While it is undoubtedly true that the discovery of the balloon has very greatly retarded the science of aerostation, yet, in my opinion, its field of usefulness as a vehicle for pleasure excursions, for explorations, and for scientific investigations, has not been fully developed for the want of certain improvements, the nature of which it is the object of this paper to point out. The improvement of which I am about to speak relates to the regulation of the buoyancy of the balloon. This is now done by throwing out ballast or by allowing some of the gas to escape - a method which necessitates the carrying of an unwieldy amount of sand and the expenditure of an unnecessary amount of gas.

From the fire balloon invented by the Montgolfier Brothers, in 1782, to the superior hydrogen balloon of M.M. Charles and Robert, no material advancement has been made, except the employment of coal gas, first suggested by Mr. Green. The vast surface presented to the wind makes the balloon unmanageable in every breeze, and the aeronaut can do nothing but allow it to float along with the current. This is a difficulty which has been partly overcome, as was seen at the recent Paris Electrical Exhibition; but no one will ever be able to guide it in a direction opposite to a current of air. The aeronaut must ever content himself in being able to float in the direction of the current or at certain angles to its course; but to do this even is a matter which has not been successfully accomplished. An inflated balloon would ascend too high unless several hundred pounds of ballast were used to weight it down. This ballast serves another purpose, it is desirable to maintain the balloon at a uniform distance above the earth's surface, and as the two per cent. daily waste of gas diminishes the buoyancy of the balloon, it must be kept from descending by throwing off a certain amount of sand. Again, the heat of the sun and the action of warm air currents cause at times the volume of gas to undergo a sudden expansion, and then to prevent the balloon from running too high, the gas must be allowed to escape from the valve. The gas, under these circumstances, must also be allowed to escape in order to prevent the balloon from bursting. Presently the balloon will pass through a colder current of air and sudden condensation takes place, and the balloon would sink unless more ballast were thrown off. This process continues until the aeronaut has neither ballast nor gas left.

Now, I suggest that a large balloon be made with the mouth closed, so that no gas can escape; and that it carry enough ballast to keep it, under an ordinary temperature, at a certain distance from the ground. A pipe must enter the mouth of the balloon, one end of which opens in its interior and the other end in a gas reservoir which lies in the "basket" or "car." As soon as the gas undergoes an expansion, and a certain amount of pressure is made in this reservoir, a valve opens and a whistle signals the moment when the force pumps must be set to work to pump the air out of the balloon into the large number two reservoir, the frame work of which forms the body of the car. Taking a certain amount of gas out of the balloon is equivalent to taking on more ballast, while by condensing this gas into a large reservoir, it is not allowed to escape, and when necessary can be sent back into the balloon and thus prevent the throwing off of ballast. Coal gas, under a certain pressure, becomes heavier than air (or at least equally heavy), and thus the gas pumped out of the balloon will of itself serve as ballast. This invention will enable the balloonist to keep himself at a uniform distance above the earth, will prevent the carrying of so much ballast and the expensive waste of gas, and will enable him to keep afloat at least ten times as long as by the old method. I have made a model and tested the above theory.

Eli C. Ohmart.

North Manchester, Ind.