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 Fourteen. Sheep in Wolves’ Clothing

Sheep in wolves’ clothing” is the name Wood applied to himself and other professors and scientists who were given commissions and uniforms in the World War. Long before we entered it, he’d been helping the War Department with technical advice, and he kept trying in vain to get his friend General Squier, Chief Signal Officer of our Army, to give him a commission and send him overseas. Then came a cable from Paris to the State Department, rubber-stamped by Prime Minister Ribot, requesting that Wood be commissioned and sent to Paris to work in collaboration with the French scientific group that formed the Bureau of Inventions.

“I was in East Hampton at the time”, said Wood, and though I (the biographer) have taken two or three shots at trying to tell what happened next, I think it’s best and safest to let him go on telling it in his own way.

I had to go down to Washington (says Wood) to take my medical examination and go through all the formalities. I irritated the Medical Corps sergeant who was testing me on eyesight. When he was giving me the test for color blindness and took out a box of different colored pieces of yarn, he produced a red piece and asked me, “What’s this?” I answered, “Worsted”. But in spite of this, I managed to finish the physical examination and returned to East Hampton to await orders. After I had been there awhile, I received a communication from the War Department ordering me to report to Washington again for a mental examination.

I thought this a bit strange, especially as the head of the Signal Corps, for which I was being examined, was General Squier, an old Johns Hopkins man, who should, I thought, be able to vouch for my mental qualifications. So I wrote a letter to Squier. This was answered by some captain who told me in rather brusque terms to do as I was ordered. Squier said afterwards, “You should have written to me at my apartment. I never even saw your letter”.

This meant another trip to Washington, where the temperature was something like 101° in the shade. At the end of this rather long and expensive trip, I presented myself in front of a fat man, who gave me a mental examination, which, as I remember, consisted of the following dialogue:

Q. “What is your name?”

A. “Robert W. Wood”.

Q. “What is your occupation?”

A. “Professor of Physics at Johns Hopkins University”. “That’s all”, he said, completing the record.

This whole business naturally irritated me a good deal.

The irritation, as Dr. Wood realized and faithfully mentions, was mutual. I am informed from other sources that after the door had closed on him, an unhappy sergeant said, “I don’t care whether he’s the greatest scientist on earth, he’s going to make a hell of a major! I’d hate like hell to be his colonel”. I don’t know how much his colonel suffered, but quite a while later in the palatial diner on the Blue Train going up from Toulon and Marseille — according to Dr. Hugh Young, who was present — Major Wood was invited to meet General Pershing for the first time and have coffee with him. The commander in chief inquired what outfit Wood was with, and Wood is said to have replied, “Well, I suppose I’m what you would call a sort of free lance”. “And just what are you doing?” Pershing asked. And Wood is reported to have replied, “Well, sir, it’s supposed to be a secret, but I don’t think there’d be any harm in letting you in on it”.

Wood had obtained his major’s commission promptly as red tape went and was soon rigged out in a fine new Rogers Peet uniform. Robert Wood, Jr., a student at Harvard in 1915, had gone to France as a volunteer in the American Ambulance Field Service, had had himself transferred, became an artillery officer with the French, won the Croix de guerre, was gassed, and recovered. There are doubtless many cases of father and son who both served as officers overseas, but these two happened to be the first I’d ever met, and I enjoy it when they exchange reminiscences of those old days. They don’t do it often — and when they do, they usually get into violent arguments.

Sailing orders came for Wood, Senior, in August, directing him to join a group of Signal Corps officers who were to sail September 9, 1917, on the Adriatic. Like most of Wood’s experiences with military routine, this embarkation seemed to him puzzling and illogical. He was ordered on board two days before the boat was scheduled to sail — all with the greatest secrecy. The ship was docked on West Street in New York in full view of a group of saloons kept by German-Americans. If there were spies around, Wood reasoned, they would be in touch with the proprietors of these saloons, all of whom must have been able to see that the Adriatic was still in dock and that company after company of officers and men had gone on board. Wood says they could swarm all over the decks until the Adriatic started down the river, but once it got under way, they had to go below for fear some spy might be on the Jersey shore with a telescope. Finally, with all hands below and no smoking allowed, the Adriatic steamed down the North River and on its way to Halifax, where they were to join the other seven ships of the convoy.

