. The railroad and engineering journal . excavated onl/ to the vancing needles between the top of the lining arch and the earthabove and around, and this prevents any subsidence. A greatsaving is effected in the quantity of excavation necessary in thepresent mode of carrying out works of this description, as bythis mode no crown bars or poling boards, as in fig. 1, are nec-essary, and the excavation is only taken out the size of thebrickwork to be built, as in fig. 2, thereby preventing waste oftimber or the extra brickwork generally built between crownbars or timbers. In driving sewers, the e
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. The railroad and engineering journal . excavated onl/ to the vancing needles between the top of the lining arch and the earthabove and around, and this prevents any subsidence. A greatsaving is effected in the quantity of excavation necessary in thepresent mode of carrying out works of this description, as bythis mode no crown bars or poling boards, as in fig. 1, are nec-essary, and the excavation is only taken out the size of thebrickwork to be built, as in fig. 2, thereby preventing waste oftimber or the extra brickwork generally built between crownbars or timbers. In driving sewers, the exact shape of thesewer can be taken out, instead of driving a square heading. It will not be so often necessary to break up the surface ofroads for the construction of subways or passages, as with thismethod there need be a thickness of only a few feet above thecrown of the arch. At Kings Cross Ihe heavy goods yard istunneled by this method to within less than 3 ft. of turntablefoundations, the traffic being unimpeded. Part of the work. SECTION aFNSCCLLS Fig. 3- would have had to be done in open cutting and traffic stopped, but for this system of working, which saves 3 ft. of headway.A great saving of time is effected by this method. The steelneedles will, of course, last many years, and will suit any shapeof arch. At the Kings Cross tunnel, experience has shownthat, besides a great saving of time, there has been a reduction, as compared with Ihe usual method, of about 50 per cent, in thecost of all that part of the work which is affected by the newmethod—that is, from the crown to the top sill of the face tim-bering, below which the work is executed in ih? ordinary man^ 96 THE RAILROAD AND [February, 1891. An Electrical Lighthouse.—The accompanving illustra-tion, which is from the report of United Slates Consul Connolly, of Auckland, New Zealand, to the State Department, shows alighthouse devised by Mr. Hannaford. a New Zealand inventor.It is an Iron tower, with a windmill at