John Chappelsmith, “Map of the Track of the Tornado of April 30th, 1852”
A closer look from the #Historical-Viz channel
“The storm came from the southwest, across the bluff from the opposite side of the river, tearing up trees by the roots, or twisting off their tops; it then crossed the river, swelling the waves to an incredible height, lift skiffs from the river bank, and dashing them to pieces against the houses. It struck the town about 6 1/4 P.M., and raged from three to five minutes, unroofing and prostrating sixty buildings, some of them the most substantial in the town, carrying off and blowing articles of every description about, killing one child, and wounding ten or fifteen individuals.” It’s the kind of destruction that only a tornado is capable of, but when John Chappelsmith began his scientific documentation in 1852, tornadoes were largely unexplored.
John Chappelsmith’s “Account of a Tornado near New Harmony, Ind., April 30, 1852, with a Map of the Track, &c.” is a modest 11-page booklet that includes a fold-out map with nine illustrations describing the damage and track of the tornado. His work was commissioned by the Smithsonian Meteorological Project, which was a massive network of volunteer observers and trained meteorologists, the results of which were printed as the lead article in the Smithsonian Contributions to Knowledge vol VII in 1855.
But this was more than a case study — Chappelsmith sought to prove the physics behind the meteorological phenomenon. He begins by outlining his intentions: “As every accurately observed meteorological fact must be of importance in the necessary accumulation of data, from which the phenomena of storms are to be understood, and the laws which govern them deduced, I am led to believe that a map and memoir illustrating the tornado which recently passed near New Harmony, Indiana, will be of some service to the cause in which so many are at present engaged.”
Chappelsmith diligently presents his well-considered research with a variety of chart styles and illustrations. He outlines his arguments in a clear structure to understand the physics behind the phenomenon, then walks the reader through each of the “figures” one at a time. He begins by tracking the storm and situating it in the region as can be seen below in Fig 1. above.
Then Chappelsmith focuses on the largest part of the map, created not by charting wind measurements, but by mapping the direction of the multitude of individually snapped trees. He outlines a single square mile of felled trees and damaged houses in the map. The storm’s movement is tracked “a little north of East.”
Chappelsmith focuses close attention on each aspect of the map. Clusters of trees are documented to denote if their roots are showing or if the tree is completely snapped. The few structures in the area also suffered damage, a small rectangle is labeled “Ormonds house, roof carried north.”
Chappelsmith describes his onerous work, “I therefore present the plot of a single square mile of track on which some 7 or 8,000 prostrated trees are represented in their relative positions, with the hope that the means will thus be furnished for more satisfactorily determining whether the immediate mechanical cause of devastation in tornadoes be a spirally involuted rotating moving column of air, or a vertical current at the centre of the tornado with a horizontal conflux from surrounding space as the moving axis.”
He then moves onto the theoretical aspects of his research. The two charts below plot the difference between the two different tornado theories as a swirling column of air (Fig. 5) and one which was presumed to represent a “horizontal conflux” (Fig. 6) — sort of like an upward jet of wind — where the wind rushes in then shoots straight up.
Chappelsmith’s tree diagrams are used not just to show their overall direction, but also their sequence. Clusters of trees that are laying on top of each other are labeled in the sequence they fell. Chappelsmith felt these clusters explained how the winds rushed into the center of the air towards a central point.
Despite the detail of his diagram, it’s important to remember that it was 1852 and since tornadoes are largely regional, readers in many parts of the united states, and the world, may not understand what the damage actually looked like. Chappelsmith wisely included drawings to illustrate exactly how the trees were twisted, ripped and toppled.
Chappelsmith finishes his book with an additional print. This shows another view of the same arrangement of trees as seen in Fig. 8 above, right. The trees are not only shown in more detail but are placed in context. He focuses on the tree with the fork in the center and notes the peculiarity of the interlocking shapes.
As mentioned at the beginning of the article, tornadoes were still poorly understood. Robert Simmon’s great article “Handcrafted Visualization: Precision” terrifically sums it up: “Despite his considerable effort, Chappelsmith’s interpretation of his own data turned out to be a bit off base. He believed the evidence showed that “tornadoes are an inward, upward, and onward moving column of air”, rather than a spiral.” But it turns out tornadoes are actually a mixture of atmosphere instability, pressure differences, wind shear.
Some takeaways from Chappelsmith’s work
There are always lessons to find in the notable works of data visualization history. Regardless of the results of his work, we can all appreciate and draw inspiration from the techniques Chappelsmith employed to create a compelling argument.
Providing your context is crucial
Imagine explaining a tornado to someone who’s never seen one before. By providing the map, charts, and illustrations together with first-hand accounts, Chappelsmith presented a compelling vision that allowed his audience to understand the damage and conceptually map it to the theoretical.
Find your own way
While you definitely should not reinvent the wheel each time you’re solving a problem, sometimes you need to find a different way of graphically communicating your data. Taking the time to visually communicate your ideas can help your audience understand something that is beyond their imagination. If the traditional chart types aren’t working, maybe it’s time to insert illustrations or even new ways of graphically presenting the information.
Structure your argument
Understanding the system beneath your data will help you make a compelling argument. Chappelsmith clearly spent a great deal of time recording and drafting this work but he also spent time in crafting a detailed plan to communicate his findings. Take the time to make sure your system and your communication plan make sense.
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