Most rivers comparatives look like stylized column graphs, where the rivers are scaled down and function as columns indicating length. Column graphs certainly lend themselves nicely to comparing lengths of rivers and at the time comparative views were popular, column graphs were still new, having been developed a few decades earlier by William Playfair. While just about any rivers comparative view resembles a column graph, the well executed among them are faithful, albeit smaller and straightened, facsimiles of the the rivers, providing more than just length, but also falls, lakes, deltas, tributaries, and adjacent cities.
Carey and Lea’s 1832 Chief Rivers does an excellent job of showing both rivers, but also the figurative and literal landscape through which they flow.
They show the Amazon (watch out for piranhas!) stretching from the Atlantic Ocean across the continent of South America, through the Andes, tracing the Beni River and showing Lake Titicica (the highest navigable body of water, by the way, at over 12,000 feet of elevation), and passing no fewer than five cities. From this image, we can tell that it supports a lot of people, with the cities serving as a proxy for population. Further, we can tell from the many tributaries that it drains a large basin, and from the mountains approximately 2/3 of the way inland from the ocean that it has alpine headwaters. Looking at the Mississippi, its delta and New Orleans–the Crescent City–are clear as day. The map shows two forts on the Mississippi, each indicated by a small cross, including Ft Mandan, where Louis and Clark spent the winter of 1804-1805. The presence of these forts and the several towns shown, with their histories in mind, tell us that this river was important in the European settlement of North America.
The detail Carey and Lea provided in the cases of the Mississippi and Amazon, as well as in the other rivers shown, makes clear that they are chief rivers in addition to simply being long rivers. Certainly being a long river is a compelling argument for it being important, however Carey and Lea show several very small rivers. The Thames and Forth rivers are tiny in the shadow of the Nile, Amazon, and Mississippi, but Carey and Lea provide context; showing London and Edinburgh provides the detail to understand that these are important rivers as they support capital cities despite being relatively short. After looking at the Mississippi and Amazon rivers, it is clear that their importance is not just in their length but also because of their ecology, the populations they support, and the commerce they facilitate. All of this insight would be lost if they were mere lines on a chart.
© Peter Roehrich, 2016.