Cm] 
tion to each other, as the Sides of a Triangle refpeft- 
ivcly parallel to the Bale, Ordinate, and Tangent. 
When the Bale is fuppoled to flow uniformly, if the 
Curve be convex towards the Bafe, the Ordinate and 
Curve increafe with accelerated Motions; but their 
Fluxions at any Term are the fame as if the Point 
which deferibes the Curve had proceeded uniformly 
from that Term in the Tangent there. Any further 
Increment which the Ordinate or Curve acquires, is 
to be imputed to the Acceleration of the Motions 
with which they flow. A Ray that revolves about 
a given Centre, being fuppoled to meet any Curve 
and an Arc of a Circle deferibed from the fame 
Centre, the Fluxions of the Ray, Curve, and circular 
Arc, are compared together - y and feveral other Pro- 
portions concerning Tangents are demonflrated 
from the Axioms. The next Chapter treats of the 
Fluxions of curve Surfaces in a fimilar manner. 
The IXth Chapter treats chiefly of the greateft and 
Icaft Ordinates of Figures, and of the Points of con- 
trary Flexure and Cufpids. The Fluxion of the Bafe 
being given, when the Fluxion of the Ordinate va- 
nifhes, the Tangent becomes parallel to the Bafe, and 
the Ordinate mod commonly is a Maximum or Mi- 
nimum* according to the Rule given by Authors upon 
this Subject. But if the Second Fluxion of the Or- 
dinate vanifli at the fame time, and the Third Fluxion 
be real, this Rule does not hold, for the Ordinate 
is in that Cafe neither a Maximum nor Minimum . 
If the Firft, Second, and Third Fluxions vanifh, and 
the Fourth Fluxion be real, the Ordinate is a Maxi- 
mum or Minimum. The general Rule demonflrated 
in this Chapter, and again in the laft Chapter of the 
Second 
