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

Chapter Eight. At Johns Hopkins

Following the death of the great, gruff Henry Rowland at Johns Hopkins in 1901, Wood was offered and accepted a full professorship in experimental physics there. It was a high honor for so young a man, no matter how fantastic a genius. Gertrude went ahead to Baltimore and selected a house on St. Paul Street in a city block that had looked upon the stoning by secessionists of the Massachusetts regiment on its way to Washington. Returning to Madison, the furniture was packed up and sent on in care of the Baltimore house agent, who installed it on its arrival. The family reached Baltimore late in September. They opened the Baltimore house, unpacked the crate containing the Stanley Steamer, and bounced over the cobblestones with which the entire city was then paved. Surface drainage disposed of all the water used for washing purposes, a thin stream, sky blue on wash day, running out under every back gate and along a shallow gutter in the brick sidewalk. Loose bricks acted as force pumps, squirting a jet of water up your trouser leg almost to the knees if you stepped on one, efficiently adjusted with respect to its neighbors. Wood called them “bath bricks”. The alleys and some of the street crossings had high stepping stones on which you crossed dry-shod in case of heavy rains, but at which the Stanley Steamer shied.

Of his work at Johns Hopkins, Wood says:

My teaching was very light, three lectures a week on physical optics, the same as at Madison, and I gave practically all of my time to research, a part of it in collaboration with graduate students working for the doctor’s degree. With J. H. Moore an investigation was made of the green fluorescence of sodium, with more powerful spectroscopes than the one I had used at Madison. This came along very well, an “infant phenomenon” being observed that became very important when it grew up in later years. Instead of illuminating the vapor in a small glass bulb with white light as I had done at Madison, we shot into it various colored rays in succession obtained by a combination of lenses and prisms called a monochromator, which sifts out from sunlight a very narrow region of the spectrum and projects the beam of pure color at any desired point. We found that when the metallic vapor was illuminated by a beam of blue light, it emitted fluorescent light of a yellow color, but as the color of the beam from the monochromator was changed to bluish green, green, and greenish yellow in succession, the region of maximum intensity in the fluorescent spectrum moved down towards the region of the exciting light and eventually coincided with it, with a suspicion of a trace of light on the further side of it. This was an exception to Stokes’s law of fluorescence, which stated that the light emitted by fluorescent substances was always made up of wave lengths longer than that of the exciting ray, that is, on the red side of it. Many years later unusual fluorescence was very clearly demonstrated in experiments that I made with sodium and iodine vapors, the discovery being of considerable importance in connection with the theory of molecular spectra.

While the sodium vapor investigation was in progress I was at work on several other problems, one having to do with the remarkable optical properties of a chemical with a terrifically long name, nitrosodimethylaniline, which was one of the substances we had been required to make in Professor Remsen’s course in organic chemistry ten years before. It had struck me at the time that the bright green flakes with a metallic luster looked interesting, and I had preserved the material in a bottle. In the course of my lectures at Madison I had come to the subject of anomalous dispersion, shown by substances having strong absorption. A prism made of such a substance produces a spectrum in which the colors are not arranged in the same order as they are in the rainbow or in a spectrum formed by a glass prism, the deviation being greatest, but in opposite directions, for the colors close to and on either side of the absorption band. This phenomenon had previously been demonstrated and studied by solutions of aniline dyes contained in a hollow prism of glass. It had occurred to me that if I could fuse the pure dye and press it between two pieces of plate glass inclined at a small angle to each other, a much greater effect would be produced. I tried it with some crystals of cyanine, the dye used for sensitizing photographic plates for infrared rays. They melted easily and made beautiful prisms, which gave the effect in a greatly enhanced degree. Trials then made with about fifty other dyes showed that all were useless; they decomposed and swelled up into a spongy black mass without fusing, and I have never been able to find anything else that answered the purpose. Even cyanine made by other chemical plants would not melt. My sample was what horticulturists would term a “sport”, I suppose. Ehrlich had 605 failures before the successful 606th. I had one success followed by fifty failures! In looking over my preparations made years before in Remsen’s course I ran across the nitrosodimethylaniline green flakes. These green flakes melted at low temperature and gave beautiful prisms, which transmitted the red, orange, yellow, and green rays in normal order but gave a spectrum fifteen times as long as the spectrum produced by a glass prism of equal angle. Moreover, in solution, the substance absorbed the violet rays powerfully but transmitted the ultraviolet, and by combining it with dense cobalt-blue glass I obtained something that had been searched for in vain — a ray filter that would be opaque to visible light but transparent to the ultraviolet. With this filter I made my first landscape and lunar photographs in ultraviolet light, and at the autumn meeting of the National Academy in Baltimore in 1902 I gave an experimental demonstration of what could be done with what is now called black light.

