AEROSTATION. 



\s MH.II us tin- parachute was scp:ir:iti-l 

 from the balloon, the- latter ascended with 

 great rapiditv, and, being of an oval form, 

 tunicd itsi-lf with a longer axis into an 

 horizontal position. 



\\ i now come to the practice of the art. 

 I'ln- shape of the balloon is one of the first 

 objects of consideration. As a sphere ad- 

 mi'ts tin greatest capacity under the least 

 surface, the spherical figure, or that which 

 approaches nearest to it, has been gene- 

 rally preferred. However, since bodies 

 of this form oppose a greater surface to 

 the air, and consequently a greater ob- 

 struction to the action of the oar or wings 

 nan those of some other form, and there- 

 fore cannot be so well guided in a calm, 

 or in a covirse different from the direction 

 of the wind, it has been proposed to con- 

 struct balloons of a conical or oblong 

 figure, and to make them proceed with 

 their narrow end forward. Next to the 

 shape, it is necessary to consider the stuff 

 that is most proper for forming 1 the enve- 

 lope of the inflammable or rarefied air. 

 Silk stuff, especially that which is called 

 lutestring, properly varnished, has been 

 most commonly used for hydrogen gas 

 balloons ; and common linen, lined within 

 and without with paper, varnished, for 

 those of rarefied air. Varnished paper, 

 or gold-beaters' skin, will answer the 

 purpose for making small hydrogen gas 

 balloons ; and the small rarefied air bal- 

 loons may be made of paper, without any 

 varnish or other preparation. The stuff 

 for large balloons of both kinds requires 

 some previous preparation. The best 

 mode of preparingthe cloth for amachine, 

 upon Montgolfier's principle, is, first to 

 soak it in a solution of sal-ammoniac and 

 si/e, vising one pound of each' to every 

 gallon of water; and when ttie cloth is 

 quite dry, to paint it over with some 

 earthy colour, and strong size or glue. 

 It may be also varnished over, when per- 

 fectly dry, with some stiff, oily varnish, 

 or simple drying linseed oil, which w ould 

 dry before it penetrates quite through the 

 cloth. The pieces of which an hydrogen 

 gas balloon is to be formed must be cut 

 of aproper size, according to the proposed 

 dimensions of it, when the varnish is suf- 

 ficiently dry. The pieces that compose 

 'he surface of the balloon are like those 

 gores that form the superficies of a globe ; 

 and the best method of cutting them is. to 

 describe a pattern of wood or stiff card- 

 paper, and to cut the silk or stuff upon it. 

 To the upper part of the balloon there 

 must be adapted a valve, opening inward, 

 to which is annexed a string passing 



through a hole made in a small round 

 piece of wood, which is fastened to the 

 .art of tlie balloon, opposite to the 

 valve, to the boat below it ; so that the 

 aeronaut may open it as occasion requires, 

 and let the hydrogen gas out of the bal- 

 loon. To the lower part of the balloon 

 are fixed two pipes of the same stuff with 

 the covering, six inches in diameter tor a 

 balloon of 30 feet, and much larger for 

 balloons of greater size, and long enough 

 to reach the boat. These pipes are the 

 apertures through which the hydrogen 

 gas is introduced into the balloon. Tin- 

 boat may be made of wicker work, and 

 covered with leather, well painted or var- 

 nished over. The best method of sus- 

 pending it is by means of ropes, proceed- 

 ing from the net which goes over the bal- 

 loon. This net should be formed to the 

 shape of the balloon, and fall down to the 

 middle of it, and have various cords pro- 

 ceeding from it to the circumference of a 

 circle, about two feet below the balloon ; 

 and from that circle other ropes should go 

 to the edge of the boat. This circle may be 

 made of wood, or of several pieces of slen- 

 der cane bound together. The meshes of 

 the net may be small at top, against which 

 part of the balloon the hydrogen gas ex- 

 erts the greatest force, and increase in 

 size as they recede from the top. A hoop 

 has been sometimes put round the middle 

 of the balloon for fastening the net. This 

 is not absolutely necessary; but when 

 used, it is best made of pieces of cam- 

 bound together, and covered with leather. 

 When the balloon and its appendages are 

 constructed, the next object of import nnci 

 is to procure proper materials for filling it. 

 Hydrogen gas for balloons may be obtain- 

 ed in several ways ; but the best methods 

 are by applying acids to certain metals ; 

 by exposing animal, vegetable, and some 

 mineral substances, in a close vessel, to a 

 strong fire; or by transmitting the va- 

 pour of certain fluids through red hot 

 tubes. In the first of these methods, iron, 

 zinc, and sulphuric acid, are the materials 

 most commonly used. The acid must be 

 diluted with five or six parts of 

 Iron may be expected to yield in the 

 common way about 1700 times , 

 bulk of gas, or 4! ounces of iron ; the 

 like weight of sulphuric acid, and 22$ 

 ounces of water, will produce one cubic 

 font of hydrogen gas; 6 ounces of zinc, 

 an equal weight of acid, and 30 ounces 

 of water, are-nect ssary for producing' the 

 same quantity. It is more proper to use 

 the turnings or chippings of great picc< s 

 of iron, as of cannon, &c. than the filings 



