12. 13. For easy Experiments; 1st, Dutch Twine, half a Mile long, on a Reel, or Pulley, or two Lengths on different Reels: also to each Reel a Flag, made of white Linen, a Yard square; and stretched by a slender Lath; one Side of the Flag being bound and stitched round it: also a Piece of Twine, two Yards long, is to be fastened by its Ends to the Ends of the Lath: a Loop is to be made in the Middle of the Twine: and to the Loop is to be applied round the Middle of the Lath another Piece of Twine, which will prevent the Lath from being bent; and will keep the Flag always stretched. By this Apparatus, Observers from below may be enabled to estimate the Height of the Balloon, as will be shewn in its proper Place. 12. 14. 2dly, To try the Density of the Air, at different Heights, _above_ the freezing Point with Water; _below_ it, with Brandy. In a Basket take two Pint-bottles, one full of Water, the other of Brandy; and six or eight empty ones: also a small Metal Tunning-dish. Let one End of a String be tyed round the Neck of each Bottle: and the other End sealed to the Top of a large Cork much tapered, to enter the Mouth easily. Round each Neck, tye a Parchment Label, large enough to contain in abbreviated Characters the Number of the Bottle; Time of Observation, Heights of the Barometer and Thermometer, while on the Ground. When an Experiment is made in the Air; pour off a full Bottle into an empty one: put the Cork into the emptied Bottle, and mark again the Time, Barometer and Thermometer: which are to be compared with an Eudiometer below, to discover the Rarity and Purity of the Atmosphere. 12. 15. A third white Linen Flag, made as above, and tyed to the upper Hoop of the Balloon, so as to hang in Sight, will give Notice of a Change in the Wind. 12. 16. A Yard of thin Ribbon, two Inches broad, tyed to the lower Hoop, will mark the Rise and Fall Of the Balloon. (12. 17. A Magnet and Iron Filings in a thin Pewter Dish with a Cover; Also The Prism and large Telescope were left, as too heavy.) And the Sextant or Quadrant coud not be procured in Time. They woud, have been of little Use, as no Horizon of the round Earth was seen during the Excursion: and it is presumed, that the circular Horizon is seldom visible, when the Balloon is at any considerable Height; the Accumulation of Vapour between the Eye and Horizon preventing it: tho’ such Vapour remains invisible to Spectators from below. 12. 18. Eight Bladders, each above half blown, and differently coloured for Ornament, tyed round the _upper_ Part of the Car, Breast high when the Aironaut stands upright: in Case the Balloon fall into Water. 12. 19. Speaking Trumpet: also a live Pigeon, in a small Basket of Matting. 12. 20. Pepper, Salt, Ginger; to try the Effects of Tastes, which have been said to become insipid on the Peak of Teneriffe. CHAPTER III.