Biography of James Watt, Inventor of the Modern Steam Engine

Biography of James Watt, Inventor of the Modern Steam Engine

James Watt (January 19, 1736-August 25, 1819) was a Scottish inventor, engineer, and chemist. He developed a workable steam engine that utilized a separate condenser; this innovation made the steam engine a useful tool for a vast range of uses. In many ways, Watt's invention-or rather, his improvement on an earlier invention, the Newcomen steam engine-was the technological impetus behind the Industrial Revolution.

Fast Facts: James Watt

  • Known For: Invention of the steam engine
  • Born: January 19, 1736 in Greenock, Renfrewshire, Scotland, United Kingdom
  • Parents: Thomas Watt, Agnes Muirhead
  • Died: August 25, 1819 in Handsworth, Birmingham, England, United Kingdom
  • Education: Home educated
  • Published Works: A System of Mechanical Philosophy
  • Awards and Honors: Many streets and schools carry his name; statues of his likeness in Picadilly Gardens and St. Paul's Cathedral
  • Spouse(s): Margaret (Peggy) Miller, Ann MacGregor
  • Children: James Jr., Margaret, Gregory, Janet, Ann
  • Notable Quote: "I had gone to take a walk on a fine Sabbath afternoon. I had entered the Green by the gate at the foot of Charlotte Street and had passed the old washing house. I was thinking upon the engine at the time, and had gone as far as the herd's house, when the idea came into my mind… I had not walked farther than the Golf house when the whole thing was arranged in my mind."

Early Life

James Watt was born on January 19, 1736, in Greenock, Scotland, as the only surviving child of four of James Watt (1699-1737) and Agnes Muirhead (1901-1754). Greenock was a fishing village that during Watt's lifetime became a busy town with a fleet of steamships. James Jr.'s grandfather Thomas Watt (1642-1734) was a well-known mathematician and local schoolmaster. James Sr. was a prominent citizen of Greenock and a successful carpenter and ship's chandler who worked at outfitting ships and working on their instruments, compasses, and quadrants. At various times, James Sr. was also the chief magistrate and treasurer of the town.


James Watt was intelligent, but because of poor health he was unable to attend school regularly. Instead, he gained the skills he would later need in engineering and tooling by working with his father on carpentry projects. By age 6, James Watt was solving geometrical problems and conducting his earliest investigation into the nature of steam, which involved experimenting with his mother's tea kettle. In boyhood, Watt was an avid reader and found something to interest him in every book that came into his hands.

When Watt was finally sent to the village school, his ill health prevented his making rapid progress; it was only when he was 13 or 14 that he began to exhibit his abilities, particularly in mathematics. His spare time was spent sketching with his pencil, carving, and working at the tool bench with wood and metal. He made many ingenious mechanical works and some beautiful models, and enjoyed repairing nautical instruments.


After his mother died in 1754, the 18-year-old Watt was sent to Glasgow to train as a merchant with his uncle John Muirhead. One of his mother's relatives was the chair of the Oriental Languages and Humanities department at Glasgow College, and Watt became a member of the literary society there. He also met other scholars at Glasgow who would prove influential and supportive of his career: Robert Dick, professor of natural philosophy, Robert Simpson in mathematics, and William Cullen in medicine and chemistry.

It was Dick who suggested that Watt go to London to get training as a mathematics instrument maker. With a letter of introduction, Watt left for London in 1755 and began working with the instrument maker John Morgan. Watt was not officially an apprentice, but he did work on mechanical instrumentation: Morgan thought he was talented but took too long to complete his work. The job with Morgan ended in June 1756 and Dick got him a short-term position to work on an astronomical clock, reflecting telescopes, and transit instruments. Watt returned to Greenock at the end of the year, but he soon went back to Glasgow where he began a small business in quadrant-making. He was appointed mathematical instrument-maker at Glasgow College, supported by Dick's replacement John Anderson, and by Cullen's replacement and chemist Joseph Black (1728-1799). Black is best known for his work on latent and specific heats and for his discovery of carbon dioxide, and he was to become a staunch supporter of Watt.

