Connecticut Yankee

Mark Twain is perhaps best known for his children's books, Huckleberry Finn and Tom Sawyer. Some forty years ago or so, I read one of his adult novels, A Connecticut Yankee at King Arthur's Court, the story of an American of the late 1800s traveling back in time to England to experience Medieval life. The only part I now remember is the Yankee saving his own skin by predicting a darkening of the daytime sky. The sun then blacked out on the day he predicted. The people were astounded. 

How was he able to do that? The event was a historically memorable solar eclipse that the Yankee had learned of during his life in America.