In 1825 a premium was offered by the Admiralty for the best plan of propelling vessels without paddlewheels; and a plan proposed by Commander S. Brown, R.N., was deemed sufficiently promising for trial: a two-bladed screw propeller placed at the bow of a vessel and actuated by a 12-horsepower engine. But though exhibiting advantages this form of the invention did not survive.

The history of the screw-propeller may be said to date from 1836. In that year two capable inventors obtained patents: Mr. Francis Pettit Smith and Captain Ericsson. So little attention had, up to that time, been given to the subject that the two proposals “were presented to the public in the character of novelties, and as such they were regarded by the few who had curiosity enough to look at them.” Smith’s patents were for the application of the screw to propel steam vessels by fixing it in a recess or open space formed in the deadwood; and, says Fincham, “the striking and peculiar merit of Mr. Smith’s plan appears to consist, chiefly, in his having chosen the right position for it to work in.” Trials were carried out with Smith’s propeller in a 6-ton boat on the City and Paddington canal, and then between Blackwall and Folkestone, with encouraging success; the boat, encountering heavy weather off the Foreland, demonstrated the advantage derived from the absence of paddlewheels, and showed the new form of propelling machinery to place no limitations on her qualities as a sailing vessel. She returned to Blackwall, having run over 400 miles at a mean speed of 8 knots.

Captain Ericsson, a Swedish army officer who had come to London and established himself as a civil engineer, had a contemporary success with a boat fitted with two large-bladed propellers each 5 feet 3 inches in diameter. So successful was he, indeed, that he invited the Board of Admiralty to take a trip in tow of his novel craft; a trip which had important and unexpected results on the subsequent progress of steam navigation. One summer day in ’37 the Admiralty barge, in which were the Surveyor and three other members of the Board, was towed by Ericsson’s screw steamer from Somerset House to Limehouse and back at a speed of 10 knots. The demonstration was a complete success, and the inventor anticipated some further patronage of his invention. But to his chagrin nothing was asked of him, and to his amazement he was subsequently informed that the proposal to propel warships by means of a screw had been pronounced impracticable. Never, perhaps, in the whole history of mechanical progress has so signally wrong a decision been made, never has expert opinion been so mistaken. Engineers and shipbuilders all failed to realize the possibilities of the screw. The naval authorities who, in the face of their personal experience, dismissed the project as impracticable (owing to some anticipated difficulties in steering ships fitted with screws) merely expressed the unanimous opinion of the time. “The engineering corps of the empire were arrayed in opposition to it, alleging that it was constructed on erroneous principles, and full of practical defects, and regarding its failure as too certain to authorize any speculations even of its success. The plan was specially submitted to many distinguished engineers, and was publicly discussed in the scientific journals; and there was no one but the inventor who refused to acquiesce in the truth of the numerous demonstrations, proving the vast loss of mechanical power which must attend this proposed substitute for the old-fashioned paddlewheel.”154 Yet in five years’ time steamers designed for paddlewheels were being converted to carry screws, and a great screw-propelled liner, the Great Britain, had been launched for the Atlantic traffic!

It was in America, we have seen, that progress in steam navigation was of the greatest interest to the public, and it was by Americans that the disabilities of the paddlewheel were most keenly appreciated. Two witnesses of the trial of Ericsson’s boat saw and admitted the advantages of the new method: Mr. Ogden, an engineer who had been U.S. consul at Liverpool for some years, and Captain Stockton, U.S.N. The latter appreciated the military advantages of screw propulsion and was soon its enthusiastic advocate. Under his influence and encouragement Ericsson threw up his engagements in London and went to America. “We’ll make your name ring on the Delaware,” said Captain Stockton to him at a dinner in his honour given at Greenwich. The prediction was fulfilled. In the course of time Ericsson saw his propeller applied on a large scale, not only to mercantile craft but in the American navy. Early in ’37 Captain Stockton had ordered an iron vessel to be built by Messrs. Laird, of Birkenhead, and fitted with a screw. In the following year she was launched, and in the spring of ’40, after giving demonstration on the Thames of the great towing power of her propeller, she left for America for service as a tug on the big rivers. On this work one of the great advantages of the screw was realized: the immunity with which the screw vessel could work in drift ice, when paddlewheel steamers were perforce laid up.