The meeting was held in the lecture room of the physical laboratory, and after the exhibition of various photographs made exclusively by ultraviolet light, the room was completely darkened and the invisible rays from an arc lamp in a light-tight iron box were passed out through a single window made of the filter combination opaque to visible light. A white porcelain plate held in front of this window was invisible. The rays were brought to a focus by a large condensing lens on a pile of crystals of uranium nitrate, which immediately glowed with a brilliant yellow-green light, of sufficient intensity to read by. Newspaper accounts of the meeting record that this experiment “was received by a burst of applause, a reception rarely accorded at dignified Academy meetings”.

Wood never denied himself the chance to make grandstand demonstrations such as this, but he didn’t let them interfere with his laboratory research. During 1902 alone ten scientific papers of his appeared in the Philosophical Magazine; and a German physicist wrote to an American friend at this time, “Wood — he produces like a rabbit”.

In the summer of 1902 the Woods all went to San Francisco to visit Gertrude’s parents, who had sold the house in Ross Valley and reopened their house at 1312 Taylor Street. A new addition to the family was expected about the middle of July, and Gertrude insisted that this was the obvious time for Robert to visit the Hawaiian Islands, where he had always wanted to go because of his father’s early life there. Wood’s protests against the infamy of a husband deserting his wife at such a time were pronounced “rubbish” by Gertrude, who finally persuaded him to abandon her. She would be perfectly all right with her mother, nurse, and the doctor to take care of her. In those days you always had your babies at home. Maternity hospitals were an unknown luxury.

Wood says:

So presently I found myself on a steamer heading out through the Golden Gate. The Islands in those days were quite free from the commercialization which they have undergone in the past quarter of a century. You could see real hula dances, while now I’m told they have an expurgated edition sponsored by the Eastman Kodak Company held every day for the benefit of tourists, in front of the beach hotels. I had one or two friends who lived in Honolulu and in a few days a lot more friends, for I was invited to a mou-mou party over a week end. The mou-mou was a native negligee, a single garment, or rather a long burlap gunny sack with three holes at one end, two for the arms and one for the head. On arriving at the large country house set back from the beach, I was informed that we were to shed our clothes and put on mou-mous, with nothing underneath. In this garment, which came down to your knees, you played a game of tennis or sat around tables with iced drinks, and then all went down to the beach for a swim, and then back under the trees, where the gunny sacks dried out in a few minutes, then another drink and another swim, then dinner all in mou-mous around a long table, with champagne, then another swim by moonlight, “and so to bed”, all of the men in one big room and the women in another in a distant part of the house, and the “roll” called before the lights went out to make sure that all were “present or accounted for” and that no one was A.W.O.L.

The tame spiders were terrifying, and were in practically every country house or bungalow on the Islands. They are non- poisonous and are never molested, as they destroy millions of mosquitoes and other insect pests. The body is the size of a small hen’s egg, and the hairy legs spread out over an area the size of a large saucer. I had not been told about them when I visited Gertrude’s cousin on the island of Hilo, and on going to bed, just as I was stooping over to blow out the candle, I was startled by the sudden impact on the top of my head of something that felt like a frog, which bounced off onto the floor and scuttled under the bed. Looking over the ceiling I discovered three more of the creatures lurking in the dark corners. This was dive bombing on a larger scale than in the hotel in Omsk, and I shouted for my host, as I did not feel secure even under the mosquito net which covered the bed. He explained that they were pet spiders and lived on mosquitoes, and would eat out of your hand. Not out of mine, however!

