Light and Heavy Engines.

In the report of the Paterson and Symington Commission and later in the report of the Select Committee of the Provincial Council, reference is made to the running of the heavier engines on the South line. The engines ordered for this line were of the same type and weight as those then running on the Lyttelton line. In view, however, of the increase of goods tonnage, and the consequent desirability of separating the haulage of the passenger and goods traffic, particularly on the Lyttelton line, it had been decided to obtain a lighter class of engine for the passenger work. Two of these engines were received in June, 1868. The Commission recommended that these lighter engines be used on the South line. They attributed damage which they found in the rails of that line to the weight of the engines used, as well as to the weakness of the formation and indifferent and insufficient ballast. The heavier engines weighed approximately 30 tons and were of 2—4—0 type, with 15 £ 22 cylinders and driving wheels of 5ft. 6in. diameter. The weight of an engine of 30 tons of the class mentioned with the weight distributed over three axles would not be considered excessive for a 651b. rail, but it had been stated that the page 46 rails were originally laid flat on the sleepers without the adzing of later practice, giving the rails the slight inward cant provided in the chair track of the standard of the Lyttelton line. In that case the oscillation due to the running of engines with coned wheels on a flat rail would contribute to the damage reported. Such a result is mentioned in the discussion of a paper on “The Railways of India,” read before the Institute of Civil Engineers in February, 1873.

The two smaller engines, each weighing approximately 24 tons, had 14 £ 22 cylinders and 5ft. Oin, driving wheels with the 0—4—2 wheel arrangement.