I quote from Wood’s notes.

Several days out from Halifax harbor, we had our first boat drill. Each lifeboat and raft was put in command of an American officer; why I don’t know. “Our little group” consisted of Professor Augustus Trowbridge of Princeton, one of my closest friends since Berlin student days, Professor Theodore Lyman of Harvard, and three men from the Western Electric Company, Buckley and Shreeve in uniform and Colpitts in civilian disguise! Trowbridge and I were put in command of a life raft and its adjacent boat respectively, and I was ordered to bring the army squad assigned to my boat from the lower deck to the boat deck at 3:00 p.m. When the time came I discovered, to my relief, a sergeant in my group, and I ordered him to bring the squad to Boat 12 on the upper deck, for I felt sure that if I attempted to accomplish the maneuver I should end by marching the squad over the rail and into the ocean. After the drill was over, I dismissed my squad, and Trowbridge and I went below and had a couple of drinks. Later on I went up to the boat deck for a breath of air before dinner, and discovered Trowbridge’s squad still standing at ease by the boat. “What are you men doing here?” I asked. The sergeant grinned and said, “We’ve not been dismissed, sir”.

We sailed on night after night, the weather growing colder and colder, and the North Star climbing toward the zenith. One afternoon it occurred to Colpitts that it was the night of the autumnal equinox, on which both latitude and longitude can be calculated from the elevation of the North Star and the time of sunset. I made a quadrant out of two sticks of wood and a protractor. By sighting one stick on the horizon and the other on the star, I determined its elevation, given which Colpitts, who had timed the sunset, worked out our position in a few minutes. This news spread rapidly in the smoking-room, eventually reaching the bridge, throwing the ship’s officers into a frenzy, as all information regarding the course we were sailing was a dead secret. Next morning we discovered the ship’s officers had set all of the clocks available to passengers three-quarters of an hour ahead, to confuse and baffle the scientists aboard.

One afternoon we were asked to have tea with the Captain, who told us the destroyer escort would pick up our convoy about half past seven. By seven everyone was on deck scanning the horizon. Presently someone said, “There they are”, and sure enough there they were, four tiny black matchsticks outlined against the sky. Presently another four, a little to one side. So great was the speed of approach that you could visualize the curvature of the earth. It was almost like watching a motorcar coming over a hill top. Presently they were all around us, and one slim gray craft with a wicked-looking, scarlet red, four-inch gun in her bow slipped by within a few yards of the Adriatic, and five hundred Americans cheered themselves hoarse.

After a dramatic trip from Liverpool to Southampton in five trains, each with a double locomotive, they finally arrived at Havre at five on a September morning, and were ordered to proceed to British Rest Camp No. 2, which they were told was on top of a hill about two miles from the city. There they were to await orders for transportation to Paris.

They waited on the dock for some time and then began to question themselves whether “the long, low, gray cars” which were provided as transportation for officers in the stories of war correspondents would materialize! Finally, they realized that they were expected to go on foot. So they marched up the dock, feeling very important — four majors and a captain, all in brand new Rogers Peet uniforms — with their coats unbuttoned and their hands in their pockets.

As they reached the head of the dock, a British sergeant who was washing his face in a basin in front of a British barracks looked at them with a grin, and, making a trumpet of his hands, bawled out in a voice that could be heard at the extreme end of the barracks, “Jesus Christ! Look who’s here!” The Americans, saving what little face they had left, passed on looking straight ahead, pretending they had not heard him.

A little further on they passed a detachment of British soldiers who were escorting a squad of German prisoners from the docks to the barbed-wire barricades. Several German officers were among them, and as they passed the group, they heard one officer say in German to his companions, “I wish I could take one of them home with me for a souvenir”. Wood had neglected to obtain authorization to report directly to the French Bureau of Inventions which had asked through the State Department to have him commissioned and sent over. Had he not neglected this, it would have freed him from a lot of red tape. As it was, he was forced to report to the Chief Signal Officer of the A.E.F., General Russell, then in Chaumont. But he managed, partly by playing hooky, to get in touch and keep in touch with most of his internationally uniformed professorial colleagues — with the other “sheep in wolves’ clothing”.

