페이지 이미지

Chief Constructor of the Navy that it was “the very thing they were looking for.” Subsequently arrangements were made for the model to be tested by Mr. Froude at Torquay, in connection with a series of experiments on resistance, which that gentleman was making for the Admiralty. It may be necessary for us to state that Mr. Froude is the originator of the generally received theory as to the relation existing between the resistance of models and of the full-sized ships represented by them. For many years it had been well known that results as to speed obtained with models were altogether illusory as indications of what might be expected in the full-sized ship. To Mr. Froude belongs the honour of having ascertained the law of the relation of speeds, which may be thus briefly and roughly stated :—If a model and a ship are moved at speeds, the ratio of which is the square root of the ratio of their dimensions, then the ratio of their resistances is the cube of the ratio of their dimensions. The trial took place in the presence of Mr. Ramus, and the results were not satisfactory; this the inventor attributes partly to the fact that his model was tried as he proposed it, without alterations being made from time to time as they suggested themselves to him. In this connection we may remark that his first proposals were of the crudest; the inclination of the planes was to be one in three, which he altered before the trial to one in eight, and now proposes to make one in thirty-five. In other respects he shows a lofty superiority to matters of mere detail. Altogether, after reading the Parliamentary papers on the invention, and, we may add, the present pamphlet, we cannot help seeing that Mr. Ramus utterly fails to appreciate the position which any inventor who hopes for success must take up. This method is to make a present to the world of one grand idea, to be worked out in detail by merely professional people. We may remind him that the real work of the successful inventor is in arrangement of details, and in overcoming the practical difficulties which always stand in the way of new schemes. When any great invention becomes a success it is usually discovered that many people have thought of its main feature before, but the honour of the invention justly goes to the man who has gone into practical details, and has grappled with and overcome practical difficulties. If the author of the pamphlet before us, instead of denouncing unbelievers in his polysphepic ship as self-interested and wilfully blind, had but put himself through the discipline we have indicated, he would, we believe, have long ago seen the impracticability of his scheme.

Mr. Froude’s results of the trials, interpreted by the rule we have given above, were: that at speeds less than 30 to 40 knots the bi-sphenic ship might be expected to be “ tipped” merely, and not perceptibly lifted; at 70 to 80 knots she would be sensibly lifted, and at a speed of 130 knots the lifting would exceed half the displacement; but up to this point the resistance would not diminish, but would, on the contrary, increase. To these conclusions Mr. Ramus offers the plausible objection, that Mr. Froude's rule of comparison of ships with models is merely the result of experiments with a ship towed at ordinary speeds, and that it is not necessarily true when unprecedented speeds are in question. There is, however, the further result of the experiments which appear to as conclusive. At the highest speed, and when the model was lifted to a greater extent than half its displacement, so far from the resistance having diminished it had considerably increased, thus proving that even if the result of driving a "polysphenie" at high velocity be to decrease the immersed surface, the resistance per square foot of surface so much increases that the total resistance is not diminished. In other words even if a ship could be made to skim over the water, it would cost more power to so propel her than to drive her through the water,

Even if a vessel built in the shape of three consecutive wedges with a superstructure on top of them could be so propelled as to glide over the water at high speeds, the question would still have to be answered, What use could be made of her ? Our inventor has in his own way approached this part of the question by stating his opinion that in a moderate sea the speed of the polysphenic ship would be increased because she would glide over the crests of successive waves, and in very rough weather her course would be no more impeded by large waves than is the case with vessels of the ordinary form. To as it appears that the lifting action of the wedges must be tangential to a large wave, and this would in

extreme cases throw the ship out of the water altogether, with the probability of her returning to it in such a direction as to bury herself in another large wave. This is of course on the false supposition that abnormally high speeds would be realised, but the absurdity of getting a vessel to glide over the ocean at fifty miles an hour, spurning the waves with her foot, is so patent to us and, probably to most of our readers, that they will excuse our stating further difficulties as to strain on structure, means of propulsion, &c.

