BACK RAILWAYS. 87 



The Abt engines used are described as follows. They are six- 

 wheeled, the lower or down hill two pairs being coupled. The 

 wheel base is 10 ft., of which 3 ft. 6 in. is between the coupled wheels. 

 Length over buffers 24 ft. The loads on the wheels are 1 1 J tons on 

 each pair of coupled, and 10 tons on the pair of uncoupled wheels, 

 total 33 tons, in steam and coal. The wheels are 2 ft. 8 in. diameter. 

 Midway between the non-coupled and the inner pair of coupled 

 wheels are two pairs of rack pinions in tandem 2 ft. 5J in. apart, 

 driven by a third pinion keyed on a crank axle. This crank axle 

 is driven by a pair of cylinders 10J in. in diameter and 14 in. stroke 

 inside the main frame of the engine. Outside the main frame, 

 and in line with the rack cylinders, is a second pair of cylinders 

 13 in. diameter and 16 in. stroke, which drive the adhesion wheels. 

 The boiler which is 8ft. 4 in. long in the barrel has a tilt of 1 in 20. 

 There are tanks and coal bunkers. The overall breadth of the 

 engine is 8 ft. 6 in. and its height over chimney 10 ft. 6 in. The 

 heating surface is 750 square feet, and the grate area about 16 

 square feet. 



The Government Inspector took two fully loaded vehicles and 

 a brake van, in all 67 tons 14 cwt., or with the engine about 100 

 tons, up 500 ft. on the 1 in 12^ gradient at about 4 miles per hour, 

 the pressure being 175 lbs. to 180 lbs. 



The permanent way proposed by the Abt patentee for the New 

 South Wales lines, has not yet reached the stages of consideration 

 by the Department, and the particulars of it have only been supplied 

 in order that some idea of its character might be before us, in 

 arriving at an estimate. As however, the design is the result of 

 the great experience of the Abt Company in similar cases, it may 

 be, with the above qualification, described in this paper, the 

 gradient in view being 1 in 12J, and the sharpest curve 9 chains, 

 the gauge being, of course, 4 ft. 8 \ in. 



The rails are of the T section 80 fibs, per yard, with fish-plates 

 59 lbs. per pair, fixed by f in. bolts to steel sleepers 7 ft. 10J in. 

 long 3 in. deep of the usual inverted hollow shape, § in. thick. The 

 rack bars three in number, are 4 J in. deep and \\ in. thick, and 



