ABSTRACT OF PROCEEDINGS. XXV1U 



prevent free passage for locomotive stock between the railway 

 systems, connected by the rack. And there is also the greater 

 special precautions as to brakes etc., which would be required. 

 When grades are easier than about 1 in 25, the difficulties of want 

 of adhesion diminish so much, that the extra complication of the 

 rack makes its adoption of doubtful advantage. The question of 

 the easy entry of the engine into the rack, of vertical curves, of 

 special care in construction and maintenance, of points and cross- 

 ings, of brakes, of precautions against creeping, of disadvantages 

 of sharp curvature, of safety sidings, and of speed are fully 

 discussed. 



Two systems of working have been applied to lines of which a 

 rack length forms a part, that of having one or more special 

 engines to work the rack part only, and that of having combined 

 rack and adhesion engines working the whole or neighbouring 

 systems, using the pinions only on the rack division, and the rela- 

 tive advantages and otherwise of these are entered into. 



In many cases the alternative presents itself of adopting for the 

 ascent of a given height, a comparatively long but easily graded 

 adhesion line, or a short and steep rack one, this being the phase 

 of the question which only, up to the present, has had to be con- 

 sidered in this colony. These alternatives are carefully discussed 

 in the paper, the author deprecating the frequent practice, in 

 published papers and discussions, of comparing results from trials 

 of various rival systems, in all branches of engineering, under 

 totally different conditions, and made in different localities, as 

 wholly misleading, not only on that account, but because generally 

 omitting the personal element, on which so much of success or 

 failure depends. The author comes to the conclusion that as a 

 rule, if the same load has to be lifted the same height, in the same 

 time, on two such lines, the working expenses cannot greatly 

 differ, as the mechanical effort is the same, and items of working 

 expenses not affected by this tend to neutralize one another, the 

 greater length of the one line going against the extra repairs, 

 mile for mile, of the other. Hence the relative cost of construc- 

 tion must be the main guiding factor. 