Here now comes a lot of unadulterated Wood, concerning what war research was — and probably still is today — among scientists and physicists. It presents a sad and at the same time stimulating picture.

Says Wood:

Along with the really valuable research that was going on there was a lot of futile or crazy war research, very technical, most of which never amounted to anything. I was continually reminded of Gulliver’s voyage to the island of Laputa, where crazy scientists were working on crazy problems.

The laboratories of the Sorbonne, École normale, Collège de France, and other institutions of learning in Paris were peopled by scientists, old and young, most of them in the horizon-blue uniforms of the French Army, puttering around on things to make war simpler, faster, or more frightful.

Captain Bougier was working on a device for determining the direction from which hostile aircraft were approaching by causing the sound vibrations falling on two widely separated horns to vibrate two light mirrors mounted at right angles to each other; a beam of light reflected from one mirror to the other and then to a screen traced a more or less complicated curve known to physicists for the past half century as a Lissajous figure, from the shape of which the direction of the source of the sound could be determined. I made a slight improvement in this apparatus by placing the mirrors closer together and viewing a minute source of light directly in the second mirror. The French now needed an instrument imitating the sound of an airplane for testing these and other direction finders. I said, “Why not use an old airplane?” (This same problem came up years later in the broadcasting studios. The sound-effect experts had spent fruitless days in searching for something that would imitate the sound of an opening or closing door, and finally agreed that the only thing that would imitate the sound perfectly was a door; in every studio you now see a little door about three feet square, with handle and latch complete, on a frame which rolls on rubber- tired wheels. Opening and shutting this does the trick.) Some objection was raised against this obvious solution, and I constructed in a half hour or so a horn made by separating the trumpet and sound box of a “Strombos” auto horn, operated by compressed carbon dioxide, and inserting a brass tube about three feet long between the parts. This, when operated by the compressed gas, produced a low note of about 120 vibrations a second, and imitated the low hum of an airplane quite perfectly. They liked this very much, as it could be carried anywhere under the arm. When operated in the laboratory the effect was very peculiar. Stationary waves were produced. At some places its roar was very loud, and at other places only a few feet away there was almost complete silence. We used to poke it out of the window at noon and turn it loose, and the crowds going to lunch down the “Boul. Mich”. would stop and gaze skyward in alarm. (This was the progenitor of the subaudible horn I made later for John Balderston for stage effect.)

Professor Jean Perrin, Nobel laureate, now disguised as a Commandant in horizon-blue uniform with red and gold tabs, but, with his white hair and beard and perpetual good humor, looking more like Santa Claus than an officer, dashed back and forth between his laboratory and the proving ground at St.-Cyr in a military car driven at a furious pace and squeaking “toot-toot” every five seconds like a Paris taxi. He was testing his gigantic “loud-speaker” or honeycomb horn, as we called it. Hundreds and hundreds of little hexagonal horns were gathered together on a plane like the cells of honeycomb, with tubes of equal length leading to a single mouthpiece, the idea being that the sound would emerge from each trumpet at the same instant, and consequently would go off into space as a parallel beam like the rays of a searchlight. It was a terrific contraption, with its tangled network of twisted brass tubes, and did not work much better, it seemed to me, than the big ten-foot megaphone with which we used to sass the policemen two or three blocks away when I was a student at Johns Hopkins. After the armistice I tried to induce the French to present one of these to the War Museum of the Smithsonian Institution, but they wanted three thousand dollars for it!

The great flat collection of small hexagonal trumpet mouths must have been eight or ten feet in diameter. It was pointed down the field, and a narrow-gauge railway led away from it, on which operated a hand car, with two officers, armed with pens and notebooks, who recorded the distance at which they could hear speech correctly. The device was designed to enable a commander to give orders during the din of battle. How this gigantic acoustic engine on its great truck would have fared in battle seems open to question. “Gutenberg soixante-quatorze deux zéros” bellowed Perrin through the cells of the honeycomb. The observers, three hundred yards away, entered this Paris telephone number in their ledger, and drew away, pumping their hand car vigorously. “Louvre quatre-vingts soixante et un” thundered Jove again. This went on for some time, when the hand car dashed back to report observations, and I, who had been standing directly in front of the horn, told Perrin I had been learning French by a surgical operation.

