270 



THE CIVJL ENGIXEEll AND ARCHITECT'S JOURNAL. 



[AlGUSt, 



The niacliinery fur the experiments consisted of tvi'o bars of 

 malleable iron for supports. These were reduced to an acute 

 anjfle on their upper ed^e, and perfectly straight longitudinally; 

 both Mere fixed in blocks of wood, laid on two stone walls about 

 5 feet hi;,'h, thus leaving enough of space for applying the weights 

 below. These bars were laid level in the direction of their 

 length, and level with each other; exactly i>arallel, and placed, 

 as correctly as could be measured, li feet apart, from the angle of 

 the upper edge of the one to that of the other. The stone or 

 slate having been previously dressed to a uniform breadth and 

 thickness throughout, and 3 it. 3 in. in length, were successively — 

 when experimented — laid on tlie iron bearings crossing them at 

 right angles, and equidistant from the ends. Another iron bar, 



RAILAI'AY POINTS AND CROSSINGS.* 



Mil. Campbeli,, the resident engineer of the Edinburgh and 

 Bathgate Railway, has invented sume im])roveinents in railway 

 points and crossings, and in setting of the rails in the chairs, 

 which liave been adopted with success on the above railway. The 

 annexed engravings show the improved points and crossings, as 

 well as the common and the patent make. 



FIC7 



FIC,2 



Fig. I is a section of the improved switch, drawn to a fourth of 

 the full size, at the points of the switches. It is on the bottom 

 side the same as the common switch, while on the top it resembles 

 the patent switch; but it is simple and equally as efficient, and will 

 stand more work. The bearing surface is neither notched nor 

 undercut, the inside of the top of the switch being bent with a 

 twist so as to pass under the top flange of the stock rail. The top 

 of the switch not being mitred into the underside of the bearing 

 surface of the stock rail, it is not liable to be locked by the barb- 

 ing over of the stock from the pressure of the wheels, as frequently 

 happens with the patent switch and others which resemble it in 

 cutting under the top flange of the stock. In Mr. Campbell's 



having its under-edge dressed to an acute angle and straight in its 

 length, was laid perfectly square across the middle of the stone or 

 slate under the experiment. This third bar of iron projected 

 over the stone or slate, sufficient to suspend therefrom, at each 

 end, an iron triangular frame. The bases of the triangles being 

 horizontal and j)arallel to each other, served to support the weight 

 applied to break the stone; which weight consisted of bars of 

 iron, laid on one by one, with great caution, so as not to commu- 

 nicate a concussion to the weight. No steelyard or levers of any 

 kind were used, so that the quantity of iron laid on, including the 

 triangular frame and cross-bar being all weighed, gave the nett 

 weight required to break the stone or slate. 



Seacombe, May 3i)th, 1850. William Stewart. 



meet the tear and wear of the crossing point, notwithstanding the 

 weight of the engines in use. Any contrivance for the main road 

 must be very secure; but at stations where there is much traffic. 



while the transit is slow, the wheels might be assisted over the 

 interval at the crossing point by a piece of iron keyed between 

 the rails, having its surface one inch below the top of the rail, and 



tapering down at each end, on which the flange of the wheel would 

 run till the face again touched the rail, and so be prevented from 

 falling, as it does, off the steeled point with a blow on the knee of 



FIG. 6 



improved switch, part of the under flange of the stock is cut away, 

 which allows a broader and steadier base for the switch, and at the 

 same time stones do not so readily rest between and prevent the 

 shutting of the switch. 

 Mr. Campbell was not aware of anything having been done to 



* Tlio description is from a paper read by Mr. Campbell, at the Bojal Scottiah Society, 

 8oili Maicli, iHbo, 



the wing rail, which is the point that gives way. This is similar 

 to what is done at the crossing of the bars on a turntable. The 

 chair is laid level on the sleeper, but the seat of the rail is inclined 

 1 in 15 in the chair, as shown in fig. 4, so as to give the rail an 

 equal cant its whole length, to meet the cone of tbe wheel. The 

 inside jaw of the joint chair should fit close up under the flange of 

 the rail, but the intermediate chairs should not rise quite so high. 



