MECHANICS AND USEFUL ARTS. 21 



* 



The fiuthor might be asked, reverting to the wave at the bow, What 

 became of the water at the bow, supposing he dragged the boat faster than 

 the water could spread itself? The answer was : With only a moderate 

 force at his disposal the boat could not be made to travel faster; but if he 

 had force enough to compel it to go in spite of the water, the water would 

 rise up and stand on both sides of the boat until the load had passed, and 

 then fall down into the hole left behind it. In a shallow canal in Scotland, 

 where the carrier-wave travelled only seven miles an hour, he had compelled 

 a boat to go ten miles, and he found that the water not only rose up, but 

 lifted the boat with it, so that she drew less water than before, and actually 

 went easier at ten miles an hour than at five. Had not railways come into 

 fashion just at the time, the country would have been covered with little 

 troughs, and people would have been riding on the tops of these waves in 

 an easier and cheaper mode than by any other means then known. 



After explaining the different results which are sometimes obtained at 

 trials in the Thames, owing to the velocities of the travelling-wave varying 

 with the depths of the water, the author described the best means of ob- 

 serving the wave on rivers and other like places, and then proceeded to the 

 application of some of the principles before laid down to practice. First, he 

 said it was a delightful circumstance that the wave-principle did not meddle 

 at all with the form of a ship's midship section, but left the conductor 

 entirely free to adopt any form of section he pleased. Next, it did not tie 

 him down to any proportion of depth to breadth. It was, therefore, a plas- 

 tic thing, and could be applied to any general form of ship whatever. The 

 third and most important proposition was, that the wave-line prescribed the 

 exact length of ship for every speed at which you wish a ship to go, and 

 explains why a long ship is indispensable to speed. To go six miles an 

 hour, your vessel must be at least 30 feet long; for eight miles an hour, 50 

 feet long; for ten miles, 70 feet; for twelve miles, 100 feet; for fifteen, 150; 

 for eighteen, 200 ; for twenty, 300; for twenty -five, 400; and for thirty, 500. 

 The author had himself tried to obtain higher velocities than these with 

 shorter vessels; and he had got them, but at such a fearful waste of power 

 that it was insanity and folly not to lengthen the vessels for the purpose. 

 The wave-line theory also told you that the length of the bow should be to 

 that of the run as 3 to 2. The cause of this was explained. 



The lines of the Great Eastern, the author said, were neither more nor 

 less than an exact copy of the wave-lines. The length of the bow was 330 

 feet; the length of the run, 220; and having got this length of entrance and 

 run, and feeling that more capacity was wanted, it was of no use lengthen- 

 ing the bow or the run, because there was already provision for greater speed 

 than the fifteen miles an hour which the poWer to be put into her could be 

 expected to give; 120 feet of parallel body were therefoi-e put into her amid- 

 ships. The great ship might be of less fine-lines and still go with the same 

 velocity. 



There was a very valuable conclusion for practical ship-builders to be' 

 drawn, independently of what had been stated about the lines. It was this : 

 That proportionate length and breadth were not necessary at all for a fast 

 vessel. It was not necessary for a fast vessel that she should be a narrow, 

 thin, long vessel in proportion to her size. The author had taken vessels on 

 the wave-line principle two hundred feet long, and had them made of every 

 variety of breadth, and as long as they were two hundred feet long, and had 

 1'ic lines belonging to fifteen or sixteen miles an hour, so long they hud gone 



