A power cable sign

It's quite funny, as I think they say: 'Danger power cables,' as a warning to boats that there are cables under the canal. I'm not sure what the boats are supposed to do. ('Well I think we'd better turn round and head back to the west coast. It's only 96 km. Shouldn't take us more than a day and a half.') I was hoping to photograph the Culloden Viaduct today, but I really need it to be bathed in sunshine. I also have to work out how to do it.
Extra of blossom: Alder or buckthorn?