Joseph Harris (1704-64) was equally distinguished as an astronomer and as an expert on coinage. From a humble background, he came to the attention of Edmond Halley, the Astronomer Royal. He spent some time making astronomical observations in South America and the West Indies, and familiarised himself with marine navigational practice, proposing improvements to measuring equipment and publishing a very popular instructional work on the uses of globes and orreries. He later observed the 1761 transit of Venus from Wales. Harris entered the Royal Mint in 1736, and became the King's Assay Master in 1749. This influential 1757 work, considered by the Victorian economist J. R. McCulloch as 'one of the best and most valuable treatises on the subject of money that has ever seen the light', argues that it is vital to a country's economy that the value of precious metal in its coinage remains constant.