I'm sure you've all noticed documents in English from the 1700's often have 'F' where, if written now, there would be an 'S'. You can see what I'm talking about a few times in this example, like at the beginning where it says "Prayers faid" or in the date "Tuefday November 26. 1700."
What's going on with this? When did it start? When did it stop?