Victor Appleton 
Tom Swift Omnibus #3: Tom Swift Among the Diamond Makers, Tom Swift in the Caves of Ice, Tom Swift and His Sky Racer [EPUB ebook] 

Tom Swift Omnibus #3 contains a trio of stories: In the seventh of Victor Appleton’s original Tom Swift novels, Tom goes in search of man-made diamonds, but winds up captured and held prisoner. In the eighth of Victor Appleton’s original Tom Swift novels, Tom flies his airship on a treasure hunt, searching for a valley of gold in Alaska. In the ninth of Victor Appleton’s original Tom Swift novels, Tom designs and builds a two-seat monoplane, but the plans go missing.