April 2 – George Brayton obtains a United States patent for a constant pressure internal combustion engine, initially using vaporized gas, and marketed as 'Brayton's Ready Motor'.[13][14]
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^Monoyer, F. (1872). "Sur l'introduction du système métrique dans le numérotage des verres de lunettes et sur le choix d'une unité de réfraction". Annales d'Oculistiques. 68: 101.