Josiah Parsons Cooke (1827-1894) obtained his A.B. degree from Harvard in 1848. Josiah Cooke was an extraordinary fellow having been given the job of starting the Harvard Chemistry Department. Initially hired as a tutor in mathematics, in 1850 he was appointed Erving Professor of Chemistry and Mineralogy, a position he held for the rest of his life. He attended chemistry lectures of Benjamin Silliman, Sr., at the age of 16, but he received no formal education in that discipline. After receiving the appointment in chemistry, he traveled to Europe and attended lectures by Jean Baptiste Andre Dumas and Henri Victor Regnault, who influenced him greatly. Cooke studied the properties of the elements, particularly H, O, and Sb. He also wrote a very interesting book titled Religion and Chemistry (Cooke, 1880). In the third chapter of that book, he wrote about the testimony of oxygen. We will examine briefly the life and contributions of Josiah Parsons Cooke as it relates to the development of atmospheric chemistry in the United States.