i8 Introduction . 
And as no Body whatfoever has in itfelf a Power of Self - motion , and as all the Changes and different Forms arc not to be effected without Motion , lo fuch Motion , from whatfoevcr external Caufe it a ri fes will always be likewife under the Influences of the Figures and Bulks of the moving Bodies , as well as under the Directions of the impelling Force . To know therefore what will be the Confequences of the Impulfe of one Body upon another , with tion to the changing the prefent Form of its Exi - itence , and giving it new Qualities , it is iiril necei - fary to find out the Laws of their Motions , and learn by why Properties in the moving Body thofc Laws are determinable . 
But to give an Inilance how thefe are influenced by the Figures only of the moving Body , let us gine two or more Bodies of the fame Magnitudes and Gravities , but unequal in their Figures ; as fup - pofe one a Globe , another a Cube , and another in the Form an Hemifphere , to fet out together from the fame Place with equal Velocities through the fame Medium , and in Directions horizontal and rallel to one another : Both their Velocities and rections would quickly be determined very different from what they were at the firft fctting out , by the different Oppofition they would meet with from the Medium - , their Velocities would foon become qual , by the different Capacities of their Figures to divide it . For to make Room for their Paffagc , fup - ' pofc the Medium to be Air , but under no Flux or Tendency towards any particular Point , it mud fi rit recede orbe moved out of the Way by the PrefTurc of the moving Body ; according to the Difference of which Preflure , the moving Body becomes more or leis retarded in every Point of the Medium it paffes through» fo that their Velocities will then be as the Breadth of their foremoft Surfaces , or as the Length 
of