Well a tumbler is where they, the buckets used to go over the top and empty into a chute into the hopper  and er went cos it was on a continual chain you see cos you had a bucket two links, a bucket two links, a bucket two links, all the way round and that's how you used to dredge all the time round and round and round and that's how it went over to the top tumbler cos you had a bottom tumbler on this layer and a top tumbler, otherwise  you couldn't dredge otherwise and that top tumbler, I am certain it had five, five sides to it because at one, at one time you'd tip a bucket on one then you'd get two lengths  so it kept the tumbler more or less equal all the way round the wear and tear of it.