Relative size and speed of sailing-ships.
About this time the important question of increased speed in combination with increased dimensions was receiving the special attention of scientific men, and was discussed with great animation at the meetings of various associations. Mr. Charles Atherton, the chief engineer of the Royal Dockyard at Woolwich,[414] had taken the lead in forming public opinion on the novel problem of steam-ship capability. As regards sailing-vessels it had been observed that the average length of their voyages to Australia bore the following relation to their tonnage:
| Tons. | |
| 750 to 1000 | took 140 days. |
| 1000 to 1500 | took 112 days. |
| 1500 to 2000 | took 95 days. |
| 3000 and upwards | took 70 days. |
Mr. Brunel proposes to build a ship five or six times as big as any existing vessel, and is supported in his views by Mr. Scott Russell.
The inference drawn from these and similar observations, more or less founded on correct data, was that, to obtain high velocities in sea-going vessels, it was merely necessary to make them large; it being argued that a mass of two or three thousand tons, once set in motion at a given speed, would overcome the resistance both of atmosphere and water with greater ease than a mass of half its weight. Mr. I. K. Brunel carried these opinions to an extreme length, and argued that there need be no limit to the size of a vessel, except what tenacity of material must impose. He further argued, from scientific theory and actual experience, that as the “tubular principle” provided the greatest amount of strength of construction with any given material, it, therefore, was possible to construct a ship of six times the capacity of the largest vessel then afloat, and one, too, that would steam at a speed hitherto unattainable by smaller vessels. Mr. Brunel, having originated this conception, communicated it, at the outset, to Mr. Scott Russell, and suggested the construction of a steam-ship large enough to carry all the fuel she might require for the longest voyage; and Mr. Scott Russell shared with Mr. Brunel in the merit of contriving the best method of carrying out these views. The idea of using two sets of engines and two propellers (screw and paddle) is solely due to Mr. Brunel, as was, also, the adoption of a cellular construction, like that at the top and bottom of the Britannia Bridge, in building the Great Eastern, the name this huge ship was now to bear.[415] These main characteristics distinguished the Great Eastern from all other vessels then afloat. Her model and general structure were in other respects identical with those of the ships built by Mr. Scott Russell, on the principle of the “wave line,” which he had systematically carried out during the previous twenty years.[416]
Plan of construction.
Having obtained the requisite capital, the directors now concluded provisional arrangements for the construction of the screw-engines with Messrs. James Watt and Co., of the Soho Works, near Birmingham, and for the paddle-engines and hull with Messrs. Scott Russell and Co., of London. But, considering the novelty and magnitude of the undertaking, it may be interesting and instructive to review, still further, the grounds on which the projectors anticipated its success.
The ship, the directors said, “would be built in the Thames, to be completed in eighteen months; and would fulfil certain conditions, the most important of which was that she should not be obliged to stop at any place on the way to take in coal, stoppages for coal not only causing great delay by the time required for taking it on board, but compelling the vessels to deviate widely from the best route, in order to touch at the necessary coaling stations;” and, in avoiding the delay of coaling on the voyage, the ships would also escape the great cost of purchasing coals at a foreign station. “These ships,” they added, “will carry, besides their whole amount of coals for the voyage (out and home[417]), upwards of 5000 tons measurement of merchandise, and will have 500 cabins for passengers of the highest class, with ample space for troops and lower class passengers. These the company will carry at rates much smaller than those of any existing steam-ships and, moreover, with an unprecedented degree of safety, comfort, and convenience which the great size of their vessels will afford.” In thus increasing the size of their ships, the directors said, “they believed they were also obtaining the elements of a speed heretofore unknown: and if, hereafter, coals applicable to the purposes of steam navigation could be supplied from the mines of Australia, their carrying capacity both for cargo and passengers would be proportionately increased. The great length of these ships will undoubtedly, according to all present experience, enable them to pass through the water at a velocity of 15 knots[418] an hour, with a smaller power in proportion to their tonnage than ordinary vessels now require to make 10 knots.”
Mr. Atherton considers the views of the directors are not supported by their data.
These views were, however, not allowed to pass unquestioned by many scientific men, and more especially by Mr. Atherton, who rejoined that, whatever pride the projectors might reasonably feel in the production of such an extraordinary vessel as the Great Eastern, the data relied on by them did not support their anticipations. He argued that, if based upon the performance of the Rattler, the size of the vessel that would be required for the due fulfilment of the conditions of the project, as announced by the directors, would, probably, be not less than 100,000 tons displacement, and that the whole capital of the company, as proposed in their prospectus would, probably, be much more than absorbed in the construction of a single vessel of the stupendous size indispensable for the performance of 25,000 nautical miles, without recoaling, at the average speed of 15 nautical miles per hour. As an engineer, Mr. Atherton was not opposed to the construction of large ships, but he, like many other scientific and practical men, questioned the fulfilment of the mechanical conditions as respects the combination of a 15-knot speed with a 25,000-mile voyage without recoaling, on which the Eastern Steam Navigation Company had founded their project. Indeed, both practically and theoretically, he declared himself in favour of the superior capabilities of large ships as respected either speed or distance, but he forewarned the proprietors of the Great Eastern of the mercantile disappointment to which extravagant expectations, as to the combination of high speed and great length of voyage without recoaling, by the mere agency of size, would, in his opinion, inevitably lead.