Wood announced one day at lunch at the pension in which they were living, “We’ve found and measured the longest heat waves ever observed”.
“How long were they?” asked his daughter Margaret.
“One tenth of a millimeter”, announced Wood triumphantly.
“I don’t call that very long”, commented Margaret in a bored tone.
These invisible rays from the lamp had very curious properties, they found. A quartz plate so heavily smoked that the sun was invisible through it was perfectly transparent to them; and the same was true for a plate covered with a thick opaque layer of finely divided metallic copper, while a plate of hard rubber half a millimeter thick transmitted about 40 per cent.
Plates of rock salt, which are extremely transparent to the greater part of the infrared spectrum previously studied, were absolutely opaque to these rays.
It was a matter of considerable theoretical interest to find out whether an extremely thin plate of salt would transmit anything.
“We need a plate half a millimeter thick, if possible”, said Rubens. “I shall order one from Steinheil [an optician and lens-maker]. He can do it, I think, and we shall have it in two weeks”.
“Why not make it ourselves?” said Wood.
“Can you, then, grind and polish a rock-salt plate?” inquired Rubens in surprise.
“I don’t know”, said Wood. “I think so”.
He took the thinnest salt plate they had and ground it against a sheet of ground glass, slightly moistened with water, until it was about half a millimeter thick. This was all that was required, but the thinner the better, so Wood thought he’d see if he could go further. Attaching the plate to a match stick with sealing wax, he dipped it into a glass of warm water and dried it quickly with absorbent cotton. It was slightly thinner, and the “ground” surface had become polished and transparent. He dipped it in the water and looked at it again (as did the Hatter at the mad tea party). It was still thinner. One more dip proved to be the limit, as the plate showed evidences of going to pieces at one corner.
Rubens breezed into the room, having finished his lecture. “Well”, he said, “and can you make us the salt plate?” “Yes”, said Wood. “It’s finished”.
“And how thick is it?”
“One tenth of a millimeter”, said Wood, who had just finished measuring it.
Early in December the Woods were invited to attend the festivities in Stockholm in connection with the awarding of the Nobel prizes, and Wood was invited to deliver a lecture there on his recent researches in optics.
While carrying on the research with Rubens, he had also been investigating the optical properties of iodine. This had led to a capital discovery which was the small but solid foundation upon which he built later on one of his most important and elaborate series of discoveries, described in numerous papers under the general title of “Resonance Spectra of Iodine”, investigations that occupied him for several succeeding years and eventually, when theory caught up with experiment, were of considerable importance in unraveling the mystery of band spectra. The discovery came about in this way: having been struck, in some of his earlier work, by the similarity of the absorption spectra of sodium and iodine vapors and having prepared some glass bulbs containing iodine vapor for the purpose of studying its fluorescence and passing through one of the rooms in which a quartz mercury arc lamp of great intensity was burning, it occurred to him that possibly the iodine vapor might yield resonance spectra similar to those which he had observed and studied under such difficulties in the case of sodium. He borrowed a small hand spectroscope, set up a large lens, and formed an image of the arc on one of his bulbs. Splendid! A bright cone of fluorescent light inside of the bulb. Pointing the spectroscope at the bulb he observed a resonance spectrum far simpler and more clearly cut than any he had found with sodium, a series of bright lines, spaced with the precision of the graduations on a foot rule, extending from the green line of mercury up through the yellow-orange to the extreme red. This observation was made only a few days before his invitation to Stockholm, so he had a very young “baby” to show at his lecture.
What impressed Wood most on arrival in Stockholm was that it offered no facilities for taking a bath, although there were plenty of places where one could be given a bath. You were placed stark naked on an ironing board and scrubbed with excelsior, like a puppy, by a muscular Swedish woman. The Woods were entertained at dinner by the American Ambassador and his wife, who told Gertrude they had had a bathtub installed in their house, but found that the plumber had put the valves that controlled the hot and cold water flow on the other side of the room from the tub. When they protested that they would have to get out of the tub every time they wanted to change or adjust the temperature, they were told they “could ring for the maid”!
At the huge banquet which followed the handing out of the Nobel prizes, Gertrude was seated at the head table next to Emmanuel Nobel, a nephew of the inventor of dynamite who had founded the prizes. He told her he was just back from St. Petersburg and had brought with him an enormous earthen crock of the finest caviar, a gift from the Czar to the King. “All I could take back as a gift to the Czar”, he said, “would be a box of dynamite — and that, I’m afraid, wouldn’t be very acceptable
When the day came for his lecture, Wood performed a number of what Professor Lorentz, the famous Dutch physicist, had once designated “his beautiful and convincing experiments on the blackboard”, making pictures for his audience of everything he was talking about. It diverted them, he said, and kept them from going to sleep. They must have been well diverted, for the Woods continued to be showered with invitations.
A luncheon was given them by Professor Mittag-Loeffler at his beautiful country home. He was the Chairman of the Nobel Committee, was in Berlin in the autumn, and had extended the invitation to the Woods to come to Stockholm. He was proud of his library, said to be the finest collection of books on mathematics in the world. It was housed in a huge tower, ascended by a great spiral stairway.
Mrs. Wood tells a story about the formal reception which formed a part of the program. The Crown Princess Maud was receiving in a small room which opened off the large hall, and the chamberlain told the Woods they would be taken in soon and presented. Wood was meanwhile introduced to the first lady in waiting, a beautiful and vivacious young Englishwoman, and Mrs. Wood says the chamberlain experienced great difficulty in prying Wood loose from her when the time came for presentation to the Crown Princess.
Wood had an absurd run-in with the German customs. Going to Stockholm he had taken along a suitcase crammed with glass bulbs, lenses, prisms, rubber tubes, and other odds and ends and gadgets for the lecture. When, on the return trip, they reached the German frontier at Malmö and were lined up at the customs barrier, Wood had to open it.
“Ach! Was haben Sie hier?”
Wood explained it had all been made in Germany and was the property of the University of Berlin; that he had taken it to Stockholm for a lecture and was returning it to the University. “That makes no difference”, said the guard. “You have duty to pay”. Wood argued, but to no avail.