44. If therefore this be added to a projecting Force downward in a Perpendicular; or subducted from such projecting Force upward; that is, to or from ((1 - _a_)/_n_)_f_: The Descent in the first Case will be ((1 - _a_)/_n_)_f_ + ((_nt - 1 + a_)/_nn_)_g_; and the Ascent in the other Case ((1 - _a_)/_n_)_f_ - ((_nt - 1 + a_)/_nn_)_g_. And in this latter Case, when the ablative Part becomes equal to the positive Part, the Ascent is at the highest; and thenceforth (the ablative Part exceeding the positive) will descend. 45. In an Horizontal or Oblique Projection, having taken ((1 - _a_)/_n_)_f_, in the Line of Projection, and thence (at the Angle given) ((_nt_ - 1 + _a_)/_nn_)_g_, in the Line of Descent; the Point in the Curve answering to these, is the Place of the Project answering to that Moment. 46. I am aware of some Objections to be made, whether to some Points of the Process, or to some of the Suppositions. But I saw not well how to wave it, without making the Computation much more perplex'd. And in a Matter so nice, and which must depend upon Physical Observations, 'twill be hard to attain such Accuracy, as not to stand in need of some Allowances. 47. Somewhat might have been farther added to direct the Experiments suggested at ¶ 21, and 31. But that may be done at leisure, after deliberation had, which way to attempt the Experiment. 48. The like is to be said of the different resistance which different Bodies may meet with in the same _Medium_, according to their different Gravities (extensively or intensively consider'd) and their different Figures and Positions in Motion. Whereof we have hitherto taken no account; but supposed them, as to all these, to be alike and equal. _POSTSCRIPT._ 49. The Computation in ¶ 41, 42, 43, may (if that be also desired) be thus represented by Lines and Spaces. The Ablatives _a_, _ma_, _mma_, &c. (being the same with the first Column taken backward) are fitly represented by the Segments of _NF_ (beginning at _N_) in Figure 5 and 6, and therefore by Parallelograms on these Bases, assuming the common height of _Fh_, or _NQ_; the Aggregate of which is _Nh_, or _FQ_. And, so many times 1, by so many equal Spaces, on the same Bases, between the same Parallels, terminated at the Hyperbola: The Aggregate of which is _hFNQn_. From whence if we subduct the Aggregate of Ablatives _FY_; the remaining Trilinear _hQn_, represents the Descent. 50. If to this of Gravity, be joined a projecting Force; which is to the Impulse of Gravity as _hK_ to _hF_ (be it greater, less, or equal) taken in the same Line; the same Parallels determine proportional Parallelograms, whose Aggregate is _KQ_. 51. And therefore if this be a perpendicular Projection downwards; then _hKkn_ (the Sum of this with the former) represents the Descent.