As I understand it, the Napoleonic Wars saw a dramatic increase in the use of artillery, including but not limited to solid, round-shot cannonballs. In some battles, the total number of artillery rounds fired by both sides soared into the hundred-thousands. At Wagram in 1809, the number was about 200,000, while at Leipzig in 1813, the number was an astounding 400,000!

My question is specifically about the round shot: with so many of these cannonballs littering the various battlefields around Europe, whatever happened to all of them? Given their sheer number, it must've taken considerable time and effort for anyone to collect them all. Did armies make any effort to collect some of them after a battle, or were they mostly left alone for anyone to come along and collect them on their own? If a random person from this time were to come across one of them, what would they have likely done with it? Take it to a blacksmith to melt it down? Sell it? Maybe even keep it as a collector's item?