I found that the Royal Hawaiian Hotel occupied the site of my father’s former residence. It was a rather unattractive commercial travelers’ sort of place, and has now, I believe, been replaced by something more suited to the rich tourist class. The Moana at Waikiki Beach was the swank hotel at the time, and it was here that I had my first experience with surfboards. Later on after we had acquired our summer home at East Hampton in 1908 I made surfboards for myself and friends and started that sport on the beach. It spread like an epidemic along the southern shore of Long Island and finally all over the map. As far as I know this was the first time the boards were seen on the Atlantic coast, and though it is very probable that I had many predecessors, it evidently had never “caught on” before, as in the case of my experiments with homemade skis when I was twelve years old.

Bradford Wood[6], one month old, was awaiting my arrival in San Francisco as I came back through the Golden Gate, with a basket of tropical fruits for his mother, all of which were confiscated at the customhouse, only just become bug conscious.

Back in Baltimore in the autumn of 1902, Wood continued his photography of the moon with invisible light. The contrasts between the dark and light lunar areas were much greater with ultraviolet than with visible light, while the reverse occurred in the case of landscapes. One interesting peculiarity of the landscapes taken in full sunshine was the almost complete disappearance of shadows, showing that the greater part of the ultraviolet rays came from the blue sky and not directly from the sun.

Later on at East Hampton he improved the method by employing a quartz lens with a heavy deposit of metallic silver, which is remarkably transparent to a very narrow range in the ultraviolet and quite opaque to all other rays. With this filter he discovered a large dark area around the lunar crater Aristarchus, which was practically invisible to the eye. Comparison experiments with terrestrial substances indicated that it was sulphur. The Germans named it the “Woodsche Fleck."

In a picture made with the silver filter a man walking in sunshine was accompanied by no shadow, like Peter Schlemihl in the German fairy story. Distant hills, clearly visible, were blotted out by atmospheric haze when photographed by ultraviolet. Wood later photographed with an infrared filter which showed distant mountains sharply outlined with all their high lights and shadows on days when the haze was so thick as to make them quite invisible to the eye. These later photographs, made in 1908, were the first infrared pictures ever taken.

In the summer of 1903, the Woods rented a cottage at North Haven, Maine, where a number of their new friends in Baltimore spent their vacation. Wood devoted himself to sailing, either in Dr. Stewart Paton’s yawl or in his own dinghy. North Haven was a small village on the island of the same name, south of Mount Desert. At the other end of the island was the still smaller fishing hamlet of Pulpit Harbor. Here apparently daylight-saving time was invented, at least so Wood asserted when making an address years afterwards following a dinner given by the London Physical Society, at the time when the subject was under violent discussion in England. This is the story, as Wood tells it.

One afternoon some of us decided to walk across the island to Pulpit Harbor. When we arrived no one was in sight except an old fisherman mending a lobster pot in the sun. We asked him what time it was, and he pulled out an old tarnished turnip of a watch and said, “Half past five”. “Why”, we said, “it can’t be as late as that. We left North Haven at a little after three and it’s only four miles”. “Oh, well”, piped the old salt, “you know we have fast time here in the Harbor”. “What do you mean by that?” we asked. “Why, we keep our clocks an hour ahead of those over in the City [meaning North Haven]”. “What’s the idea of that?” we inquired. “Oh, I dunno”, he replied. “I reckon it’s ’cause night seems to come sooner. An’ then, too, you see, in the wintertime, the women folk don’t mind gitting up at half past four, but they’d hate like hell to have to git up at half past three”.

