Richard A. Fortey reviews Charles Darwin, Geologist, by Sandra Herbert, in the Times Literary Supplement:
In 1838, Charles Darwin wrote in his Notebook M, “I a geologist have illdefined [sic] notion of land covered with ocean, former animals, slow force cracking surface &c truly poetical”. When the young naturalist set forth on the Beagle late in 1831 he thought of himself not as a biologist, but as a geologist first and foremost. Our subsequent picture of him has been altogether coloured by the overwhelming impact of The Origin of Species, which was not published until 1859. But for a dozen years or so Charles Darwin was mostly concerned with geological problems, and it was a geological underpinning that led to much of what was most original in his subsequent work on evolution.
Sandra Herbert charts these early years – the era before Darwin became plagued by ill health and turned into the Sage of Down. This was a young man bursting with vigour, and not immune to poetical thoughts (years later he was to confess a little ruefully that he latterly preferred novels to the poetry of his youth). He was a naturalist let loose upon a world of uncharted wonders – flexible and fervent with enthusiasm, but already blessed with the dedicated, systematic approach to collections and observations which would so unfailingly serve him in the years to come.
More here.