Father and Sally, Andy and Alice, were spending a morning down on the rocks.
The tide was out, and the jagged, uneven, rocky shore lay brown and dry under the hot summer sun. Soon the tide would turn and roll in again, dashing up higher and higher over the rocks until every one would be forced to run farther inland to escape the wash of the waves and the dashing spray.
But now the rocks were well out of water, and over them climbed Sally and Alice and Andy, hunting for treasures that the sea had left behind in little pools and hollows everywhere.
‘Here is seaweed,’ called Sally, holding up the long, wet, brown strands. ‘It is what the mermaids wear in their hair, Andy, you know.’
‘I don’t think my mermaid wore any,’ answered Andy, who still liked to tell the story of how his mermaid, as he called her, had saved his boat, ‘but then her green cap was very tight and I couldn’t see her hair. Oh, Sally, Sally, what is this?’
Andy was dancing about a little pool as he pointed to something on its edge, as excited as if he saw another mermaid rising from its clear and shallow depths.
‘It is a crab,’ said Sally, laughing at Andy’s puzzled face, ‘a baby crab. See him run.’
And Andy and Sally laughed happily together as the little crab scuttled hastily away out of sight.
‘These are periwinkles,’ explained Sally, as she came upon Alice gingerly poking with a stick a number of small gray shells. ‘That shell is a house, and the periwinkle lives inside. When he goes walking he carries his house on his back.’
‘Sit very still for a moment,’ said Father, who had come up behind the little group, ‘and perhaps you will see the periwinkles walking away.’