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

During all this hectic time, while Wood was inventing war gadgets and later, when we went in, pulling every possible human wire to get into uniform and actual service “over there”, he wasn’t neglecting his purely scientific work.

In the early part of the summer of 1916, he was busy in East Hampton developing a new filter for the photography of the planets by ultraviolet light, which he planned to use with the great sixty-inch reflecting telescope of the Mount Wilson Observatory in California. The filter consisted of a cell made by covering the ends of a short section cut from a square glass bottle with plates of “uriol” glass. This cell was filled with bromine vapor, which he had found to be transparent to ultraviolet light but opaque to all other rays capable of acting on the photographic plate.

In late September Wood went with his wife and daughter Margaret to San Francisco, their first visit with the grandparents since before the earthquake in 1906. Wood immediately went down to Pasadena and was quartered in the so- called “Monastery”, the sleeping quarters of the observatory staff on Mount Wilson. The sixty-inch telescope was assigned to him for four evenings, and, to his delight, he found Harlow Shapley, who had assisted him in Princeton, now a member of the staff and ready to help him again. The bromine cell was mounted on a brass frame directly in front of the plateholder, which covered an aperture in the side of the great tube near the top, the huge mirror of “silver on glass” being at the bottom of the tube. Photographs of Jupiter and Saturn were made with infrared, yellow, violet, and ultraviolet light, the latter showing an equatorial belt on Saturn that had never been seen before, the cause of which gave rise to considerable discussion among astrophysicists. It was finally decided to be a circular cloud of very fine dust that bordered the “ring” on its inner edge.

As this research neared its end, a “terrible” tragedy occurred.

We had cleaned and charged the cell with fresh bromine vapor (Wood says), leaving as usual a drop or two of the liquid to make up the loss due to its slow combination with the beeswax cement. One of us had clamped it in position, and the great telescope was slowly swung into its nearly vertical position. Suddenly there was a crash like that made by a glass bottle shattered on a cement floor. “Good God”, we both (I think) gasped. “The bromine cell on the silver mirror”. I leaned over the edge of the tube and looked down. Sure enough, on the great circular shining silver surface, five feet in diameter and twenty-five feet below me, there was a large irregular black splotch, some eighteen inches across. There was nothing that could be done at the moment, and I was relieved to see that the spot was not spreading, which indicated the bromine had all been used up. But had the glass surface been damaged? That was the question that caused a sinking feeling in the pit of my stomach. Shapley said that it was his fault, as he believed he had attached the cell, but I insisted (I hope) that it was mine, as I felt sure I had done it. However, it turned out all right: the glass mirror was not damaged, they were planning to resilver it anyway in a couple of weeks, and the amount of silver removed had not caused enough loss of light to interfere with the program arranged for the intervening time. We felt better when told by the director that worse things than this had happened. One of their mechanics had once let a small monkey wrench fall on the mirror, which made a large nick in the surface.

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Returning to Baltimore late in October, he started a new line of investigation with Professor Okano, a Japanese scientist who had been sent to work with him. They investigated what is known as the “ionizing potential” of sodium vapor, which had never been determined. Defined in words, they were to determine the lowest voltage that would cause sodium vapor to glow or emit light in a vacuum tube. The final result was interesting, though they did not feel sure of it until a number of sources of error had been discovered and conquered. A sodium lamp could be operated with an electric potential of only 1.5 volts on its terminals or by one dry cell, provided free electrons were present. Wood had, in 1910, in collaboration with R. H. Galt, one of his students, studied the spectra of the electrical discharge in dense sodium vapor, and been struck by the overpowering brilliancy of the yellow light in some cases. “It was like looking at the sun through a yellow glass”, he says. He had dreamed of sodium lamps, naturally, but at the time there was no way of preparing a glass tube or bulb that would not blacken and become opaque after a few minutes’ exposure to the corrosive vapor. It was this circumstance that had caused Lord Kelvin to ask, “Have you succeeded yet in taming sodium vapor?” Modern sodium lamps are of course the latest development for street lighting.

Chapter Fourteen.