Cylinder Construction.—A mode of con struction which has been very successful on the Pacific Coast was invented by the writer and has been in use in the San Francisco Harbor for many years. It is the wooden cylinder pier construction. (See Fig. 2). The foundation proper consists of cylinders of con crete and piles placed about 15 feet on centres. The details of construction are as follows. The core consists of one or more piles, gener ally three; these are driven to a firm foundation and are left at different heights from the fin ished top of the proposed wharf, for ex ample, say one pile is 50 feet in length, one 55 feet and one 60; this is for two reasons first, for economy, as in the San Francisco Bay most of the piles depend absolutely on the friction of the mud for sustainingpurposes (there being no known bottom) and it will readily be seen that the 50-foot piles will be as deep in the mud as the 60; secondly, it admits of a larger body of concrete at the top of the cylinder where required. After this cluster of piles is driven, there is then driven over and encircling same a wooden stave cylinder, gen erally four feet inside diameter; these staves are from three to four inches thick and bound together with wrought-iron hoops having ad justable lugs; these hoops are placed about two feet on centres and the cylinder is made per fectly water-tight It is driven with an ordi nary pile-driving machine from 10 to 15 feet into the mud. The water and mud in the
interior is then pumped out to a depth of from two feet to five feet below the mud on the out side; then inside of this cylinder of wood, be tween it and the piles, is placed an interior cylinder of expanded metal or similar metallic interstitial web about one foot less in diameter than the interior of the wooden cylinder. The ulterior is then filled with a rich concrete of hydraulic cement and broken rock. The cylinder per is complete and forms a teredo-proof con crete pier, having a wooden core reinforced with an interstitial web of expanded metal and protected for at least four years with an iron wooden jacket. (See Fig. 3). These cylinders are then capped with caps of struc mral steel, generally two 15-inch 1-beams and the balance of the superstructure is as in the ordinary wharf. The fender system is some what different from that in general use and is as follows: The fender piles are driven in pairs about 10 feet apart and about one foot away from the wharf proper; they are con nected together longitudinally with a ribbing composed of three timbers both at the surface and below the top of wharf. (See Fig. 4). Be