A 'generational theory', with phases running in fairly well-defined thirty-year cycles, has been applied to the development of the British children's book from the first attempts to write its history. The evangelical best-selling authors for children like Sherwood and Cameron have, with Hannah More, been relegated to the canon's fringes because of conservative politics. The strongly utilitarian bent of early Victorian children's book publishing is most closely associated with the works of 'Peter Parley'. The presence of the re-engravings represents a wholesale incursion into the publishing industry of the 1840s and 1850s of influences from Europe, and especially Germany. By the end of the 1850s all the elements were in place that would characterise children's books as a genre down to the coming of the electronic revolution of the late twentieth century. Population growth and increased life-expectancy continued to enlarge readership during this period, and the level of literacy rose steadily as well.