In the meantime, fortunately, Pettit Smith’s successes had not been without their effect on opinion in this country. A company was formed to exploit the screw, and a vessel, the Archimedes, was built amid a strange chorus of detraction, opposition and ridicule. She made her trials in October, ’39. Her propeller was at first in the form of a complete convolution of a helical screw of 8-foot pitch and of 5 foot 9 inches diameter; but subsequently this blade was replaced by two, each of which formed half a convolution, with the two halves set at right angles to one another. Comparative trials were ordered by the Admiralty in the following year to test the merits of the Archimedes’ screw as compared with the ordinary paddlewheels applied to her Majesty’s mail packets on the Dover station. The results were inconclusive.155 But a subsequent voyage round the coasts of Great Britain, during which the machinery of the Archimedes was laid open to the inspection of the general public, and a later voyage from Plymouth to Oporto which recreated a new record for a steam passage, went far to establish in public estimation the merits of the new propeller. But generally the invention was discouraged. Prejudice and vested interests, rather than a reasoned conservation, seem to have operated to oppose its progress. “A striking instance of prevailing disinclination to the screw propeller was shown on the issue of a new edition of the Encyclopædia Britannica, in which the article on steam navigation contained no notice whatever of the subject.”

But in spite of all prepossessions against it the screw had won a decisive victory over its rival. So striking were the results recorded by the Archimedes, that a decision was made in December, 1840, to change the Great Britain, an Atlantic liner then under construction, from paddlewheel to screw propulsion. In two ways she was a gigantic experiment: she was the first large ship to be built of iron, and it was now proposed to fit her with a screw. Mr. Brunel took all the responsibility for advising the adoption of both these revolutionary features; the result was a splendid testimony to his scientific judgment, boldness of enterprise, and “confident reliance on deductions from facts ascertained on a small scale.”

Before the completion of the Great Britain the Admiralty had initiated experiments which were to furnish important information as to the power and efficiency of the screw propeller in its various forms, and to settle beyond cavil the question of its superiority over the paddlewheel for the propulsion of warships. The sloop Rattler, 888 tons and 200 horsepower, was fitted with screw machinery. Several forms of screw were tried during the winter of 1843–4. First the screw as used in the Archimedes was fitted: a screw of 9-foot diameter, 11-foot pitch, and of 5½ feet length, consisting of two half-convolutions of a blade upon its axis. Then a screw was tried of the same diameter and pitch but of only 4-foot length; and then the length was again reduced to 3 feet. The effect of cutting down the length was to give an increase of efficiency.156 The screw was again shortened by 2 feet, and finally to 1 foot 3 inches; with each reduction in length the slip diminished and the propulsive efficiency increased. Various other forms of screws were tried, and it was shown that Pettit Smith’s short two-bladed propeller was on the whole the most efficient.

The best form of screw having been determined, it still remained to compare the screw propeller with the paddlewheel. Accordingly the Alecto, a paddlewheel sloop of similar lines to the Rattler, was selected as the protagonist of the older form of propulsion, while the Rattler herself represented the screw. Naval opinion was still completely divided on the great question, while in the competing sloops the utmost emulation existed, each captain advocating his own type of propeller. The speed trials took place, and showed the Rattler to have an undoubted advantage. The paddlewheel, however, laid claim to a superiority in towing power. So a further competition was ordered, as realistic as any, perhaps, in the history of applied science: nothing less than a tug-of-war between Paddle and Screw, those two contending forms of steam propulsion! Lashed stern to stern and both steaming ahead full power, one evening in the spring of ’45 the two steamers struggled for mastery. And as Rattler slowly but surely pulled over Alecto, the question which had been for years so hotly debated was settled; the superiority of the screw was demonstrated. With the adoption of the screw the problem of disposing the armament was settled. The broadsides and the spaces between decks were once more free to the guns along the entire length; moreover the action of the screw was in complete harmony with that of the sails. With the screw as an auxiliary to sail power, and subsequently with the screw as sole means of propulsion, a change came over the character of the pivot armament. Whereas with the paddlewheel the pivot gun was the chief means of offence, when the screw was introduced the broadside was restored, and though the heavy pivot guns were retained (steam and the pivot gun had become associated ideas), yet by their comparatively limited numbers they became a subordinate element in the total armament.