Early Experimentation

In 1759, John Robison, a student at Glasgow, showed Watt a model of the Newcomen steam engine and suggested it might be used to propel carriages. The Newcomen was invented and patented in 1703 by Thomas Newcomen (1664-1729), and Watt began building miniature models using tin steam cylinders and pistons attached to driving wheels by a system of gears. In his own experiments he used, at first, apothecaries' trials and hollow canes for steam reservoirs and pipes, and later a Papin's digester and a common syringe. The latter combination made a noncondensing engine, in which he used steam at a pressure of 15 pounds per square inch. The valve was worked by hand, and James Watt saw that an automatic valve gear was needed to make a working machine. This experiment, however, led to no practical result and for the next several years, he abandoned this research.

Watt stayed with the college until the 1760s, when he took up a partnership with a merchant named John Craig, financed partly with Black. One venture of theirs was producing alkali from salt-in the 18th century, alkali could only be produced from plants. Craig and Watt were one of several people looking for a way to create it chemically, an effort not achieved until 1820. Watt and Craig also worked on pottery kilns and glazes for making tin-glazed delftware.

Marriage and Family

In 1764, Watt married Margaret Millar, known as Peggy, a cousin he had known since they were children. They were to have five children, only two of which lived to adulthood: Margaret, born in 1767, and James III, born in 1769, who as an adult would become his father's main support and business partner.

The Newcomen Steam Engine

Over the winter of 1763-1764, John Anderson at Glasgow asked Watt to repair a model of the Newcomen engine. He was able to get it running, but he was curious as to why the machine consumed so much steam and condensing water. Watts began studying the history of the steam engine and conducted experimental research into the properties of steam.

The Newcomen steam engine model had a boiler that was made to scale and was incapable of furnishing enough steam to power an engine. It was about nine inches in diameter; the steam cylinder was two inches in diameter and had a six-inch piston stroke. Watt made a new boiler that could measure the quantity of water evaporated and the steam condensed at every stroke of the engine.

Watt soon discovered that the engine required a very small quantity of steam to heat a very large quantity of water. He immediately started to determine with precision the relative weights of steam and water in the steam cylinder when condensation took place at the down stroke of the engine. James Watt independently proved the existence of "latent heat," which had been discovered by his mentor and supporter Joseph Black. Watt went to Black with his research, who shared his knowledge with Watt. Watt found that, at the boiling point, his condensing steam was capable of heating six times its weight of water used for producing condensation.

Watt's Separate Condenser

Realizing that steam weight for weight was a vastly greater absorbent and reservoir of heat than water, Watt saw the importance of taking greater care to economize it than had previously been attempted. At first, he economized in the boiler and made boilers with wooden "shells" in order to prevent losses by conduction and radiation. He also used a larger number of flues than Newcomen had to secure more complete absorption of the heat from the furnace gases. He also covered his steam pipes with non-conducting materials and took every precaution to secure the complete utilization of the heat of combustion.

He soon discovered that the sources of heat loss in the Newcomen engine- were:

  • The dissipation of heat by the cylinder itself, which was of brass and was both a good conductor and a good radiator.
  • The loss of heat consequent upon the necessity of cooling down the cylinder at every stroke in producing the vacuum.
  • The loss of power due to the pressure of vapor beneath the piston, which was a consequence of the imperfect method of condensation.

His first attempt at a cylinder of non-conducting material was made of -wood soaked in oil and then baked, which did increase the economy of steam. He then conducted a series of very accurate experiments upon the temperature and pressure of steam by measuring the amount of steam used at each stroke of the engine. He was able to confirm his previous conclusion that three-fourths of the heat supplied to the engine was wasted.

Further Improvements

After his scientific investigations, James Watt worked on improving the steam engine with an intelligent understanding of its existing defects and a knowledge of their cause. Watt soon saw that in order to reduce the losses in the working of the steam in the steam cylinder, it would be necessary to find a way to constantly keep the cylinder as hot as the steam that entered it.

