Doctor Wood. Modern Wizard of the Laboratory: The Story of an American Small Boy Who Became the Most Daring and Original Experimental Physicist of Our Day-but Never Grew Up

Wood next regaled them with his tornadoes. The atmospheric conditions (a layer of hot air close to the ground, with cooler air above) which exist with mirages also give rise to the “dust whirls” so often seen on American deserts and, on a larger scale, to tornadoes. One of the metal plates (cleared of sand) was sprinkled with precipitated silica powder and heated by a few burners. In a few minutes beautiful little whirlwinds began to run about over the surface, spinning the light powder up in funnel-shaped vortices, which lasted sometimes ten or fifteen seconds. By sprinkling a large square plate of sheet iron with sal ammoniac and heating it strongly by Bunsen burners, white fumes were given off, and presently, at the center of the plate, there mounted to a height of six or eight feet a most perfect miniature tornado of white smoke!

A little later in the year he invented a new form of pseudoscope. When viewed through this instrument, an old-fashioned washbowl appeared as a white dome, and when a marble was dropped into it, it seemed to roll up and down over the surface of the dome in defiance of the law of gravitation, finally stopping on the summit!

Another memorable lecture-room stunt was his demonstration of the curved flight of baseballs as pitched by the then Dizzy Deans — leading on to the parabolic orbits of planets and comets as pitched by the Lord God Almighty. The limited space in the lecture room had raised difficulties. If the curve was to be made at all apparent in that limited space, the ball would have to be exceedingly light and the axial rotation very rapid. Wood found the ordinary oak ball or oak apple suitable for this purpose. A ping-pong ball might have been even better. A strip of rubber band six or eight inches long and one- eighth inch wide was wound under tension around the ball, two or three turns being enough, and the ball catapulted forward by means of the remainder of the band. A total deflection of forty-five degrees was easily obtained, and when pitching the “rise” (in which case the free part of the band is below) the ball, starting in horizontal flight, would often ascend half way to the ceiling. Try it for yourself, if you don’t believe it.

An experiment followed showing in miniature the elliptical and parabolic orbits of the planets and comets around the sun. The conical pole piece of a vertical electro-magnet was covered with a large sheet of plate glass, and a steel bicycle ball projected toward a point a little to one side of the magnet, which represented the sun. The ball whirled around in a beautiful ellipse with the sun at one focus, as Wood demonstrated with a glass plate covered with a thin film of soot, obtained by holding it over a smoking flame. In this case the ball left a record of its path on the film.

The publication of a scientific paper on this experiment led Wood into his first brief polemic. An older professor of physics in one of London’s universities criticized the paper in a letter to the London Nature, saying that the experiment did not illustrate Newtonian orbits, as the magnetic attraction varied as the inverse fifth power and not as the inverse square as in the case of gravitation. This was young Wood’s first slap — but he sat down and drew a diagram of his experiment with the lines of magnetic force put down and realized at once that the ball was not coming in along the lines of force, but was cutting across them at an angle, and that it was the horizontal component only that governed the orbit. He set one of his young students to measure the effective force in the plane of the glass plate, and it turned out to be very nearly proportional to the inverse square. In the meantime, letters of criticism had appeared in several other English technical journals, and Wood joyfully sent off a rejoinder giving the results of the actual measurements.