The excursionists who go down in summer weather to Margate and Ramsgate scarcely think that ships could be cast away and broken up upon the hidden sands beneath the sparkling waters. They know not that scarce one of these sands but at low water is dotted with low, black timbers, and that there are few more dangerous pieces of navigation in the world than the passage up the mouth of the Thames on a wild night when a fierce gale is blowing and the snow and sleet driving before it, obscuring the guiding lights that mark the channels between the sands.