SLIPPERY ENGINES.
These remarks apply to ordinary engines with ordinary rail-conditions. Occasionally we find an engine inveterately given to slipping, and no conditions seem able to keep it down. Such an engine is as ready to whirl its wheels as an ugly mule is to kick up its heels, and upon as little provocation. With a dirty, half-wet rail, an engine of this kind loses half its power. The causes that make an engine bad for slipping are various. Very hard steel tires, or excess of cylinder power, are the most frequent causes of slipping; but badly worn tires sometimes produce a similar effect; or the blame may rest in a short-wheel base, deficient in weight, or in too flexible driving-springs. To get a slippery engine over the road when the rails are moist and dirty, requires the exercise of unmeasured patience by the engineer. Job was a cantankerous old Arab beside the engineer who passes cheerfully through this ordeal. The tendency of an engine to slip may be checked to some extent by working with the lever well ahead towards full stroke, and throttling the steam. This gives a more uniform piston-pressure than is possible while working expansively. Of two evils, it is best to choose the least. The smallest in this case is losing the benefits of expansion, and getting over the road.