From which Experiments, I think, we may safely conclude, that the Elater of the Air is reciprocal to its extension, or at least very neer.  So that to apply it to our present purpose (which was indeed the chief cause of inventing these wayes of tryal) we will suppose a Cylinder indefinitely extended upwards, [I say a Cylinder, not a piece of a Cone, because, as I may elsewhere shew in the Explication of Gravity, that triplicate proportion of the shels of a Sphere, to their respective diameters, I suppose to be removed in this case by the decrease of the power of Gravity] and the pressure of the Air at the bottom of this Cylinder to be strong enough to keep up a Cylinder of Mercury of thirty inches:  Now because by the most accurate tryals of the most illustrious and incomparable Mr. Boyle, published in his deservedly famous Pneumatick Book, the weight of Quicksilver, to that of the Air here below, is found neer about as fourteen thousand to one:  If we suppose the parts of the Cylinder of the Atmosphere to be every where of an equal density, we shall (as he there deduces) find it extended to the height of thirty five thousand feet, or seven miles:  But because by these Experiments we have somewhat confirm’d the hypothesis of the reciprocal proportion of the Elaters to the Extensions we shall find, that by supposing this Cylinder of the Atmosphere divided into a thousand parts, each of which being equivalent to thirty five feet, or seven geometrical paces, that is, each of these divisions containing as much Air as is suppos’d in a Cylinder neer the earth of equal diameter, and thirty five foot high, we shall find the lowermost to press against the surface of the Earth with the whole weight of the above mentioned thousand parts; the pressure of the bottom of the second against the top of the first to be 1000 — 1 = 999. of the third against the second to be 1000 — 2 = 998. of the fourth against the third to be 1000 — 3 = 997. of the uppermost against the 999. or that next below it, to be 1000 — 999 = 1. so that the extension of the lowermost next the Earth, will be to the extension of the next below the uppermost, as 1. to 999. for as the pressure sustained by the 999. is to the pressure sustain’d by the first, so is the extension of the first to the extension of the 999. so that, from this hypothetical calculation, we shall find the Air to be indefinitely extended:  For if we suppose the whole thickness of the Air to be divided, as I just now instanced, into a thousand parts, and each of those under differing Dimensions, or Altitudes, to contain an equall quantity of Air, we shall find, that the first Cylinder, whose Base is supposed to lean on the Earth, will be found to be extended 35-35/999 foot; the second equal Division, or Cylinder, whose basis is supposed to lean on the top of the first, shall have its top extended higher by 35-70/998 the third