rNEUMATICS. 171 



Large balloons for inflammable air must be made 

 of silk, and varnished over, so as to be air-tight. 

 To the upper part of the balloon there should be 

 fitted a valve, opening inwards, to which a string 

 should be fastened, passing through a hole made in 

 a small piece of wood, fixed in the lower part of the 

 balloon ; so that the aeronaut may open the valve 

 when he wishes to descend. The action of the valve 

 is effected by a round brass plate, having a hole 

 about two or three inches diameter, covered on both 

 sides with strong smooth leather: on the inside 

 there is a shutter of brass, covered also with 

 leather, which serves to close the hole: it is 

 fastened to the leather of the plate, and kept 

 against the hole by a spring. To the lower part 

 of the balloon a pipe is fixed, made of the same 

 materials with the balloon, which serves to fill 

 it by. 



The car, or boat, is made of wicker-work, covered 

 with leather, and well varnished, or painted, and is 

 suspended by ropes proceeding from the net which 

 goes over the balloon. This netting should cover 

 the upper part, and come down to the middle, with 

 various cords proceeding from it to the circumfer- 

 ence of a circle, about two feet below the balloon. 

 From that circle other ropes go to the edge of the 

 boat. This circle may be made of wood, or of 

 several pieces of slender cane bound together. 

 The meshes of the net should be small at top 

 (against which part of the balloon the inflammable 

 air exerts the greatest force), and increase in size 

 as they recede from the top. 



The inflammable air for filling the balloon is 

 procured, by putting a quantity of iron-filings, or 

 turnings, with some oil of vitriol diluted with 

 water, into casks lined with lead. From the top of 



