I thought that it was really interesting, and funny, about that long s that appeared in the old printing of “The Flea.â€Â I decided to look up older letterform and find out more about why texts appeared this way. The practice of using the Å¿ in place of s died out before the 1800s in Roman and Italic type faces. The International Phonetic Alphabet uses a similar symbol: ʃ to represent the “sh†sound. There is even an example of a long s in the United States Bill of Rights.Â
Some times French and German printing still uses ligatures for s’s though.
berlin 2002
In calculus a version of the long s symbol is used to stand for the latin word “summa,†or sum. The way it made us laugh in “The Flea†others have used the confusion between the long s and the letter f for humor.  The long s was never used to end a word. For example the word sentiments would look like fentiments.Â
           Another letterform used in the past was the “half r†or r rotunda, which was used to replace the letter r if it followed another letter. This may have been to save space. It certainly would not be able to give words double meanings like the long s though.Â
Here you can see the half r and long s in the title Hystoriae ecclesiastica:

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