The purpose of graphical displays of data is to allow the viewer to get an overall sense of the distribution of the data in a direct, immediate way that is not possible just from a list of numbers. Examples of the power of graphical displays of data are the famous chart by French civil engineer Charles Joseph Minard showing the size of Napoleon's army during his ill-fated invasion of Russia, in which the width of the lines indicate the size of the army as it marches toward Moscow (tan line) and as it retreats (black line)