Victor Appleton 
Tom Swift in the City of Gold [PDF ebook] 
Or, Marvelous Adventures Underground

Tom Swift in the City of Gold is the 11th book in the original Tom Swift series. "Every boy possesses some form of inventive genius. Tom Swift is a bright, ingenious boy and his inventions and adventures make the most interesting kind of reading." "These spirited tales convey in a realistic way, the wonderful advances in land and sea locomotion and other successful inventions. Stories like these are impressed upon the memory and their reading is productive only of good." This series of adventure novels starring the genius boy inventor Tom Swift falls into the genre of "invention fiction" or "Edisonade".