External affairs now lent a spur to screw propulsion. In ’44 the French navy came under the reforming power of the ambitious Prince de Joinville, and from this year onwards the attitude of France to this country became increasingly hostile and menacing. The thoughts of the French were turned toward their navy. No sooner had de Joinville been placed in command than schemes of invasion were bruited in this country; and the public viewed with some alarm the altered problems of defence imposed on our fleets by the presence in the enemy’s ports of a steam-propelled navy. Sanguine French patriots sought to profit by the advent of the new power. A pamphlet appeared in Paris claiming to prove that the establishment of steam navigation afforded France the very means by which she could regain her former level of naval strength. The writer, using the same arguments as Colonel Paixhans had used in ’22, reviewed the effect of steam power on the rival navies, and pointed to the Duke of Wellington’s warnings in parliament of the defencelessness of the English coasts and to his statement that if Napoleon had possessed steam power he would have achieved invasion. These cries of alarm, said the writer, should trace for France her line of policy. She should emulate the wise development of steam propulsion as practised by Great Britain. “We think, England acts; we discuss theories, she pursues application. She creates with activity a redoubtable steam force and reduces the number of her sailing ships, whose impotence she recognizes.... Sailing vessels have lost their main power; the employment of steamers has reduced them to the subaltern position of the siege artillery in a land army.” The writer praised English policy in the matter of steam development: its wise caution, its reasoned continuity. There had admittedly been some costly deceptions. Nevertheless the method was to be commended, and France should proceed in a similar manner: by a succession of sample units while steam was still in the experimental stage, by far-sighted single strides, and then by bold and rapid construction of a steam navy which would compete on more even terms with that of her hereditary rival.157

Faced with the probability that our rivals would pursue some such progressive and challenging policy as outlined by the pamphleteer, the Admiralty acted rapidly. Before the Rattler trials were complete a decision was made favourable to the screw propeller, and an order was made for its wide application to warships built and building. It was resolved, on the advice of Sir Charles Napier, that the screw should be regarded solely as an auxiliary to, and in no way as in competition with, sail power. The Arrogant was laid down, the first frigate built for auxiliary steam power; and screws driven by engines of small horse-power were subsequently fitted to other ships with varying degrees of success.

Two important features were specified for all: the machinery was required to be wholly below the water-line, and the screw had to be unshippable. Engines were now required for Block Ships and for sea-going vessels. So the principal engineers of the country were called together and were asked to produce engines in accordance with the bare requirements given them. A variety of designs resulted. From the experience obtained with this machinery two important conclusions were quickly drawn: firstly, that gearing might be altogether dispensed with; secondly, that no complex contrivance was necessary for altering the pitch to enable engines to work advantageously under varying conditions, the efficiency of the screw varying very little whether part of the ship’s velocity were due to sail power or whether it were wholly due to the screw.158

And here it may not be amiss to note, in relation to a nation’s fighting power, the significant position assumed by naval material. In land warfare a rude measure of force could always be obtained by a mere counting of heads. At sea man was in future to act, almost entirely, through the medium of the machine.

However we may have deserved the eulogy of the French writer in respect of developing the paddlewheel war steamer, the development of screw propulsion in the next decade was marked by a succession of failures and a large outlay of money on useless conversions and on new construction of poor fighting value, most of which could have been avoided. Had our methods been less tentative and more truly scientific the gain would have been undoubtedly very great; we should have laid our plans on a firmer basis and arrived at our end, full screw power, by a far less circuitous route than that actually taken. In this respect France had the advantage of us.

Although a decision had been made to maintain the full sail power of our ships and install screw machinery only as an auxiliary motive power, attempts were naturally made to augment so far as possible the power exerted by the screw; and within a short time new ships were being fitted with machinery of high power, in an endeavour to make the screw a primary means of propulsion. The results were disappointing. As the power increased difficulties thickened. The weight of the machinery grew to be excessive, the economy of the comparatively fast-running and short-stroke engines proved to be low, and the propulsive efficiency of the screws themselves grew unaccountably smaller and smaller. So poor were the results obtained, indeed, that in the case of a certain ship it was demonstrated that, by taking out the high-power machinery and substituting smaller engines an actual gain in speed was obtained, with the reduced displacement. The first screw ship in which an attempt was made to obtain full power with the screw was the Dauntless, of 1846. Although a frigate of beautiful lines she was considered a comparative failure. It was agreed that, equipped with paddlewheels and armed with guns of larger calibre, she would have constituted a faster and more powerful warship than, with her 580-horse-power engines, her 10 knots of speed, and her 32-pounder guns, she actually was.

