5-The Boy Inventors' Electric HydroAeroplane

This is the long-missing 5th book in this series. From the Publisher's scanty description: The restless, inventive spirit of Jack Chadwick and the persistent enthusiasm of his cousin, Tom Jesson, once more clamor for a new expression, and this book describes the unique result of their labors and the use to which it is opportunely put. Basically, the boys make a new friend and set out to create an electric aeroplane that can take off from and land on water. Adventure ensues!