It is impossible to make powder magazines too dry, and every care should be taken to ventilate them as much as possible during dry weather, by opening all doors, windows, loopholes, &c. Magazines are generally made bomb-proof, and are furnished with lightning conductors. They are divided into chambers, and these again divided by uprights into bays. At Purfleet, which is the grand depÔt for gunpowder in England, there are five magazines capable of containing 9,600 whole barrels each. Each magazine is divided into two chambers, and each chamber into 24 bays, and in each bay is placed 200 whole, 400 half, or 800 quarter barrels of powder. Total in the five Magazines, 48,000 barrels, equal to 4,800,000 pounds.