Harriot's cancer was due to excessive tobacco consumption. He died on 2 July 1621, three days after writing his will (discovered by Henry Stevens). His executors posthumously published his Artis Analyticae Praxis on algebra in 1631; Nathaniel Torporley was the intended executor of Harriot's wishes, but Walter Warner in the end pulled the book into shape. It may be a compendium of some of his works but does not represent all that he left unpublished (more than 400 sheets of annotated writing). It is not directed in a way that follows the manuscripts and it fails to give the full significance of Harriot's writings. Thomas Harriot was buried in the church of St Christopher le Stocks in Threadneedle Street, near where he died. The church was subsequently damaged in the Great Fire of London, and demolished in 1781 to enable expansion of the Bank of England. Legacy Harriott also studied optics and refraction, and apparently discovered Snell's law 20 years before Snellius did; like so many of his works, this remained unpublished. In Virginia he learned the local Algonquian language, which may have had some effect on his mathematical thinking. He founded the "English school" of algebra. Around 1600, he introduced an algebraic symbolism close to modern notation; thus, computation with unknowns became as easy as with numbers. He is also credited with discovering Girard's theorem, although the formula bears Girard's name as he was the first to publish it. His algebra book Artis Analyticae Praxis (1631) was published posthumously in Latin. Unfortunately, the editors did not understand much of his reasoning and removed the parts they did not comprehend such as the negative and complex roots of equations. Because of the dispersion of Harriot's writings the full annotated English translation of the Praxis was not completed until 2007. A more complete manuscript, De numeris triangularibus et inde de progressionibus arithmeticis: Magisteria magna, was finally published in facsimile form with commentary by Janet Beery and Jackie Stedall in 2009. The first biography of Harriot was written in 1876 by Henry Stevens of Vermont but not published until 1900 fourteen years after his death. The publication was limited to 167 copies and so the work was not widely known until 1972 when a reprint edition appeared. Prominent American poet, novelist and biographer Muriel Rukeyser wrote an extended literary inquiry into the life and significance of Hariot (her preferred spelling), The Traces