CANAL NAVIGATION. 79 



result from the wave, from which it will be apparent, that a given velocity against 

 the stream may, in certain circumstances, require less force to produce it, than 

 the same velocity in the direction of the stream. Thus I have seen the current 

 moved at the rate of about 1 mile an hour, and the wave about 4 miles an hour, 

 on the surface of the water ; when the velocity of the vessel, drawn against the 

 stream, was 4 miles an hour in regard to the land, it was before the wave with 

 diminished resistance, and when it was draAvn with the stream also at the rate 

 of 4 miles an hour, the vessel being then behind the wave, experienced the di- 

 rect resistance arising from that cause, the velocity of the wave in regard to the 

 land being in the one case 3, and in the other 5 miles an hour. Analogous phe- 

 nomena to this, of a very curious nature, are to be recognised in the motion 

 of a wave against a current. I have seen a wave move in the opposite direc- 

 tion to a stream, until it reached a rapid in which there existed a part of the 

 stream where the current had a velocity equal to that of the wave, and in the oppo- 

 site direction, and there, in consequence of the equality of velocities in opposite 

 directions, I have seen the wave come to rest, and retaining its form unchanged, 

 remain as a stationary heap of fluid, until, by the adhesion of the successive 

 portions of water, it was at last rendered insensible. From these remarks it will 

 be apparent, that the navigation of rivers may, in certain cases, be much facilitat- 

 ed by the action of the wave. 



Section IX. — Applications and Illusti'ations of the Lam of the Wave in the Prac- 

 tical Navigation of Canals. 



Canal navigation furnishes at once the most interesting illustrations of the 

 interference of the wave, and most important opportunities for the application of 

 its principles to an improved system of practice. 



It is to the diminished anterior section of displacement, produced by raising 

 a vessel with a sudden impulse to the summit of the progressive wave, that a 

 very great improvement recently introduced into Canal transports owes its exist- 

 ence. As far as I am able to learn, the isolated fact was discovered accidentally 

 on the Glasgow and Ardrossan Canal of small dimensions. A spirited horse in 

 the boat of William Houston, Esq., one of the proprietors of the works, took 

 fright and ran off, dragging the boat with it, and it was then observed, to Mr 

 Houston's astonishment, that the foaming stern surge which used to devastate 

 the banks had ceased, and the vessel was carried on through water comparative- 

 ly smooth, with a resistance very greatly diminished. Mr Houston had the tact 

 to perceive the mercantile value of this fact to the Canal Company with which 

 he was connected, and devoted himself to introducing on that canal vessels mo- 

 ving with this high velocity. The result of this improvement was so valuable in a 



