1^ AEROSTATION. 



LESSON 74. 



Aerostation. 



Wick'er, made of small sticks. A'eronaut, one who sails through. ! 



the air. i 



Meteorolog'ical, relating to the phenomena of the atmosphere, \ 



such as the alterations of its weight and temperature, changes \ 



produced by evaporation and rain, its excessive agitations, its \ 



electricity, &c. ' 



Aerostation, in the modern application of the term, sig- i 

 nifies the art of navigating through the air, both in its prin- I 

 ciples and practice. Hence also the machines which are ; 

 employed for this purpose, are called aerostats, or aerostatic \ 

 machines ; and on account of their round figure, air-balloon^. 

 Air-balloons are of two kinds, those filled with rarefied air, j 

 and those filled with hydrogen gas. The best forms for bal- 

 loons are globular or oval. Large balloons, for hydrogen 

 gas, must be made of silk, and varnished over so as to be 

 air-tight. The car, or boat, is made of wicker-work, cover- ; 

 ed with leather, well varnished or painted, and is suspended ; 

 by ropes proceeding from the net which goes over the bal- ^ 

 loon. The hydrogen gas for filling the balloon is procured : 

 by putting a quantity of iron-filings, or turnings, with some | 

 sulphuric acid diluted with water, into casks lined with lead. 

 From the top of these casks tin tubes proceed, which unite 

 into one that is  connected with the silk tube of the balloon, j 

 Balloons of oiled silk cannot be made smaller than five or ^ 

 six feet in diameter, as the weight of the material is too \ 

 great for the air to buoy it up. i 



In 1 729, Bartholomew Gusman, a Jesuit of Lisbon, caus- \ 

 ed an aerostatic machine, in the form of a bird, to be con- 

 structed, and made it ascend, by means of a fire kindled un- 

 der it, in the presence of the king, queen, and a great con- 

 course of spectators. Unfortunately, in rising, it struck 

 against a cornice, was torn, and fell to the ground. The 

 inventor proposed renewing his experiment ; but the people 

 had denounced him to the inquisition as a sorcerer, and he 

 withdrew into Spain, where he died in an hospital. In 1766^ 

 the Honourable Henry Cavendish discovered that hydrogen, 

 gas (then called inflammable air,) was at least seven times 

 lighter than common air. It occurred soon afterwards to 



