William Garrow Lettsom

William Garrow Lettsom was a British mineralogist and diplomat. He is best known as co-author of the Manual of the Mineralogy of Great Britain and Ireland, published in 1858, which remained a standard reference work for a century afterward; the mineral lettsomite is named in his honor. He was elected a Fellow of the Royal Astronomical Society in 1849 and pursued scientific interests beyond mineralogy, including spectroscopy and electrical and bioelectrical studies. Alongside his scientific work he served as a British diplomat with postings including Berlin, Washington, Mexico, and Uruguay, and while serving in Uruguay he was instrumental in revealing the text of the secret Treaty of the Triple Alliance.