Charles Dickens, Dombey and Son chapter 19 pg 270,

In Charles Dickens Dombey and Son chapter 19 pg 270, the lines reads, “ he saw his uncle hanging down his head in the boat, and Captain Cuttle rapping him on the back with the great silver watch ( it must have been very painful ), and gesticulating hopefully with the teaspoons and sugar tongs."

So my question is; Does any one know why the Captain would be hitting his friend Uncle Sol (Solomon Gills)?