"Bob Wood" <[EMAIL PROTECTED]> wrote: >2008/7/17 Brian J Goggin [EMAIL PROTECTED]: > >> "Having reached the highest level of the great table-land, we >> traversed a space of fifteen miles without a lock; and here a curious >> phenomenon, illustrating the incompressibility of water, arrested our >> attention. About every twenty or thirty minutes, the horses are >> obliged to stop for five or six minutes, to take breath, the cause of >> which was this: --- The velocity of the boat impelled the water with >> such force that it gradually rose so as to approach the summits of the >> banks, when it began to recoil, so as actually to form a back-water or >> stream, when the horses were unable to make head, and therefore >> stopped until the equilibrium of the canal was restored." >> >> I have not heard of that phenomenon before. Has anyone else come >> across it? > >I think everybody who has tried to go too fast along a narrow and >shallow canal has suffered from this effect.
Both this thread and the simultaneous one on URW have confused two phenomena. A soliton is a single wave. Once created (and moving) it keeps moving along the channel at a surprisingly high speed and for a surprisingly long time. It is a short (measured along the direction in which it is travelling) hump in the surface -- i.e. the water level rises briefly as it passes, and immediately returns to its previous level once it has passed. The "tide" effect is quite different. It is a long-lasting (and increasing) rise in the water level of a long length of waterway ahead of oncoming traffic, which can occur in unusual circumstances as described in the quote above. It is not a wave at all. Adrian . Adrian Stott 07956-299966
