“And we haven’t our side lamps going!” cried Betty, in alarm, as she realized the danger.  “Quick, girls, come up here!” she called to Grace and Amy.  “One of you switch on the electric lamps.  At least they can see us, then, and can avoid us.  Oh, I don’t know what to do!  I never thought of this!”

A sudden glow told that Amy had found the storage battery switch, for the red and green lights now gleamed.  Again the on-coming steamer whistled, sharply—­ interrogatively.  Betty answered, but she was not sure she had given the right signal.

“Why don’t you start the motor?” she called to Mollie.

“I can’t!  It doesn’t seem to work.”

“The switch is off!” exclaimed Grace, as she came out of the cabin.  With a quick motion she shoved it over.

“How stupid of me!” cried Betty.  “I should have seen to that first.  Try again, Mollie!”

Again Mollie pressed the button of the self-starter, but there was no response.  The Gem was still drifting, seemingly in the very path of the steamer.

“Why don’t they change their course?” wailed Amy.  “Can’t they see we’re not under control?  We can’t start!  We can’t start!” she cried at the top of her voice, hoping the other steersman would hear.

“The steamer can’t get out of the channel—­ that’s the reason!” gasped Betty.  “I see now.  It’s too shallow for big boats except in certain places here.  We must get out of her way—­ she can’t get out of ours!  Girls, we must start the motor!”

“Then try it with the crank, and let the automatic go,” suggested Aunt Kate, practically.  “Probably it’s out of order.  You must do something, girls!”

“Use the crank!” cried Betty, who was hobbling the wheel over as hard as she could, hoping the tug of the current would carry the Gem out of danger.  But the craft hardly had steerage way on.

Mollie seized the crank, which, by means of a long shaft and sprocket chain, extending from the after cabin bulkhead to the flywheel, revolved that.  She gave it a vigorous turn.  There was no welcome response of throbbing explosions in the cylinders.

“Try again!” gasped Betty, “Oh, all of you try.  I simply can’t leave the wheel.”

The steamer was now sending out a concert of sharp, staccato blasts.  Plainly she was saying, loudly: 

“Get out of my way!  I have the right of the river!  You must get out of my way!  I can’t avoid you!”

“Why don’t they stop?” wailed Grace.  “Then we wouldn’t bump them so hard!”

As if in answer, there came echoing over the dark water the clang of the engine-room bell, that told half-speed ahead had been ordered.  A moment later came the signal to stop the engines.

“Oh, if only Uncle Amos—­ or some of the boys—­ were here!” breathed Betty.  “Girls, try once more!”

Together Mollie and Grace whirled the crank, and an instant later the motor started with a throb that shook the boat from stem to stern.