2 British Association for the Advancement of Science. { 
a heavy body would acquire in falling through half the depth of 4 
the fluid, so that ‘ 
In a channel about 4 inches deep, the Mei of the wave 
y 2 miles an hour. 
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It also appears that the breadth of the channel, when the depth 4 
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 a priort for 
a channel of any form, however irregular. _ 
_ The manner in which the wave was observed, was by succes- 
sive 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 ; and it was stated, that in many cases, 
above sixty transits of the same wave had been observed, so as to 
a high dearer. of accuracy to the observations. The instant 
of the wave’s transit had been observed by the reflection of a lu- 
minous image, thrown down by a series of mirrors, so as to cross 
micrometer wires with perfect precision. For a mode of deter- 
mining the length of the wave, Mr. Russell acknowledged him- 
self indebted to Prof. Stevelly, of Belfast. 
These observations, having determined the laws of the propa- 
gation of waves on a small experimental scale, were then extended 
to the analogous phenomena of the great tidal wave. In his 
observations on the River Dee, Mr. Russell found that the tide 
wave followed precisely the same laws as those in his experimen- 
tal channel; that its velocity was exactly proportioned to the 
square root of the depth of the fluid, that its form changed inthe 
same manner, and the existence of the same law was sufficient to 
“eee be the different rate of propagation of different tides be- 
tween ti wae of Sfleen oot deep anil ‘ 
RES ey 
— % 
