x$8 Sir Is a ac Newton’s Book I.

that by this inequality in the superficies of the fluid, thatpart of it, which at the head of the body is higher thanthe fluid behind, will resist in some measure after themanner of discontinued fluids 4 , analogous to what was be-fore observed to happen in the air through its elasticity,though the body be surrounded on every side by it b . Andas far as the power of these causes extends, the figure of themoving body affects its resistance ; for it is evident, that thefigure, which presses least directly against the parts of the fluid,and so raises least the surface of a fluid not elastic, and leastcompresses one that is elastic, will be least resisted.

2.Z. The way of collecting the difference of the resistancein rare fluids, which arises from the diversity of figure, isby considering the different effect of the particles of the fluidupon the body moving against them, according to the diffe-rent obliquity of the several parts of the body upon whichthey respectively strike ; as it is known, that any body im-pinging against a plane obliquely, strikes with a less force,than if it fell upon it perpendicularly; and the greater theobliquity is, the weaker is the force. And it is the famething, if the body be at rest, and the plane move against it c .

iq.. That there is no connexion between the figureof a body and its resistance in compressed fluids, is provedthus. Suppose A B C D (in fig.88.) to be a canal, having such afluid, water for instance, running through it with an equable

* Vid. Newt. princ. in schol. to Lea. 7, of I b Sect. r 7. of this chapter.

3 Lib.II. pag. 341. J c See Princ. phiios. Lib.II. prop.34.

velocity ;