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Rh but bogies, springs and slide valves would be allowed to run 20,000 miles between each periodical examination. Before the engine is sent into the principal shops for heavy repairs, a special report is sent there some weeks in advance, giving full particulars of the condition of the principal portions, so that the new parts are ready and no unnecessary delay occurs after the engine has been sent in.

An engine may be in service from one to two years between its visits to the principal shops. The time depends upon the class of engine, the service upon which it has been employed, the mileage run, and the general condition in which it is.

Boiler. The boiler requires more supervision than any other part of the locomotive, and is the most expensive in the matter of upkeep. Sir John Aspinall, an eminent locomotive engineer, once made a statement which will be endorsed by every locomotive man that “there was only one thing which caused trouble, namely, the boiler. The engine part was quite satisfactory, and never gave any trouble, but the boiler was an everlasting trouble.”

To make a thorough examination of the boiler, the tubes are withdrawn, and the incrustation due to the water is removed from the plates by means of suitable chipping tools, in the use of