Then there was Chilofski, who was experimenting with a seventy-five millimeter shell fitted with a slender rod in front, at the tip of which a flame of burning phosphorus streamed back over the shell during its flight. This was supposed to decrease the air resistance and increase the range. Since he could not fire the shells in his little laboratory from a “seventy-five”, he mounted them on the arm of a “dynagraph” and secured records of the pressure exerted by a blast of air having a velocity of 1,200 feet per second, with and without the flame. These tests showed a marked decrease in the pressure, but ballistic experts have since told me that an equal decrease could be obtained by giving the shell a long, tapering point.

The work of Professor Paul Langevin was much more promising, however. He was developing a method of locating submarines by sweeping the sea, under water, with a narrow beam of high-frequency sound waves, and picking up the “echo” reflected from the submarine by suitable electrical apparatus. As I had asked permission to devote particular attention to this work, I spent more time with Langevin than with the others. We went together to the Naval Arsenal at Toulon where the apparatus was in operation. The source of the supersonic vibrations was a system of square quartz plates properly oriented and cemented side by side to a steel disk. The quartz plates have the remarkable property of expanding and contracting when the opposite sides are put in electrical contact with the terminals of a high potential electrical generator, at the same frequency as that of the electrical oscillator. In this way sound waves of such high frequency can be caused to radiate from the steel disk that, instead of spreading out in all directions, as do audible sound waves, they are projected in a narrow beam. We saw fish die and turn belly up when they swam across the beam, and if a hand was held in the water in front of the plate, there was a painful burning sensation in the bones.

Throughout all this time, Wood’s chief, General Russell, who had the military martinet’s horror of anything that savored of free-lancing, had been trying to hold Wood in one groove. He had sensed, however, the great importance of Langevin’s work, and had willingly let Wood give all the time he wanted to that. The Creusot gun works had asked the Bureau of Inventions for suggestions on a method to measure the pressure in high caliber guns, from point to point, as the shell traveled along the barrel. Wood suggested the insertion of piezoelectric cylinders of quartz, each of which would give out an electrical impulse of magnitude proportional to the applied pressure. This method is standard procedure today, and is generally ascribed to Sir J. J. Thomson, who developed it independently in England a year or two later. It was fortunate for pure science that General Russell gave Wood free rein with Langevin, for it led later to the important researches in supersonic vibrations which were carried out by Wood and Alfred Loomis in the latter’s laboratory at Tuxedo Park in 1927.

There was a good deal of shuttling of scientific and technical officers back and forth across the pond, and toward the end of the year Wood began to feel that he could obtain better laboratory facilities and consequently be more useful for a while back in America. So he applied for transfer, and arrived in New York in January, 1918.

He stopped in on Professor Michael Pupin of Columbia University, the great electromechanical wizard, who was working for the Navy on submarine detection. Pupin was interested in hearing of Wood’s work with Langevin and spent some time, with his staff, getting the details of the piezoelectric quartz vibrations.

He wanted Wood to work with them at their laboratories at Columbia and asked General Squier, Chief Signal Officer of the Army, if he might stay. But Squier refused. He wanted Wood to work in his own laboratory on his own ideas, realizing that he worked best as his own boss. As there was no use stifling the originality of a versatile man under mountains of Army red tape, Squier assigned him to detached service in Baltimore.

Here he developed the first device offered by the Science and Research Division which was actually put into production for use overseas. The Signal Corps of the army needed, among other things, a blinker-type signal which would not spread its beam so widely as to enable the enemy to read its messages. Their standard signaling lamp was something like an automobile spot lamp. It threw its beam far enough, but spread it so widely that there could be very little privacy at the receiving end. This made it impossible for the Army to use it in the trench warfare then in progress on the Western Front in France.

