Lecture III.

Advantages of coffer-dams.—Various forms of coffer-dams.—Half-tide dams.—New Eddystone lighthouse.—Rubble coffer-dam.—Coffer-dams of ordinary construction,—Underpinning dam at Trent Bridge.—St. Katherine's Docks dam.—Houses of Parliament dam.—Grimsby Docks dam.—Puddle.—Portable dams.—Pile driving.—Ringing engine.—Crab engine.—Horse power.—Steam power.—Signals requisite.—Endless chain.—Atmospheric engine.—Nasmyth's steam pile-driver.—Calculation of force of blow.—Table of velocities.—Practical deductions.—Ringing and shoeing.—Sheet-pile shoes.—Grooving and tongueing.—Whole balks best.—Desirability of ascertaining nature of ground by boring before commencing pile-driving.