His improvements to the steam engine were a significant factor in the Industrial Revolution, and when the Watt engine was paired with Thomas Edison’s electrical generator in the late 19th century, the generation of electricity on a large scale was possible for the first time. Soon after, the streets of New York and other cities were illuminated with electric lamps. Many other uses for electricity were developed in the following years, so that it has become thoroughly integrated into the daily lives of people around the world.
James Watt was born in the village of Greenock in Renfrewshire, Scotland, on January 19, 1736. He received his earliest education at home from his mother and in his father’s workshop, where his father oversaw a prosperous house- and ship-building business. At the workshop, Watt developed a keen interest in tools, instruments and model-making. He later attended grammar school, where he studied Greek, Latin, mathematics and other subjects. Watt’s penchant for building shaped his choice of a career, as the young man decided to apprentice himself to an instrument maker in London. Of a sickly nature, Watt soon found himself ill-suited for the bustling and noisy atmosphere of London. He moved to Glasgow, Scotland, where he had relatives, before he was yet 21 years of age.
In Glasgow, Watt obtained a position as a mathematical instrument maker at the local university. Through this appointment he came into contact with a number of prominent scientists, including Joseph Black, with whom he would correspond throughout his life. Watt’s work with the steam engine began in 1764, when he was requested to repair a Newcomen steam engine used at the university. Designed by English engineer Thomas Newcomen in the early 18th century, the engine was incredibly inefficient. Only about 1 percent of the thermal energy in steam was converted to mechanical energy by Newcomen engines, but they were better than any other steam engines available at the time. Watt, however, would soon remedy this problem.
After thorough consideration of the matter, Watt determined that the steam engine could be drastically improved by the addition of a separate condenser to reduce the loss of latent heat, which is the heat associated with changing the state of a substance (a concept first described by Watt’s friend, Joseph Black). After obtaining enough money to build a small engine of his own design from Black, Watt formed a partnership in 1768 with John Roebuck and obtained a patent for a steam engine with a separate condensing chamber in 1769. The process involved in transforming an invention into a marketable product can be long and laborious, however, and while still working out practical problems with the modified steam engine, Watt began working as a land surveyor to support himself. His new job entailed planning and marking routes for canals, leaving him little opportunity to advance the steam engine.
It was not until Watt gave up surveying and moved to Birmingham, England, in 1774 that progress with his steam engine began anew. In 1772, Roebuck had gone bankrupt and had given his share of Watt’s patent to the manufacturer Matthew Boulton in lieu of monetary debt payment. Watt and Boulton obtained a patent extension from Parliament in 1775, and the new partnership resulted in great forward strides with the engine. In the next year, the first two Watt engines were installed, and many more would follow. Business improved significantly when Watt invented a rotary motion steam engine in 1781 that could be used for a wider variety of applications and a double-acting engine, which featured pistons that pulled as well as pushed. Other improvements, such as a centrifugal governor for controlling engine speed and an automatic pressure gauge, later followed. With so many modifications, the steam engines found in many mills and factories in the late 1800s bore little resemblance to the Newcomen engines that had dominated the market earlier in the century.
The increasing demand for Watt steam engines eventually made both Watt and Boulton considerable fortunes and garnered them substantial renown. In 1785, the partners were elected into the Royal Society of London. They were also key members of the Lunar Society, a group that included many prominent British scientists and industrialists, such as Erasmus Darwin and Josiah Wedgwood. In 1794, Watt and Boulton established a new firm, which their sons would take over by the beginning of the 19th century, when their main patents expired. After 1800, Watt spent much of his time traveling throughout Europe with his second wife, Ann, with whom he had two children. His first wife, with whom Watt had produced several other children, had died in 1773. Watt's death came in 1819. He is buried next to his longtime partner, Boulton, in Birmingham.
During the course of his work with the steam engine, Watt developed the concept of horsepower as a unit of power output. Since his engines replaced animals as a source of power, to Watt it seemed natural to describe the power of the engines in terms of how many horses would have been required to generate it. Watt established one unit of horsepower to be equivalent to 33,000 pounds lifted one foot per minute. In honor of his work related to efficiency and power, a unit of power commonly used for both electricity and mechanics, the watt, was named after him.