Stories of Useful Inventions

by S. E. Forman

FIG. 5.—AN ANCIENT METHOD OF DRAWING WATER.

Worcester spent a large part of his fortune in trying to improve the steam-engine, yet he received neither profit nor honor as a reward. He died poor and his name was soon forgotten. His service to the world was nevertheless very great. In his time the mines of England had been sunk very deep into the earth; and the deeper they were sunk the greater was the difficulty of lifting the water out of them and keeping them dry. The water was lifted up from the mines by means of buckets drawn by horses or oxen (Fig. 5). Sometimes it took several hundred horses to keep the water out of a single mine. It was Worcester's object to construct an engine that would do the work of the horses. The engine he built could not do this, yet it furnished the idea—and the idea is often the most important thing. It was not long before engines built upon Worcester's plan were doing useful work at the mines. At the opening of the eighteenth century the steam-engine had been put to work and was serving man in England and throughout the continent of Europe.

The first engines were not safe. Often the steam pressed too heavily upon the sides of the vessel in which it was compressed and there were explosions. About 1680 Denis Papin, a Frenchman, invented the safety valve, that is a valve that opens of its own accord and lets out steam when there is more in the vessel than ought to be there. About ten years later Papin gave the world another most valuable idea. In Worcester's engine the steam in the steam chest pressed directly on the water that was to be forced up. Papin showed a better way. He invented the engine shown in Figure 6. In this engine a small quantity of water was placed in the bottom of the cylinder A. Fitting closely in the cylinder was a piston B such as Papin had seen used in ordinary pumps. We will suppose that the piston is near the bottom of the cylinder and that a fire is built underneath. The bottom being made of very thin metal the water is rapidly converted into steam and thus drives the piston up to the top as shown in the figure. Here a latch E catches the piston-rod H and holds the piston up until it is time for it to descend. Now the fire is removed and the steam, becoming cold, is condensed and a vacuum is formed below the piston. The latch E now releases the rod H and the piston is driven down by the air above it, pulling with it the rope L which passes over the pulleys TT. As the rope descends it lifts a weight W or does other useful work. As the inventor of the piston Papin ranks among the greatest of those whose names are connected with the development of the steam-engine.

Our story has now brought us to the early part of the eighteenth century. Everywhere men were now trying to make the most of the ideas of Worcester and Papin. The mines were growing very deep. As the water in them was getting beyond control something extraordinary had to be done. Now it seems that whenever the world is in need of an extraordinary service someone is found to render that service. The man who built the engine that was needed was a humble blacksmith of Dartmouth, England, Thomas Newcomen. This master mechanic in 1705 constructed the best steam-engine the world had yet seen. We must study Newcomen's engine (Fig. 7) very carefully. The large beam ii moved freely up and down on the pivot v. One end of the beam was connected with the heavy pump-rod k by means of a rope or chain working in a groove and the other end was connected with the rod r in the same way. When steam from the boiler b passed through the valve d into the cylinder (steam-chest) a it raised the piston s and with it the piston-rod r thus slackening the rope and allowing the opposite end of the beam to be pulled down by the weight of the pump-rod k. As soon as the piston s reached the top of the cylinder the steam was shut off by means of the valve d and the valve f was turned and a jet of cold water from the tank g was injected into the cylinder a with the steam. The jet of cold water condensed the steam rapidly—steam is always condensed rapidly when anything cold comes in contact with it—and the water formed by the condensation escaped through the pipe p into the tank o. As soon as the steam in a is condensed, a vacuum was formed in the cylinder and the atmosphere above forced the piston down and at the same time pulled the pump-rod k up and lifted water from the well or mine. When the piston reached the bottom of the cylinder the valve d was opened and the piston again ascended. Thus the beam is made to go up and down and the pumping goes on. Notice that steam pushes the piston one way and the atmosphere pushes it back.

In Newcomen's engine the valves (f and d) at first were opened and shut (at each stroke of the piston) by an attendant, usually a boy. In 1713 a boy named Humphrey Potter, in order to get some time for play, by means of strings and latches, caused the beam in its motion to open and shut the valves without human aid. We must not despise Humphrey because his purpose was to gain time for play. The purpose of almost all inventions is to save human labor so that men may have more time for amusement and rest. Humphrey Potter ought to be remembered not as a lazy boy but as a great inventor. His strings and latches improved the engine wonderfully (Fig. 8). Before his invention the piston made only six or eight strokes a minute; after the valves were made to open and shut by the motion of the beam, it made fifteen or sixteen strokes a minute and the engine did more than twice as much work.

Newcomen's engine as improved by Potter and others grew rapidly into favor. It was used most commonly to pump water out of the mines but it was put to other uses. In and about London it was used to supply water to large houses and in 1752 a flour mill near Bristol was driven by a steam-engine. In Holland Newcomen's engines were used to assist the wind-mills in draining lakes.