Mailed in 1908, with stamp and postmark from sending or receiving station on either side.  In case you’ve forgotten, Joseph Louis Gay-Lussac was a French chemist and physicist. He is known mostly for his discovery that water is made of two parts hydrogen and one part oxygen (with Alexander von Humboldt), for two laws related to gases, and for his work on alcohol-water mixtures, which led to the degrees Gay-Lussac used to measure alcoholic beverages in many countries.  So the next time you’re in a bistro in Limoges, with aperitif in hand, you have double reason to celebrate.  Grade: 2