the Inflection , Reflection , and Colours of Light. 235 
and secondly, what proportion the different flexibilities of the 
different rays bear to one another. But the nature of the co- 
loured fringes must first be understood, so that I defer this 
inquiry till after I have made use of the principles now laid 
down, for the explanation of natural phsenomena, and proceed 
in the mean time to 
Part II. Of Reflection. 
That bodies reflect light by a repulsive power, extending to 
some distance from their surfaces, has never been denied since 
the time of Sir Isaac Newton.* Now this power extends to 
a distance much greater than that of apparent contact, at 
which an attraction again begins, still at a distance, though 
less than that at which before there was a repulsion ; as will 
appear by the following demonstration which occurs to me, 
and which is general with respect to the theory of Bosco- 
vicH.-f In fig. 4. let the body A have for P an attraction, 
which, at the distance of AP, is proportional to PM ; then let 
P move towards A so as toocome to the situation P', and let 
the attraction here be P'M' ; as it is continual during the mo- 
tion of P to P', MM' is a curve line. Now in the case of the 
attraction of bodies for light, and for one another, PM is less 
than P'M', and consequently MM' does not ever return into 
itself, and therefore it must go, ad infinitum , having its arc be- 
tween AB and AC, to which it approaches as asymptotes; 
the abscissa always representing the distance, and the ordinate 
the attraction at that distance: let P' now continue its motion 
to P", and M' will move to M", and if P" meets A, or the 
* Optics, Book II. Part III. prop. 8. 
t Nova Theoria Philosophies Naturalis. 
Hh 2 
