Expense Magazine

In order to reduce the risk of a massive explosion should the main gunpowder magazine catch fire or be destroyed all gunpowder used in battle was stored in ready-to-use form in a smaller expense magazine. Expense magazines could be very simply constructed out of wooden timbers buried in thick turf. Powder for muskets was rolled in brown paper. Each cartridge also contained a lead musket ball. These in turn were placed in small wooden, portable boxes for easy transport. Artillery cartridges consisted of a linen bag for powder which was attached to the back of a disc shaped wooden shoe or sabot. The projectile, which could be a solid ball, a shell, a canister, or a cluster of small metal balls called grape shot, was attached to the front of the sabot. 

The magazine was built as a brick and stone arch covered in earth and part of the earthen wall. Arches are extremely strong and the covering of earth concealed the magazine from the enemy and provided protection against fire and enemy artillery. Archaeologists recovered evidence of a square mortar platform which would have been positioned on top of the earthwork directly over the earth covered expense magazine.