine, introduced in 1854, was developed into the triple-expansion system in 1882, and later into the quadruple-expansion type; but this latter has not been much adopted, only some 3 per cent. of the vessels registered at Lloyds being so fitted. This is in a large measure due to the satisfactory economy attained with triple-expansion engines. As to the progress made, Table II., giving average results at different periods, is instructive.[51]

TABLE II.--PROGRESS IN THE ECONOMY OF THE MARINE ENGINE, 1872 TO 1901.

+-----+-----+------+------ |1872.|1881.|1890. | 1901. -------------------------------------------+-----+-----+------+------ Boiler pressure in pounds per square inch |52.4 |77.4 |158.5 | 197 Coal consumption in pounds per indicated | | | | horse-power per hour | 2.11| 1.83| 1.52 | 1.48 Consumption on prolonged sea voyages in | | | | pounds per indicated horse-power per hour |... | 2 | 1.75 | 1.55 Piston speed in feet per minute |376 |467 |529 | 654 -------------------------------------------+-----+-----+------+------

The advance of the century may be popularly expressed by stating that, whereas in the first coasting steamships built by the Scotts the fuel consumed in carrying 1 ton of cargo for 100 miles was 224 lb., the expenditure to-day is from 4 lb. to 5 lb. The economy of the steam engine has accounted, as is shown in the Table, for a considerable part of this improvement. But, at the same time, the growth in the size of ships has enabled the normal speed of 10 knots to be realised, with an addition to engine power of much less ratio than the increase in the capacity of the steamer. As to speed, recent progress has been most marked in the Navy, and it is therefore fitting that here we should direct our attention to Naval work.

FOOTNOTES:

[17] Woodcroft's "Steam Navigation," page 20, etc.

[18] Woodcroft's "Steam Navigation," page 54.

[19] Deas' "Treatise on the Improvements and Progress of Trade on the River Clyde" (1873), page 24.

[20] Muirhead's "Life of Watt," pages 428 and 429.

[21] Williamson's "Clyde Passenger Steamers," pages 348 to 351.

[22] James Napier's "Life of Robert Napier," page 21.

[23] This was the second of the name--a favourite one after the Duke of Wellington's great victory, and gave rise to the following poetic effusion:--

And now amid the reign of peace, Art's guiding stream we ply; That makes our wheels, like whirling reels, O'er yielding water fly. As our heroes drove their foes that strove Against the bonnets blue; On every side the waves divide Before the _Waterloo_.

--Millar's "Clyde from Source to Sea," page 179.

[24] Millar in "Lecture on Naval Architecture and Marine Engineering at Glasgow Exhibition, 1880-81," page 138.

[25] "Greenock Advertiser," August 6th, 1819.

[26] "Steamboat Companion" for 1820.

[27] Millar, "On the Rise and Progress of Steam Navigation." Lectures at the Glasgow Exhibition (1880-81), page 138.

[28] Hodder's "Life of Sir George Burns, Bart.," page 161.

[29] Williamson's "Clyde Passenger Steamers," page 32.

[30] Lindsay's "History of Merchant Shipping," vol. iii., pages 78 to 80.

[31] Weir's "History of Greenock," page 89.

[32] Williamson's "Memorials of James Watt" (1856) page 228.

[33] "Greenock Advertiser," July 5th, 1839.

[34] "Greenock Advertiser," February 5th and May 25th, 1835.

[35] Fincham's "History of Naval Architecture," page 294.

[36] Sir Thomas Sutherland, in the "Pocket Book of the P. and O. Company" (1890), page 15.

[37] Fincham's "History of Naval Architecture," page 235.

[38] Sir John Ross's "Steam Communication to India by the Cape of Good Hope" (1838), page 31.

[39] "Greenock Advertiser," January 22nd, 1839.

[40] Fincham's "History of Naval Architecture," pages 320 and 321.

[41] Lindsay's "Merchant Shipping," vol. iv., page 86.

[42] "Practical Mechanic's Journal," vol. i., 1853.

[43] The number of steam vessels belonging to the United Kingdom in 1849 was only 1142, of 158,729 tons; Sweden, which was second among the nations of the world, had only about one-tenth of this tonnage.--Porter's "Progress of the Nation," page 626.

[44] Holmes' "Marine Engineering," page 74.

