Edgar Rice Burroughs 
The Lost Continent [PDF ebook] 

The Lost Continent is one of the least-known of Burroughs’ thrilling science-fiction tales. In the year 2137, civilization has been in decline for nearly two centuries, and war-torn Europe is but a distant memory to the inhabitants of the isolated United States. But an American adventurer rediscovers the Old World, which has become a strange and savage land.