7 books
The Airship Boys' Ocean Flyer
The Boy Scouts of the Air in Indian Land
The Boy Scouts of the Air at Greenwood School (Classic Reprint)
The Airship Boys' Ocean Flyer, or New York to London in Twelve Hours (Classic Reprint)
On the Edge of the Arctic
The Air Ship Boys
On the Edge of the Arctic Or, an Aeroplane in Snowland