LONDON, England (CNN) -- An American professor doing research in London stumbled across a series of previously unknown letters written by, to, and about Benjamin Franklin, a stunning find that sheds new light on early U.S. history. 

The letters cover Benjamin Franklin's success in dealing with a British general. 

The collection of 47 letters are hand-written copies made 250 years ago, when Franklin lived in London. That they were filed under the copyist's name, not Franklin's, may explain why they were overlooked by historians until now, said a curator at the British Library, where the letters are held. 

The find is reported in the April issue of the William & Mary Quarterly, a journal of early American history and culture. 

The letters are important in large part because they offer a "wealth of new details" that affect modern understanding of Franklin, writes Alan Houston, the political science professor who discovered the letters in the spring of 2007. 

They also raise the question of how many other documents remain waiting to be found on Franklin and his life. 

Houston, a professor at the University of California at San Diego, discovered the letters on the last day of his last research trip to London, just before the library's closing time. 

"The first item was a letter from Benjamin Franklin to the secretary of the governor of Maryland, and I looked at it and I started to read, and I thought, 'This doesn't look familiar,'" Houston told CNN. "I've read everything Franklin ever wrote." 
Did they reveal anything new?
The letters are important in large part because they offer a "wealth of new details" that affect modern understanding of Franklin