[45] Rankine's "Steam Engine," page 502.

[46] "Transactions of the Institution of Naval Architects," vol. xxviii., page 141; and vol. xxx., page 278.

[47] Lindsay's "Merchant Shipping," vol. iv., page 434.

[48] "Proceedings of the Institution of Naval Architects," vol. xi., page 152.

[49] Lindsay's "Merchant Shipping," vol. iv., page 435.

[50] Pollock's "Modern Shipbuilding, and the Men Engaged in it," page 199.

[51] "Proceedings of the Institution of Mechanical Engineers" (1901), page 608.

A Century's Work for the Navy.

The work for the Navy by the Scotts began with the building, in 1803, of a sloop-of-war named _The Prince of Wales_; a photograph from the model of this vessel is reproduced on Plate XIV. Since the construction of this ship the firm have carried out several important Admiralty contracts, including the first machinery manufactured in Scotland for a dockyard-built ship, the first steam frigate built in the North, and several later ships, with their engines; the most recent order being for the machinery of the armoured cruiser _Defence_, of 14,600 tons displacement, and 27,000 indicated horse-power, to give a speed of 23 knots.

The progress demonstrated by a contrast between the small sloop-of-war and this latest powerfully-armed and well-protected high-speed cruiser, is a record of research and invention, not only on the part of the naval architect, but also of the chemist, the metallurgist, and the engineer; the triumph is greater than that reviewed in the case of the Merchant Marine. Great speed has been achieved, notwithstanding that the problems to be solved in its attainment have been intensified by the limitations in the size of the ship in order to minimise the target presented to the enemy's fire, and by the necessity of providing for heavy armour, armament, and ammunition in the displacement weight.

When a comparison is made of the Navy ships at the beginning of the nineteenth century with those of a hundred years earlier, it is found that little progress had been made, either in design or in gun-power. The largest vessel in 1700 was of 1809 tons burden, with a hundred guns. A century later, the size had increased only to 2600 tons, with a hundred and twenty guns.[52] But even this was an exceptionally large vessel. The British ships were, as a rule, smaller, and perhaps slower, than the French ships; but then--as now and always--skill in strategy, courage in combat, and devotion to duty were the most powerful factors in action. No fault in these respects could be found with the work of our Navy in the various engagements which terminated in the epoch-marking victory in Trafalgar Bay.

The peace following the Napoleonic wars was not conducive to advancement, as there was little incentive to pursue the sciences which contributed to the development of destructive weapons. Steam as a motive power and iron as a constructive material were not so readily adopted in the Navy ship as in the Merchant Marine. Progress in the utilisation of iron was not continuous. The first application of steam was belated, and its popularity was not unalloyed.

The Admiralty ordered their first ship of iron in 1839--a small, non-fighting boat for the Dover station--and there followed other vessels for the exploration of the River Niger. But the first iron fighting ship was not built until 1843. In 1848-9 the Scotts constructed the iron steam frigate _Greenock_, the largest iron warship of her day, and the first steam frigate built on the Clyde. The over-all length of this vessel was 213 ft., the beam 37 ft. 4 in., and the depth of hold 23 ft. She was of 1413 tons burden, and carried ten 32-pounder smooth-bore muzzle-loading guns. The illustration on Plate XV. is a reproduction from an old engraving of the launch of the vessel. It is a noteworthy feature that the figure-head was a bust of John Scott, the second of that name. This compliment by the Naval authorities of the time was well merited, as he did much not only for the advance of naval architecture, but also for the development of Greenock.

As a writer of the day put it, this vessel was the _experimentum crucis_ of the principle of constructing fighting ships of iron.[53] By 1850 there were six large iron vessels, ranging downwards from the 1980 tons of the eighteen-gun ship _Simoon_, with eleven smaller vessels; but they were all condemned, because it was found by experiment[54] that the 32-pounder gun at short range could perforate the side of the iron ship, and that the projectile carried its "cloud of langrage" with great velocity into the interior of the ship, so that men could not stand against it. Tests were also made with sixteen wrought-iron plates superposed, to give a total thickness of 6 in., but these also were perforated by the 32-pounder projectiles at 400 yards range; so that the adoption of iron on the main structure of the ship was practically delayed until armour-plates were first rolled in 1859.

