CAUSES DETRIMENTAL TO MAKING STEAM.
When an engine is steaming badly, almost the first action of an experienced engineer is to examine the petticoat-pipe. The influence which this pipe exercises on the steaming qualities of an engine has already been adverted to, but its importance can not be too strongly urged upon the attention of the young engineer. It is one of the most successful devices invented for regulating the vacuum in the smoke-box, so that the currents of hot gases shall flow evenly through all the flues. Any thing which interferes to disturb the flow of these currents, crowding them away from any section of the flue-surface, will have a prejudicial effect upon the steam. The pipe may be set too high to produce an even draught, or the fault may be in the opposite direction. Its diameter may not be suitable for the conditions of smoke box and stack, or its shape may be at fault. Not unfrequently the pipe is fastened obliquely, so that the blast impinges on the side of the stack, producing evil results; or the braces which keep it in position occasionally break, and the draught is permitted to shoot in every direction but the direct way to the atmosphere, and the effect is immediately apparent on the steam-gauge.