James Hargreaves (1720–1778) was a weaver, carpenter and inventor from Lancashire, England. He invented the spinning jenny, a multi-spindle spinning frame, in 1764. Enabling a worker to work eight or more spools at once, the spinning jenny greatly reduced the amount of work needed to produce yarn (thread). His invention was an important breakthrough in the manufacture of textiles, and helped to start the Industrial Revolution.

Before the jenny

Until the 1770s, textile production was a cottage industry, carried out by family members. Women or children would "card" the wool, combing it with two pads of nails, until all the fibres lay in the same direction. Using a spinning wheel, the carded wool, called roving, was wound as threads, called yarn, on to a spindle, a spike weighted at one end by a disc-shaped or spherical part called a whorl. Spinning was usually carried out by women, called spinsters. The yarn was then taken to a loom to be woven. Working the loom, which required both hand and foot movements, was traditionally the work of men.

Spinning jenny

When cotton began to be imported to Britain in the mid-18th century, the supply of cotton yarn could not keep up with demand: the one-thread spinning wheel simply could not work fast enough. In 1764, James Hargreaves realised that if a number of spindles, placed side by side, instead of just one, were linked to the spinning wheel, several balls of yarn could be spun at the same time.

The spinning jenny produced yarn that was too coarse to be used for warp threads—those that extended lengthways on a loom. It could produce only weft threads (crossways yarn).

The labour-saving device Hargreaves had invented threatened the jobs of textile workers. In 1768, a group broke in to Hargreaves' house in Blackburn, Lancashire, and destroyed his machines. Hargreaves was forced to flee to Nottingham.