So Wood devised and made the “flash telescope”, a signaling device which projected a beam of light the width of which at a distance of a mile was less than ten feet. On looking into the eyepiece the distant landscape, highly magnified, and the minute coiled filament of the lamp were both seen in good focus. The telescope was aimed by bringing the point at which the signals were to be received, say, a window of a ruined house, into coincidence with the filament and then clamping the telescope on its tripod. The first model was made up of a piece of galvanized iron stovepipe, a six-volt auto lamp bulb (later replaced by special hydrogen-filled lamps which were made to cool quickly for quick flashes), a fairly good achromatic lens from an old projection lantern, and a good eyepiece.

Wood took it to Washington and showed it to General Squier. There it was tried out in the presence of officers of the Signal Corps; two of them stood ten feet apart, at a distance of a mile, and the lamp was clearly visible to one and not to the other. This old-junk lamp was sent over with some other apparatus and was demonstrated at the battle of Seicheprey, where it sent signals back to Divisional Headquarters at a distance of five kilometers from the front-line trenches during a German bombardment. An immense French signaling lamp had failed to make satisfactory contact at this range. Winchester, the American officer who took the Wood lamp over, established communication in five minutes after his arrival on the scene. Pershing immediately ordered a hundred of the new signaling lamps to be manufactured and sent over. They were wanted of course for signaling from the rear to front-line positions.

Winchester also took over with him a very dark red signal light invented by Wood. Its signals could be received in daylight only by field glasses equipped with special dark red filters. Another lamp developed by the Baltimore Station projected a beam through an ultraviolet filter, which could be received only on a special phosphorescent screen. These last two lamps so intrigued Signal Corps officers in France that they insisted they be incorporated in the original lamp, and it was this which resulted in so complicating its construction that the job was not finished until just before the armistice.

Although of no practical use to American troops at the time, the research incident to making the ultraviolet lamp resulted in the discovery of a totally new type of glass, now the standard in thousands of scientific and industrial applications of ultraviolet light. The original batch of five hundred pounds was melted at the Carr-Lowry Glass Company in Baltimore, under Wood’s supervision. Corning at about the same time developed a similar glass independently, but later changed their batch formula as the result of suggestions from Kettering of the General Motors research laboratories, who had been in communication with Wood.

While Wood was experimenting on this new glass, he was troubled by the fact that he was spending too much of the government’s money on crucibles for melting small batch samples. In an attempt to economize, he found he could replace this costly laboratory ware with unglazed coffee cups, which could be had from a local pottery in gross lots at a few cents apiece.

He was just beginning to congratulate himself on his thriftiness when the government forced him to spend $30,000 merely to prove he was right when he insisted on the impossibility of making a hot-air sausage balloon!

Of this episode, Wood says:

It seems that a crackpot had, for some months, been pestering the air force of the Army and Navy to give a trial to his scheme of inflating an observation balloon with hot air instead of hydrogen, thus rendering it fireproof against attack by phosphorus incendiary bullets. His plan was to install a long iron pipe inside of the “sausage” along the bottom of the bag. This pipe was to supply gasoline vapor to huge Bunsen burners rising from the pipe, the flames heating the air with which the balloon had been filled. The Army and Navy said no over and over again, so the crackpot did what all discouraged crackpots do — he got some congressmen interested in his invention, and the congressmen said to the Army and Navy, as they always do, “This man’s invention must be tested. Army and Navy officers are old fogies, too conservative. Don’t appreciate genius. Our army must have it, or he’ll sell it to the enemy”, etc., etc. And the Army said, “O.K., have it your own way”, as the Army and Navy are apt to do when a congressional committee gets after them. But the air force was too busy with more important work to make the test, so they passed the buck to the Science and Research Division, saying, “Give the guy a break and test his invention”, and the officer commanding the division assigned the job to the Baltimore Experiment Station. I begged to be excused, saying that the idea was preposterous: the weight of the pipe, fuel, etc., could never be lifted by hot air, even senatorial hot air. I showed that the temperature would have to be so high that the fabric of the balloon would burn, but was told that the Bureau of Standards had already made preliminary experiments and had found that you could have a “temperature gradient”, i.e., very hot air in regions not too near the fabric. I was shown the apparatus. It was a box the size of a trunk lined with asbestos, filled with heating coils of wire and bristling with thermometers. I said, “No, No, and NO. You will have a convection current of hot air from the long gasoline burner rising in a sheet and breaking against the top of the bag, which will char the rubberized cloth before the buoyancy will be sufficient to even lift the balloon fabric alone, without the weight of the observer, iron pipe, gasoline tank, air compressor, and other paraphernalia”. It was useless, however, and Lieutenant Paul Mueller of the balloon section, a sergeant, and four privates, one of them Edison Pettitt, now a very distinguished astronomer at the Mount Wilson Observatory in California, were assigned to the Baltimore Experiment Station. They came over at once, and were very useful in connection with the construction of the various signaling devices during the months occupied in the erection of the balloon hangar. This was taking shape over the concrete floor, which had been laid on an unused part of the university campus, and a five-inch gas main brought in from Charles Street, distant some three or four hundred yards, with a special gasometer as big as a large wardrobe trunk. The burner tube was a three-inch iron pipe supported at the center and running the whole length of the standard observation balloon sent over by the air force.

