"Benjamin Franklin: In Search of a Better World," Benjamin Franklin Tercentenary traveling exhibition, 2005-2008

In Franklin's correspondence is a June 1752 letter to his London friend, William Strahan, asking him to buy and ship to Franklin a large burning glass "of about 12 inches Diameter." Because of its small size, this glass cannot be the lens Strahan purchased at that time. However, it was given to the Historical Society of Pennsylvania by Callendar Price in 1846 as having been Franklin's; the early date of the gift makes it possible that the glass could have belonged to him.