ENGINEERING. 



Irrigation purposes. Yet, owing to the gentle 

 flow of the river which at low Nile, with a 

 (litharge of 800 cubic metres a second, is seven 

 eighths of a mil.', and at high Nile, when tho 

 discharge is 14,000 feet a second, becomes 4f 

 miles per hour tho works required are very 

 litfht. Owing to a bend in the river at this 

 point, there is slack water for nearly the whole 

 breadth of the river, where the bottom is sandy ; 

 and where the current passes near the left bank 

 a rocky foundation is found. The bridge will 

 consist of 16 spans of 20 metres each, sup- 

 ported on cast-iron piles filled with concrete, 

 6 spans resting on screw-piles, and a continu- 

 ous girder-bridge with two central spans of 50 

 metres and two side spans of 39 metres, resting 

 on four pairs of cylinders filled with concrete. 

 The deep portion of the river is crossed by two 

 continuous girders, which are of the lattice 

 type and single-webbed, with deep trusses for 

 cross-girders. The weight of the superstruc- 

 ture of the four large spans is 236 tons, and 

 that of the twenty-two small spans 254 tons. 

 In the piers 600 tons of iron are used, and in 

 the caissons 200 tons. 



A new interoceanic railroad is being con- 

 structed in Mexico. Edward Learned of Pitts- 

 field, Massachusetts, has obtained for this pur- 

 pose a land grant from the Mexican Govern- 

 ment, together with the complete control of the 

 harbor at the mouth of the Coatzacoalcos Riv- 

 er and of the lakes on the Pacific side. The 

 railroad is pushed forward with energy, labor- 

 ers and engineers having been sent to the spot 

 immediately, and supplies shipped on from Gal- 

 veston and other places. The work is expect- 

 ed to be completed in three years. The road 

 starts from the harbor, and will terminate at 

 the Upper Lagoon on the Pacific shore, its 

 length being 90 to 100 miles. The creation of 

 a new harbor at Coatzacoalcos is an important 

 consideration to the Government at Mexico, 

 as the harbor at Vera Cruz is rapidly being 

 sanded and will soon be worthless. The mouth 

 of the Coatzacoalcos River where the railroad 

 commences is 110 miles southeast of Vera Cruz. 

 The company is bound to complete annually, 

 to the satisfaction of the Government, 39 miles 

 of road. The track, of 4-J feet gauge, may be 

 either single or double. The path of this road 

 across the Isthmus of Teh uan tepee has easy 

 grades and contains no serious natural obsta- 

 cles ; the climate is wholesome and temperate, 

 and the country rich in natural productions. 

 The maximum estimate of cost is $5,600,000. 

 This route, it is claimed, has substantial advan- 

 tages over all other lines of communication be- 

 tween the Atlantic and Pacific seaports. 



The Canadian Government proposes to ex- 

 pend $5,000,000 per annum, which is to be 

 raised on bonds, on the Pacific Railway, and 

 to keep the road built after tho present year 

 fifty miles in advance of the settlements. For 

 the distance between the head of Lake Su- 

 perior and Lake Winnipeg the road has been 

 nearly completed; contracts have been awarded 



for a stretch of 100 miles beyond Winnipeg; 

 and funds are in hand for 200 miles more. It 

 is expected, therefore, that these 700 miles of 

 railroad beyond Lake Superior will be com- 

 pleted within two years. Fifty or sixty thou- 

 sand tons of steel rails have lately been par- 

 chased in England for this purpose. 



The foundation-stone of the new Eddystone 

 Lighthouse, now constructing under the man- 

 agement of John N. Douglass, was laid by the 

 Duke of Edinburgh on the 21st of June, 1879. 

 The plan of the new structure is essentially 

 the same with regard to its general form as 

 that of Smeaton's lighthouse, and is described 

 by the engineer as a concave elliptic frustum, 

 the generating curve of which has a semi-trans- 

 verse axis of 178 feet and a semi-conjugate 

 axis of 87 feet. While the old tower was built 

 of granite for tho outside walls and with blocks 

 of Portland stone for the interior, the new one 

 will be constructed entirely of granite, which 

 is of a quality superior to that used before. 

 The dimensions and illuminating range of the 

 new lighthouse exceed considerably those of 

 the old one : instead of a base of 32 feet and a 

 light 72 feet above high water, with a range of 

 14 nautical miles, the new tower will have a 

 base 44 feet in diameter, the focal plane of its 

 light will be 130 feet above high water, and its 

 range of illumination 17 nautical miles. The 

 old tower contained four rooms besides the 

 lantern, each 12J feet in diameter; the new 

 one will have nine rooms, not counting the 

 lantern, the seven uppermost chambers having 

 a diameter of 14 feet. The stone used in the 

 construction of Smeaton's column was 13,843 

 cubic feet; for the new tower 69,100 feet will 

 be required. Smeaton was the inventor of the 

 process of dovetailing stone, and the ingenuity 

 which he applied to the adapting and fitting ot 

 the blocks in the lighthouse was the especial 

 feature which made it the wonder of the age; 

 still he required 636 stone joggles, 1,800 oak 

 treenails, 4,570 pairs of oak wedges, 8 circular 

 floor-chains, and 226 iron clamps, to join and 

 fit the blocks. In the new structure, such im- 

 provements have been made upon his system 

 of dovetailing, and such still greater superiority 

 do the modern quick-setting cements possess for 

 hydraulic work over the blue lias and pozzolana 

 lime of Smeaton's day, that no treenailing, 

 joggling, nor other such appliances are used in 

 the new tower, except some composition-metal 

 bolts, slit and wedged at both ends, for anchor- 

 ing down the foundation-stones. The latest 

 method of dovetailing, invented by Nicholas 

 Douglass, is described as consisting "in having 

 a raised dovetailed band, 8 inches in height, on 

 the top bed and one end-joint of every stone. 

 A corresponding dovetailed recess is cut in 

 the bottom bed and end-joint of the adjoining 

 stones, with just sufficient clearance for the 

 raised band to enter it freely in setting. The 

 work which is cut and fitted in this manner 

 and set in Portland cement is as firm and solid 

 as though it were continuous granite. While 



