Weather data is originally tracked with the intention of preventing disease outbreaks. The primary understanding of disease at this time is the "miasma theory." It is believed that gasses from swamps and other wetlands create epidemics like yellow fever and malaria. The Surgeon General begins tracking weather patterns, such as rainfall, in order to prevent outbreaks. While miasma will be disproved with the rise of germ theory in the later part of the century, the Army's role in weather tracking will eventually lead to the establishment of the National Weather Bureau.