84 



MR RUSSELL'S RESEARCHES IN HYDRODYNAMICS. 



cately poised than at any other time ; the waves coinciding form a wave equal 

 to their sum, on which the centres of gravity receive an additional elevation. 



It appears fi'om the experiments of 1835, that a vessel has conve^'^ed on a 

 canal given weights with the following forces : — 



Moving Force. 



Weight Moved. 



Velocity. 



71.5 lbs. 



19,222 lbs. 



4 miles an hour 



86 



19,222 



4.5 



112.7 



19,222 



6.2 



243 



8,022 



11.3 



264 



19,262 



1.3.6 



331 



10,262 



15.1 



The examples are taken from the experiments made with the vessel named 

 " The Wave," which was constructed according to the form which I have assigned 

 as the solid of least resistance. 



PART II. 



The Experiments of 1834. 



The experiments of 1834 were directed chiefly to the determination of the 

 velocity of the wave, the emersion due to the velocity, and the amount of animal 

 force required to overcome the resistance of the water at various velocities. The 

 experiments of 1835 were the result of the experience of 1834, in consequence of 

 which a vessel of a peculiar form had been constructed, and a mode of estimating 

 the absolute and comparative resistance of the fluid at various velocities, with 

 different vessels, and at several degrees of immersion, had been obtained, giving 

 results more accm-ate, more uniform, and more worthy of confidence than those 

 of the former year. 



On the Velocity oftJie Wave. — The Progressive Wave, which forms the sub- 

 ject of these experiments, differs entu'ely in its nature and laws from the small 

 undulations or oscillations of a fluid Avhich are occasioned by the sudden elevation 

 or depression of a small portion of the fluid, in which case we have a series of 

 successive small undulations and depressions succeeding each other at nearly 

 equal intervals. The progressive wave, sent forward by a floating body in rapid 

 motion, is not necessarily preceded nor followed either by a depression, or an ele- 

 vation, or any series of such depressions or elevations, but is a single elevation. 