Finally after months of labor the day came for the test. Mueller and I crawled inside of the big bag which had been pumped full of air and was resting on the floor. We ordered the gas turned on, and held our burning torches over the burners nearest the central vertical pipe of the long-armed T. As soon as these blazed up we ran rapidly, Mueller north and I south, lighting burner after burner as quickly as we could. When all were going we hurried back to the air trap which was the only means of escape. It was a fine sight. We were inside of a great cylindrical tent, partly luminous by transmitted daylight, which showed the geometrical patterns of the overlapping sections of the balloon fabric, and partly illuminated by the great blue gas flames, which were tipped with yellow and fluttered with a dull roar. I had my camera of course, and by the time I had set up the tripod, focused, and made the three-second exposure, it was getting pretty hot and very “close” inside the balloon. We crawled out through the air trap and drew several very long breaths. Our crew, augmented by a half dozen volunteers now, lifted the big bag from the ground to estimate its diminishing weight. It was not attached to the heavy burner, or to anything else, and just as it was showing an inclination to be self-supporting, I smelt a strong odor of burning rubber. Letting go of the supporting rope which ran along the side of the bag, I stepped back. A cloud of blue smoke was rising into the air all along the top of the balloon. “Shut off the gas. It’s all over — finished”. We had used possibly a dollar’s worth of gas, but the “test” had cost the government $30,000, we afterwards learned. The photograph, however, was a great success.

Wood still had his yen for flying, despite the fact that in the 1912 naval flight with Tower — in an old box-kite Curtiss machine made with “strips of bamboo, piano wire, and bicycle saddles to sit on” — he had gone up over three thousand feet and came down (next morning) with the mumps. He now had a legitimate pretext in a lamp he’d invented for testing the use of ultraviolet rays in blind landings. He took it to Langley Field, near Norfolk, for the test flights, and was invited to go up in the afternoon for some stunt and acrobatic flying. They told him he could choose between Major So-and- So of the Air Corps, who was a great war-stunt acrobat, and Art Smith, the barnstorming circus pilot whom he’d seen skywriting at the San Francisco Fair in 1916…

Says Wood:

I chose the major, since I was in uniform myself and felt it would be more dignified to be made a monkey of — or crash — with a fellow-officer than with a circus man! As the machine took off, a lot of grinning officers came out with field glasses prepared to watch me suffer and doubtless hoping I’d get sick, which was a usual part of the fun. At three or four thousand feet we did about everything except straight upside- down flying. Loops, multiple loops, Immelmann turns, etc., ended with a proper spinning nose dive which interested me enormously, as the plane seemed merely plunging straight down without spinning toward an earth that was rotating like a great turntable, with the rim of the horizon whirling at what seemed to be twenty-five miles per second! Our morbid spectators were disappointed, I fear, despite the beauty of the stunting, for I hadn’t the expected dizziness and nausea.

