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The Pamphlet Collection of Sir Robert Stout: Volume 78

Limit of Elasticity

Limit of Elasticity.

Again I must turn to the engineer. In tracing out a rough analogy between the working of the nervous system and the working of machinery, and in trying to find a simple broad fundamental basis for determining on general principles the loads that may be imposed with safety in either case nothing is mere helpful than a consideration of the relationships existing between the "limit of elasticity" and the "breaking strain."

The "breaking strain" is the extreme limit of strength of anything—the point at which it would break down under stress. The "limit of elasticity" is the point at which a material begins to be injured by stress. The "limit of elasticity" should never be reached, though the "breaking strain may be far beyond. The French now fix their "working stress" in relation to the "limit of elasticity," and not in relation to the "breaking strain," because the former is the point at which the material begins to suffer permanent injury, and at which it becomes incapable of perfect rebound and recoporation, though the machine world not actually break down, at the time until subjected to far greater stress -viz., the actual "breaking strain."

What I am asking for in connection with education is practically that when imposing school tasks the teacher shall keep his "working stress" below the estimated "limit of elasticity" of the brain of the average boy or girl, instead of adopting the actual "breaking strain" of the stronger and more capable pupils as the standard for loading. Not only are pupils liable to be loaded to the breaking stain under the existing system, but they may be kept at work after they have actually broken down, as shown by some of Dr Ferguson's cases and by cases of debility in various directions which come under our notice as medical practitioners. When a school-master defending over-pressure, has to admit that "in the sixth form of a secondary school, in the course of a year's work, necessarily certain boys get a good deal fagged," but is satisfied that there is no cause for anxiety, "seeing there are holidays in the year that relieve any pressure," we can only conclude that he takes practically no notice of the most obvious indications of over-pressure. He allows work to go on after a breakdown has actually taken place. Let Mr Wilson submit some of his boys who are "a good deal fagged" at the end of a term to expert medical examination, and he will be afforded proof of my contention. Or let him weigh and measure such pupils from time to time, and he will find out for himself that most of their growth takes place between terms, and that when at school such boys show comparative arrest of development.