80 MR RUSSELL'S RESEARCHES IN HYDRODYNAMICS. 



mercantile point of view, as to bring, from the conveyance of passengers at a 

 high velocity, a large increase of revenue to the Canal Proprietors. The passen- 

 gers and luggage are conveyed in light boats, about sixty feet long, and 6 feet 

 wide, made of thin slieet-iron, and drawn by a pan- of horses. The boat starts 

 at a slow velocity behind the wave, and at a given signal it is by a sudden jerk 

 of the horses drawn up on the top of the wave, where it moves with diminished 

 resistance, at the rate of 7, 8, or 9 miles an hour. 



It was a natm'al consequence of this successful mode of transport on this one 

 canal, that it should be immediately attempted on others, and numerous experi- 

 ments were accordingly made with varying results. In some canals, and with 

 certain vessels, similar phenomena were observed, and the like favourable results 

 obtained. But in others the experiment totally failed, as it was not found that 

 the tumult of the water subsided as in former cases, or that the resistance ex- 

 perienced any similar diminution. The cause of these variations was not then 

 kno^\^l. Many experunents were made, which failed in ehciting any solution of 

 the difficulty. Many scientiiic and practical men, unable to account for such dis- 

 crepancies, satisfied themselves with an unquaUfied denial of their existence, 

 while those who were eye-witnesses of the fact could not assign .any satisfactory- 

 cause. 



It wUl not be difficult for us to account for these discrepancies, by what we 

 have brought to light regarding the law of wave. In the canal where the fact 

 was originally observed, having a depth of 3 or 4 feet, and a wave moving 

 at about G miles an hour, it is obvious that the resistance of the anterior wave 

 would only be encountered at velocities less than that of the wave, and the di- 

 minished resistance would be obtained by moving upon the wave, at a velocity 

 of more than 6 miles an hour. Now, in making the same attempt in canals that 

 were 5 or 6 feet deep, with a wave moving at the rate of eight miles an hour, 

 the resistance would not be observed to suffer any diminution, till the velocity 

 exceeded that of the wave ; but would accumulate rapidly up to that point. 

 While in canals that had a depth of 8 or 9 feet, and a wave moving at 

 eleven miles an hour, no diminution could be observed till a velocity above that 

 of the wave had been obtained, after which, the advantage of diminished ante- 

 rior section could be acquired. Since the discovery of the law of the wave, I 

 have had the experiments tried in such cases, the wave being passed, and the 

 boat carried along on its summit at the rate of thirteen mUes an hour. 



When once the summit of the wave is attained, or its velocity exceeded, a 

 comparatively small force may sustain the motion. But the resistances increase 

 so rapidly in the vicinity of the wave, that this may become impracticable. If 

 the increase of the velocity up to that of the wave be very slow and continuous, 

 the waves will be closely crowded, and deeply accumulated around the bow of the 



