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.