Useful Knowledge have done, and are still doing, more to ruin the Book trade than all the change of times, the want of money, the weight of taxes, and even the law of Libel have accomplished; yet they – a committee of Noblemen and pretended Patriots – are permitted to go on in their unfeeling, nay, considering the hundreds of thousands engaged in the Book trade, we may add brutal, career, without interruption. Activities The SDUK publishing programme began with the Library of Useful Knowledge. Sold for sixpence and published fortnightly, its books focused on scientific topics. Like many other works in the new genre of popular science—such as the Bridgewater Treatises and Humphry Davy's Consolations in Travel—the books of the Library of Useful Knowledge imbued different scientific fields with concepts of progress: uniformitarianism in geology, the nebular hypothesis in astronomy, and the scala naturae in the life sciences. According to historian James A. Secord, such works met a demand for "general concepts and simple laws", and in the process helped establish the authority of professional science and specialised scientific disciplines. The first volume of the Library of Useful Knowledge, an introduction to the series by Brougham on the "objects, advantages and pleasures of science", sold over 33,000 copies by the end of 1829. Despite the initial success of the series, however, it soon became clear that it was too demanding for many readers, and the Society began to offer more varied and attractive publications, starting with the Library of Entertaining Knowledge (1829–38) and the Penny Magazine (1832–45), a lavishly illustrated weekly that achieved unprecedented success, with sales in excess of 200,000 copies in the first year. The scope and scale of the Society's activities expanded further over the following decade, and included the production of a Penny Cyclopaedia (1833–43) in 27 volumes. Although sales of these publications may have been more among the middle- than the working-classes, the Society had a significant role in pioneering "the idea of cheap, improving publications, freely and easily available, well produced and distributed on a scale hitherto unknown," and became iconic of the "March of Intellect". The publisher Charles Knight bears much of the credit for the success that SDUK publications had; he engaged in extensive promotional campaigns, and worked to improve the readability of the sometimes abstruse material. The Society's continuing commitment to the high intellectual standards with which it was conceived