discontented because he did not see a corresponding increase in his remuneration. From about 1830, when the rapid development of the use of mechanical appliances began, to the late eighties and early nineties when the new regime was meeting its sternest conflicts in the trust problem and the militant labor unions, the army of the wage earner was growing faster than the population. Between 1870 and 1890, for example, the population increased 63 per cent., while the number of laborers engaged in manufacturing increased nearly 130 per cent. By the latter year, 6,099,058 persons, about a tenth of the total population, were employed in transportation, mining and manufacturing. It was noticeable, also, that the wage earners tended to concentrate. The laborers engaged in manufacturing were to be found, for the most part, in the Northeast, and especially in such leading industrial cities as New York, Chicago and Philadelphia. Furthermore, the development of the factory system and the consolidation of many small companies into a few great ones tended to localize the labor problem still further--in a relatively small number of plants. The concentration of industry in great factories where large numbers of workers labored side by side ended the paternal care which the old-time employer had expended upon his employees. With the introduction of machinery, the danger of accidents due to the ignorance or carelessness of fellow workmen increased. The use of mechanical appliances also gave opportunity for the employment of women and children, and thus raised the question whether any restrictions ought to be placed upon the employment of these classes of people. The construction of factories, their ventilation, sanitary appliances, and safe-guards for health and comfort became subjects of importance.