What did Edward Nairne invent in 1770?

Edward Nairne (1726 – 1 September 1806) was an English optician and scientific instrument maker. He was born in Sandwich, England. He was apprenticed to the optician Matthew Loft in 1741 and established his own business at 20 Cornhill in London after Loft's death in 1748. In 1774 he took his apprentice Thomas Blunt into partnership, a relationship that lasted until 1793 when Blunt opened his own shop at 22 Cornhill.

One of the earliest references to rubber in Europe appears to be in 1770, when Edward Nairne was selling cubes of natural rubber at his shop at 20 Cornhill. The cubes, meant to be erasers, sold for the high price of 3 shillings per half-inch cube. Nairne is credited with creating the first rubber eraser. Prior to using rubber, breadcrumbs were used as erasers. Nairne says he inadvertently picked up a piece of rubber instead of breadcrumbs, discovered its erasing properties, and began selling rubber erasers.

Nairne was a regular contributor to the "Philosophical Transactions" of the Royal Society of London, and was elected a fellow of that institution in 1776. He enjoyed an extensive international reputation, and was in correspondence with Benjamin Franklin for whom he made a set of magnets and a telescope around 1758. In 1770 he was elected a member of the American Philosophical Society, which was founded by Franklin. He died 1 September 1806 in London, England.