the first use of the submarine in warfare, was an oaken chamber about five-and-a-half feet (1.6 m) wide and seven feet (2.1 m) high. It was propelled by a front-mounted, pedal-powered propeller at a speed of up to three miles per hour (5 km/h), had a barometer to read depth, a pump to raise or lower the submarine through the water, and provision for both lead and water ballast. When Bushnell learned that the candle used to illuminate instruments inside the "turtle" consumed the oxygen in its air supply, he turned to Benjamin Franklin for help. The solution: the phosphorescent weed, foxfire. Heavy tides thwarted the first sabotage operation. A copper-clad hull that could not be penetrated by the submarine's auger foiled the second. (The "turtle" did blow up a nearby schooner, however.) The secret weapon would almost certainly have achieved success against a warship if it had not gone to the bottom of the Hudson River when the mother ship to which it was moored was sunk by the British in October 1776. An early device developed for concealing intelligence reports when traveling by water was a simple weighted bottle that could be dropped overboard if there was a threat of capture. This was replaced by a wafer-thin leaden container in which a message was sealed. It would sink in water, melt in a fire, and could be used by agents on land or water. It had one drawback—lead poisoning if it was swallowed. It was replaced by a silver, bullet-shaped container that could be unscrewed to hold a message and which would not poison a courier who might be forced to swallow it. Deception operations To offset British superiority in firepower and number of troops, General Washington made frequent use of deception and disinformation. He allowed fabricated documents to fall into the hands of enemy agents or be discussed in their presence. He allowed couriers carrying bogus information to be "captured" by the British, and inserted forged documents in intercepted British communications that were then permitted to continue to their destination. He had army procurement officers make false purchases of large quantities of supplies in places picked to convince the British that a sizable rebel force was massing. Washington even had fake military facilities built. In all this, he managed to make the British believe that his three-thousand-man army outside Philadelphia was forty thousand strong. After learning from