2d. Hypothesis of a semicircular vaulting with arched extrados. Pressures and resistances. In similar arches the pressure is proportional to the square of the radius.
[FOURTH PART.—HYDRAULIC CONSTRUCTION.]
1st. Classification of ground on which it may be necessary to place a foundation. Soundings. Their object. Various kinds of sounding line. Dams in earth, and in wood and earth combined. Case of an unstable foundation. Construction on rock. Thickness of dams and of the clay work. General disposition of a dam. Bottom-springs. Means of choking or smothering them or of diverting them. Use of sunk dams. Service bridges. Their height and disposition. Railways in great constructions. Their disposition.
2d. Summary review of draining or pumping machines. Choice between the different methods of draining. Table of the useful effect of such machines.
Pile driving. Pile driving machine with band ropes. Preparation of the pile and operation of driving. Pile driving machine with catch. Choice between the two kinds of pile driving machines. Precautions to be taken in the driving of piles. Distribution of piles, the space to be left between them, and the squaring of them. Disposition and driving of planks. Method of drawing up piles and planking. Execution of a foundation on piles. Driving stakes out of water. Machine for squaring piles.
3d. Parafouilles. Their object and construction.
Foundations in mortar under water. Preparation and immersion of the mortar. Examples.
Thickness of sunk dams with the enceint in mortar.
4th. Foundation frames and platforms. Their object and their construction. Preparation of the foundation frames in masonry.
Foundation by packing.