According to James Watt: "The idea came into my mind that, as steam was an elastic body, it would rush into a vacuum, and, if a communication were made between the cylinder and an exhausted vessel, it would rush into it, and might be there condensed without cooling the cylinder. I then saw that I must get rid of the condensed steam and injection water if I used a jet, as in Newcomen's engine. Two ways of doing this occurred to me: First, the water might be run off by a descending pipe, if an off jet could be got at the depth of 35 or 36 feet, and any air might be extracted by a small pump. The second was, to make the pump large enough to extract both water and air."

He continued, "When analyzed, the invention would not appear so great as it seemed to be. In the state in which I found the steam engine, it was no great effort of mind to observe that the quantity of fuel necessary to make it work would forever prevent its extensive utility. The next step in my progress was equally easy-to inquire what was the cause of the great consumption of fuel. This, too, was readily suggested, viz., the waste of fuel which was necessary to bring the whole cylinder, piston, and adjacent parts from the coldness of water to the heat of steam, no fewer than from 15 to 20 times in a minute."

James Watt had invented his all-important separate condenser. He proceeded to make an experimental test of his new invention. His little model worked very well, and the perfection of the vacuum was such that the machine lifted an 18-pound weight suspended from the piston rod. He then constructed a larger model, and the result of its test confirmed the results of his first experiments.

Watt Builds His Own Steam Engine

It took years for Watt to figure out the details of the new steam engine. To start with, Watt had to find a way to prevent the condenser from filling with water. He tried several approaches, including an air pump, which relieved the condenser of the water and air which collected in the condenser and lessened the vacuum. He next substituted oil and tallow for the water used to lubricate the piston, keeping the steam tight and preventing the cooling of the cylinder. Another cause of refrigeration of the cylinder and consequent waste of power in its operation was the entrance of air, which followed the piston down the cylinder at each stroke, cooling its interior by its contact. The inventor prevented this from happening by covering the top of the cylinder and surrounding the whole cylinder with an external casing, or "steam jacket," that allowed the steam from the boiler to pass around the steam cylinder and press on the upper surface of the piston.

After building his larger experimental engine, Watt rented a room in an old deserted cottage. There, he worked with mechanic Folm Gardiner. Watt had just met John Roebuck, a wealthy physician, who had, with other Scotch capitalists, recently founded the celebrated Carron Iron Works. Roebuck began to support Watt's efforts financially and Watt frequently wrote to Roebuck describing his progress.

In August 1765, he tried the small engine and wrote Roebuck that he had "good success," although the machine was very imperfect, and informed Roebuck that he was starting to make the larger model. In October 1765, he finished the large steam engine. The engine, while ready for trial, was still far from perfect. It nevertheless did good work for such a crude machine.

Financial and Personal Setbacks

Unfortunately, by 1765, James Watt was reduced to poverty, and, after borrowing considerable sums from friends, he finally had to seek employment in order to provide for his family. During a span of about two years, he supported himself as a civil engineer, surveying and managing the building of several canals in Scotland and exploring coal fields in the neighborhood of Glasgow for the magistrates of the city. He did not, however, entirely give up his invention.

In 1767, Roebuck assumed Watt's liabilities to the amount of 1,000 British pounds and agreed to provide more capital in exchange for two-thirds of Watt's patent. Another engine was built with a steam cylinder seven or eight inches in diameter, which was finished in 1768. This worked sufficiently well to induce the partners to ask for a patent, and the specifications and drawings were completed and presented in 1769.

Watt also built and set up several Newcomen engines, partly, perhaps, to make himself more thoroughly familiar with the practical details of engine building. Meantime, he prepared plans for and built a moderately large engine of his own new type. Its steam cylinder was 18 inches in diameter, and the stroke of the piston was 5 feet. This engine was built at Kinneil and was finished in September 1769. It was not all satisfactory in either its construction or its operation. The condenser was a surface condenser composed of pipes somewhat like those used in his first little model and did not prove to be satisfactorily tight. The steam piston leaked seriously, and repeated trials only served to make its imperfections more evident. He was assisted with financial and moral support by both Joseph Black and John Roebuck, but he felt strongly about the risks he ran of involving his friends in serious losses and became very despondent.

