Above is a selection from a 1711 printing of Milton's Paradise Lost. Notice that what appears to be the modern letter f appears in the place of the modern letter s. This is the "long s"--a typographical practice of past centuries. When did it fade away? Evan Soltas used Google's N-gram function to assess when "Paradife Loft" became "Paradise Lost". This is what he found:
The switch occurred over a century spanning 1750-1850.
Link -via Marginal Revolution | More Info on the Long S