Gondola - Falkirk Wheel boat lift, Scotland - 11th Sep 2008

I don't know the answer to that, but maybe the aqueduct has a second door that shuts off a boats length of water and maybe water is introduced between the aqueduct doors and gondola before the doors open. I don't get how they make the seal unless there is a rubber seal that can be filled with water.

Thanks for these pictures - lots of interesting detail to study. Rather amusing that the tour boat is named the "Archimedes"! :-) The one thing I remain to wonder about is how they make the seal at the upper canal extension, without significantly torquing the lift arms.