On this head, as regards the requirements of industry in the way of general information on the part of the skilled workmen, the contrast is sufficiently marked, _e. g._, between Elizabethan times and the Victorian age. At the earlier period illiteracy was no obstacle to adequate training in the skilled trades. In the seventeenth century Thomas Mun includes among the peculiar and extraordinary acquirements necessary to eminent success in commerce, matters that are now easily comprised in the ordinary common-school instruction; and in so doing he plainly shows that these acquirements were over and above what was usual or would be thought useful for the common man. Even Adam Smith, in the latter half of the eighteenth century, shrewd observer as he was, does not include any degree of schooling or any similar pursuit of general information among the requisites essential to the efficiency of skilled labour. Even at that date it appears still to have been true that the commonplace information and the general training necessary to a mastery of any one of the crafts lay within so narrow a range that what was needful could all be acquired by hearsay and as an incident to the discipline of apprenticeship. Within a century after the first inception of the machine industry illiteracy had come to be a serious handicap to any skilled mechanic; the range of commonplace information that must habitually be drawn on in the skilled trades had widened to such an extent, and comprised so large a volume of recondite facts, that the ability to read came to have an industrial value; the higher proficiency in any branch of the mechanic arts presumed such an acquaintance with fact and theory as could neither be gained nor maintained without habitual recourse to printed matter. And this line of requirements has been constantly increasing in volume and urgency, as well as in the range of employments to which the demand applies, until it has become a commonplace that no one can now hope to compete for proficiency in the skilled occupations without such schooling as will carry him very appreciably beyond the three R’s that made up the complement of necessary learning for the common man half a century ago. It follows as a consequence of these large and increasing requirements enforced by the machine technology that the period of preliminary training is necessarily longer, and the schooling demanded for general preparation grows unremittingly more exacting. So that, apart from all question of humanitarian sentiment or of popular fitness for democratic citizenship, it has become a matter of economic expediency, simply as a proposition in technological efficiency at large, to enforce the exemption of children from industrial employment until a later date and to extend their effective school age appreciably beyond what would once have been sufficient to meet all the commonplace requirements of skilled workmanship.[140]