Googling for something else I ran across this feature article on Tesla from 1899: http://homepage.ntlworld.com/forgottenfutures/tesla/tesla.htm I've read other similar accounts of visits to his lab quoted in biographies of him, and he included similar dazzling displays of high frequency AC effects in his public lectures. This ball of flame is not the chemical flame produced by magicians but is some high frequency/high voltage AC effect Tesla discovered in the course of his experiments. It is probably the same phenomenon as ball lightning, and Tesla is the only man I've ever heard of who was able to reproduce this in the lab. I don't know if he, himself, was familiar with reports of naturally occuring ball lightning, and I suspect this effect was something he discovered by accident while experimenting toward other goals. Like the ball of flame, this sourceless illumination is another high frequency/high voltage AC effect. I suspect that the shutters "as tight as a vice" are probably also air tight and that he is causing the ambient air in the lab to glow with the discharge from an unseen tesla coil at the right frequency. After next turning himself into "electric man," an effect that alot of people with large tesla coils have been able to reproduce, he goes on to talk about half developed inventions: solar steam power, wireless transmission of electricity, a telephone that sent what we would now call a "video" image along with voice (he was very close to the idea of television - in 1899!), and a machine for electrically fertilizing soil. (I don't believe he completed and patented any of these ideas except the elements of the wireless transmission of electricity. It's a pity he didn't persue the rather basic, obviously workable, solar steam generator. With his post-Niagra credibility he could have gotten large scale versions of it into operation and we might be using refinements of them today.) The article is a very good, typical, picture of Tesla: half magician, half Utopian dreamer. He was constantly spurred by the notion that invention could lead to a world without want or war.