RECENT PROGRESS IN AERIAL NAVIGATION. 297 



weight of the water they should hold, or the crushing force of the 

 atmosphere after exhaustion. Unlike the product of Bacon's imagi- 

 nation, his conception was a correct application of demonstrated physi- 

 cal laws ; but, had it been tested by experiment, he would at once 

 have found that there were other laws which he had not taken into 

 account. In his view, the only obstacle to success was that " the Al- 

 mighty would never allow an invention to succeed by means of which 

 civil government could so easily be disturbed." Air-ships floating 

 beyond the reach of missiles, if only capable of being accurately di- 

 rected, might well have been thought more terrible than dynamite is 

 to-day. 



Soon after the discovery of hydrogen gas by Cavendish and Watt 

 in 1766, experiments were made with a view to utilizing it for the pur- 

 pose of lifting bodies into the air. But, until 1783, nothing more sub- 

 stantial than a soap-bubble could be made thus to ascend. Joseph Mont- 

 golfier, who was a successful manufacturer of paper, tried bags of this 

 material ; but hydrogen was found to diffuse so rapidly through it 

 that the idea was abandoned by him. Observing that clouds of vapor 

 and smoke remained floating at various heights, he thought that, if 

 they could be confined in bags of paper, these might be made to float 

 in like manner. Since the experiments of Franklin in 1752 had proved 

 the existence of atmospheric electricity, the idea gained currency that 

 the lightness of clouds and of smoke was in some way due to electric 

 charge. A paper bag was made, and, with its opening downward, a 

 fire was kindled, " as well to increase the layer of electric fluid upon 

 the vapor in the vessel as to divide the vapors into smaller molecules 

 and dilate the gas in which they are suspended." The bag was carried 

 up to a considerable height. Montgolfier seems not to have attributed 

 the ascension to the effect of heat in diminishing the specific gravity 

 of the contained air. The first successful experiment in ballooning 

 was thus based on a misconception. 



Montgolfier's first public exhibition of his invention was made on 

 June 5, 1783. The news of his success was rapidly spread ; and at 

 Paris a balloon was soon constructed under the superintendence of M. 

 Charles, who substituted hydrogen for smoke, confining it in a bag of 

 varnished silk instead of paper and linen. The ascension was success- 

 fully accomplished on the 27th of August. Charles at once proceeded 

 to the construction of a new and much larger balloon, in which he 

 ascended with his colleague, Robert, on the 1st of December, making 

 a journey of more than twenty-five miles. This balloon was provided 

 with a safety-valve of Charles's invention, a hoop, to which the car 

 was attached, and netting intended to equalize the distribution of 

 weight upon the balloon. It was in all important particulars the same 

 as the balloon almost universally employed throughout a century after- 

 ward. Montgolfier made several exhibitions of his hot-air balloons 

 at Paris, and in one of these, on the 15th of October, M. Pilatre de 