Returning to Baltimore in the autumn, Wood went on with his work on sodium vapor. With the aid of a $500 grant from the Carnegie Institute, he had engaged one of his former graduate students at Madison, A. H. Pfund, to help him during the year, and with $1,000 from his mother to buy necessary apparatus, he started a quite new line of attack on the measurement of the dispersion of sodium vapor with a Michelson interferometer — a bold and delicate undertaking. This was his most important investigation up to that time, and when the results were published in the United States, Great Britain, and Germany, scientists from all over the world congratulated him. Lord Kelvin, dean of British physicists, wrote him a warm letter praising his “astonishing and splendid” experimental results. Years later, when Dr. Karl Darrow presented Wood with the Ives Medal of the Optical Society of America, he cited this experiment as an example in saying that “the term, ‘a Wood experiment,’ has come to be employed of any which is distinguished by unusual ingenuity and efficacy, and especially if it is made by simple means”.

Early in the summer of 1904 the Wood family sailed for France from Baltimore on the Hamburg-American Line, going directly to Paris for a visit with Gertrude’s married sister, Alice Robbins. The Robbins apartment was on the Boulevard Montparnasse over the Cafe du Dome, where Wood had his first taste of sidewalk cafe life on the Left Bank. Lionel Walden, the marine painter, Alexander Harrison, Jim Wilder of Honolulu, and Jimmy Sullivan, all artists, inducted the Woods in the gentle pastime of piling up white saucers on the tables along the front of the Dome.

This entire outfit, Wood found, was going to Beg-Meil, a seaside resort near Concarneau, the Breton fishing village, for the summer, and the Woods decided to join them. Wood bought a two-cylinder Darracq touring car, upholstered in scarlet leather, which he said “buttoned up the back”. You entered the tonneau or rear compartment by a little door; when closed it formed the back of the middle seat, which was hinged to the door. The French had to have a strapontin in their autos, of course. Wood called it the “Darracket” on account of its engine noise.

Concarneau was an artist’s paradise, with its brilliantly painted tunny boats with their great colored sails and the smaller sardine boats with their gossamer veils of blue nets floating in the air from masts and spars to dry. Wood, who had for years entertained himself with water colors and drawings, plunged into oils, and spent a gay summer painting, swimming, and talking art with his Left Bank friends.

In September Wood attended the Cambridge meeting of the British Association for the Advancement of Science. Lord Rayleigh had asked him to make them a visit at “Terling”, his country home near Witham, where he had his private laboratory, and promised to have some continental physicists as guests at the same time. It was Wood’s first visit at an English country house and he had never heard of being “unpacked”. For his demonstrations of various phenomena with sodium vapor and his diffraction process of color photography he had a large suitcase full of glass tubes and bulbs, longish pieces of dirty rubber tubing, lenses and prisms of various sizes, and a long gas burner made of an iron pipe pierced with many pinholes. These oddments were wrapped up in underwear and old rags, some of it none too clean, and it was not to be opened until his arrival in Cambridge. The valet took charge of Wood’s luggage of course, and Wood joined the company at tea. Professor H. Kayser of Bonn, Germany’s leading spectroscopist, with whom Wood had corresponded frequently, was a guest, also Professor Otto Lummer, another celebrated physicist from Breslau University.

When Wood went up to his room to dress for dinner, he found to his horror that all of his numerous pieces of rubber, glass, iron, and brass hardware had been unpacked and arranged in neat rows on the dressing table, alongside the combs, brushes, etc. It was an appalling sight! He found the old rags and undergarments that he had used to wrap up his instruments carefully put away in the lower drawer of a dresser.

Wood says:

When dinner was announced, Lady Rayleigh came up and, signifying that I was to be her escort, took my offered arm.

Professor Lummer glared his disapproval at what he evidently considered a violation of precedence and great presumption on my part. He was a privat docent somewhere, I believe, when I was only a student. Further and very strong disapproval of Lady Rayleigh’s table arrangements was shown presently. A card with my name on it marked the place next to Lady Rayleigh’s chair. Lummer looked at it and elbowing me along took his place behind my chair and announced in a fairly loud voice, “I think I will me here sit”. Lady Rayleigh gasped in horror and gave me an agonized but half-amused look. “In that case”, I said, moving along to Lummer’s reservation, “with Lady Rayleigh’s permission, I will me here sit”. I have never forgotten the expression on the face of the venerable butler, who was standing behind Lady Rayleigh’s chair during this drama.

