“Now I’m going to begin my lesson,” announced Grace, who, having gotten herself ready for breakfast, took up the book showing how various sailor knots should be made.  With a piece of twine she tied “figure-eights,” now and then slipping into the “grannie” class; she made half-hitches, clove hitches, a running bowline, and various other combinations, until Amy declared that it made her head ache to look on.

The girls had breakfast, strolled about on shore for a little while, and then started off, intending to stop in Dunkirk, which town lay a little below them, to get some supplies, and replenish the oil and gasoline.

It was while Betty was bargaining for the latter necessaries for her motor in a garage near the river that she heard a hearty voice outside asking: 

“Have you men seen anything of a trim little craft, manned by four pretty girls, in the offing?  She’d be about two tons register, a rakish little motor boat, sailing under the name Gem and looking every inch of it.  She ought to be here about high tide, stopping for sealed orders, and——­ "

“Uncle Amos!” cried Betty, hurrying to the garage door, as she recognized his voice.  “Are you looking for us?”

“That’s what I am, lass, and I struck the right harbor first thing; didn’t I?  Davy Jones couldn’t be any more accurate!  Well, how are you?”

“All right, Uncle.  The girls are down in the boat at the dock,” and she pointed.  “The man is going to take down the oil and gasoline.  Won’t you come on a trip with us?  We expect to make Rainbow Lake by night.”

“Of course I’ll come!  That’s why I drifted in here.  I worked out your reckoning and I calculated that you’d be here about to-day, so I come by train, stayed over night, and here I am.  What kind of a voyage did you have?”

“Very good—­ one little accident, that’s all,” and she told about getting adrift.

“Pshaw, now!  That’s too bad!  I’ll have to give you some lessons in mooring knots, I guess.  It won’t do to slip your cable in the middle of the night.”

The girls were as glad to see Betty’s uncle as he was to greet them, and soon, with plenty of supplies on board, and with the old sea captain at the wheel, which Betty graciously asked him to take, the Gem slipped down the river again.

At noon, when they tied up to go ashore in a pleasant grove for lunch, Mr. Marlin demonstrated how to tie so many different kinds of knots that the girls said they never could remember half of them.  But most particularly he insisted on all of them learning how to tie a boat properly so it could not slip away.

Betty already knew this, and Mollie had a fairly good notion of it, but Grace admitted that, all along, she had been making a certain wrong turn which would cause the knot to slip under strain.

They motored down the river again, stopping at a small town to enable Mollie to go ashore and telephone home to learn the condition of little Dodo.  There was nothing new to report, for the operation would not take place for some time yet.