The obstacle to the adoption of steam was the unsuitability of paddle-wheel machinery for fighting ships. The wheel was exposed to gun-fire, and the whole of the machinery could not be located below the water line. Moreover, the side wheel limited the number of guns which could be utilised for broadside fire. The first steam craft ordered by the Admiralty was a small vessel of 210 tons and 80 nominal horse-power, built in London in 1820.[55] Several other non-fighting steamships followed. By 1837, the largest steam vessel in the fleet was a sloop of 1111 tons and 320 horse-power.[56] In 1839 five steam vessels were built, and two of them--the _Hecate_ and _Hecla_--were engined by the Scotts. These wooden steamers were the first Naval vessels sent to Scotland to have their machinery fitted on board. They were of 817 tons and 250 horse-power. The paddle-wheels had a diameter of 25 ft. 1/2 in., and there were seventeen floats. The main engines, illustrated on page 29, represent the type adopted, not only in the Naval, but in the Merchant service of this time. The steam pressure was then about 3 lb. per square inch.

On Plate XVI. we illustrate the general arrangement of the machinery in the _Hecate_ and _Hecla_. There were four boilers of the rectangular type, each with two wet-bottomed furnaces at one end and large return flues at the other end. The uptakes passed up inside the boilers through the steam space, uniting in one funnel.

Smith's screw-propeller was tried experimentally in 1837, and Ericsson's about the same time. The comparative trials of the _Archimedes_ fitted with Smith's screw against existing paddle-steamers did much to prove the efficiency of the new system.[57] The screw-ship excelled the performance of paddle-steamers on the service, and the screw-propeller was adopted by the Admiralty in 1845; twin-screws followed twenty-five years later.

The _Greenock_, built in 1848, was the first war vessel by the Scotts fitted with the screw-propeller. We have already referred to her construction in iron, and to her launch. She had a displacement of 1835 tons, and her engines were of 719 indicated horse-power. The speed realised on the trial was 9.6 knots. The _Greenock's_ machinery, which is illustrated on the next page, is specially interesting, as it represents one of the earliest attempts to drive the screw-propeller by gearing. Two horizontal cylinders were fitted, each 71 in. in diameter, with a stroke of piston of 4 ft. The gearing consisted of four sets of massive spur-wheels and pinions, in the ratio of 2.35 to 1, so that 42 revolutions per minute of the engines give 98.7 revolutions to the propeller-shaft. The propeller was 14 ft. in diameter, and was so fitted that it could be detached and raised to the deck. There were four rectangular brass-tube boilers, each with four wet-bottomed furnaces, and all the internal uptakes united in one funnel, which was telescopic, so that when it was lowered and the propeller raised out of the water, the vessel had the appearance, as well as the facility, of a sailing frigate.

As will be seen from the drawings, both the engines and boilers were arranged very low in the hull, to be safe from the enemy's fire. The engine and boiler compartment occupied 72 ft. of the length of the ship--about one-third of the total length--and the seating for the machinery was specially constructed, with a very close pitch of frames which were only 1 ft. apart. For comparison with the drawings of the machinery in the _Greenock_, we give on page 49 a similar drawing of the machinery of the _Canopus_, of 12,956 tons displacement, seven times that of the _Greenock_. To double the speed, the power of machinery had to be multiplied twenty times, and yet the space occupied is only about trebled.

In 1850 the largest of the steam vessels in the Navy[58] had a displacement of 3090 tons, but the most noted was the _Dauntless_, of 2350 tons displacement, with engines of 1347 indicated horse-power to give a speed of 10 knots. It is true that there were three smaller vessels of greater speed, one of 196 tons steaming 11.9 knots; but this was the highest rate reached in the Navy service. By this time some of the fast mail steamers made 13-1/2 knots. These latter were suited for war service, but we have already dealt with them.

Following the adoption of the screw-propeller in warships came the abandonment of gearing for the engines. For many years various forms of horizontal engine were used; first with return-connecting rods, and subsequently with direct-acting rods. Steam pressures steadily increased, largely owing to stronger materials being available. It was, however, not until the 'seventies that the cylindrical boiler, the compound engine, and the surface condenser admitted of an increase to 60 lb. per square inch[59]--several years after these improvements had been introduced in the Merchant Marine.