In striking contrast to the long history of general maps, it was not until the latter half of the seventeenth century that thematic maps appeared. A. Hettner, (1927), who fully discussed the unique properties and importance of maps in geography, did not yet use the term “thematic maps, ” but stated instead that new types of maps had been introduced in the nineteenth century. A. Kircher (1665) and E. W. Happel (1685) were among the first thematic map makers. The contribution of E. Halley deserves special mention. His world map of trade winds and monsoons (1686) was the first map which used iconic symbols to depict wind directions, and even the seasonal reversal of the Indian monsoon was well demonstrated. Very few had ever used isolines before Halley, who made a chart of compass variations in 1701.
Thematic maps made rapid progress in the eighteenth century, when maps of geology, biology, linguistics, population density, economics, administrative divisions, etc. were made.
In the author's opinion, Alexander von Humboldt and Karl Ritter made full use of thematic maps to establish the firm foundation of modern geography. “Sechs Karten von Europa” by Ritter, attached to his book “Regional Geography of Europe, ” was the first printed atlas of thematic maps. An incredible amount of information concerning individual locations on the earth's surface was put into an orderly system of knowledge in the form of thematic maps. By making distribution maps of trees and shrubs and of cultivated plants, he delineated several natural regions which were almost parallel to the latitudinal zones. His famous definition of geography, that is, geography deals with the earth's surface as long as it is earthly filled (irdisch erfüllt), can be well understood through his intention to make various thematic maps, because comparable information must be collected for the whole region to complete a map.
Halley's isoline map was followed only by those of Ph. Buache (1752) and J. I. Dupain-Triell (1791) until Humboldt made an isothermal chart in 1817. The isoline map is unique in that it can be made with a limited number of data. Humboldt used only 58 cities to produce his chart of a wide area in the Northern Hemisphere. In addition, isoline maps are also unique in that, once made, interpolation and extrapolation allow determination of the figure for every arbitrary point. With the aid of Humboldt, H. Berghaus, the eminent cartographer, published the “Physische Atlas” which included many thematic maps. It cannot be denied that Humboldt was also very keen to illustrate the regularities of physical phenomena and the interrelationships between them using thematic maps.
Scrutiny of the history of modern geography from the viewpoint of thematic maps, discovering what type of map was developed for what purpose, etc., is a promising research area.
For example, C. Darwin made a distribution map of coral reefs to test his subsidence theory explaining the formation of three types of coral reef. Emphasizing the shapes that maps can describe better than language, O. Peschel believed that a precisely prepared map could illustrate the hidden factors explaining the formation of fjords and other phenomena. F. Ratzel also recognized the importance of map representation in the science of “Anthropogeographie.” His movement theory was highly appreciated by the Kulturkreis school in cultural anthropology. L. Frobenius developed the culture-complex diffusion theory with the help of a number of thematic maps.
K. Yanagita (1930), a Japanese folklorist, assembled more than three hundred parochial expressions for the word “snail” into a map. Identifying a concentric pattern with the center in Kyoto from a seemingly chaotic map, he concluded that the distribution pattern of some Japanese dialects resulted from a slow diffusion from the ancient cultural core.
