Maps and the Ideas they Express

The nineteenth century was a period of consolidation and diversification. Except for the polar regions, the main coastlands and islands of the world had been explored and charted at least at the reconnaissance level by 1800. However, much remained to be delineated, especially in the continental interiors (except Europe, which was reasonably well mapped by this date). Expeditions, mostly originating in Europe, were dispatched to all parts of the world in the nineteenth century, and small-scale general mapping became a large part of the activity of geographical societies that were founded at this time. Similarly in the Americas, interior areas were explored and mapped, at first in a provisional manner, but using instrumental surveys. Thus the world's great rivers, inland seas and lakes, mountain ranges, deserts, and so forth appeared on general sheets and atlas maps, and geography became an important school, college, and university subject.

Along with this was an interest in thematic cartography, in which distributions of phenomena hitherto little known were investigated and mapped. The beginning of regular censuses in this period in many countries provided a large body of mappable data, especially on the human population. Soon demographic maps were produced, and so-called qualities of population also received attention from cartographers—disease (as in the highly informative maps of deaths by cholera in London of Dr. John Snow), crime, poverty, and so forth. Land-use maps of crops, forest cover, and urban forms soon followed, but perhaps the most remarkable development at this time was in geologic mapping.

Geologic mapping.

Great scientists turned their attention to studying the strata of the earth, as mines and canal and railroad cuts revealed the earth's substrate. Those associated with the new science of geology included James Hutton (1726–1797) in Figure 9. Section of 1729 isobathic chart of the Merwede River by Nicholas Cruquius. Scotland, Abraham Gottlob Werner (1749–1817) in Germany, and Georges Cuvier (1769–1832) in France. But it was a contemporary of these natural philosophers, the English civil engineer William Smith (1769–1839), who is credited with successfully correlating fossils with associated strata. Smith used conventional colors and notations for rock types, based on age and lithology, and thus greatly advanced geological mapping (Fig. 10). So influential was Smith's work that when a federal, general topographical mapping agency was founded in the United States (much later, in 1879), it was named the United States Geological Survey (USGS), in contrast to the earlier, military or quasi-military topographic surveys in the Old World.

A man with vision large enough to put all of the preceding geographical knowledge into a logical framework was the Prussian Alexander von Humboldt (1769–1859) in his Kosmos; his fellow Prussian, Carl Ritter (1779–1859), was a great geographical educator. Both contributed original ideas to cartography: Humboldt with continental maps and profiles, and isothermal diagrams; and Ritter with the concept of altitude tints on general relief maps (this was later formalized with conventional colors for elevation in use today).

The growing United States was the beneficiary of European expertise, as when Humboldt visited Thomas Jefferson, who (like his predecessor in the U.S. presidency, George Washington) was a surveyor and cartographer. It was through Jefferson that the rectangular method of cadastral survey was applied to the Public Domain, the most extensive example of uniform property mapping in the world. This method contrasts with irregular (metes and bounds) cadastral surveys used in the eastern United States and over most of the land area of Earth. Other Americans made signal contributions to mapping; for example, Matthew Fontaine Maury's (1806–1873) wind and current charts greatly reduced the time taken on long voyages in the period of sailing ships. Great progress was also made in land travel through the railroad, with maps used in determining the best routes and later, when the railways were built, to assist travelers in planning trips.

The traffic-flow maps of Ireland by Henry D. Harness (1804–1883) are especially innovative contributions to transportation geography. More rapid travel in an east-west or in a west-east direction necessitated the development of uniform time zones. This was accomplished in 1884 at an International Meridian Conference held in Washington D.C., when Greenwich (England) was approved as the global Prime Meridian, and the center of the first of twenty-four (one hour) time zones, which were mapped. Lithography, which eventually led to color printing of maps, was also a nineteenth-century innovation as far as cartography was concerned.