allowed to those who had made the great work of marine engineering their study, and that they should not be interfered with by the departments who undertook to control matters of which they had only a superficial knowledge. He cordially agreed with the Author that the introduction of the screw had immensely advanced steam navigation. In speaking on that subject, he thought there was one name that could not properly be overlooked, the name of the late Mr. Brunel. His works had had the most important influence upon the department of engineering dealt with in the Paper. Mr. Brunel was literally sending his first ship the "Great Western across the Atlantic, when lectures were being given to the public to prove the impossibility of any vessel reaching America by steam. The "Great Western was followed by the “Great Britain," and whatever the shortcomings of that vessel might have been, there was in her the very best possible arrangement to make every particle of material of the utmost use in giving strength to the whole structure. With regard to the "Great Eastern "-which was in some respects a most unfortunate undertaking, having, he believed, cost Mr. Brunel his life-it was no doubt far in advance of the times; it had conferred great benefit on steam navigation generally, and had led up to the characteristics and features adopted in vessels of a subsequent type. Where such bold and signal departures from previous methods had been carried out, as those which had been effected by Mr. Brunel in his contribution to steam navigation, they ought to be cordially recognised. With regard to the alleged success of American wooden steamers used with a screw, he thought it was a fallacy to suppose that wooden steamers could achieve any amount of success as compared with iron steamers. A wooden steamer might be made with great advantage to be worked with paddles; but when an attempt was made to drive the power through the stern, where every fastening put in the vessel by being agitated was a continual source of destruction by enlarging the hole and diminishing the size of the fastenings, the state of things was very different from that existing in an iron vessel, which was practically a homogeneous sheet of iron. If it were not so, the latter would not stand as it did twenty years' continual rack brought upon it by the whole of the power being passed through the stern. His statement might be confirmed by what took place in the early period of screw navigation. The Government were then the only persons who used very large power through screws, but it was found so incompatible with the existence of the vessels, that it became a question of giving

them up altogether or of substituting iron vessels; and iron vessels had fully realised all the expectations formed of them, there being no longer any fear of the difficulty of passing power through the stern. With regard to the question of subsidies, he could not quite accept the view expressed in the Paper. He thought Government had done right in giving large subsidies to steamers. If they had not thus encouraged the development of steam navigation, shipbuilders could not have produced the kind of steamer that they were now enabled to construct. It was quite true, as the Author had stated, that since an opportunity had been afforded of watching what had been accomplished by subsidised lines, other steamers had been brought into competition with them, so that they would be placed at a considerable disadvantage when the subsidies had run out, since the other steamers would be able to take their place and do the same work on cheaper terms. Vessels, which would work at a profit aided by a subsidy, might be left stranded when thrown upon their own resources. The public, however, had had the full benefit of the system; they had had the advantage of steamers of enormous size and of a speed that never would have been dreamed of at so early a period. He believed that steam navigation was now far ahead of what it would have been but for the subsidies that had encouraged it.

Mr. E. REYNOLDS did not know whether it would be possible in the discussion to keep as clear of detail as the Author had done, because his own specialities were matters of detail to a very large extent. The Author had advocated the single engine, and had used it with great success. That was a matter of some consequence in regard to the advance of navigation, because if those engines were cheaper or more economical in working, they took up less room, and ought to be adopted. But it did not appear to him that they were the most economical arrangement, because a single engine must apply the power to a yielding medium like water by fits and starts; it must be at one portion of the revolution a force acting upon the water one-third greater than the average force, and at another part of the revolution the propeller must really be propelled by the water. It was therefore difficult to imagine that it could be the most economical arrangement; and he was strongly inclined to think that in practice it had not proved itself to be so. In his indirect connection with marine engineering he had made several screw propellers for American steamboats, and in all those cases the blades were unequally placed, two near together and the others wider apart, so that the

Americans recognised the difference of effort of the engine, and he believed that the Author had practically recognised the same evil by introducing a tolerably heavy fly-wheel. Of course the fly-wheel was not a complication, but it was ineffective weight, and it remained to be seen whether with the same total weight greater efficiency could not be secured by two engines. From the reference to the construction of the engines of the White Star ships it would appear that the Author recognised that it was partly a question of size and convenience. It was possible that the introduction of the single engine in the United States might have been to a large extent a matter of economy, in consequence of the rather crude construction to which the Americans had been driven by the excessive dearness of labour and the great cost of iron. That state of things had since been altered, and so, he believed, had been their practice in marine engineering. The designer of the engines of one of the largest lines of American steamboats had recently shown him his drawings for those engines. In some of them the English plan of two cylinders had been adopted, and in others there were four cylinders with four cranks. On the whole, it appeared to be a matter of expediency with reference to the particular circumstances. With regard to indicator diagrams, to which the Author had alluded, they were, no doubt, too much relied upon by a large number of engineers. It was possible to get almost any results from an indicator diagram; but the sole question for shipbuilders was how far a ship could be driven, and at what speed, by a certain consumption of coal. With reference to the White Star fleet, to which allusion had been made in the Paper, the first two ships were built with the intention of working with a moderate rate of expansion. They had engines with ten boilers containing twenty furnaces. One of those ships was now in existence, and she was notoriously a good one, except that she was short of steam. The actual speed of those vessels (as shown in the Blue Book on the loss of the "Atlantic ") had been about 12 knots. In the next four ships with similar engines there were two additional boilers with four furnaces, in all twenty-four; and there had been an actual increase of speed almost in the direct ratio of the increased number of furnaces. That went to show that a good indicator diagram made out by a large measure of expansion was not all that was wanted. In the last two ships one-sixth had been added to the cylinder capacity and one-third to the boiler capacity, with the result that one-third more tonnage was propelled not merely at the same speed as before, but at an increased speed of 1 knot an hour, the latter being of itself

