I have a 3.5"solid shot James (with lead/tin case, canvas, greae) found nearby in DC near one of the forts. In the forts it was mandatory to refill shells every once in a while--scrape out the power, dicard, refill with fresh, restore. What may have happened is that the shell in question was simply not re-loaded and found itself into a caisson. When powder was scrape out it was done outdoors with a wooden spoon, a task that was awkard and timeconsumeing...There is a documented story of a young offcer who, in order to speed things up, gave the troops priming wires to dig out the caked and hardened power. That was the last thing heard form the working party--the resulting explosion blew several thousand tons of one of the Washington Forts into the adjacent valley. Question: was the shell in question found with a fuse in place? A paper fuse (such as Confederates might have had to use) could have decayed, with the power, over time? Let me know. M