# Gunpowder engine

 Huygens' 1678 gunpowder engine. 1682 demonstration of Huygens gunpowder engine, where a dram of gunpowder creates enough vacuum to lift 7-8 boys into the air.
In engines, a gunpowder engine is one that employs gunpowder to produce a vacuum inside the piston and cylinder causing the atmospheric pressure to perform work in driving the piston downward to eliminate the vacuum. [1]

History
The central problem of this period was that of raising water from the Seine to supply the palace of Versailles. Two individuals, Samuel Morland (1661) and Jean de Hautefeuille (1678) seemed to have published designs for engines that used gunpowder to facilitate the raising of water; but, it seems, their designs did not employ a piston and cylinder.

The first gunpowder engine, using a piston and cylinder, was invented and built in 1678 by Dutch mathematical physicist Christiaan Huygens called Huygens gunpowder and air engine. This is considered to have been the first true motive engine. It is inferred that Huygens was aware of earlier attempts at gunpowder-created vacuums designed to raise water.

An account of Huygens’ invention was published in the 1680 memoir “A New Motive Power by Means of Gunpowder and Air”. [2] By 1682, the device had successfully shown that a dram (1/16th of an ounce) of gunpowder, in a cylinder seven or eight feet high and fifteen or eighteen inches in diameter, could raise seven or eight boys (or about 1,100 pounds) into the air, who held the end of the rope.

Operation
Huygens’ engine consisted of a hollow cylinder A, well polished within and of uniform size throughout. B, a moveable piston inserted into the top of the cylinder, the upper portion of which is surrounded by a small quantity of water. C, C, two apertures, each one-half the diameter of the cylinder. D, D, tubes of moist and soft leather secured to little cylinders which are fastened to the main cylinder at the apertures (one of the tubes being shown extended, the other hanging). E, E, holdfasts, by which the cylinder is joined to the case in which it sits, which is not shown in the figure. F, F, a cord attached to the piston and passing over a pulley G, for the purpose of raising whatever is attached to it. H, a small box for receiving the charge of gunpowder, attached to the bottom of the cylinder by means of a screw, a leather ring being employed to aid in making the joint air-tight.

On the explosion of the charge, the air contained in the cylinder was driven out through the leather tubes C D, C D, which were momentarily extended, but immediately closed again by the external air; and the cylinder being vacuous, the piston B was driven down by the atmospheric pressure, drawing with it the cord F, and raising whatever was suspended by it.

References
1. Galloway, Robert L. (1881). The Steam Engine and its Inventors (ch. II: Attempts to Derive a New Motive Power from the force Exerted by the Atmosphere in Rushing into a Vacuum, pgs. 17-). London: MacMillan and Co.
2. Huygens, Christiaan. (1680). “A New Motive Power by Means of Gunpowder and Air”, Royal Academy of Sciences.