More of interest from Charles A. Hamm, Mind and Hand:

It is easy to juggle with words, to argue in a circle, to make the worse appear the better reason, and to reach false conclusions which wear a plausible aspect. But it is not so with things. If the cylinder is not tight the steam engine is a lifeless mass of iron of no value whatever. A flaw in the wheel of the locomotive wrecks the train. Through a defective flue in the chimney the house is set on fire. A lie in the concrete is always hideous; like murder, it will out. Hence it is that the mind is liable to fall into grave errors until it is fortified by the wise counsel of the practical hand.