Gibbon on difference between Augustine & Calvin

Edward Gibbon (1737-1794), in "The History of the Decline and Fall of the Roman Empire," made this observation about Augustine of Hippo (354–430) and John Calvin (1509–1564),

"the real difference between [Augustine & Calvin] is invisible even to a theological microscope...."

See the quote in a scanned edition of the book at Google Books, or in an edition retyped for the
web.