7 Inventions from James Watt that Changed the World

James Watt's inventions revolutionized the industrial revolution and changed the world.
Trevor English

James Watt was a pivotal inventor that helped push forward the industrial revolution. Born in 1736 in Scottland, Watt grew up being homeschooled by his mother. His father ran a successful shipbuilding business, where growing up James would spend a lot of time. He learned how to work with tools, forges, and even started making small scale models of different devices. 

At age 17, Watt decided that his passion was mathematical instrument making, so he went to university and then found a master instrument maker to train him in the craft. By 1757 at the age of 21, Watt opened up a shop in Glasgow, England where he made mathematical instruments – compasses, scales, etc.

Notably in his personal life, in 1764 he married his cousin and had six children with her. 

All that said, James Watt was a great inventor who contributed a great deal to modern machines and the industrial revolution. Take a look at 7 of his most prominent inventions. 

Steam engine

By far the best-known invention for James was that of the steam engine. The engine he developed would go on to define the industrial revolution and essentially change the world, still impacting society today. 

With credit where credit is due, Watt didn't invent the steam engine in its entirety, but he did create a version that was practical, effective, and allowed for its use in industry. 

The inventor was inspired by an existing steam engine that he was tasked with fixing. Being a respected mechanical engineer in Glasgow, he was asked to fix a steam engine currently in use at the University of Glasgow. While working, he realized that the current design wasted a ton of energy and was overall very inefficient. 

James Watt developed a system that enhanced the design by adding a new condenser to capture the wasted energy and make the machine more efficient. 

Copy machine

Another one of Watt's big inventions was that of the first copy machine. In the 1780s he developed a way of making precise copies of drawings without having to trace them by hand. 

7 Inventions from James Watt that Changed the World
Source: Wikimedia/Rau Antiques

The device he created would transfer ink from the original photo's front to the back of another sheet of paper, where the image was duplicated exactly. Part of this machine involved a large press that could effectively do the transfer. This device marked a milestone in the realm of documents for the time. 


While the watt steam engine revolutionized the industrial revolution, the great inventor also made significant contributions to science and other industries. Notably, the unit of the Watt was named after him.

It's equivalent to one joule of work performed per second.


Watt also coined the term horsepower as a measure of work to accurately represent the output of his steam engines. He essentially compared the power output of steam engines to the power output of draft horses at the time. 

This actual conversion of "horse power" was widely adopted at the time for a measure of machines and engines. 

The unit is equivalent to 550 foot-pounds per second, or 746 watts

REV counter

James Watt created the first revolution counter or tachometer in the 1800s. He developed it to measure the rotation speed of a shaft on his steam engines and it was implemented across various steam locomotives at the time.


In 1770, James Watt designed a micrometer, though it's a device that probably doesn't do what you think it does. Modern micrometers measure incredibly tiny distances, usually used in machining or metal working. However, Watt's micrometer functioned more like a rangefinder to measure distances in land surveying. This would have functioned more like a modern theodolite.

Watt's micrometer was adapted from a telescope and contained cross-hairs in the eyepiece that could be adjusted as desired. He used the device to measure exact distances between hills or canals.

This was an improvement of "chain surveying" done at the time, where chains of known lengths were laid out and the land was measured in standard chain lengths. 

The rotary engine

Watt worked to develop other engines too on top of his revolutionary steam engine design. Notably, he worked on the rotary engine that replaced up and down piston movement with a rotary one.

The rotary engine Watt designed was ideal for looms, bellows and other mechanical devices used in the industrial revolution. It helped replace animals and water as key power sources for these devices, helping expand where factories could be located. 

Watt also developed an engine called a "double-acting engine" which let the steam condense on both sides of the piston. This let the engine essentially double it's power, providing a greater punch in the same relative size of engine. 

7 Inventions from James Watt that Changed the World
Source: Birmingham Museums Trust/Wikimedia

 In essence, Watt became a leading mind in engine technology during his time. 

Flexible water main

Watt worked as a civil engineer too, aside from his mechanical engineering endeavors. When he was in his 70s in Glasgow, he developed a more efficient way to provide clean water for the local water company. 

The water supply for the Glasgow Water Supply Company was located on the south side of the river while the city was on the north. In 1801, he created flexible water mains to allow mains to be laid on the bed of the river. 

While most modern water mains are hard pipes, flexible water lines are still common in household construction and sewage design. 

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