Late in the evening I made the serious flight, in a thunderstorm, with an Air Corps lieutenant, for the purpose of testing my ultraviolet landing beacon. In the course of the flight, the pilot looked back at me, made a circular gesture with his arm, and nodded. I thought he was asking if I wanted to loop, and shook my head vigorously. I’d had all the looping I wanted in the afternoon. In about two seconds I discovered that he hadn’t been asking me — he’d been telling me. Down we plunged, and then sweeping up, we practically stalled at the top of the loop. I dangled by the straps as the plane hung upside down for a second or two. When we landed, the pilot said, “Well, how did you like it?” “Fine”, I replied, “but that was a rotten loop you made”. “I thought so too”, he replied cheerfully. “It was the first time I ever tried it… at night”.

Major Wood was working with General Squier’s Signal Corps in America when the armistice came. After the armistice, in February, 1919, Wood decided he wanted to return to France and see what four years of war had done to the country. It occurred to him it would be interesting to see what scientific instruments he could collect for the War Museum of the Smithsonian, either in London and Paris or in the German trenches and dugouts of the battlefields. This served as a plausible excuse for going over, and he was given a special passport. The start of this chimerical expedition is told in a letter to his wife.

When we docked at Liverpool who should come on board with a couple of British intelligence officers, but Captain Robb, whom I had known years before at Cambridge… He said not a room was to be had in Liverpool or London, but he had a big room with two beds and would take me in for the night. Two hundred and fifty first-class passengers went ashore, where they went then I can’t imagine. Went up to London the next morning and telephoned to a dozen hotels. Tonight I dine with Boys at the Royal Society Dining Club, after the meeting of the R. S. in the afternoon. Lord Rayleigh and everyone else will be there. I’m down for a talk at the Physical Society on military signaling with invisible light. None of my scientific friends who are on the British Inventions Board ever heard my name mentioned in connection with any of the suggestions or inventions I sent over. They were surprised to find I had been in military service. A special branch has been established to develop one of my things, and I’ve been asked to go down to the Portsmouth Navy Yard tomorrow for a conference with the naval officers in charge. Yesterday I was taken to a secret bureau, the laboratories of the base-censor…

Here’s the story Wood tells me about what happened at the Base Censor Bureau.

One of its departments made tests of suspected passports and other dubious documents for erased writing, superimposed writing, invisible inks, etc. They also tested similarly shirt fronts, cuffs, handkerchiefs, linen of suspected spies — even panties and petticoats if the suspected spies were female. These articles of apparel might have been written on with invisible ink — or they might have been treated with chemicals which could be used in making invisible ink when soaked in water — to be used elsewhere for invisible writing and later developed by another chemical. The British experts showed me all the various chemical methods in use for developing secret writing. They showed other interesting activities, and I was waiting with some anticipation to see what was going on inside a small cabinet with no window which stood in the middle of the laboratory with wires running through the wall and along the ceiling. I suspected its use, and finally, when no mention of the cabinet was made at all, I asked, “What goes on in there?”

“Oh, I’m sorry”, said the captain who was showing me about, “but that’s very secret. We don’t show that to anybody”.

“Ultraviolet light, I presume”, said I in a detached manner.

“What!” said the amazed captain. “What makes you think so?”

“Because I invented the method and the black glass that cuts off the visible light, and sent the formula to your Admiralty from our Science and Research Division over a year ago”.

“Will you wait a moment”, said the captain, “while I speak to the colonel?”

I was presently ushered, with suitable apologies, into the dark room.

They had a quartz mercury arc in a box, with a window of dark-blue cobalt glass, under which they placed a German passport. When you looked at it through a yellow glass plate which cuts off the blue light reflected from the paper, you could see here and there German words, not supposed to be on any passport, which gave off a small amount of yellow light when stimulated by the violet rays. I remarked that this was the method of detecting fluorescence employed by Sir George Stokes more than half a century before. I asked why they did not use ultraviolet light to start with, which produces a strong fluorescence and is invisible.

“I’ll show you what I mean”, I said. “Come back into the dark room”. I happened to have a small plate of my black ultraviolet glass in my pocket, and we fitted it before a hole in a sheet of cardboard and stood it in front of the lamp window. The passport was now seen to be covered with previously invisible writing, practically all of the German words shining with a pale blue light.

