class="c009">“No, but there might be some sharp German spy hanging around this place,” replied the other earnestly. “You know they do say they’re everywhere. I’ve heard British soldiers in Calais and Dunkirk tell of mysterious strangers who disappeared when approached as if they were made of smoke. This spy system the Kaiser’s men have down to a fine point. It’s hard to keep anything from being carried to German Headquarters these days.”

“Still, there are a lot of things they haven’t learned before they happened,” declared Billy. “That first British army of some eighty thousand soldiers came over to France, and nobody knew a thing about it until they were on the firing line. But, Frank, do you reckon the Germans have been watching the three of us working here with our hangar and hydro-aëroplane?”

“I’m as sure of it as I am of my own name,” declared the other firmly. “Why, the very fact that our hangar differed so much from ordinary ones, being so much larger for one thing, would make them suspect. Then there has been a heap of talk going on about this wonderful airship of ours, which was carried, every word of it, to German Headquarters.”

“Batter and butterflies!” spluttered Pudge, who seemed addicted to strange exclamations, especially when excited, “we’ll certainly have to watch out, then, now that our wonderful Sea Eagle is in working order.”

“Yes,” said Billy Barnes earnestly, “it would be a tough joke on the company to have some clever thieves get away with it, just when we are ready to show the French Government that it is away above ordinary seaplanes.”

“There’s the hangar, boys,” remarked Frank, with a vein of relief in his voice, as though grave fears may have been giving him more or less uneasiness. “Stir your stumps, Pudge, and we’ll soon be under our own roof. I may have a suggestion to make after we’ve looked around a bit that I hope both of you will agree with.”

While the three chums are advancing on the strangely elevated building that had been erected to accommodate their seaplane, we may take advantage of the opportunity to glance backward a bit, in order to see who and what they were. We do this for the benefit of those readers who may not have had the good fortune to peruse previous volumes in this series.

Two bright, inventive brothers, New York boys, who had actually built an aëroplane which they named the Golden Eagle, had shipped it to Central America when given a chance to save a plantation owned by their father, and threatened by the revolutionists in Nicaragua. This they had managed to accomplish, through the assistance of a young reporter friend named Billy Barnes. In this book, which was called The Boy Aviators in Nicaragua, were also related the thrilling adventures that befell the young air pilots when their craft was carried out to sea in an electrical storm; and also how they were rescued by means of a wireless apparatus through which they communicated with a steamer.

In the second volume, The Boy Aviators on Secret Service, the reader was taken to the mysterious Everglades region of Florida where the young inventors once more demonstrated their ability to grapple with emergencies. They proved that they were patriotic sons of Uncle Sam by discovering and putting out of commission a factory that was making dangerous explosives without the consent of the Washington Government.

It was a long jump from Florida to the depths of the Dark Continent, but the occasion arose necessitating their taking this trip to Africa. If you want to learn how theirs was virtually the first aëroplane to soar