He served as the assayer of the Dahlonega Mint in Dahlonega, Georgia in the 1840s. He received his diploma as an assayer from the Royal Mint. A sample sent away to the assayer in Cloncurry confirmed their value. In "The Assayer" in 1623, he accused Marius of plagiarism. Among his best known works is ""Manuel de l'essayeur"" (Manual of the assayer). An official, Giovanni di Guevara, said that "The Assayer" was free from any unorthodoxy. "The Assayer" was Galileo's devastating reply to the "Astronomical Balance".