312 



ENGINEERING. 



is increased to thirty feet. Daring the past 

 two years work has been progressing in the 

 direction of widening the channel in the small 

 lakes in the Kabret section, and some impor- 

 tant work, to dimmish the number of accidents 

 by stranding, has been completed. The carry- 

 ing out of the programme of these improve- 

 ments will absorb the greater part of the year 

 1885. 



The Forth Railway Bridge. Work on the great 

 Forth bridge, which was begun in January, 

 1883, by Messrs. Tancred, Arrol & Co., who 

 took the contract for 1,600,000, has been 

 thus far directed chiefly to the building of the 

 three main piers known respectively as the 

 Fife pier, the Inch-Garvie pier, and the Queen's- 

 ferry pier upon each of which is to be built a 

 huge cantilever stretching both ways. The 

 total length of the bridge is about a mile and 

 a half, including two 1,700-foot spans, two 

 675-foot spans, the shoreward halves of the 

 outer cantilevers, fifteen 168-foot spans, and 

 five 25-foot spans. The clear headway under 

 the center of the bridge is 150 feet above high 

 water. The Fife pier, which stands between 

 high and low water mark, like the other main 

 piers, comprises four columns carried down to 

 the rock, of which three are completed, while 

 the fourth is in progress. At the Inch-Garv 7 ie 

 pier, which is partly founded upon a rocky 

 island in mid-stream, one of the columns is 

 complete and one is building, while at the 

 Queen's-ferry pier, which is at the edge of the 

 deep channel, the work on the caissons is ad- 

 vancing. The latter are seventy feet in diam- 

 eter at the bottom edge, have a double skin, 

 and are stiffened with girders, which are sub- 

 ject to a heavy stress, owing to the fact that 

 the range of the tide is fully twenty feet. 

 These pneumatic caissons are provided with 

 special facilities for landing material. In the 

 case of one of the columns of the Queen's-ferry 

 pier, the full depth to which the caisson is to 

 be sunk is not less than ninety-six feet below 

 high water. When in place, the caissons are 

 filled with concrete up to low-water mark, 

 above which cylindrical masonry piers, fifty- 

 five feet in diameter at the bottom and thirty- 

 six feet high, are carried up, forty-eight heavy 

 steel bolts being provided to hold down the 

 bed-plates and the superstructure of the main 

 spans. The whole work is on a magnificent 

 scale, and has thus far been carried out with 

 much skill. It is expected that it will take 

 five or six years more to complete the bridge. 



One of the leading features in the design of 

 the superstructure is the tubular struts of hith- 

 erto unequaled length, of which nearly six 

 miles will be required in the completed bridge. 

 Some of them are as much as twelve feet in 

 diameter. As no machinery was in existence 

 to deal with such work, a special plant was de- 

 signed, which has been described by Andrew 

 S. Biggart in a paper read before the Institu- 

 tion of Engineers and Shipbuilders of Scotland. 

 It includes a heavy hydraulic press for bend- 



ing the steel plates when hot, which weigh 

 as much as a ton and a half apiece, and planing 

 and drilling machines of special size. 



The Isthmus of Corinth Canal. According to the 

 recent report to the Isthmus of Corinth Canal 

 Company, by M. Bazaine, 1,300,000 cubic me- 

 tres of earth had been removed at the close of 

 1884, leaving about 8,000,000 cubic metres to 

 be dealt with. There has been delay in the 

 building of the workmen's houses, the erection 

 of workshops, the providing of water-supply, 

 the construction of the railroad across the 

 isthmus, and in the delivery of the two large 

 dredges, which, it is believed, will be able to 

 handle 10,000 cubic metres a day. M. Bazaine 

 says that thus far the difficulties have not been 

 great on the Corinth side, but adds that it is 

 possible that the favorable conditions may not 

 continue. At the Kalamaki end, however, the 

 outlook is by no means so promising. A good 

 deal of hard conglomerate has been met with, 

 necessitating an almost constant employment 

 of dynamite. 



The Tehuantepee Ship-Railroad. The Isthmus 

 of Tehuantepee lies immediately north of the 

 Isthmus of Yucatan, is the narrowest part of 

 Mexico, and furnishes the most northerly of 

 the three routes proposed for joining the At- 

 lantic and Pacific Oceans the Panama, the 

 Nicaragua, and Tehuantepee. The latter pos- 

 sesses the advantage of affording the most di- 

 rect course from China, Japan, Australia, Ne.v 

 Zealand, California, and the whole Pacific coast 

 of North America, to New York and Europe. 

 The following table of distances will show the 

 lengths of a few of the principal maritime 

 courses by different routes : 



The ground has been frequently surveyed, 

 with the idea of cutting a canal ; notably in 





