_Drawbridges with Plyers._--Special theory of this bridge. Reduction of it to practice. Alteration of equilibrium and means of remedying it. Disadvantages of the drawbridge with plyers. 16th. Spiral drawbridge of Captain Berché. Trace of the spiral. Determination of the radius of the chain-roller, and of the greatest radius of the spiral. 17th. Drawbridges with variable counterbalances, invented by M. Poncelet. Construction of the chains of the counterbalance. Establishment of the leverage. Calculation of the counterbalances for the special case of the pulleys in front corresponding to the axis of the platform. Influence of the nature of the chains. Method of allowing for the weight of the small chains. Definitive construction of the chains of the counterbalance. Provision of loose cords. 18th. Succinct ideas upon the motion of the sea, and its action on the shore. Undulating movement. Height of the waves, and depth at which the agitation is perceptible. Effects of the waves on the coasts. Tides; spring-tides; neap-tides. Height of tides and hour of flood. General currents. Action of the sea on its shores. Protection of level and steep shores. 19th. Sea-ports. Requisites of a good port. Ports in the Mediterranean. Conditions of a good roadstead. Moles and breakwaters. Ocean ports, channel tide-dock, floating dock, and sluice of floating dock, laying-up dock, and sluice for the ditch of fortifications. General arrangement of a harbor. 20th. Construction of moles. Stones dropped for foundations. Profile of a loose heap. Volume of the materials which insure their stability. Settling of masonry resting on a heap. Instances of masonry constructed at sea. 1. Wall of Cherbourg. 2. Fort Boyard. _Piers._--Direction, length, form of interval between, and profile of piers. Their construction. Passages reserved through piers. RECAPITULATION. First Part.--Parts of Buildings 18 Second Part.--Architecture of Military Buildings 12 { First Section. Resistance of Materials, 6} Third Part.--{ } 15 { Second Section. Stability of } { Constructions, 9} Fourth Part.--Hydraulic Constructions, 20 -- Total 65 WORKS OF APPLICATION. Name of work. No. Days allowed for execution of work to Students of Artillery. / Engineers. Subject employed on. Observations.