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fore. In case the water which may have sinks and keeps the orifice open; but as collected in the radiator comes into the soon as water surrounds it, it rises and valve, it might be forced out and cause closes the orifice. damage in the room. To provide for this in order to utilize the exhaust steam emergency, a float F is attached to the from engines for heating purposes and spindle ; and in case of a sudden rush of without producing additional back pres

sure, 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, 1/2-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.

111llllllllllllllllllllllll

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

Fig. 4. AUTOMATIC Air-Valve For Hot-WATER

HEATING SYSTEM.

through the pipe connected with the vacuum pump.

The importance of the air-valve cannot be overestimated. Upon the failure of any room to heat properly, the airvalve should first be looked to as a prob

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Flight of the “Arrow" at the World's Fair-Great Triumph of Baldwin and

Knabenshue Demonstrates the Dirigibility of Balloons

By ELBERT E, DEWEY

HE first wholly satisfactory dem- cure an aëronautic exhibition. The alonstration of aëronautics in leged accident that prevented Santos DuAmerica was made at the St. mont from sailing in his airship, was

Louis World's Fair on Monday, followed by other adversities; and the October 31, by the California Arrow, public began to believe that the reports owned by Capt. Thomas S. Baldwin and of airship flying exhibitions were merely managed by A. Roy Knabenshue. The advertising ruses. craft on that day ascended 2,000 feet; Captain Baldwin, who invented and was driven about at will, with and against built the Arrow, is a native Californian; the wind; and descended gracefully, land- and A. Roy Knabenshue, the daring little ing within a short distance of the place aëronaut who successfully piloted it above from which it started. The success was the cheering throngs at the Exposition, repeated the next day; and in later trials is from Toledo, Ohio. His trips on the the craft has fully demonstrated the com- Arrow mark his first experience as an plete dirigibility of balloons of the Arrow aëronaut. Knabenshue is but twentytype, thereby adding wonderfully to the nine years old. interest in aëronautics among Americans. When the people beheld the unassum

Baldwin and Knabenshue's success is ing Baldwin and his airship, which was a dramatic climax to an epoch of repeated an unpretentious-looking craft of very failures and disappointments on the part simple mechanism, and saw the frail-lookof the World's Fair management to se- ing, youthful aëronaut, they feared it was PREPARING FOR FLIGHT. to be another case of pretension, and lit- silk, varnished, and has a capacity tle dreamed of the triumph these men of 8,000 cubic feet. It is said to were destined to attain.

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have a lifting power of 1,135 pounds. But while the public continued in its The frame in which the daring little skeptical comments, and the World's Fair aëronaut rides is hitched to the bag by management had almost lost hope over its cotton cords. This is built of spruce, and 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

PROPELLER OF BALDWIN AIRSHIP.

Mr. Baldwin standing in front of prow. made of closely woven

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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. Knabenzhue, the aëronaut, is standing in the frame.

is merely a skeleton, bolted and braced depressing the bow and causing the prowith steel wires in such a way that strains peller to draw the craft downward. The all come as a pull on the fine wire. This handling of the ship depends largely on permits an extremely light construction, the proper shifting of weight, fore and the exact weight being but 520 pounds. aft. It somewhat resembles the bridge trestle On Tuesday, October 25, an attempt 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

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DippiXG TIE 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. A. Roy KNABENSHUE, OF TOLEDO, Ohio, SuccessFUL OPERATOR OF THE BALDWIN AIRSHIP.

Momentous Day Arrives Born in Lancaster, Ohio, July 15, 1875. Has experimented with balloons for years; and after visiting the

October 31 arrives. This is the moWorld's Fair, became a partner in the Bald

mentous day Baldwin and Knabenshue win enterprise. His brother also is

had announced as the one on which they would surely make the airship fly. As

a result of this announcement and the form, the main body being of varnished partial success of the previous expericloth. Each blade is 412 feet long and ment, the spectators are more numerous 11/2 feet wide. In descending, only a and somewhat more curious than before. small portion of gas is allowed to escape. They gather around the Stadium, and see The aëronaut throws his weight forward, the big gas bag inflated until it seems

an experienced aëronaut.

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