sufficient to account for the increase of fuel. He had no doubt that by enlarging the capacity of the cylinders of those ships better indicator diagrams could be obtained, or rather a larger amount of power could be shown upon the indicator cards by a higher measure of expansion; but he thought the performance of the ships would be materially worse. The Author had joined in the general condemnation of the interference of the Board of Trade, which was, no doubt, annoying to the enterprising and highly instructed persons who managed the most important steam trade of the world. But that was not the whole steam trade of the world; and it was impossible for the public to forget that at the time when the interference became serious they were accustomed to hear of iron ships breaking their backs at sea without warning; of such cases as that of the "London,” a wellfound ship, but probably overloaded, and too deep in the water for her length, lost in the Bay of Biscay, with an enormous sacrifice of life, a large portion of the crew, however, escaping in open boats. Such being the case, it was impossible to say that some supervision was not necessary; but it would be desirable that such supervision should extend more to essentials and less to details. One point to which he desired to direct attention was that some of the best class of engine-men were kept out because they did not pass a Board of Trade examination. He had no hesitation in saying that if a similar examination were required of railway engine-drivers accidents would be increased tenfold. It was as if, in engaging a turner, he should examine him as to his capability for designing a lathe, and not as to his power to make the best use of the tool before him. Another question was the substitution of steel for iron in steamships, as to which it was important to lay down good rules, but he feared that the Board of Trade would fall into the same error as other bodies had done in devising rules for the use of that material. The English Government appeared to have adopted rules taken from those of the French Government; and he saw with regret that Lloyd's had adopted similar ones. The material was to be tested by subjecting strips sheared from every plate to tensile strain, and also by cold bending to ascertain the capability of flexure without cracking (which was right enough); but they were further tested-not, as might be expected, as to the amount of indentation which a riveted seam would bear without splitting at the holes, or anything of that sort-but by heating strips red-hot, dipping them in cold water, and afterwards doubling them up. Now, surely, if there was one risk to which a ship's bottom was less liable than another it was that of getting red

hot. Such a test could only prove the softness of the material, and that it was not of the highest strength that might with propriety be used for the purpose.

Mr. MERRIFIELD agreed with the Author in what he had stated with regard to the length of ships. As he had said, the middle part was that which carried and paid, and consequently there was a natural tendency to lengthen it. He also agreed with him that a decided limit was placed on the possibility of lengthening ships by any restriction on their size, and that for distant and rough voyages, like those across the Atlantic, it would be impossible to have with any degree of safety long ships of small size. He supposed also that there was a practical limit to the size of ships in the ports they had to serve. That was emphatically the case in the Channel passage, for it was entirely owing to the restriction on the size of the ships imposed by the ports that the service was so bad as compared with that which might be established with better ports and better ships. There was also a sharp commercial limit imposed in most trades to the size of the ships by the amount of cargo they could take in at a particular time at a particular port; he doubted, however, if that restriction applied to some of the great lines of steamers, such as those on the Atlantic ferry (so to call it) between Liverpool and New York; and it would not surprise him if at no distant period vessels as large as the "Great Eastern" crossed the Atlantic in considerable numbers. With regard to indicator diagrams, there could be no doubt that they recorded the pressure in the cylinder, and absolutely nothing else, telling nothing of what took place in the boiler or in the fire. In many cases where the application of the engine was almost direct, and where the loss of efficiency in the engine was well known, as in the Cornish pumping engine, the indicator might be to some extent a guide to the work actually done; but in the screw propeller that was very far from being the case, for the work done in the engine by no means represented the work done in driving the ship. The screw was not only an indirect propeller, but it was primarily a reaction propeller; it did not push against a rigid substance, but drove the ship by the stream of water thrown back. By virtue of the principle that action is equal to reaction, the natural tendency of things in those circumstances was that the action and reaction should tend to equality; consequently, although it was possible to do a great deal better than that, and by means of various artifices to make a propeller that did not throw away anything like half its power in the reaction, still the tendency was [1877-78. N.S.]

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