Joseph Louis Gay-Lussac (1777-1850) and Johann Georg Tralles (1763-1822) developed other means of measuring alcohol content. These units are usually measured in degrees, noted °GL, or °GT. The scale Gay-Lussac developed is almost equal to the ABV scale described above. There may be slight different, because Gay-Lussac measured the alcohol content at 15° centigrade, and not 20°.