THE CONQUEST OF THE AIR. 345 



g"ift of the people, who at last grasped the outcome of heroic and 

 noble work. Accidents will always happen whenever we deal with 

 locomotion of any sort. Personally I feel convinced that the 

 airship invented by Zeppelin will be the ship of the future. 

 Mishaps must be expected to occur while the lessons of aeronautics 

 are being- learnt. Count Zeppelin has the satisfaction that in all 

 his accidents, not a single person has been killed. When once 

 the country possesses landing halls all over, the danger of having 

 accidents will practically disappear. The landing is not the most 

 dangerous part in the conducting of the huge Zeppelin airship. 

 Nearly all the accidents have occurred after the landing. For 

 nearly forty hours at a time have Zeppelin ships been in air, 

 journeying over 600 miles, more than any other tye of dirigible 

 so far invented. 



Having given a general outline of the progress in balloon 

 aeronautics, I intend now to deal with the balloon and airship 

 somewhat in particular, i.e. with the second part of my lecture. 

 I commence with the ordinary balloon. Balloons will never be 

 out of date. A person who intends to become the conductor of a 

 dirigible must first thoroughly understand a free balloon. 



The material used for the covering is a cotton fabric covered 

 on the inside with rubber so as to prevent the leakage of the gas 

 and resist the damp. Varnished cloth and gold beaters skin are 

 also employed. 



The covering is usually made in layers. Beginning with the 

 outside : — A layer of cotton cloth impregnated with a yellow 

 chromate of lead to keep out the blue to ultra violet rays which 

 do damage to rubber ; two layers of vulcanised rubber to retain 

 the gas ; three layers of cotton to reinforce that on the outside ; 

 four thin layers of rubber to protect the cotton against the 

 chemical action of the hydrogen. 



By means of templates the cloth is cut into strips or gores, 

 which are sewn together to form a sphere. The poles of the latter 

 are provided with openings, the upper one for the valve with 

 which gas might be let out at will, the lower opening is joined to 

 the hose for filling the balloon. Strong springs prevent an acci- 

 dental opening of the valve. When the balloon is inflated the 

 lower opening ending in a short hose is temporarily closed. It 

 must, however, be opened before the baUoon rises, in order to 

 prevent a bursting when sun rays heat and expand the gas or the 

 expansion is due to thinner air in high regions. 



Besides these openings, the balloon is provided with a third 

 one, which, however, is closed with the so-called ripping gore. 

 The latter, which is not sewn but stuck on, is pulled off shortly 

 before the balloon reaches the ground in order to empty it quickly 

 and prevent the balloon from bouncing about. The ropes which 

 control the valve and the ripping gore pass through the inside of 

 the balloon on a net placed over the envelope. The basket carries 

 from two to five persons according to the size of the balloon, along 

 with instruments such as thermometers, barographs, pocket baro- 

 meters, aspiration psychrometer for temperature measurements, 

 hygrometers for measurement of dampness, the usual outing 

 instruments, such as camera, maps, provisions and ballast. 



