Inventions in the Century

by William Henry Doolittle

Mention has been made of the cannon. It was probably the earliest attempt to obtain motive power from heat. The ball was driven out of an iron cylinder by the inflammatory power of powder. Let a piston be substituted for the cannon ball, as was suggested by Huygens in 1680 and by Papin in 1690, and the charge of powder so reduced that when it is exploded the piston will not be thrown entirely out of the cylinder, another small explosive charge introduced on the other side of the piston to force it back, or let the cylinder be vertical and the piston be driven back by gravity, means provided to permit the escape of the gas after it has done its work, and means to keep the cylinder cool, and we have the prototype of the modern heat engines. The gunpowder experiments of Huygens and Papin were not successful, but they were the progenitors of similar inventions made two centuries thereafter.

Jan Baptista van Helmont, a Flemish physician (1577-1644), was the first to apply the term, gas to the elastic fluids which resemble air in physical properties. Robert Boyle, the celebrated Irish scholar and scientist, and improver of the air pump, and Edwin Mariotte, the French physicist who was first to show that a feather and a coin will drop the same distance at the same time in a reservoir exhausted of air, were the independent discoverers of Boyle’s and Mariotte’s law of gases (1650-1676). This was that at any given temperature of a gas which is at rest its volume varies inversely with the pressure put upon it. It follows from this law that the density and tension, and therefore the expansive force of a gas, are proportional to the compressing force to which it is subjected. It is said that Abbé Hauteville, the son of a baker of Orleans, about 1678 proposed to raise water by a powder motor; and that in 1682 he described a machine based on the principle of the circulation of the blood, produced by the alternate expansion and contraction of the heart.

The production of heat by concentrating the rays of the sun, and for burning objects had been known from the time of Archimedes, and been repeated from time to time.

Thus stood this art at the close of the 17th century, and thus it remained until near the close of the 18th.

In England Murdock, the Cornish Steam Engineer, was the first to make and use coal gas for illuminating purposes, which he did in 1792 and 1798. Its utilisation for other practical purposes was then suggested.

Gas engines as motive powers were first described in the English patent to John Barber, in 1791, and then in one issued to Robert Street in 1794. Barber proposed to introduce a stream of carbonated hydrogen gas through one port, and a quantity of air at another, and explode them against the piston. Street proposed to drive up the piston by the expansive force of a heated gas, and anticipated many modern ideas. Phillipe Lebon, a French engineer, in 1799 and in 1801 anticipated in a theoretical way many ideas since successfully reduced to practice. He proposed to use coal gas to drive a piston, which in turn should move the shaft that worked the pumps which forced in the gas and air, and thus make the machine double-acting; to introduce a charge of inflammable gas mixed with sufficient air to ignite it; to compress the air and gas before they entered the motor cylinder; to introduce the charge alternately on each side of the piston; and he also suggested the use of the electric spark to fire the mixture. But Lebon was assassinated and did not live to work out his ideas.

At the very beginning of the 19th century John Dalton in England, 1801-1807, and Gay-Lussac in France began their investigations of gases and vapours. Dalton was not only the author of the atomic theory, but the discoverer of the leading ideas in the “Constitution of Mixed Gases.” These features were the diffusion of gases, the action of gases on each other in vacuum—the influence of different temperatures upon them, their chemical constituents and their relative specific gravity.

Gay-Lussac, continuing his investigations as to expansion of air and gases under increased temperatures, in 1807-10, established the law that when free from moisture they all dilate uniformly and to equal amounts for all equal increments of temperature. He also showed that the gases combine, as to volume, in simple proportions, and that several of them on being compounded contracted always in such simple proportions as one-half, one-third, or one-quarter, of their joint bulk. By these laws all forms of engines which were made to work through the agency of heat are classed as heat engines—so that under this head are included steam engines, air engines, gas engines, vapour engines and solar engines. The tie that binds these engines into one great family is temperature. It is the heat that does the work. Whether it is a cannon, the power of which is manifested in a flash, or the slower moving steam engine, whose throbbing heart beats not until water is turned to steam, or the sun, the parent of them all, whose rays are grasped and used direct, the question in all cases is, what is the amount of heat produced and how can it be controlled?

It, then, can make no difference what the agent is that is employed, whether air, or gas, or steam, or the sun, or gunpowder explosion, but what is the temperature to be attained in the cylinder or vessel in which they work. Power is the measure of work done in a given time. Horse power is the unit of such measurement, and it consists of the amount of power that is required to raise one pound through a vertical distance of one foot. This power is pressure and the pressure is heat. The unit of heat is the amount of heat required to raise the temperature of a pound of distilled water one degree—from 39 degrees to 40 degrees F. Its amount or measurement is determined in any instance by a dynamometer.

These were the discoveries with which Philosophy opened the nineteenth century so brilliantly in the field of Pneumatics.