The Museum Until the 1870's, gunpowder was virtually the only practical explosives available. More powerful substances were in existence - in 1847 Ascanio Sobrero of Italy had developed nitroglycerine, and Christian Schonbein of Switzerland had produced guncotton (nitrocellulose) - but at the time these were far too unstable to use in guns and shells. From the 1870s, guncotton, which retained its explosive capacity when wet, was used in mines and torpedoes, but it was only when cordite was introduced into naval service in 1893 that gunpowder was replaced as the main propellant.
At Priddy's Hard four new magazines were built outside the earthworks to store these explosives. The old gunpowder magazines were used to store ammunition. Indeed storage space was at a premium, and as new 'high' explosives were introduced - TNT, amatol, torpex and others - new stores had to be built to house them. Even floating magazines made reappearance.
In the 20th century Priddy's Hard was a bustling, sprawling naval ordnance depot. Items entered the site either via the piers or by rail and were carried on the internal railway to magazines and stores or transit sheds. As needed, they went then to the laboratory section, where inspection, filling and repair of shells, cartridges, bullets, fuzes, primers, igniters, and detonators went on.
Undoubtedly the depot's finest hour was its ordnance supply to Operation Neptune, the naval support for D-Day in 1944, when the Allies successfully entered Nazi-occupied Europe, the biggest amphibious landing in history.
