94 C. O. BURGE. 



delivering them over to other ordinary engines at the top, and 

 vice versa, or possibly where the grade is not very severe, for the 

 ordinary engine also to go through, assisting the rack one by 

 adhesion only, even if the power exerted by the latter is only 

 sufficient to take itself up. This system only works economically 

 when the traffic is sufficient to employ fully the special rack 

 engines, and if the grade is severe, it has the disadvantage of 

 isolating from one another, as far as ordinary locomotive stock is 

 concerned, the railway systems, if there are such, at each end of 

 the incline. 



The other plan is to provide locomotives which combine the 

 pinion and the adhesion principles, so as to be thoroughly effective 

 in both, in order that they may go through, gearing the pinion 

 when required in addition to their adhesion work, which latter up 

 fairly steep grades will share the work to a small extent, in good 

 weather. This system appears to gain more favour, as it is subject 

 only to the comparatively minor defect of carrying the useless 

 mechanism of the pinions, and the weight incident to them, over 

 a possibly considerable mileage of easy grading where it is not 

 wanted. 



In many cases the alternative presents itself of adopting for the 

 ascent of a given height, a comparatively long adhesion line, or a 

 short and steep rack one, and this is the phase of the question 

 which only, up to the present, has had to be considered in this 

 Colony. So that it becomes interesting to ascertain as nearly as 

 possible, where both these methods are practicable, which is 

 economically the best. 



An actual comparison from experience which would be trust- 

 worthy is out of the question for no two lines have the same data 

 or are under similar conditions. An attempt was made at this in 

 a paper by Mr. R. Wilson 1 as regards the cost of raising and 

 hauling 1,000 foot tons by the rack system on the Hartz Moun- 

 tain Railways, and on the Semmering incline with adhesion 



1 Institution of Civil Engineers, Min. Proc, Vol. xcvi. 



