“The word employment is merely a concise form of designating toil, trouble, exposure, and fatigue. All these, per se, are evils, and the less of them that is required for obtaining a given amount of subsistence and comfort, -- or, in other words, the greater the facility of obtaining that given amount,--the better, caeteris paribus, will be the condition of the laboring classes; indeed, of all classes in the community.”