This chapter would not be complete without an adequate reference to the gliders devised by Professor Montgomery of Santa Clara, California. These machines were sent up with ordinary hot-air balloons to various heights, reaching 4,000 feet in some instances, when they were cut loose and allowed to descend in a long glide, guided by their pilots. The time of the descent from the highest altitude was twenty minutes, during which the glider travelled about eight miles. The landing was made accurately upon a designated spot, and so gently that there was no perceptible jar. Two of the pilots turned completely over sideways, the machine righting itself after the somersault and continuing its regular course. Professor Montgomery has made the assertion that he can fasten a bag of sand weighing 150 lbs. in the driver’s seat of his glider, and send it up tied upside down under a balloon, and that after being cut loose, the machine will right itself and come safely to the ground without any steering.

Lilienthal in Germany, Pilcher in England, and Chanute in the United States are names eminent in connection with the experiments with gliders which have been productive of discoveries of the greatest importance to the progress of aviation. The illustration of the Chanute glider shows its peculiarities plainly enough to enable any one to comprehend them.

The establishment of glider clubs in several parts of the country has created a demand for ready-made machines, so that an enthusiast who does not wish to build his own machine may purchase it ready made.

Chapter XIII.
BALLOONS.

First air vehicle—Principle of Archimedes—Why balloons rise—Inflating gases—Early history—The Montgolfiers—The hot-air balloon—Charles’s hydrogen balloon—Pilatre de Rozier—The first aeronaut—The first balloon voyage—Blanchard and Jeffries—Crossing the English Channel—First English ascensions—Notable voyages—Recent long-distance journeys and high ascensions—Prize balloon races—A fascinating sport—Some impressions, adventures, and hardships—Accident record—Increasing interest in ballooning.

The balloon, though the earliest and crudest means of getting up in the air, has not become obsolete. It has been in existence practically in its present general form for upwards of 500 years. Appliances have been added from time to time, but the big gas envelope enclosing a volume of some gas lighter than an equal volume of air, and the basket, or car, suspended below it, remain as the typical form of aerial vehicle which has not changed since it was first devised in times so remote as to lie outside the boundaries of recorded history.

The common shape of the gas bag of a balloon is that of the sphere, or sometimes of an inverted pear. It is allowed to rise and float away in the air as the prevailing wind may carry it. Attempts have been made to steer it in a desired direction, but they did not accomplish much until the gas bag was made long horizontally, in proportion to its height and width. With a drag-rope trailing behind on the ground from the rear end of the gas bag, and sails on the forward end, it was possible to guide the elongated balloon to some extent in a determined direction.

In explaining why a balloon rises in the air, it is customary to quote the “principle of Archimedes,” discovered and formulated by that famous philosopher centuries before the Christian era. Briefly stated, it is this: Every body immersed in a fluid is acted upon by a force pressing upward, which is equal to the weight of the amount of the fluid displaced by the immersed body.

It remained for Sir Isaac Newton to explain the principle of Archimedes (by the discovery of the law of gravitation), and to show that the reason why the immersed body is apparently pushed upward, is that the displaced fluid is attracted downward. In the case of a submerged bag of a gas lighter than air, the amount of force acting on the surrounding air is greater than that acting on the gas, and the latter is simply crowded out of the way by the descending air, and forced up to a higher level where its lighter bulk is balanced by the gravity acting upon it.