Waking up early next morning, I thought I would slip out and make a water-color sketch before breakfast. The heavy curtains were drawn over the windows, but there was plenty of light to dress by, and there seemed to be some concealed gadget which had to be uncovered before the daylight could be admitted, so I started to dress in the gloom. Suddenly there was a loud rap at the door. I was in undershirt, drawers, and socks, but I leaped back into bed, pulled up the bedclothes to my chin, and waited to see what came next; a second rap, and then the door opened softly, and the valet tiptoed into the room. I turned over and gave a poor imitation of a sleepy yawn, for I am always wide awake and alert in a fraction of a second, even if aroused from a deep sleep. The valet glided noiselessly to the window, and drew the curtains. I yawned again and stretched out my arms. “Good morning, sir, and a fine day, sir”, said the valet, after the manner of all English valets. “And how will you have your bath, sir?”. “Cold”, I said. ” ’Kyou, sir”, said the valet and vanished silently. Presently a large circular tub was brought in, planted on the floor in the center of the huge bedroom, and its basement space filled from pitchers innumerable. “Anything more, sir?” said the valet. “No”, said I emphatically, fearing that he might try to take me out of bed and bathe me, and thus discover the fact that I apparently slept in my underclothes. “Very good, sir. Thank you, sir”. So I got out of bed, undressed, and got busy with the problem of how to take a bath in a circular tin platter six feet in diameter.

After breakfast, Lord Rayleigh took us out to his laboratories, which were in a wing of the house. Here I felt more at home, for it was much like my own laboratory only more so: homemade mercury air pumps, the glass tubes mounted on weather-beaten boards which had outlived their usefulness elsewhere. There was a profuse use of laths, string, and sealing wax, which delighted my soul, for I realized that it was with this primitive apparatus that England’s foremost physicist had made his most important discoveries. Finally he turned to me and said with his warm and genial smile, “Professor Wood, I wonder if you could repeat for us here any of your very interesting demonstrations with sodium vapor”. I said, “Possibly, if I can use your glass-blowing lamp and you have some metallic sodium”. While I was busy blowing glass bulbs, Lord Rayleigh was hunting for his sodium. There were endless glass cases, the shelves covered with cobwebbed bottles of chemicals of very old vintage. Finally I joined him in his search. “I have a jarful somewhere, but it seems to have disappeared. I’m afraid we’ll have to give it up”. As we walked along I spied, over in the corner of a top shelf, a glass preserve jar half full of yellowish liquid with some dark lumps in it. I opened the door and said to Lord Rayleigh, “I have a feeling that if this was my laboratory I should be inclined to keep my bottle of sodium about here”, and reaching back with my arm, I drew out the dust-covered jar. “Ha, ha”, said Rayleigh, his eyes twinkling, “I believe you have it! There seems to be nothing about sodium that you can’t discover, even its hiding place”. So we went at it. I loaded the bulbs with the metal, pumped out the air, and sealed them with flame; formed the colored deposits; and showed the remarkable color changes produced by local cooling. I then got my long gas burner, and in half an hour set up the demonstration with the long sodium vapor tube showing anomalous dispersion.

As we were walking back to lunch Lord Rayleigh turned to Professor Kayser and said, “Well, we have had a most interesting morning”. “Yes, indeed”, said nice old Kayser, “very, very interesting”. Lummer, who was walking beside us, thrust his hand inside the breast of his long frock coat, threw back his head, and sniffed. “Was mich anbetrifft, ich habe nichts Neues gesehen” (As for me, I have seen nothing new).