Part of the trouble was due to the unsuitability of our ships’ lines for screw propulsion. It has already been noted that, owing to the carriage of heavy weights at their extremities, war vessels were always given very full bows and sterns. In the case of the Rattler, whose records served as a criterion for later designs of screw ships, the lines of the stern were unusually fine: partly, no doubt, in imitation of the Archimedes. Also, since it had been necessary to allow space enough for a long screw to be carried (a screw of a complete convolution was thought possible) the Rattler’s short screw as finally adopted worked at some distance aft of the deadwood, and thus suffered no retarding influence from it when under way. But in the case of later ships these advantages did not obtain. They were built with the usual “square tuck,” a bluff form of stern which prevented a free flow of water into the space ahead of the propeller and thus detracted from its efficiency. It was not appreciated at this time that, for efficient action, the screw propeller demands to be supplied with a body of unbroken, non-eddying water for it to act upon, which with the square-cut stern is not obtained. At low speeds, and in the ship to which the screw was fitted as an auxiliary, the effect of the square tuck was not marked. But as power and speed increased its effect became more and more evident; the increase in power gave no proportionate increase in speed; and many, ignorant of the cause, surmised that there was a limit to the power which could be transmitted by a screw and that this limit had already been reached. The inefficiency of the square tuck was exposed by trials carried out in H.M.S. Dwarf at Chatham. As a result of these, future new and converted ships were given as fine a stern as possible.

For several years, however, the policy of the Admiralty remained the same: the screw was regarded solely as an auxiliary. The French, on the other hand, took a less compromising line of action. After waiting for some time and watching our long series of experiments, they convened in 1849 a grand Enquête Parliamentaire: a commission which, primed with the latest information as to British naval material, was to decide on what basis of size, number, armament and means of propulsion future French warships should be built. For two years the commission sat sifting evidence. And then it recommended screw propulsion of the highest power for all new ships, as well as the conversion of some existing classes to auxiliary screw power. England had fitted her ships with screws capable of giving them small speed; France must fit hers with screws of greater power. Speed, said the commission, is an element of power. Superior speed is the only means by which the English can be fought with a good chance of success. Sails must be secondary, therefore, and full reliance must be placed on the screw. The recommendations of the commission were duly realized. In the following years a powerful force of fast screw battleships, frigates, transports, and despatch boats was constructed which by ’58 had brought the aggregate of the horse-power of the French fleet almost to a level with that of England.

When the Crimean War brought the two navies together as allies in ’54 the full effect of the new policy of the French had not yet been made apparent. Some apprehension existed in this country as to the adequacy and efficiency of our navy, when compared directly with that of France. But from then onwards this country became aware of the increasing hostility of the French public and government; speeches were made, and letters appeared in the press of both countries, which tended to fan the flames of fear and suspicion.159 It was not till ’58, however, that general attention was drawn to the great strides which the French navy had made in recent years, and to the skilful way in which its position, relative to that of its great rival, had been improved. An article entitled “The Navies of England and France” appeared in the Conversations Lexicon of Leipsic, and caused a great sensation. Reprinted in book form, with a long analysis and with a mass of information about the French, English and other navies and arsenals,160 this notorious article brought apprehension to a head. Though written by no friendly critic, it was in most respects an accurate presentment of the respective navies and of their condition. The analysis of Hans Busk, while ostensibly exposing its bias and its inaccuracies, in effect confirmed the main contentions of the German article; in addition his book gave in spectacular columns a summary of the units of the rival navies, which gave food for thought. The article itself professed to show how much France had benefited by the bold and scientific manner in which she had handled the problem of naval construction since the coming of steam. Other factors were discussed, the forms of ships, the Paixhans system of armament, problems of manning and of education; but the factor which had caused the greatest accession of strength to France, by her wise divergence from the English policy, was (according to the critic) steam propulsion. In the case of paddlewheel steamers England, by her unscientific and ruinous experiments, had squandered millions of money and produced a series of crank and inefficient war vessels. In the case of screw ships England’s waste of exertions and money was even more surprising; the building of new ships and the conversion of others was carried out at an enormous cost with many galling disappointments. The French, on the other hand, took longer to consider the principle of the screw, but then, when their more scientific constructors had completed their investigations and analysed the new power, they acted thoroughly and without delay. From all of which the German critic inferred that England had good reason to watch with anxious eye the significant development of strength on the part of her neighbours across the Channel. “We must pronounce,” he concluded, “that with a nearly equal amount of matériel, the French navy surpasses the English in capacity and in command of men. France need feel no hesitation in placing herself in comparison with England.... Never was the policy of England so yielding and considerate towards France as at the present day. And then, with respect to the vexed question of the invasion, it is certain that Napoleon III has the means of effecting it with greater ease and far greater chance of success than his uncle.”

The means was steam power. But the much-talked-of invasion was never to be attempted. Other events intervened, other developments took place, which reduced the tension between the two great naval powers and removed for an indefinite time the danger, which the Leipsic article disinterestedly pointed out, of war under novel and unprecedentedly terrible conditions: with shell guns and wooden unarmoured steam warships.