The hydroplane ran easily along the ground, for the bicycle wheels were always kept in first class condition; and as the speed kept on increasing Frank soon uptilted the plane, and like a great bird rising from the ground, with a graceful sweep the flying machine took to the air.

Long practice had made the Bird boys familiar with every movement connected with the actions of an aeroplane, but at the same time they tried to be always on their guard against being incautious.  That is the trouble with most aviators; they grow so familiar with danger that they forget the terrible risk that always hangs over the head of every one who soars aloft in his frail airship; and then, when finally something happens after they have become too reckless, they never get another chance.

Sweeping along not more than three hundred feet above the ground, the boys were home in almost no time.  They could see the car containing Percy Carberry, and his crony, Sandy, just vanishing among the houses of Bloomsbury; and the Chief, about half-way there, waved his hat at them as they sped past him.

Then the aeroplane dropped lightly down close to the hangar back of the Bird home, where Andy and his father, the professor, lived, together with old Colonel Whympers, the veteran who used crutches or a cane on account of his rheumatism, brought on, he always declared, not by age, oh! no, but the wounds he received many years ago, when he was fighting for his country in the great civil war.

He was sitting there on a pile of lumber waiting for them, a quaint old fellow, who was greatly beloved by both cousins; and who believed firmly that some fine day Andy Bird was bound to even eclipse the fame which his father had gained in the field of science and aviation.

It happened that the professor was away at the time delivering a series of lectures before some body of scientists in a distant city.  And whenever the boys were in their shop the old veteran was in the habit of coming around, to see what new and wonderful things engaged their attention, as well as chatting with them.  And he was as welcome as the sun in May.

Of course, just then he was bristling with questions as a hedgehog would be with sharp-pointed quills.  And knowing the Colonel of old, Frank and Andy lost no time in telling him all that had happened to them, from the time of their little accident, down to when they heard the latest news from Percy Carberry.

“And I warrant now,” remarked Colonel Whimpers, as soon as the tale was finished, “that you two boys get the first clew to where the robbers are hiding.  Didn’t you beat the wonderful Chief out before, and doesn’t history have a habit of repeating itself?  Oh; if only I was ten years younger, how I’d love to be along, when all these glorious things are happening.  I hate to think I’m put by on the shelf and never can be any good again.”

That was the old man’s only fault; he was forever complaining because his day for indulging in exciting scenes had passed; but any one who knew the half that he had passed through, would think the colonel had no reason to say anything; and that it was only right that someone else had a show.