And 21 ⁄ 25 _c_: _b_∷ _v_: 25_b_ ⁄ 21_c_ _v_ the veloc. _per_ sec. in
the water-way between the obstacles. _Princip. V._
Also (2_a_)²: _vv_∷ _a_: _vv_ ⁄ 4_a_ the height fallen to acquire the
vel. v. I. & II.
And (2_a_)²: (25_b_ ⁄ 21_c_)² × _vv_∷ _a_: (25_b_ ⁄ 21_c_)² × _vv_ ⁄
4_a_ the height fallen to acquire the vel. 25_b_ ⁄ 21_c_ _v_. I. & II.
Then (25_b_ ⁄ 21_c_)² x (_vv_ ⁄ 4_a_) - (_vv_ ⁄ 4_a_) is the measure of
the fall required. VII.
Or ((25_b_ ⁄ 21_c_)² - 1) × _vv_ ⁄ 4_a_ is a rule, by which the fall
may be readily computed.
Here _a_ = 16,0899 feet and 4_a_ = 64,3596.