>Can anyone tell me why and how the ligatures "ct" and "st" came about? I've
>read about all the other ligatures but find nothing of these two.
These ligatures are very old (CAxton, 1476, Alde Manuce, Garamond, etc. used them).
At that time, they was more ligatures (actualy bigrammes and trigrammes) than single
letters, like in Gutenberg character set, as scribes were used to use them. This habit
desappears during the XVI0 century. They are what we call "aesthetic" ligatures, nothing else.
I have edited, last quarter, a 140 page magazine (so called Cahier GUTenberg), on ligatures,
however it is in French!