THE CONQUEST OF THE AIR. 

 By Prof. H. Bohle, M.I.E.E., M.V.D.E. 



{Evening Discourse delivered in the Engineering Laboratory 

 Lecture Theatre of the South African College, Cape Town, on 

 Thursday, November 3, 1910 : Illustrated by 70 Lantern Slides. 



I have divided the subject into three parts. In the first part I 

 give a general account of the progress made in aviation since the 

 year 1782. The second part deals with balloons and airships, the 

 last with aeroplanes. 



Just a few years before 1782 the waves of the French revolution 

 dashed against the throne of the Bourbons. The time of great 

 inventions had commenced. Some insight had also been obtained 

 into the laws of atmospheric pressure, although Frederick the 

 Great refused to be convinced of them, and a scientist who lectured 

 before him on the subject was taken to the theatre where, pointing 

 out the pretty dancer Barberini, the king said : — "Do you, ass, 

 still believe that 200 ctrw. presses on a human being?" 



At Annonay in France, there lived at this time two intelligent 

 papermakers : — Jacques Etienne and Joseph Michael Montgolfier. 

 "Air heated," said Etienne one day to his brother, "is lighter than 

 cold air. If then we take a cylinder, closed at the top and heat 

 the air in it, the cylinder must rise." "Certainly not," said 

 Joseph, "unless you make the cylinder exceedingly light." 

 Etienne tried his luck with paper, but it was found to be too fragile. 

 But finally the brothers managed to build a large sphere of linen, 

 lined with paper, about 10 metres in diameter with a contents of 

 over 500 cubic metres. Even by driving out only about one quarter 

 of the air, an upward pressure of about 125 kgs. could be obtained, 

 and as long as the balloon weighed less, it would have to rise. 

 The lower end of the balloon was open, the opening being formed 

 by a wicker ring one metre in diameter. 



It is the 5th of June, 1783. The balloon hangs about one yard 

 above ground between two masts. The willow ring carries, by 

 means of six iron wires, a metre below, a pan with a charcoal 

 fire. Slowly the balloon expands. Before long the pan is raised 

 from the ground. The ropes holding the balloon are placed under 

 tension. A pull, and majestically, for the first time, there rises 

 into space a product of human intelligence. 



The success at Annonay made the scientists at Paris jealous, 

 and something had to be done by one of them. The one who 

 succeeded was Charles. Said he, "If a sphere filled with hot air 

 will rise, how much more if hydrogen gas is used"? No sooner 

 said than done. On August 27th, 1783, he set free a number of 

 balloons 4 metres in diameter, but this time filled with hydrogen. 

 One half of the Paris population was present. Thus followed on 

 the Montgolfiere, the Charli^re. 



But the brothers Montgolfier were not idle. On Seotember 19th 

 of the same year they sent up a balloon in the presence of the 



