All the guide books suggest that the lock keepers on the Canal du Midi do not expect to receive a tip. However, many of them have a little stall displaying Mon Mammon preserves and Vin de Table at highly inflated prices. Sometimes a purchase from these stalls might not speed your passage through this time but might do on the return. The lock keepers also have telephones. They might communicate with the next lock keeper if you are sypathetic to their wares, the next lock keeper might also expect you to be.
At one lock, the lock keeper displayed a large number of wood sculptures. Many were obviously fixtures but there were some smaller works of art that were definitely for sale. I must say that I am not a collector of sculpture and it didn't really interest me. This lock keeper also had a large yellow labrador dog. He was particularly fond of mooring ropes and would not let go of ours nor would he let us get to it to retrieve it, pulling the end with great strength and gusto, dropping it and then barking furiously before attaching himself to it again. This game went on for quite a time. Long enough for us to get a picture anyway.
I wondered whether he was trained to hold on to our rope until we had bought a sculpture or left a tip!
19 hours ago