Writing to Black, Watt said: "Of all things in life, there is nothing more foolish than inventing; and probably the majority of inventors have been led to the same opinion by their own experiences."

Partnership With Matthew Boulton

In 1768, James Watt traveled to London to get his patent submitted, and on the way he met Matthew Boulton. Boulton was the owner of a Birmingham manufacturing company known as the Soho Manufactory, which made small metal goods. He had inherited his father's business and built it up considerably. He and his business were very well known in the mid-18th century English enlightenment movement.

Boulton was a good scholar, with a considerable knowledge of languages and science-particularly mathematics-despite having left school as a boy to go to work in his father's shop. In the shop, he soon introduced a number of valuable improvements and he was always on the lookout for other ideas that might be introduced into his business.

He was also a member of the famous Lunar Society of Birmingham, a group of men who met to discuss natural philosophy, engineering, and industrial development together: other members included the discoverer of oxygen Joseph Priestley, Erasmus Darwin (grandfather of Charles Darwin), and the experimental potter Josiah Wedgewood. Watt joined the group after he became Boulton's partner.

A flamboyant and energetic scholar, Boulton made the acquaintance of Benjamin Franklin in 1758, who then visited Soho. By 1766, these distinguished men were corresponding, discussing among other things the applicability of steam power to various useful purposes. They designed a new steam engine and Boulton built a model, which was sent to Franklin and exhibited by him in London. They had yet to become aware of the existence of James Watt.

When Boulton met Watt in 1768, he liked his engine and decided to buy an interest in the patent. With Roebuck's consent, Watt offered Boulton a one-third interest. Although there were several complications, eventually Roebuck proposed to transfer to Matthew Boulton one-half of his proprietorship in Watt's inventions for the sum of 1,000 pounds. This proposal was accepted in November 1769.

Working Steam Engines

In November 1774, Watt finally announced to his old partner Roebuck that he had made a successful trial of the Kilmeil engine. He did not write with his usual enthusiasm and extravagance; instead, he simply wrote: "The fire engine I have invented is now going, and answers much better than any other that has yet been made, and I expect that the invention will be very beneficial to me."

One reason for his lack of enthusiasm was that his wife had died during childbirth the previous year, in September 1773. Heartsick, Watt buried himself in work. From mid-February 1774 he was working on thermometers and barometers. He ended his civil engineering business in Scotland (in part because of a financial crisis in Scotland) and in May he journeyed south to Birmingham, where he joined the Lunar Society. In 1775, he went into a full-time partnership with Matthew Boulton.

From that point forward, the firm of Boulton and Watt was able to produce a range of working engines with real-world applications. New innovations and patents were taken out for machines that could be used for grinding, weaving, and milling. Steam engines were put into use for transportation on both land and water. Nearly every successful and important invention that marked the history of steam power for many years originated in the Boulton and Watt workshops.

Retirement and Death

Watt's work with Boulton transformed him into a figure of international stature among men of letters. His 25-year-long patent brought him wealth; and he and Boulton became leaders in the technological Enlightenment in England, with a solid reputation for innovative engineering. Watt married Ann Macgregor in 1776 and they had two children (Gregory and Jessy), both of whom would die young. James Watt Jr., his son from his first wife, survived his father and went on to have a role in the continuing English Enlightenment.

As a result of his partnership with Matthew Boulton, James Watt became a very wealthy man, building an elegant mansion known as "Heathfield House" in Handsworth, Staffordshire. He retired in 1800 and spent the rest of his life in leisure and traveling to visit friends and family. He died on August 25, 1819, at Heathfield. He was buried in the graveyard of St Mary's Church in Handsworth.


In a very meaningful way, Watt's inventions spurred on the Industrial Revolution and innovations of the modern age, ranging from automobiles and trains to factories and the social issues that evolved as a result. In addition, Watt's name has been attached to streets, museums, and schools. His story has inspired books, movies, and works of art, including statues in Piccadilly Gardens and St. Paul's Cathedral.

On the statue at St. Paul's are engraved the words: "James Watt… enlarged the resources of his country, increased the power of man, and rose to an eminent place among the most illustrious followers of science and the real benefactors of the world."


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