The capture of a 4-lb. grilse in the Thames estuary in December, 1901, raised some hopes that we might in course of time see salmon at London Bridge. Mr. R. Marston, a great authority, in an article on "The Thames a Salmon River," in the Nineteenth Century, has given many reasons why he fears that this will not be realised. The question is not so much whether the salmon can come up, as whether the smolts, or young salmon, could get down through the polluted water.