Hunter Dukes writing at Public Domain Review:

Electrical engineer Nikola Tesla, “the man who invented the twentieth century”, reignited his correspondence with friend and mentor William Crookes in an arresting way. On a photograph of himself seated beneath a giant “magnifying transmitter”, arcing twenty-two-foot-long bolts of electricity, Tesla inscribed: “To my illustrious friend Sir William Crookes of whom I always think and whose kind letters I never answer!”

The photograph originally appeared in a Century Magazine article from 1900 describing Tesla’s ambition to develop wireless energy transmission. The cartoon below explains his (theoretical) process.

It was this project, and its proposed use in warfare—a “death ray”—that made Tesla the model for every “mad scientist” in films and pulp fiction of the 1930s.