Steam digester Torricelli and further developed by German scientist Otto von Guericke with his Magdeburg hemispheres. Guerike's demonstration was documented by Gaspar Schott, in a book that was read by Robert Boyle. Boyle and his assistant Robert Hooke improved Guericke's air pump design and built their own. From this, through various experiments, they formulated what is called Boyle's law, which states that the volume of a body of an ideal gas is inversely proportional to its pressure. Soon the ideal gas law was formulated. Based on these concepts in 1679 a Boyle's associate, named Denis Papin, built a "bone digester", which is
Jacques Charles noticed that they all increased in volume by the same amount. This experiment was referenced by Gay-Lussac in 1802 when he published a paper on the precise relationship between the volume and temperature of a gas. Charles' law states that under constant pressure, an ideal gas' volume is proportional to its absolute temperature. The volume of a gas at constant pressure increases linearly with the absolute temperature of the gas. The formula he created was "V"/"T" = "V"/"T". Jacques Charles was elected to the Académie des Sciences, in 1795, and subsequently became professor of physics at the Conservatoire des Arts