sinks and keeps the orifice open; but as soon as water surrounds it, it rises and closes the orifice. In order to utilize the exhaust steam from engines for heating purposes and without producing additional back pressure, what are known as "low-pressure" or "vacuum" systems are used. It is manifest that the air-valves described above could not be used satisfactorily here, because, the pressure within the radiator being less than the atmospheric pressure, the air would pass into the radiator instead of out as is desired. A special relief valve is used in such cases. To the outlet of the valves, 11⁄2-inch return pipes are usually connected. On the ends of these main returns, there are connected vacuum pumps. The valves themselves are similar to those already described, one form consisting of a rubber or vulcanite stem, closing against a valve opening when made to expand by the presence of steam. When water or air fills the valve, the stem contracts and allows the water or air to be sucked out FIG. 3. AUTCMATIC AIR-VALVE. Works by expansion of gas. water, it rises and closes the opening. This action, however, cannot altogether be relied upon. There are other types of valves acting on the principle just explained. In place of metal strips, however, a composite material which expands rapidly may be substituted. The valve shown in Fig. 3 acts on a somewhat different principle. The float C is made of thin brass, closed at top and bottom, and is partially filled with wood alcohol. When steam strikes the float the alcohol is vaporized, and creates a pressure sufficient to bulge out the ends slightly, which raises the spindle and closes the opening B. The common pet-cock air-valve is the most reliable for hot-water radiators, though there are several forms of automatic which are claimed to give satisfaction. An automatic air-valve for hotwater radiators is shown in Fig. 4. The air escapes at A, the orifice being closed by the float F acting on the lever L. So long as only air surrounds the float, it T By ELBERT E. DEWEY HE first wholly satisfactory demonstration of aeronautics in America was made at the St. Louis World's Fair on Monday, October 31, by the California Arrow, owned by Capt. Thomas S. Baldwin and managed by A. Roy Knabenshue. The craft on that day ascended 2,000 feet; was driven about at will, with and against the wind; and descended gracefully, landing within a short distance of the place from which it started. The success was repeated the next day; and in later trials the craft has fully demonstrated the complete dirigibility of balloons of the Arrow type, thereby adding wonderfully to the interest in aëronautics among Americans. Baldwin and Knabenshue's success is a dramatic climax to an epoch of repeated failures and disappointments on the part of the World's Fair management to se cure an aëronautic exhibition. The alleged accident that prevented Santos Dumont from sailing in his airship, was followed by other adversities; and the public began to believe that the reports of airship flying exhibitions were merely advertising ruses. Captain Baldwin, who invented and built the Arrow, is a native Californian; and A. Roy Knabenshue, the daring little aëronaut who successfully piloted it above the cheering throngs at the Exposition, is from Toledo, Ohio. His trips on the Arrow mark his first experience as an aëronaut. Knabenshue is but twentynine years old. When the people beheld the unassuming Baldwin and his airship, which was an unpretentious-looking craft of very simple mechanism, and saw the frail-looking, youthful aëronaut, they feared it was to be another case of pretension, and little dreamed of the triumph these men were destined to attain. But while the public continued in its skeptical comments, and the World's Fair management had almost lost hope over its former disappointment, and while the press filled its columns with reports of the other exhibits of the Fair, paying little attention to the aëronautic concourse, the work of preparing the Arrow for its flight progressed steadily and surely. Curious crowds would peep in and utter contemptuous remarks about the big balloon now being cradled in its wooden trestles, and they would smile derisively at the slender, youthful Ohioan. The airship they were working on was far less imposing than the ill-starred Santos Dumont machine. The big gas bag is made of closely woven silk, varnished, and has a capacity of 8,000 cubic feet. It is said to have a lifting power of 1,135 pounds. The frame in which the daring little aëronaut rides is hitched to the bag by cotton cords. This is built of spruce, and BALDWIN AIRSHIP ARROW, WHICH SUCCESSFULLY DEMONSTRATED ITS DIRIGIBILITY AT THE WORLD'S FAIR, OCTOBER 31. Showing network of cotton cords by which gas bag is held to frame. One of the two propeller blades, located at the prow, may be seen above the heads of the spectators at the right. The rudder, at the stern, is seen at the left. Knabenahue, the aeronaut, is standing in the frame. is merely a skeleton, bolted and braced with steel wires in such a way that strains all come as a pull on the fine wire. This permits an extremely light construction, the exact weight being but 520 pounds. It somewhat resembles the bridge trestle or the laced bicycle wheel. There is no basket or carriage. The seat for the aëronaut consists of a four-inch pine board near the stern. The motor, which was taken from an automobile, is situated forward of the middle; at a point where it exactly counterbalances the weight of the aëronaut when on his seat. It is of the 2-cylinder 2-cycle type, capable of developing 7 horse-power; is operated by gasoline from a small storage tank near the top of the craft; and is air-cooled. The propeller blades are in the bow, and are geared to the main shaft of the motor. They are also built of spruce in skeleton DIPPING THE PROW OF THE AIRSHIP TO DESCEND. The operator accomplishes this by throwing weight of his body forward. was made to fly the machine, but it met with only partial success and attracted but little attention. It was Knabenshue's first attempt at sailing an airship; and while the Fair management seemed discouraged, Knabenshue was now confident. He had taken his first lesson and had learned the "how" of the new art. Momentous Day Arrives October 31 arrives. This is the momentous day Baldwin and Knabenshue had announced as the one on which they would surely make the airship fly. As a result of this announcement and the partial success of the previous experiment, the spectators are more numerous and somewhat more curious than before. They gather around the Stadium, and see the big gas bag inflated until it seems |