The same decimal number will apply to any given diameter, and you see by this rule that a balloon of two feet diameter will contain four cubic feet of gas, and that the quantities of ingredients, &c., required are as given above. I hope you will excuse me for taking you to school again, but I am anxious to make this chapter as complete as possible.
COST.
With reference to the cost of the materials to be used in the construction of balloons, it is obviously impossible to enter into details without knowing the size of the balloon to be constructed. The following general instructions, however, may be found useful.
Strong tissue-paper, which measures twenty by thirty inches, costs about sixpence per quire, one quire being amply sufficient for a three-foot balloon.
Scotch cambric, which is forty-four inches wide, costs one shilling and twopence per yard, and you will be able to calculate how many yards are requisite for your purpose.
Boiled oil costs about fourpence per pint, half a pint being sufficient to varnish a three-foot paper balloon.
Tissue-paper can be had of all colours.
With regard to the netting, which is technically known and must be asked for as ‘netting line,’ it varies in size, and costs about two shillings per lb.
With these few remarks I leave you to the construction of your balloon, which I hope you will find an agreeable and not too difficult task.
