XEE4404934: Sappeurs Pompiersde Paris. The ladder's behind the scenes. Manoeuvring the ladder behind the scenes is the simplest. Weighing 34 kilos, 0m45 wide, having, redeployed, a height of 4 meters, it is in two planes, the uprights of the second being embedded in a double groove or slide practiced throughout the height of the uprights of the first. The second plane slides easily on the first and gives it a total height of 7m20., French School, (19th century) / Bridgeman Images
LSE4403207: Scientific experiment: the calculation of the speed of sound, by Humboldt, Louis-Joseph Gay-Lussac (Louis Joseph Gay Lussac), Bouvard, Prony and Mathieu, which determine the time elapses between the perception of light and that of a gun shot, on the night of 22 June 1822, near Paris., French School, (19th century) / Bridgeman Images