. L'ingénierie et la sous-traitance. imate déclaration du costsinvolved. Deux types généraux de la construction ont suivi en fonction du conditionsfound dans le sous-sol. Sur le rebord rocheux ou bot-tom, le mur de soutènement en pierre probablyfirst a été utilisé et est un type commun d'aujourd'hui. Ou sous-sol est de sable, de limon ou d'argile le tas orpile et la construction de la plate-forme havegeneraly été utilisé. La crèche peut-être utilisé sur n'importe quelle cloison de fond. Cloisons Crih-Les premiers exemples de ce type se composent de quelques journaux d'laidalong rugueux bord de l'eau, le remplissage derrière être-ing terre et sable. Plus tard, la crèche a été bui

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. Engineering and Contracting. imate statement of the costsinvolved. Two general types of construction havebeen followed according to the conditionsfound in the subsoil. On rocky or ledge bot-tom, the stone retaining wall was probablyfirst used and is a common type today. Wherethe subsoil is sand, silt or clay the pile orpile and relieving platform construction havegeneraly been used. The crib bulkhead maybe used on any bottom. Crih Bulkheads—The earliest examples ofthis type consist of a few rough logs laidalong the waters edge, the filling behind be-ing earth and sand. Later the crib was builtof rough logs, notched at the junctions toform a kind of rectangular framing, weightedwith stone to sink it to the bottom, the fillingbeing rock, earth and sand as before. Asthe crib sank into the subsoil additional logswere placed, building it up to the properheight. Many of these bulkheads are in usetoday and are strong and substantial. Themodern crib is made of squared timber, halved vwvv^^vwvvvv ^vvvvsvvv £2iH/!/7Jf. •A paper by Geo. A. Orrock lead at the an-nual convention of the Connecticut Society otEngineers for 1910. ^V/^»or or/ccr-ners iMFig. 3—Crib Bulkhead on Rock Bottom. together at the corners and splices, the suc-cessive corners held together with drift bolts.Mooring piles and string pieces are providedand a deck of 6-in. plank is usually added. Where timber is cheap and a good hard;lay or gravel bottom may be found at a rea-sonable depth, the crib bulkhead is perhapsthe best method of cheap construction, and ingood locations its life is from 50 to 75 years. Crib bulkheads are also used on rocky bot-tom swept clean by swift currents. See Fig. 4.The cribs are built on shore with the lowercourses fitted to the contour of the bottom, floated to the location, held in place by haws-ers while being sunk, and then anchored bydrilling holes in the ledge at the internal cor-ners of the crib for the insertion of heavyiron bars. A bulkhead of this type in goodwat

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