7

Hydr au Lies*

Hence also the Descent of "Water inRivers, Streams, and Canals, from Springs

and

can descend in a Channel to any Part of the Earth'sSurface between B and D, because every Point in theLine E D is nearer to the Centre of the Earth, andtherefore below the Point or Place E > and its Velocitywill be so much the greater as it tends to a Point nearerB, and (lowest of all, when it moves in the Directionof the Tangent ED.

4. Hence it appears that the Source E of all Riversand Streams must be more than a Semi-diameter of theEarth CB distant from the Centre C. And since allgreat Rivers run to the Sea or Ocean, where they dis-embogue their Waters at the Point D, the Line DCis a Semi-diameter, and — 4000 Miles nearly. Also,the Course of all long Rivers being in the Directionof the Tangent at the Point D, if they were representedby the Tangent-Line E B, then the Height of theSource E above the common Surface of the Earth at BWould be easily found. Thus, suppose E D were theRiver Niger in Africa, whose Source is more than 30OOMiles from the Sea; but put ED — 3000, and sinceCD — 4000, we (hall have CE = 5000, and CE—-CB 1000 —BE ^2 the Height of the Source. Butsince we know of no Mountains above three or fourMiles high, it is plain the River Niger, and all suchlong Rivers, are so far from moving in a Tangent, thattheir Course must be very nearly of the same Curva-ture with the Earth’s Surface, and insensibly distantfrom it.

5 - Since Bodies move on Planes ever so little in-clined, except so far as they are prevented by Friction,and since the Friction of the Particles of Water among,themselves is inconsiderable, it follows that the \Vatersituated on a Plane ever so little inclined will commence:a Motion; and if the Plane be considerably inclined,and the Quantity of Water great, its Velocity will beproportional, and its Momentum such as will soon beginto wear away the Earth, and create itself a Course or

B 4 Channel