‘The mad fancy has seized me’, wrote Humboldt to the German diplomat Karl Varnhagen von Ense in autumn 1834, ‘of representing in a single work the whole material world’ (Humboldt 1860: 15). It would contain

Humboldt's final, magisterial, work, Kosmos, was arguably the greatest holistic narrative of the natural world to be written in the nineteenth century. It was not just its content that was so ambitiously all-embracing. By employing a ‘lively’ style, Humboldt deliberately aimed his work at scientific specialists and general readers alike. Knowledge, he recog¬nised, could never be divorced from the techniques of its presentation. Yet even for an experienced author like Humboldt, writing a work such as Kosmos was fraught with difficulty. ‘The besetting sins of my style are’, he confessed to Varnhagen von Ense, ‘an unfortunate propensity to poetical expressions, a long participial construction, and too great concentration of various opinions and sentiments in the same sentence’; these were evils, he reflected, that only a strict agenda of simplicity could remedy (Humboldt 1860: 19).

Like Humboldt, Darwin was obsessed with style. ‘Some are born with a power of good writing,’ he wrote to the entomologist Henry Walter Bates in December 1861. ‘Others like myself’, he continued:

Darwin's concern to be direct and clear underpinned the conviction that language should facilitate the communication of scientific ideas, making them comprehensible to a range of different audiences.