Drink a Toast to James Prescott Joule!

by Nicholas Mee on October 6, 2020

Manchester was a boom town in the late eighteenth century. The industrial revolution was well under way and cotton mills were springing up around the city drawing an influx of workers from surrounding villages and towns. William Joule was one of the newcomers enticed by the industrial gold rush.

William Joule came from the village of Youlgrave in Derbyshire where his father was an innkeeper. The letter ‘J’ is a late-comer to the English alphabet, only gradually becoming distinguished from the letter ‘I’ during the eighteenth century, and records survive where the family name has the alternative spelling Youl. So it seems the family name Joule arose from the name of their home village Youlgrave. 

Youlgrave in Derbyshire.

The Joule family business was brewing. By 1780 William’s brother Francis had established a brewery in the town of Stone in Staffordshire, and some time around 1788 William set up a brewery in Salford near Manchester. William’s business prospered and by 1798 he had installed a steam engine. It wasn’t long before William Joule & Son became the biggest brewery in the Manchester area. 

An Atomic Education

The brewery was passed on to William’s son Benjamin who as a wealthy Manchester businessman obtained the best possible education for his own son James Prescott Joule. For two years James was tutored by the great John Dalton (1766-1844), famous for explaining chemistry in terms of atoms.

When James Prescott Joule inherited a share in the family business he began experimenting with ways to make the brewing process more efficient. In particular he was interested in whether it might be profitable to replace the now ageing steam engine with a newly invented electric motor powered by a zinc battery. These investigations revealed that each pound of coal burnt in a steam engine could generate five times as much work as a pound of zinc consumed in an electric battery. And, as coal was far cheaper than zinc, Joule concluded it was much more economical to continue using the steam engine.

The Conservation of Energy

James Prescott Joule (1818-1889).

Joule soon became interested in the fundamental principles of physics rather than the practical considerations of brewing beer. Throughout his career he exchanged ideas with his renowned contemporary John Thomson, better known as Lord Kelvin. Together they worked to understand the connections between energy, work, heat and temperature, a subject known as thermodynamics. Joule’s investigations led to one of the most important principles in physics—the conservation of energy.

This principle remains at the heart of physics. It means that although energy may be converted from one form into another, if all types of energy are taken into account, including heat, then the total amount of energy never changes. In a power station, for instance, coal or gas is burned to heat water and produce steam that drives a turbine and generates electricity, which is fed across the grid to power our computers and other appliances at home. At each step in this sequence energy is transformed from one form to another. But, even though the details of each process might be very complicated, we can be sure that the total amount of energy always remains the same if we take into account the heat that is dissipated along the way.

The Unit of Energy

James Prescott Joule’s gravestone.

Joule studied the relationship between energy and temperature, which we now know is a measure of the energy in the random motions of an object’s molecular constituents. As these internal motions increase the object feels hotter. Conversely, a decrease in the internal motions makes the object feel colder. In his laboratory, Joule measured the amount of energy in the form of physical work that is required to raise the temperature of a body of water by one degree. He would refine these measurements throughout his life.

Joule died in 1889 and is buried in the town of Sale just outside Manchester. The number 772.55 is engraved at the top of his gravestone, shown here. This number is the crux of Joule’s investigations in the laboratory. It is the amount of work in foot pounds required to raise the temperature of one pound of water by one degree Fahrenheit. Fortunately, physicists no longer deal in such arcane units as foot pounds. Today the standard unit of energy is known as the joule in honour of James Prescott Joule and his work. (Incidentally, one foot pound is equivalent to 1.35582 joules.)

Joule’s brewery in Staffordshire, originally established by James Prescott’s great uncle Francis, was resurrected in 2010. So once again it is possible to drink a pint of Joule’s ale and raise a toast James Prescott Joule.

Further Information

There is more about the re-established Joule’s brewery here: https://www.joulesbrewery.co.uk/our-story

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