88 C. O. BUKGE. 



are If in. apart, set in cast iron chairs, with two jaws 2 J in. high, 

 through which, and the three racks, f in. bolts pass. The base of 

 the chair, which is 9f- in. wide, is attached to the sleeper by J in. 

 bolts. In this case also the dimensions given are in millimetres, 

 and have been converted into the nearest fraction of an inch. 



In the Mount Morgan 3 ft. 6 in. line in Queensland, which is also 

 a comparatively recent work, the maximum grade is 1 in 16£, on 

 which there are 10 chain curves, and the engines used are four wheel 

 coupled, with rear truck, having adhesion cylinders and valve 

 gear outside and rack cylinder and mechanism inside, this latter 

 being arranged with four pinions for double rack bars. The 

 adhesion cylinders are 11 J in. diameter, stroke 20 in., driving two 

 pairs coupled wheels 3 ft. diameter, with a base of 6 ft. 3 in. The 

 rack cylinders are 11J in. diameter and 15 J in. stroke, and the 

 diameter of the pinions at pitch line is 22- 1 2 - 6 - in. The heating sur- 

 face is 454 J square feet, and the grate area 11-28 square feet. 

 The weight of the engine is 26 tons 17 cwt. in working order, and 

 it takes 50 to 60 tons besides its own weight, up the incline of 1 

 in 16|. 



In the Strub system of rack, which has chiefly come into promin- 

 ence by its adoption for the ascent of the Jungfrau metre gauge 

 electric line, there is only one rack, but it is of very strong section 

 forming a heavy central cogged bar 2§ in. thick, and it is of special 

 design in order to throw off accummulation of snow and prevent 

 lodgement of ice, which was specially necessary in that case. To 

 guard against consequence of breakage a very powerful grip brake, 

 which will be referred to later, is in use. There is a grade of 1 

 in 4 on this line, full particulars of which are given in the Bulletin 

 of the International Railway Congress for May 1899. 



The grades dealt with by the rack system seldom exceed 1 in 4, 

 but there is one of 1 in 2 built on the Locher system, in which 

 the racks are horizontal, extending outward from a central rail, 

 the pinions being horizontal. Except under special circumstances 

 such as light weighted tourist traffic, nothing steeper than 1 in 10 

 should be used, in fact in regard to a line, now under survey in 



