a 2 —— 
British Association for the Advancement of Science. 285 
The general result was, that in a rectangular channel the velocity 
was that due to the fall through half the depth of the channel. 
Thus the velocity of a wave of one foot was three miles an hour, of 
one of four feet eight miles, of one of fifteen feet fifteen miles. In 
all cases the rectangular channel was found to be the preferable one. 
Such a channel would generally be the most expensive, but some- 
times, where, as on the Thames, the land adjoining was of high 
value, and gentle slopes to the banks were therefore not attainable, 
the rectangular would be the cheaper form. 
The next wave generated was what Mr. Russell termed the wave 
‘of unequal displacement,” arising solely, it was found, from the 
form of the vessel. ‘This wave was seen diverging on both sides of 
the vessel, from the bow towards the stern, arranged in two straight 
lines extending to a great distance behind it. ‘This wave might be 
greatly diminished, and sometimes almost entirely removed, by giv- 
ing the lines of displacement a slight concavity towards the stern, 
the vessel being sharpened out. When the vessel does not raise 
the water in giving uniform progression, but is so bluff that certain 
points displace more than others, an anterior wave is formed of ex- 
cessive displacement, the injury done by which is only inferior to 
that of the stern surge. 
Mr. Fairburn, of Manchester, stated, in reply to a question put 
by Dr. Lardner, that the results of his experiments corresponded 
with those obtained by Mr. Russell, and mentioned one instance 
where, at a velocity of seven miles an hour, the channel being five 
feet deep, the stern was dragging on the ground.—Mr. Herapath 
inquired what posterior form of vessel Mr. Russell had found the 
best. Mr. Russell stated that on this point the result of his experi- 
ments indicated a form very different from that approved of by na- 
val officers in general. They preferred a form bluff in front, and 
tapering towards the stern. Mr. Russell’s experiments went to 
show that this should just be reversed, and he had made sixteen of 
them at different velocities, from three to fifteen miles an hour. In 
the navigation of the Clyde, the progress of the formation of vessels 
had been in accordance with this opinion. At first they were built 
very bluff, with their maximum breadth at a distance from the stern 
of one-third of the whole length ; thus a wave of excessive displace- 
ment was generated, going off at right angles, and making a break 
Vou. XXXIII—No. 2. 37 
