81 
of Edinburgh, Session 1884 - 85 . 
tice of the maritime engineer, which was considered at the time to 
he sound, and which the majority of the profession until lately 
regarded of universal application, from its having for many years 
been practically tested in many different cases with the most grati- 
fying success. 
The principle to which I allude is the confining of the ebb and 
flow of the river and tidal water to one fixed channel of a certain 
width by means of what are called training walls. These are low 
structures of stone or timber, placed in tidal estuaries, and carried 
to such a height only as is just sufficient to guide the direction 
of the first of the flood tide and last of the ebb. It was found, 
in practice, that a very small elevation of those walls above the 
bottom was sufficient to restrain and direct the course of the 
heaviest land floods and strongest tide currents ; and this, because 
such floods and currents always increase in Volume more or less 
slowly, so that if the walls project only high enough to guide the 
comparatively gentle beginnings of those discharges, they will be 
sufficient to direct them after they have attained their greatest 
volume and highest velocity ; for, as the flood increases gradually, 
the depth will in like manner always go on increasing in the line of 
the directing wall, since the flood must necessarily continue to 
follow the line of least resistance, which will always be in the line 
of greatest depth ; so that (excepting in very rare cases) all that is 
needed to control the direction of the heaviest land flood or the 
highest tide is to fix the direction of the first of either tide or 
freshet — obsta principiis by the time that either flood or tide has 
submerged the training walls ; the line of direction of such flood 
or tidal current has been already permanently fixed. 
Principally, by means of those walls and steam dredging, the 
river Clyde has been increased from a depth of 13 feet 8 inches 
to no less than 26 feet up to Glasgow ; but the soundness of this 
system, which was so triumphantly carried out on the Clyde, has 
also been, as I have said, proved over and over again to be no less 
applicable to other rivers as well. 
The Kibble, the Tyne, the Tees, the Mth, the Lune, &c., though 
varying in many of their physical characteristics, have all been 
improved in the same way, without producing any reduction in 
depth by the silting up of their sea approaches. 
VOL. XIII. 
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