Colonial administrators have a chat in this postcard from the French Congo, 1905. The French Congo, later called French Equatorial Africa, was split upon independence into Republic of Congo (aka Congo-Brazzaville), Gabon, and Central African Republic.

Graph showing England’s trade deficits and surpluses with Denmark and Norway in the 1700s by William Playfair. Playfair, who lived from 1759-1823, invented line graphs, bar graphs, and area graphs, which hugely enhanced the ability of statisticians to display their work to the public and each other. Playfair was also a secret agent for the British, successfully spreading counterfeit currency in Revolutionary France in order to cause inflation and wreck the French economy.

Cross section of the New York transit system on Fourth Avenue, showing the subway, sewage, gas, and trolley infrastructure. Scientific American, 1902.

A worker stands next to one of the graphite lattice components of Chicago Pile 1. This was he first nuclear reactor, consisting of 45,000 graphite blocks and over 50 tons of different types of uranium. It was built in 1942 by Leo Szilard and Enrico Fermi, among others, under the bleachers in Stagg Field, the University of Chicago’s football stadium.

Photograph of lightning, 1882, by William Jennings. Jennings, who lived in Philadelphia, worked to develop photographic equipment that could work quickly enough to capture a lightning bolt.