Medieval inventions or ???

I do now one thing. Salt-petre became so valuable that cargos of it were hidden and disguised as ballast, secretely unloaded and stored for the manufacture of gun powder.

I would suggest some investigation to weapons sometimes referred to variously in ancient and medieval documents as "missiles", "darts", etc. Just what weapons fired such things? Guns?, cross-bows?,or what? For some very famous personages it seems "millstones" or "tiles" or "crockery" were very deadly!

Also, by the way, in certain paintings / etchings, etc. from the past, we sometimes see either one or two windmills, or sometimes large groups of them! Some times they are located on the top of hills, and other times at sea ports! I understand thier use in grinding grains, and pumping water, etc., but just what other uses could they have? For example could they have powered winches? Could windpower have raised and lowered the great chains that are either seen in paintings, etc., or mentioned in literature as protecting harbors?