FARMERS' REGISTER— INCREASING THE RAPIDITY OF BOATS. 



303 



INCB EASING THE RAPIDITY OF BOATS, 



Without using more propelling power — Explained 

 on scientific principles. 



[From the New-York Evening Tost.] 



Some notice of a discovery recently made in 

 England, ^vith respect to the degree of power re- 

 quisite to draw or impel a boat or other vessel on 

 tiie surface of water, has already appeared in this 

 paper. This subject has excited much attention in 

 England, as might naturally be supposed, when it 

 is considered that the yearly income from canals in 

 the United Kingdom amounts to two millions of 

 pounds sterling. Mr. Macneill of London, has re- 

 cently published a book detailing a series of expe- 

 riments, made with a view to try the soundness of 

 the opinions hillierto received on this subject, and 

 giving the results of his inquiries, with tables of 

 the degree of force which he ibund necessary to 

 draw a boat on the surface of water at different gi- 

 ven velocities. The conclusion to which he has 

 arrived is, that the old theory, by wliich the resist- 

 ance, to a boat moving on water is supposed to in- 

 crease in the duplicate ratio of the velocity of the 

 boat, however, it may be true in i-egard to low ve- 

 locities, as for example, under five miles and a half 

 an hour, is not true as applied to the higher veloci- 

 ties. He remarks, that " it is not necessary to con- 

 sider the old law of the squares to be incorrectly 

 stated. In so far as the boat remains immersed in 

 the water to the same water-line, that law may be 

 correct; but whenever the velocity of the boat is 

 increased beyond a certain point, the boat emerges 

 out of the water, and skims near the surface, the 

 traverse section of immersion being lessened." — 

 The experiments made in London have not been 

 unnoticed in this country ; and as the suc( essful 

 application of Mr. Macneill's new principle, ob- 

 viously must depend on the form of the boat, we 

 understand that some attempts are making to con- 

 struct the steamboat in such a manner as to take 

 advantage of this tendency to emerge from the wa 

 ter when in rapid motion. From a notice of Mr. 

 Macneill's book, which Me find in a late English 

 periodical, we copy the following passage relating 

 to this part of the subject: 



" It has often been asserted, that such advant- 

 ages as we contend arise from the boat's emerging 

 from the water at high velocities, have never been 

 attained by boats ' with a {)ower in them ;' for in- 

 stance, by such as a rowboat or a steamboat. — 

 With regard to the first of these, the rowboat, we 

 can venture a suf3f]cient reason for such having hi- 

 therto been a just remark. When the boatman is 

 rowing his boat, with his face to the stern, by vvhich 

 position he is enabled to bring all the nmscles of 

 his legs to his aid, the antagonist muscles, flexors 

 and extensors, are so caused to balance or counter- 

 act each other, that his body is for a part of the 

 stroke, not on the seat of the boat, but suspended 

 as it were by a muscular rigidity, very much upon 

 the heels. When, however, the blade of the oar 

 has passed astern of the row-locks, and the inten- 

 sity of muscular force is relaxed, the boatman 

 seats himself with a thump, which, together with 

 the resistance met with when lifting the oar, inva- 

 riably dips the bow of the boat deeper and so pre- 

 vents her emerging from the water. With very 

 little attention to a boat when rowed upon smooth 

 water, she may be seen to act in this manner ; and 

 oscillation will be perceived to a very considera- 



ble extent, occasioned by thisshiftingof the centre 

 of gravity, not merely in short skiffs, but in the 

 longest wlierries or Galleos on the Thames, at 

 every stroke of the oars. In the case of steam- 

 boats, it is also clearly to be seen, that no attempt 

 has been made to cause an emergence from the 

 water. The improved speed of steamers within 

 twenty years, has its foundation in the improved 

 character of the machinery, and in the elongation 

 and sharpening of the bows, but it has not been in 

 any instance by attempting to draw less water in 

 proportion to her increased velocity." 



Mr. Macneill, from these and the other conside- 

 rations adduced in his book, draws the conclusion 

 tiiat navigation, whether by tiaction or by impul- 

 sion of tiie oar and the paddle, is yet in its infiincy. 

 The attention of the ship-wright, he remarks, has 

 hillierto been directed to giving the vessel velocity 

 through the water ; but he confidently anticipates 

 the time "when, the velocity already gained, be- 

 ing aitled by the advantage of decreased draught, 

 and the vessel being forced over the water, safety 

 and comfort will be tl)e only limit of nautical sci- 

 ence." The follov/ing is his general reasoning 

 on the suliject of the principle he attempts to es- 

 tablish : 



" The object immediately in view, when we 

 place a boat or barge uj)on water, is a good con- 

 veyance for j)ersons and property. So is it when we 

 place a wheeled carriage upon a gravelled road, or 

 a sledge upon snow. The difference, however, in 

 the modes of attaining tliis object, has been most 

 striking. In each of these cases, the body to be 

 removed has rested on soft or yielding matter, and 

 whilst, in the two latter cases, no mechanician 

 would provide for the wheels of the carriage, or 

 the runners of the sledge, a facility for cutting 

 along, immersed in the softer matter under them, 

 the boat-builder seems to have studied how he could 

 best keep his vessel ploughing her way. The case 

 may be different with sea-going vessels, which are 

 impelled by the action of a wind ' on the beam,' ami 

 ships of war, with their decks loaded with weighty 

 guns ; in such cases it is necessary that the vessel be 

 a good deal immersed. Nor can it be satisfactorily 

 shown that even sea-going ships would not be im- 

 proved by such a build as would enable them to 

 rise to the surface of the water. But to pursue our 

 reductio ad absurdiim ; there are many cases in na- 

 vigation where a sharp ' cutwater' shape to a boat 

 would be as unphilosophical, as a knife-edged fel- 

 low would be to a wheel intended for ploughed 

 land. A cart-w heel on gravel or other yielding 

 matter, sinks to the determined line of gravitation 

 with as much certainty as will a boat upon water; 

 and a boat resting in water, will (according to the 

 velocity given to it, and the form of its prow and 

 bottom) rise nearer the surface of the water, as 

 well as a cart-wheel will rise, when put rapidly in 

 to motion. The difference of density is, no doubt, 

 much greater in one case than in the other, but the 

 water will resist the penetration of the boat in the 

 same manner, though not in the same degree, as 

 the soft gravel or mould resists the wheel. Not- 

 withstanding a conclusion so obvious to those who 

 know the laws of gravitation and the properties of 

 matter — so easily calculated by every one who un- 

 derstands any thing of the combination of forces, 

 we find it has been neglected, in order to determine 

 what law regulates the movement of a body im- 

 mersed to the same depth, at all velocities. 



