Compressed Air Work And Diving 1909

88 COMPRESSED AIR WORK. New Jersey and Long Island may be described as the suburbs of New York. The two parallel tunnels under the Hudson River are about 5,500 ft. in length, and have been driven through silt and mud by means of shields and compressed air. They are 23 ft. outside diameter and have flanges 11 in. deep. The chief engineer is Mr Charles M. Jacobs, and the contractors Messrs The O’Rorke C011- struction Co. These two tunnels should not be confused with the Hudson Tunnels further south which are 19 ft. 6 in. in outside diameter and 18 ft. inside flanges. One of these two latter tunnels is the original Hudson Tunnel starteel in 1879. The Hudson is sometimes called the North River. The foLir parallel tunnels under the East River are each about 4,000 ft. long, and follow the clirection of Hunters Ferry from Thirty-fourth Street to Hunters Point. Their outside diameter is 23 ft. with 11-in. flanges, and rings 2 ft. 6 in. wide. This portion of the work is a separate contract, and also the largest in the scheme. It was let to Messrs S. Pearson & Son, LtcL, of Westminster, and has been carriecl out by them under the personal supervision of one of the directors, Mr E. W. Moir, with Mr H. Japp in charge locally. The chief engineer is Mr Alfred Noble. The work was started in 1904, and at the date of writing (1908) is practically complete. The following description will deal with this portion of the work only. The rectangular caissons used for sinking the shafts on each side of the river were 74 ft. long by 40 ft. wide, and had double shells 5 ft. apart. The space between was fillecl in with concrete. There was also a 6-ft. wide division across the centre of the caissons, which formed two wells 29 by 30 ft. One line of tunnel started from