British Association. 1 1 S 



observations made at nine different stations on the river. A series of 

 observations had also been made on the waves at the surface of the 

 sea, and the series had terminated by a course of experiments made 

 in artificial channels of different forms, for the purpose of determining 

 the nature of the mechanism of the generation and propagation of 

 waves, so as to determine the identity of their nature with the tidal 

 wave. 



Of this series of experiments and observations the following are 

 some of the results : — 



It appears that there exists a species of wave different from all the 

 others, and which Mr. Russell calls *• The Great Primary Wave of 

 Translation," which is generated whenever an addition is made to the 

 volume of a quiescent fluid, in such a manner as to affect simulta- 

 neously the whole depth of the fluid, and this species of wave is ex- 

 actly of the same nature as the tide wave. In a rectangular channel 

 this primary wave moves with the velocity which a heavy body would 

 acquire in falling through half the depth of the fluid, so that 

 In a channel about 4 inches deep, the velocity of the wave 



is nearly 2 miles an hour 



12 



2 feet deep 5|^ 



3 6i 



4 7f 



.5 8| 



6 9A 



7 10^1 -5th 



8 11 



9 jji 



10 12V5th 



15 15 



30 20 



&c. &c. 



It also appears that the breadth of the channel, when the depth is 

 given, does not at all affect the velocity or form of the wave -, and 

 Mr. Russell then proceeded to assign a general rule, by means of 

 which the velocity of the wave might be assigned d priori for a chan- 

 nel of any form, however irregular. 



The manner in which the wave was observed, was by successive 

 reflections from opposite surfaces, so as to make it pass and repass a 

 given station of observation, the interval being noted by an accurate 

 chronometer j and it was stated that in many cases above sixty tran- 

 sits of the same wave had been observed, so as to give a high degree 

 of accuracy to the observations. The instant of the wave's transit 

 had been observed by the reflection of a luminous image thrown 

 down by a series of mirrors, so as to cross micrometer wires with 

 perfect precision. For a mode of determining the length of the 

 wave Mr. Russell acknowledged himself indebted to Professor Ste-^ 

 velly, of Belfast. '■[ 



These observations having determined the laws of the propagatibri 

 of waves on a small experimental scale, were then extended to the 



Phil. Mag, S.3. Vol. 12. No. 71. SuppL Jan. 1838. Q 