“But where can we procure those plates?” they asked.

“I don’t understand why you haven’t got them”, I replied. “Your government has them. I sent the formula over a year ago to the Admiralty. A lot of them have been made and are in actual use at your Portsmouth Navy Yard…

“Oh, but you know”, said they, “the liaison between our Navy and Intelligence Department is not as good as it might be. We’ll call up Portsmouth and see if they can supply us…”. Portsmouth obliged at once.

By this time, it seems, they were not only keenly absorbed but also a little on the defensive for the moment. So they proudly explained that they had devised a note paper on which it was impossible to inscribe secret writing. This paper had been on sale at all post offices, and letters written on it were not subject to the long delay necessary for applications of their various tests for secret writing. This paper had proved very popular, as the letters passed the censor immediately. It was ordinary note paper on which fine parallel lines had been printed close together, in pale red, green, and blue ink — the red being soluble in water, the green in alcohol, and the blue in benzine. (The paper looked gray to the naked eye.) Since practically all liquids employed for making invisible writing fall into one of these three classes, one set of colored lines must dissolve in the colorless fluid flowing from the pen and produce colored writing. I recalled I had discovered years before that the pigment Chinese white comes out black as charcoal in photographs made with ultraviolet light, so I said, “Suppose I write on it with a fine crayon of Chinese white; then none of these lines will dissolve, yet it can be read by photography”.

“Oh, no”, they told me, “you can’t even write on it with a toothpick or glass rod without making legible writing. The colored inks are made slightly soft or ‘tacky,’ so that they smear together and produce dark gray letters. Here, try to write on it with this glass rod”.

I tried to write invisibly with the glass rod, and failed, but was obstinate in my belief I could write on it invisibly with something. I had an inspiration and said,

“I still think I can beat it if you’ll let me try again”. “Impossible!” they said. “We’ve tried everything”.

I said, “Well, let me try once more. Bring me a clean rubber stamp and some vaseline”.

The large, smooth, clean rubber stamp was brought. I smeared it with vaseline, then wiped it carefully with a cloth until it made no visible grease mark on paper. Then I pressed it down firmly on the spy-proof paper, taking care not to let it slip sideways.

“Can you discover any writing here?” I asked.

They studied it by reflected light and by polarized light and said, “Nothing here”.

“Now let’s look at it with the ultraviolet”, I said. We took it into the cabinet and held it in front of my black window. In brilliant blue letters, as if the nice clean rubber stamp had just been pressed on its own ink pad, stood the words:

NO SECRET

WRITING HERE

Professor Wood, now in mufti and with a discharge paper indorsed “Honest and Faithful”, began traveling again over the battlefields in the war zone to see whether any signaling apparatus used by the Germans could be picked up. He started off in an Army Cadillac with Lieutenant Winchester and Dike of the American Embassy.

They went through trenches and down into dugouts, but the only pieces of German optical apparatus they discovered were primitive signal lamps for giving a narrow beam, made out of old brass shell cases, with a candle at the bottom and a narrow slit in the side.

Of Wood’s final days in Europe after the war, he writes:

Before leaving Paris I was asked to give a lecture with demonstrations at the Sorbonne. The war was over, and “Now it could be told”. The show came off on May 18 in the large lecture hall, before an audience of two hundred or more, composed of physicists and army officers, some with their ladies. With the room darkened and a very powerful ultraviolet lamp, I flooded the audience with what the French had named Lumière Wood, causing teeth and eyes to phosphoresce brilliantly, and various textiles to shine with subdued colors. A lady’s dress in the center of the hall glowed with a brilliant scarlet color, attracting much attention. Everyone was looking at the glowing teeth and eyes of their neighbors, and a wave of laughter swept the hall when I explained that false teeth appeared as black as charcoal in the light. With a flash telescope, I demonstrated the narrow beam of light, and the lecture closed with “Vive la France”, rapidly executed with the spot of light on the wall in Morse code, which was read by a sufficient number of officers to cause applause.