Steve Parkes, Ian, I believe that shells were not used on ships prior to about 1820, because the shot was held in "garlands"; gratings with removable lids on the gun decks. The powder, being awfully dangerous stuff, was brought up from a magazine deep below the waterline (and therefore safe from enemy shot) by "powder monkeys", boys who scuttled up and down carrying at most four charges at a time.

If shell was to be used, the choice was between having the unfortunate monkeys clambering up the ladders while burdened with heavy shells (as a rough guide, the powder charge for a cannon was about one quarter of the weight of the shot or shell), or leaving lots of shells on the gun decks, where a chance hit could crack them open and cause an explosion.

The change over to shells on warships began with the advocacy of a Captain Paixhans of the French Navy, and was confirmed at Sinope in 1853, when the Russians set a Turkish squadron ablaze.



You are quite right; when firing a howitzer, the shell was loaded fuse-first so that firing the piece also ignited the fuse. When firing larger shells from mortars, the fuse was lighted manually first, then the mortar was fired. (There is a scene in the film, "Last of the Mohicans" which shows this.

The British Army only, during the Napoleonic Wars, used "spherical case-shot", the invention of a Lt. Shrapnel of the Royal Artillery. This was a shell which was stuffed with musket balls and a small amount of powder, and fired by the field and horse artillery on the battlefield. This would not have had any Naval application, so far as I know.