The following map displays the rates of malarial disease in the Union Army of the Potomac from July 1, 1861 to March 31, 1862, and can be compared to the map on the previous tab, displaying the rates for its Confederate counterpart. This data is taken from Table XXXVI of Charles Smart's Medical and Surgical History of the War of the Rebellion. (Smart, 103) The data on this heat map displays the varied intensity in number of malarial cases recorded monthly for the Union Army of the Potomac between these dates. From the comparison of this map to the one that precedes it, it can be concluded that the Federal Army of the Potomac suffered more from malarial disease in the late summer months than the Confederate Army of the Potomac.