the years between 1776 and 1778, Volta studied the chemistry of gases. He researched and discovered methane after reading a paper by Benjamin Franklin of the United States on "flammable air". In November 1776, he found methane in the marshes of Angera on Lake Maggiore, and by 1778 he managed to isolate methane. He devised experiments such as the ignition of methane by an electric spark in a closed vessel. Volta also studied what we now call electrical capacitance, developing separate means to study both electrical potential difference (V) and charge (Q), and discovering that for a given object, they are proportional. This is called Volta's Law of Capacitance, and for this work the unit of electrical potential has been named the volt. In 1779, he became a professor of experimental physics at the University of Pavia, a chair that he occupied for almost 40 years. Volta's lectures were so crowded with students that the subsequent emperor Joseph II ordered the construction (based on a project by Leopold Pollack) of a new "physical theater", today the "Aula Volta". Furthermore, the emperor granted Volta substantial funding to equip the physics cabinet with instruments, purchased by Volta in England and France. At the University History Museum of the University of Pavia there are 150 of them, used by Alessandro Volta. Volta and Galvani Luigi Galvani, an Italian physicist, discovered something he named, "animal electricity" when two different metals were connected in series with a frog's leg and to one another. Volta realised that the frog's leg served as both a conductor of electricity (what we would now call an electrolyte) and as a detector of electricity. He also understood that the frog's legs were irrelevant to the electric current, which was caused by the two differing metals. He replaced the frog's leg with brine-soaked paper, and detected the flow of electricity by other means familiar to him from his previous studies. In this way he discovered the electrochemical series, and the law that the electromotive force (emf) of a galvanic cell, consisting of a pair of metal electrodes separated by electrolyte, is the difference between their two electrode potentials (thus, two identical electrodes and a common electrolyte give zero net emf). This may be called Volta's Law of the electrochemical series. In 1800, as the result of a professional disagreement over the galvanic response advocated by Galvani, Volta invented the voltaic pile,