In 1660 Robert Boyle announced that removing the air in a chamber extinguishes a flame and kills small animals showing a connection between combustion and respiration. The next year he announced the modern concepts of the element, alkali, and acid. In 1662 he published what came to be known as Boyle's Law: For a gas under constant temperature, the volume is inversely proportional to pressure. He stated that gases are made of tiny particles spaced very far apart. After improving Guericke's pump, he demonstrated that a feather and a lump of lead fall at the same rate in a vacuum. In 1670, almost 100 years before Cavendish, he found a flammable gas was produced when some metals were treated with acids. (Cavandish named it Inflammable air and Lavoisier named it hydrogen.)