ENGINEERING IN 1892. 



249 



rih <>f the isthmus are in Colorado, whore 

 tin immense system of irrigating ditches has been 

 greatly extended. During tin- past twenty years 

 tin- tuiiil i.iiiiiagu transported on New York ca- 

 ll not far short of 110,000,000 tons, with 

 an e-ti mated value of about $3,250,000,000. Such 

 enornn>u> commercial interests naturally suggest 

 the practicability of a ship canal from Lake Erie 

 ti> the Hudson. This would not far exceed the 

 c<t i>r the Manchester Ship Canal, and therecan 

 hardly ! H doubt that it would prove largely re- 

 munerative. 



Improvements in tunneling devices rapidly in- 

 eivase the possibilities of that branch of engi- 

 neering. No tunnels are sufficiently near com- 

 pletion tn merit description at this time, but 

 tlinsi- under the Thames at London and the Hud- 

 son at New York are under way, and will no doubt 

 l>e pushed forward rapidly. Detailed estimates 

 alike for a bridge across and for a tunnel under 

 the British Channel, from England to France, 

 have been completed to the minutest detail. The 

 cost of a bridge from Cape Blanc Nez to the South 

 Foreland is estimated at $164,000,000, while the 

 smallest revenue is calculated at about $20,000,- 

 000 annually. The only obstacle to the construc- 

 tion of one or both of these works is found in the 

 conservative dread on the part of the British pub- 

 lic lest such means of transit should open a weak 

 point in the defensive armor that Nature has pro- 

 vided for Great Britain. On the whole, the year 

 has not been conspicuous for the completion of 

 great engineering projects. 



Tbe Viaduct du Lonp. One of the most 

 picturesque and, from an engineering point of 



VIADUCT DU LOUP. 



view, one of the most difficult regions in southern 

 France, has recently been traversed by a new 

 railway running through Nice, Puget Theniers, 

 ami Grasse. Although only 62^ miles long, the 

 rnail has been very costly, owing to the broken 

 character of the country. The most notable of 

 the bridges, of which there are many, is tin- 

 viaduct, shown in Fig. 1, crossing the Vallee du 

 Loup, on a curve of 75 feet radius. We are so 

 accustomed to solving problems of this kind 



with iron or steel, that the construction of such 

 a work in masonry seems almost a waste of ma- 

 terial. It has been done, however, in the present 

 instance, and the effect is described as very beau- 

 tiful, the curving line of eleven arches, each 63 

 feet span, sweeping from side to side of the deep 

 valley at a height in the middle sections of 170 

 feet. The total length of the viaduct is 1,050 

 feet. It is hardly conceivable that the building 

 of such a structure with stone at this day is 

 really good engineering, considered in the ab- 

 stract, but it is nevertheless a fine piece of work. 

 Steel Bridge at .Memphis. The formal 

 opening of the great steel bridge across the Mis- 

 sissippi at Memphis, Tenn., occurred on the 12th 

 of May, when the structure was opened for traf- 

 fic with appropriate ceremonies and great public 

 rejoicing. Between this bridge and the Gulf of 

 Mexico the Mississippi is not bridged, and above 

 it the nearest bridge is at St. Louis. It is the 

 third largest of its Kind in the world. Work was 

 begun in the autumn of 1888, when the first cais- 

 son was sunk. There are 5 spans and 6 piers, 

 including the anchorages. The system of con- 

 struction is the cantilever ; the main span, con- 

 sisting of 2 cantilever arms and 1 intermediate 

 span, is 794 feet. The other spans range from 

 621 feet to 225 feet. The total length of the 

 bridge is 2,597 feet. An iron viaduct extends the 

 structure westward 2,500 feet, and then changes 

 to timber trestle for 3,000 feet, and nearly a mile 

 of embankment, to a junction with the tracks of 

 the Kansas City, Fort Scott and Memphis Rail- 

 road. This junction is near Sibley, Ark. The 

 river piers are sunk to depths varying from 75 

 to 131 feet below 

 high-water mark ; 

 all these were sunk 

 into position by 

 the pneumatic pro- 

 cess. They are of 

 masonry from the 

 caissons to the 

 bridge seats. The 

 main posts are 80 

 feet high, weighing 

 28 tons each, and 

 many of the single 

 smaller members 

 weigh from 10 to 

 16 tons. The main 

 pin of the canti- 

 lever truss is 14 

 inches in diam- 

 eter and weighs 

 2,200 pounds. The 

 bridge crosses the 

 river, as nearly as 

 can lii' decided, at 

 the veryspotwhere 

 Ferdinand de Snt<> 



crossed it in 1541. In support of this theory or 

 tradition is the fact that, while excavations were 

 being made for the shore piers on the Tennessee 

 side, several Spanish halberds and sword blades 

 were found, which could hardly have be-on there 

 legitimately unless left by the early explorers. 



IVros River Bridge. Owing to difficult 

 grades and numerous bridges the Southern Pa- 

 cific Railway has undertaken to straighten its 

 line by a cut-off about 800 miles west of New 



