Savery, Thomas (1650–1715)

views updated

SAVERY, THOMAS (1650–1715)

In the study of seventeenth-century life, mystery often pervades the lives and deaths of even the most famous people and Thomas Savery is no exception. There is no record of his birth in local registers, but it is believed that he was born near Plymouth in Shilston, England, around 1650. There is no known portrait of him available today, although there was purportedly a drawing of him in a reprint of A Miner's Friend, published in 1827. After 1700 he became known as Captain Savery, with little evidence as to why, although he had done service as a military engineer, working as a Trench Master in 1696. According to folklore, many who were placed in charge during that era were likely to be called "Captain."

What isknown is that Savery is sometimes left out of listings of the great mechanical inventors, even though he played a decidedly major role in the invention of the first steam engine. In fact, he was called "the most prolific inventor of his day" by the very book that set out to give proper due to the oftneglected Thomas Newcomen as the steam engine's true inventor—The Steam Engine of Thomas Newcomen(Rolt and Allen, 1997).

Savery's career was hardly preordained, although he came from a family of prosperous merchants in Totnes, who acquired the manors of Shilston and Spriddlescombe in the parish of Modbury in the early seventeenth century. Savery's family was well known in the West Country and he may have been a merchant in Exeter for a period of time. At the age of twenty-three, he was protected by a writ from Charles II forbidding the local politicians to molest him. The writ in 1673 cited Savery's "many losses, particularly in the last Dutch wars," while serving as a freeman for the Merchant Adventurers Company.

Continuing a career that began in military engineering, his first patent was granted on July 25, 1698, for his historic work entitled "Raising water by the impellent force of fire." He called it "The Miner's Friend." Captain Savery's most important contribution was to evaluate the advances and frustrations of more than a century of experiments with steam power and create important innovation by combining steam with the effects of atmospheric pressure. His inventiveness was stimulated by his keen knowledge of copper and tin mining operations.

The principle of his pump was that steam was passed from a boiler into a closed receiver filled with water where its pressure forced the water through a nonreturn valve and up an ascending delivery pipe. When all the water was expelled, the steam supply was shut off and a new supply of cold water was poured over the outside walls of the receiver. This cooled the receiver and condensed the steam within. A vacuum was therefore created in the receiver, forcing water up a suction pipe, though a second nonreturn valve by atmospheric pressure. When the receiver was refilled the cooling water was shut off, steam turned on, and the cycle was repeated.

In subsequent years, Savery made important improvements that benefited future steam inventions. In June 1699 he demonstrated to the Royal Society a pump with two receivers, each with a separate, hand-controlled steam supply. This ensured improved continuity of operation, allowing one receiver to operate in its vacuum stage and the other under steam pressure. In 1701, he added two more critical steps: a second boiler, avoiding the need to shut down the fire and pump, between stages; and he replaced the two interconnected steam cocks with a single valve, run with a manually operated long lever. This may have been the inspiration for the modern slide valve and his inventiveness created, in effect, the world's first feed-water heater.

Savery appeared to be the first to take the huge step out of the lab and into the practical workshop. His equipment was made of brass and beaten copper, using firebrick furnaces. It was said that Salisbury Court (extending from Fleet Street to the river Thames) was the site of the world's first steam pump factory, although there is evidence that Savery abandoned his project in 1705. The limitations of his progress became known, literally under fire.

When tested, his engines generated too much heat and steam pressure for the technology of the times. Soldering would melt or machine joints would split. In order to solve the need for pumping water from mines, the necessary system of pumps would be far too costly and dangerous. In light of the dangers, both historians and scientists might find it intriguing that Savery never saw fit to add a safety valve, invented around that time.

In one of the more amusing assessments of this danger, Steven Switzer commented in Hydrostatics and Hydraulics (1729) about the steam power, "How useful it is, in gardens and fountain works ... in the garden of that noble peer, the Duke of Chandos, where the engine was placed under a delightful banqueting house, and the water was being forced up into a cistern on top, used to play a fountain in a delightful manner." Rival steam inventors derisively chided that the guests might forego the delight of the water fountain, had they known exactly what pressures were building under their feet.

Savery's work at the turn of the century preceded Newcomen's radically different and more successful engine in 1712. It also followed on the heels of noteworthy early experimenters, such as Giambattista della Porta in Italy in the early 1600s, Salomon de Caus in England in the 1620s, David Ramsay of Scotland in 1631, Edward Somerset of England in 1663, Sir Samuel Morland in 1667, Otto von Guericke of Magdeburg in 1672, and Denis Papin in the 1690s.

Savery's name and work remained in the public eye, followed by many scientists and inventors during the eighteenth century. The most important was Englishman Thomas Newcomen, who is believed to have known Savery and also to have seen his engines at work. Although Newcomen created a very different engine to solve the needs of the mines, the similarities were sufficient and Savery had earned his patent first. As a result, Newcomen and Savery entered into a joint patent agreement, whereby each shared the benefits of the other's work, while saving themselves the expense of a costly battle over separate patents.

The practical, if limited, use of Savery's incrementally successful efforts were permanently inscribed in history, as highly important advancements of his time.

Dennis R. Diehl

See also: Steam Engines; Turbines, Steam.