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SUppose any Wall, Dam, or Banck, to be just sufficient to keep out or resist the Sea, or other Stream against the appulse of its waters, being of a cer∣tain force; I say, that to make this Wall or Damm strong enough against a
double swiftness of ap∣pulse, it must be augmen∣ted by quadruple thic∣kness; and if it must be made sufficient against the greatest violence which e∣ver was observed, then that violence being known, is the Root of the number by which the Walls thickness must be augmented.
So Cannon-Bullets do Execution or batter in du∣plicatâ ratione of their swiftness; and therefore Ramperts must be strong
and thick in duplicatâ ra∣tione of the said swiftness, which depends upon the Distance of the Battery, and the degrees of Tardati∣on, which Bullets make in every part of their way be∣tween the Gun and the Rampert, which they are to batter. Where note, that Bullets commonly beat out a Cone of Wall, whose Vertex is in the Bullets En∣try, and like the Conical Fovea to be seen in the Sand of an Hourglass.