French chart giving details of the balloons which left Paris during the siege of the city in 1870-1871. In 1870, Germany had defeated the armies of France in the Franco-Prusian war. Paris, surrounded by German troops waiting for the city to surrender, was effectively cut off from the outside world. Balloons already inside Paris when the siege began were used to observe troop movements outside, and as a means of transporting both mail and people to, and from, the besieged city. Of the 66 balloons which left Paris during the siege, 59 succeeded in escaping to safety, while five were captured by the enemy and the remainder lost at sea.
© Science Museum / Science & Society Picture Library