“Well, you saw smoke all right, and if you’d listened sharp, you’d have heard a sassy little bark at the same time, Andy.”

“A what, Frank?”

“Call it a snarl, then.  Take up your glasses, Andy, and look; while I drop out even a little more of our speed, so we’ll fall back further.”

Hardly had Andy clapped the glasses to his eyes than he gave vent to an exclamation of mingled amazement and alarm.

“That greenhorn is looking this way, Frank, and as sure as goodness he’s pointing at us right now.  Oh! he did something then, for I saw another puff of smoke, and it came right from his hand.  Why, he’s shooting at us, Frank!  That must be a gun he’s got in his hand, and he’s trying to hit us!  If our motor didn’t keep up such a constant whirl we might have heard the whine of that lead when it went singing past us!”

“Yes, perhaps we might,” Frank went on to say, composedly.

“But what can we do?” demanded the other, nervously.

“Nothing more than decrease our own speed as often as they do, and play the game of tag backwards.  If they get going it too strong, why, just as I said before, I’ll turn tail, and head back toward Bloomsbury, daring them to follow, which you can be sure they won’t, because our town is a mighty unhealthy place just now for Casper Blue and his pal.  There! he fired again.”

“That makes three times he’s tried it, Frank!”

“And I guess he can try the other three without doing us any damage, Andy.”

“You believe that, do you?” asked the one spoken to.

“Sure thing,” Frank replied positively.  “Why, it would be one chance in ten thousand that he could strike any part of our aeroplane at that distance, going as both of us are, and with only a revolver.  I’d be willing to let him blaze away all day, without being a bit afraid.  But I’m bound that the two air crafts must keep at least this distance apart.”

The man in the other airship did fire three more times, but without any success whatever.  And as though the rival navigator realized that Frank’s tactics would effectually prevent his coming into closer contact with the pursuing craft, he no longer tried to close in, but increasing his speed, was quickly about the old distance away.

Whereupon Frank Bird also hit up the pace cautiously.

“That’s the ticket!” cried out Andy, presently.  “I guess we’re holding our own again now.  For a little while I began to be afraid that they were going to just make us take their dust, and give us the merry ha-ha, vanishing in the distance.  But now I know you’ve got the twist of the thing down fine, Frank, and can haul up on the biplane, or drop back, just as you feel like.”

For a long time they kept on, neither saying anything, for talking is always more or less of an effort when speeding along in an aeroplane, with the wind striking one in the face.

Frank had had no time to fully adjust the muffler which he usually wore about his neck when about to soar to a dizzy height, so he would have to do the best he could; and besides, there was little chance of the other aeroplane venturing to bore upward to any unusual degree, all the efforts of the bank thieves being directed toward making their escape.