In the pamphlet before us Mr. Ramus, with much Christian charity, accounts for the careful consideration which his proposals received by supposing that “it must have been by surprise that my invention was fortunate enough to have been admitted at the Admiralty, where every obstacle has generally been thrown in the way of all inventions tending to produce great changes ;” but now he can only conclude that they “see in it a great interruption of their own case, and it may be some fancied interference with their own dignity, in the fact that they are to be taught by one who is not connected with the department.” He also proposes an adaptation of the wedge-formed ships to rocket floats, which he believes will develope a sufficient force to destroy ironclads. He thinks that Government officials, although they know his views are correct, reject this last invention because it will take their work from them by rendering all war-ships useless, in fact it will “ annihilate all the present armaments of naval warfare.” He is patriotically apprehensive that our people may at some future time “ find that iron-armoured ships, which can only be procured by means of millions of money, and by the operations of highlyorganized bodies of skilled labourers, may be as easily used to crush their own liberties at home as to take away the freedom of the sea from other nations." Let us be thankful that there is a remedy: “ The rocket-float, which will render all ironarmoured ships useless, will be the ready armament of liberty, and its safeguard on every shore.”

When Mr. Ramus thus “ drops into poetry” he is hardly more amusing than when in sober earnest trying to convince us that a projectile will gain in velocity by having to drag a tail through the water. After what we have quoted our readers will not be

surprised to hear from Mr. Ramus that the vested interests of the owners of the present Mercantile Marine and of shipbuilders have induced them also to reject an invention which will supersede existing ships, but that if they persist in their prejudices we “shall utterly and for ever lose our supremacy at sea."

General Arerage: York and Antwerp Rules. By Herr Jacob

Ahlers. Hamburg: L. Friedrichsen and Co. London: Trübner

and Co. 1878. A USEFUL and well-written pamphlet has been published by Herr Jacob Ahlers on the York and Antwerp Rules, agreed to at the Antwerp Conference of the Association for the Reform and Codi. fication of the Law of Nations, in September, 1877. After giving a summary of preceding meetings on this, to the commercial world, important question, held at Glasgow, 1860, in London, 1862, and in York, 1864, the author proceeds to render an account of the Antwerp Conference and the important conclusions arrived at. What constitutes a general average does not appear to be much disputed; indeed a singular agreement exists in all maritime states on this score, but what shall be held to be a damage resulting from such act, has been a matter of indifference for generations passed. Even the well-expressed 702 Article of the Common Code is at the best only directive, not a definition. It has thus resulted that in interpreting what damages shall be included in general average losses two systems have arisen, the universally adopted general benefit rule of the Continent and the United States, and the general safety rule of England. The author points out with great acumen that no option is left. Either the first must govern, held within bounds by reasonable restrictions, or the latter must prevail, which will ultimately compel each risk to be separately insured. That the latter result has not been accepted by the great shipping interests is proved by the assent given by a large proportion of our leading shipowners to the York and Antwerp Rules, which form a reasonable compromise between the two conflicting systems. With these preliminary comments the writer enters into a close analysis of the respective merits of the 12 rales voted at Antwerp, accompanied by an instructive summary of the discussion which took

place on each of them. It would take us beyond the limits we have allowed ourselves to do more than notice what the author has done referring the reader to his pamphlet for details. The appendix contains Mr. E. E. Wendt's address read at the Antwerp Conference, the Reports of the German Branch Association, of the Swedish, the Philadelphia Committee, that of the Sub-Committee of Lloyd's appointed to consider the York and Antwerp Rules, that of the Antwerp Committee, and finally the text of the York Rules and the York and Antwerp Rules. Of the many pamphlets published in Holland (Dr. Rahnsew)'; Berlin (Herr Ulrichs); New York (Mr. F. C. Condut); in Copenhagen (M. Thidt), etc., the treatise now before us may claim, it is thought, to be one of the most useful and well-considered hitherto given to the public, and we confidently recozamend it to the consideration of the practical lawyer, the shipowner, and underwriter.


SHIPPING AND DISCHARGE FEES. To the Editor of the Nautical Magazine.” DEAR SIR,—Have you space for a few words on a subject causing ihe strongest indignation just now among those concerned ? I mean the frequent recurrence of “Shipping Fees.”

The present law is the Act of 1840, before the advent of steam, and Jack was not intended to pay out of his hard-earned wages more than once a year on long voyages, or twice on shorter ones.

These fees have been steadily increasing, and now a New York liner, with her crew of 160 men making 10 voyages in the year, pays 5 or 6 times (not the men, but the ship), so that after paying all up on joining a ship hitherto laid up they must pay all over again on this new account possibly 12 times in all.

Now a change is to be made from the 1st of January, and these fees are to be payable after each voyage, which means 20s. per annum for seamen, 30s. for officers and stewards.

There are steamers (signally), Liverpool to Oporto, which make

« 이전계속 »