At the end of our visit we were all taken over to Cambridge and quartered in the college dormitories. Arthur Balfour, Lady Rayleigh’s brother, was the president of the Association that year and gave the opening address. The meeting then broke up into sections, and the members read their papers or showed their new tricks. I had set up half a dozen or so demonstrations with sodium vapor which were kept in continuous operation with the help of two student volunteers; also a row of transparent photographs in color, made by my diffraction process. There was a crowd milling around the tables most of the time. Lummer was further down the hall in a small dark room, showing the fine structure of the green mercury line with one of the interferometer plates that he and Professor Gehrke had recently developed. I was very much interested in it and stopped in later in the morning. There was only one other visitor, so I was given full opportunity to show my interest by asking all sorts of questions, which, however, were answered in a slightly haughty manner. Later on, a Cambridge don came up to me and said, “Oh, I say, what sort of a chap is this fellow Lummer? He’s grousing to everybody about everyone’s crowding into your show and not coming to his, which he says is far more important!”

The afternoon session of the physics group was crowded.

Lord Rayleigh was the chairman, and there were some eight or ten prominent physicists seated on the platform. There was one vacant chair next to Lord Rayleigh, who caught my eye, smiled, and pointed to the empty chair. As I was half way back and the room had quieted down for the opening, I shook my head, but he pointed to the chair again and beckoned me to come. Slightly embarrassed, I walked up the aisle, climbed up on the platform, and sat down. Then, to my amazement, I saw Lummer, who was also seated far back, leap to his feet and advance toward the platform, on which he seated himself with his feet on the floor, determined to occupy, at all costs, his “place in the sun”. When the time for my paper came, Lord Rayleigh, in announcing the title, added with an amused smile that I had even succeeded in discovering the missing bottle of sodium in his laboratory after he had searched for half an hour with no results.

On his return from France in the autumn of 1904, Wood moved all of his spectroscopic apparatus from his room on the ground floor to a small room in the tower of the laboratory that supported the dome of the Johns Hopkins astronomical telescope. Here he was able to have sunlight all day, as he was above the shadow of McCoy Hall, which was just across the street. The light of the electric arc which he had used for the study of the fluorescence during the previous year was not intense enough for the complete solution of his problem, but with sunlight he had high hopes of bringing out some new and interesting phenomena.

The American Academy of Arts and Sciences in Boston had given him a liberal grant from the Rumford Fund, which enabled him to construct a large and powerful spectrograph, with three huge prisms of dense flint glass five inches square and large achromatic lenses. These were mounted on a rigid metal frame of steel rods and aluminum, together with the slit and plate holder, and the whole was placed in a cheap, unpainted pine box, the shape of a grand piano. This design was characteristic of all his subsequent apparatus. He didn’t care how the apparatus looked on the outside, provided that the concealed optical parts were of the highest perfection. A later instrument he called his tombstone spectroscope, as its base was a slab from a cemetery. His object now was to amplify the results that he had obtained the previous year with Moore, namely, that, as the color of the light employed in exciting the fluorescence of the sodium vapor was slowly altered from the blue to yellowish green, the region of maximum intensity of the fluorescent band spectrum was shifted in the opposite direction, i.e., from yellow to green. The simple steel tube used in the previous work had to be recharged with sodium after an operation of an hour or so, owing to the comparatively small amount of metal that could be used and its rapid distillation to the colder parts of the tube, where it hung in festoons of black spongy material from the wall of the tube. Cleaning the tube was a hazardous operation, as the metal had formed an explosive compound either with the hydrogen or nitrogen or both. The glass windows were removed and the tube was stood on end against the wall of the laboratory in the back yard. A pailful of water was then poured from a second-story window down into the open end of the tube. This operation caused a rapid series of terrific explosions, with great belches of yellow flame, which sometimes brought policemen into the vicinity in search of the lawbreaker who was discharging firearms within the city limits.

Says Wood:

To avoid these frequent annoyances to the police, I arranged a hollow three-inch drum of steel, which fitted snugly into the long steel tube, and had two small apertures, one for the entrance and the other for the exit of the concentrated beam of colored light. This drum was three-quarters filled with fragments of sodium before its introduction into the large tube, and the tube could now be operated for a hundred hours before it was necessary to clean it out and refill it.

