Defects in hearing can be easily determined by means of an "acoumeter." This little instrument measures the acuteness of the hearing very accurately by means of shot dropped from varying heights upon strips of glass, copper and cardboard. Tests with this device indicate whether the subject's hearing is above or below normal. [Sidenote: _Mental Friction and Inner Whirlwinds_] _Stop wasting your energy._ Heretofore you have used your powers in a more or less haphazard way, with a vast amount of waste and no efficient direction. From now on you are to exercise more intelligence in this respect and make all your energies contribute to your business progress and your personal success. You are losing power in fruitless outward activities. You are losing power in the thinking of useless thoughts. You cannot stop the ceaseless activity of the mind. But you can conserve its forces by directing them into channels that are worth while. You are losing power in a turmoil of inward mental strains and inharmonies. Catch yourself at some moment when you are forging ahead in a crowded day's work. You will then see what an inner whirlwind of excitement is in progress, what stresses and strains are at work, what contrary impulses, what frictions and obstacles are being overcome. Now, to the engineer every one of these words--friction, obstacle, strain--spells loss of efficiency, and in this _Course_ we shall teach you how you may do away with antagonistic impulses, may bring your combined mental forces to bear upon the common enemy, and may hurl yourself into the struggles of business and practical life with a joyful and headlong impetuosity that no obstacle can withstand. [Sidenote: _Prominent Traits of Great Achievers_] Professor Walter Dill Scott, of Northwestern University, has said: "In studying the lives of contemporary business men, two facts stand out pre-eminently. The first is that their labors have brought about results that to most of us would have seemed impossible. Such men appear as giants in comparison with whom ordinary men sink to the size of pygmies. The second fact, which a study of successful business men (or any class of successful men) reveals, is that they never seem rushed for time. "Such men have time to devote to objects in no way connected with their business. It cannot be regarded as accidental that this characteristic of mind is found so commonly among successful men during the years of their most fruitful labor. According to the American ideal, the man who is sure to succeed is the one who is continuously 'keyed up to concert pitch'--who is ever alert and is always giving attention to his business or profession."