James Pollard Espy was born in Pennsylvania on May 9, 1785. He grew up there and in Kentucky and then graduated from Transylvania University in 1808. After teaching school for several years, he developed an interest in the mechanics of storms, and formulated a compelling general convection theory of storms. Although many of its ideas were incorrect, the theory contained one valuable piece of insight: that the progressive expansion and cooling of upward currents of air was the cause of precipitation.
Espy lectured widely on his theory and published it in his Philosophy of Storms in 1841. Gaining immediate recognition, he received a congressional appointment as meteorologist to the War Department in 1842; and six years later, he assumed a similar position with the navy. Over a number of years, he organized weather observations, compiled annual reports, and made effective use of the telegraph as a means of collecting current data.
He died in Cincinnati on January 24, 1860.