Accepting this view is no barrier to progress. It will not ultimately delay the work of a reformer if he is induced to act in accordance with this principle. It only prevents a wreck. The knowledge of the force of habit of man should therefore be used in two ways: First, when the designer is trying to make the most natural machine for the purpose. Then he must overcome his own tendency to follow precedent. Second, when considering the kind of a machine that can be easily made, sold, and used, he must give due consideration to the inertia of others, for their inertia he cannot hope to quickly change. Reformers in this world generally have a hard time whenever they under estimate the inertia of men's minds and bodies. A designer of machinery, by close application to his tasks, should obtain a clearer view than it is possible for others to possess, of the way a machine should be designed, made, and used. It is not necessary to assume he has a better brain. An ordinary mind applied to a given subject sees it more clearly than an abler mind which has not considered the subject with the right interest. Inventions Should Not Mix With Details. In first working out the mechanical schemes no energy should be wasted in trying to make the sketches correct in proportion. The very functioning of the brain along the draftsman's line shifts it away from the inventive mood. The exact drawing frequently shows the necessity of change in general scheme, but that is only one of the after-steps. The fundamental idea is the starting-point, and must be sketched out as fully as possible without losing the very frail thread of thought. A clear view of the scheme is not to be obtained on demand. The schemer must wait in patience, as the astronomer waits for steady air, and, like the astronomer, he must have every facility in shipshape. The clear view is only clear to the watching eye. The coast-wise skipper in making a fog-bound harbor will see a buoy through a slight shift in fog, while a landsman might look in vain. The wanderer in the happy dreamland of mechanical scheming must not be looking for complete drawings, specifications, and working model of the invention he wishes to bring into the breathless and waiting world. He must be looking through the mist of the thickened senses as the skipper looks through the fog. The buoy and the scheme may be never so faintly shown, but yet with sufficient clearness to give a positive guide for the course. Inventive schemes cannot be forced by strenuous effort. Such effort may result in slight refinements of a given type, but never would have invented the DeLaval or Tesla turbine.