ELEVATED KOAD IN THIRD AVENUE. 



passengers. The single posts afford abundant 

 lateral stability, as they are subjected to but 

 very little lateral strain. But considerable 

 difficulty was found in giving them sufficient 

 stability to meet the longitudinal strain oc- 

 casioned by the momentum of the train when 

 the brakes are applied, there being a space 

 left between the ends of the girders to allow 

 for the expansion and contraction caused by 

 changes of temperature, which prevented the 

 longitudinal strain from being transmitted to 

 more than two or three columns. The diffi- 

 culty was met by bolting the longitudinal 

 guard-timbers through the cross-ties to the top 

 chord of the girders, and thus making the road 

 longitudinally rigid by distributing the strain 

 over the whole row of posts. One of the prob- 

 lems connected with building the road arose 

 from the difficulty, in carrying it around the 

 corners in small streets, of making the necessary 

 curve of 90 degrees. To make the curve at a 

 corner where the breadth of one street was 30 

 and that of the other 40 feet, a long girder 

 was carried across diagonally from corner to 

 corner, and a cross-girder carried to meet this 

 perpendicularly from the inside corner. As 



the corner is approached the tracks are carried 

 out on each street almost to the edge of the 

 framework, so as to get a wide sweep at the 

 corner. 



A design for a cheap and readily constructed 

 pioneer or military railway for temporary pur- 

 poses was experimented upon in England late- 

 ly. It was planned by J. L. Haddan. It was 

 built entirely of timber on posts, and had a 

 central rail 7 feet from the ground, upon 

 which the engine and carriages were balanced 

 like panniers, and.two guide-rails, one on each 

 side, upon which the wheels worked, which 

 were horizontal, gripping the side-rails. .Such 

 a structure was hastily put up at Whitehall 

 by a few soldiers upon very uneven ground, 

 the posts driven into the ground, the cross- 

 timbers fixed and bolted, and wedges driven 

 in to make up for any slack in the trusses, all 

 in a short time and with ease. 



The new Eddystone lighthouse will require, 

 it is expected, five years in building. The site 

 chosen by the engineer, Douglas, is the south 

 reef, which will make the work of building the 

 lower part of the structure much more difficult 

 than in the case of the old tower, as it lies in 



