hiding, had made a nest for themselves among the stalks of loosestrife,
and sat watching the canal for sign of a moorhen or a water-rat.
The afternoon was bright and very still, with a dazzle on the water and
a faint touch of autumn in the air--the afterglow of summer soon to pass
into grey chills and gusts of rain. For many minutes neither had
spoken.

"Look!" said Tilda, pointing to a distant ripple drawn straight across
the surface. "There goes a rat, and I've won!"

The boy said--

"A boat takes up room in the water, doesn't it?"

"0' course it does. But what's that got to do with rats?"

"Nothing. I was thinking of Sam's puzzle, and I've guessed it. A boat
going downwards through a lock would want a lock full, all but the water
it pushes out from the room it takes up. Wouldn't it?"

"I s'pose so," said Tilda doubtfully.

"But a boat going up will want a lock full, and that water too. And
that's why an empty boat going downhill takes more water than a loaded
one, and less going up."

To Tilda the puzzle remained a puzzle. "It _sounds_ all right," she
allowed. "But what makes you so clever about boats?"

"I've _got_ to know about them. Else how shall we ever find the
Island?"

She thought for half a minute.

"You're sure about that Island?" she asked, a trifle anxiously.

Arthur Miles turned to her with a confident smile.

"Of course I'm sure."

"Well, we'll arsk about it when we get to Stratford-on-Avon."

She was about to say more, but checked herself at sight of a barge
coming down the canal--slowly, and as yet so far away that the tramp of
the tow-horse's hoofs on the path was scarcely audible. She laid a hand
on 'Dolph's collar and pressed him down in the long grass, commanding
him to be quiet, whilst she and the boy wriggled away towards an alder
bush that stood a furlong back from the bank.

Stretched at length behind the bush, she had, between the fork of its
stem, a clear view of the approaching boat. Its well coverings were
loose, and by the upper lock gate the steersman laid it close along
shore and put out a gang-plank. His mate, after fitting a nosebag on
the horse, came at a call to assist him, and together they lifted out a
painted wooden steed wrapped in straw, and carried it to the store.

Having deposited it there, they returned and unloaded another. Five
horses they disembarked and housed thus; and then, like men relieved of
a job, spat on their hands and turne