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ENGINEERING. 



gineering difficulties, is from Sydney to Kiama 

 (73 miles). This was, at last advices, partly 

 finished, but work had been suspended, owing 

 to suspected political jobbery, which called 

 for official investigation. The section of the 

 line already open includes a bridge 956 feet 

 long, similar to that over the Paramatta. 

 Other authorized extensions are from Glen 

 Innes to Grafton (103 miles), crossing two 

 large rivers and requiring numerous cuttings 

 and twelve tunnels through granite; from 

 Glen Innes to Inverell (45 miles), from Ten- 

 terfield to the Queensland border (12 miles), 

 from Muselbrook to Cassilis (70 miles), Gunda- 

 gai to Tumut (33 miles), and numerous other 

 connecting lines. It will be inferred from 

 these data that the local governments have 

 suffered from a railway fever that has in- 

 volved them in heavy expenditures, and may 

 cause a suspension of the important work in 

 progress. It is noteworthy, however, that a 

 large proportion of the proposed systems is 

 confessedly light and cheap in construction, 

 estimated in some cases as low as $15,500 a 

 mile. Of these "light" lines, that from 

 Forbes to Willcannia (340 miles) is the most 

 important. Altogether the railway system of 

 the colony, present and prospective, as author- 

 ized by legislative acts, aggregates something 

 like 3,000 miles, and represents a total outlay 

 up to the present time of not far from $100,- 

 000,000, while half as much more for works 

 alone not including equipment is to be ex- 

 pended, if the projects are carried out in the 

 immediate future. 



The Tay Viaduct. During a heavy storm on the 

 night of Dec. 28, 1879, a section of the great 



an act of Parliament authorized a new bridge, 

 and the contracts were given out in April, 

 1882. The new viaduct, now well advanced 

 toward completion, is parallel to and 60 feet 

 distant from the standing portions of the old 

 bridge, which are utilized so far as possible for 

 purposes of construction. The total length is 

 3,600 yards, with eighty spans varying from 50 

 to 230 feet. The height of the rails above high 

 water varies from 25 feet at the northern to 83 

 feet at the southern end, leaving 79 feet for 

 the four navigable spans in mid-channel. For 

 purposes of classification the work is divided 

 into three sections: (1) the arching at the 

 southern end ; (2) the esplanade spans at the 

 northern or Dundee end ; (3) the viaduct proper, 

 which extends over tidal water. Of the arches 

 at either end no description is necessary, since 

 they are of ordinary brick and stone construc- 

 tion. The viaduct proper comprises 74 spans 

 of various lengths, consisting of wrought-iron 

 girders resting on piers. The girders are of the 

 usual lattice construction. The piers, which 

 were devised in the light of the terrible experi- 

 ence gained in the destruction of the former 

 bridge, consist of pairs of cylinders connected 

 just above high water, the connection forming 

 the foundation for the superstructure. The 

 method adopted for sinking the cylinders is 

 especially ingenious. It was devised by the 

 Messrs. Arrol, the contractors. A rectangular 

 pontoon is fitted at each corner with a verti- 

 cal wrought-iron tubular leg, capable of being 

 raised or lowered by hydraulic machinery. 

 When these rest on the bottom, the pontoon or 

 platform can be raised above the water, form- 

 ing a working stage for sinking and fitting the 

 pier cylinders. In the stage are 

 two openings within which the 

 cylinders are pitched and adjusted 

 in position. The excavation is ef- 

 fected by steam diggers, the cylin- 

 ders sinking until the desired level 

 is reached. TV hen the cylinders 

 are fixed and filled, the pontoon 

 is raised and floated clear, the rise 

 of the tide being utilized to facili- 

 tate the operations. Four of these 

 pontoons are in use in prosecuting 

 the work. At latest advices the 

 arches and esplanade spans have 

 been finished to the roadway level, 

 and the greater part of the para- 

 pets are completed. Of the viaduct 

 proper 58 of the pier - cylinders 

 have been sunk. The girders for 

 most of the spans are in position, 

 and all the rest of the girders are 

 ready for placing. The girders and 

 flooring for each of the spans are 

 made on a staging at the south end 



CONSTRUCTION PONTOON FOB THE TAT BBIDGB. 



of the viaduct, and when wanted 

 bridge over the Firth of Tay, Scotland, was are floated out into position and raised by hy- 

 blown down, and, of about 90 persons known to draulic machinery. 



have been on an express train that was cross- The Forth Bridge. In the " Annual Cyclop- 

 mg at the time, not one escaped alive. In 1881 dia " for 1884 a condensed description of this 



