[40] It consists of a Frame, made by placing two strong Posts, moveable at Pleasure, each nine or ten Feet high, upright in the Ground, at the Distance of two Yards: the Posts being well secured by broad Pedestals, to keep them firm: a strong horizontal Iron Axis goes throu’ the Top of the Posts; and throu’ the Centers of four Arms or Levers at their Junction. Between the four corresponding Ends of each two Arms, (which Arms are also strengthened by Beams from one to the other), are fixed four Seats or Boxes, well secured, each holding three or four Persons, and moving on Iron Pivots, near the Top of the Boxes, so as always to preserve the _vertical_ Equilibrium. [41] [Sidenote: Recommended to _Invalids_.] Why not recommend the Use of that Machine to Invalids? who woud find Refreshment in the +open+ Air: as its Rotation communicates a gentle Motion to the System,[42] without the least Fatigue; _rather_ encreasing the _Animal_ Spirits. [42] Particularly the Stomach and Diaphragm. See “Berdoe’s Enquiry.” [43] Talis Aër qualis Spiritus. See “_Health’s Improvement_,” by Dr. Moffet, Chapter 3, Of Air, Page 79. [44] Or Solid of _least_ +resistance+, see Chambers’s Dictionary, with the Supplement. [45] It will be found, that, on comparing the _two_ Calculations in Section 52, Note (_a_), _corrected_; the circular _Distance_ from the Eye, above the Clouds, was 102 Miles, 1 Quarter, 320 Yards: while _that_ above the Earth, seen from the same elevated Situation, (supposing the Day to have been +clear+ for such a View,) was 102 Miles, 1 Quarter, 307 Yards: whose Difference is only 13 Yards: that is, the _Distance_ above the Clouds to the _nebulous_ Horizon, was _rather_ more extensive, than _that_ above the Earth to the _terrestrial_ Horizon. It may not, to some Readers, be deemed either unentertaining, or foreign to the Subject; if the Distance of the _Prospect_ from the Balloon at its greatest _barometric_ Altitude, viz. 2332 Yards, or a Mile and Half within 33 Yards, be compared with the Distance which may be seen from the _Summit_ of the principal Mountains in different Parts of the Globe. 1. Cotopàzy, a Mountain in the Province of Quito, in America, and under the equinoctial Line, is _said_ by Ullòa (Vol. 1. Page 422) to be 3126 Toizes or Fathom, i.e. 6252 Yards, or 3 Miles and a Half and 92 Yards in Height. 2. White Mountain, called by the French Mount Blanc, near Geneva, is considered by Sir G. Shuckburgh (Phil. Trans. Vol. 67, Part 2d, Page 598, for the Year 1777) as the highest Land in Europe, Asia, or Africa (known to Europeans) and calculated by him at 5220 Yards, or 3 Miles within 60 Yards above the Level of the Mediterranean Sea. Mons. Bourit just returned from his last Tour, see his “Description de Glacieres” in 1773, makes the White Mountain but 5102 Yards in Height, (which is 30 Yards lower than Teneriffe) including the 410 Yards for the Level of the Lake of Geneva above the Mediterranean.