Long before the development of the sciences of biology and chemistry in the 18th century, people knew that some substances were toxic. It did not matter whether these poisons were biological or chemical in nature; their impact was what counted. European, Indian, and Chinese writers discussed the efficacy of poison smokes in siege warfare. The Greek historian Thucydides described efforts of Sparta to conquer Plataia with sulfur fumes in 429 bce, and Pliny the Elder catalogued some [Page 260]7,000 poisons in the 1st century ce. Much later, Leonardo da Vinci described a container containing sulfide and arsenic that might be hurled onto warships to kill enemy sailors. Flame weapons like “Greek fire” used in Middle East wars, both on land and sea, consisted of some ...