Sunlight, reflected from a heliostat on the window sill, was focused on the slit of the monochromator, and the colored radiation emerging from the second slit was focused on the front aperture of the drum, forming a colored spot of fluorescence where the rays entered the sodium vapor that was streaming out through the aperture. An image of this spot was formed on the slit of my new spectrograph, by means of a mirror and condensing lens. The spectrum could be observed visually or photographed, and the changes in the distribution of the intensity as the prisms of the monochromator were turned, altering the color of the light thrown into the tube, were very remarkable. With blue-light excitation of the fluorescence, the spectrum consisted of two or three narrow yellow bands, but as the color was changed to blue-green and then to green, new bands appeared in the fluorescence spectrum which widened rapidly on the green side until it met the narrow band of the exciting light and finally extended beyond it on the short wave-length side, a certain and very striking exception to Stokes’s law of fluorescence. The very crude theories of fluorescence which had been developed up to this time broke down completely in this case, indicating clearly that the physical processes concerned in the case of fluorescence were enormously more complicated than had been assumed.

And now came the greatest discovery of all. Observing the spread of the fluorescent spectrum from yellow through green to blue, as the color of the exciting ray was slowly altered from blue to green, I thought I saw a slight trace of a fluttering movement in the broader bands in the green. Narrowing the slits of the monochromator, which made the exciting ray more nearly of a single wave length (purer color), to the point at which I could just barely see the fluorescent spectrum, I threw a black cloth over my head and the spectrograph, and saw to my amazement, in place of the more or less continuous spectrum of bands, a series of sharp narrow lines at regular intervals, like the divisions on a measuring stick. On slowly turning the screw of the monochromator which rotated the prisms and altered the color of the exciting light, the lines of the fluorescent spectrum appeared to be in rapid motion, vibrating to the right and left, the appearance being not unlike that of moonlight on rippling water.

The sight of a spectrum with lines wavering to and fro with an undulating motion was as unbelievable as would be the sight of a foot rule on which the divisions of the scale were moving about in an irregular manner. Closer observation showed that the lines were not actually moving, but were disappearing in one place and appearing in another. I now had a method of causing the appearance of various groups of widely separated lines in a complicated band spectrum of thousands of closely spaced lines, a method that would greatly simplify the study of these very imperfectly understood spectra. To cite another analogy from acoustics, it was as if one trying to form a theory of the structure of a piano by listening to the noise produced by slamming a board down over the entire keyboard had suddenly found that the keys could be struck successively or in groups[7].

Wood was jubilant as Archimedes! He had no bathtub to jump out of. But he wanted to celebrate, and did, in a manner which terrified the eyewitnesses and stampeded a mule team.

Never before (Wood says) had anyone ever seen the lines of a spectrum jiggle about in this manner. And just then a black cloud came over the sun, and there was a rumble of distant thunder. The storm came up rapidly, and in a few minutes it was so dark that lights went on in many of the rooms across the street. Then the rain came, a cloudburst, and soon a muddy torrent which stretched from curb to curb was running down the hill. A crowd had sought shelter from the rain in the wide porch of McCoy Hall across the street, and I suddenly thought of a splendid way of celebrating my discovery.

The thunder crashes were following the lightning at intervals of only a second or two. From my bottle of metallic sodium I picked out a lump the size of a small hen’s egg and, opening the window, waited for another lightning flash. A Negro was driving a cart up the grade against the wind and muddy stream half a block away, lashing a decrepit horse. Presently a terrifying flash occurred. I threw the metallic ball down, and it struck in the middle of the street, going off with a gigantic yellow flame and a bang that were coincident with the retarded detonation of the thunder. The crowd in the doorway fled precipitately into the building, and the Negro hurriedly turned his horse and cart and dashed off full speed down the hill, looking back over his shoulder at the volcano of yellow fire that was floating on the surface of the water and pursuing him.