While Darwin was still on the voyage, Henslow carefully fostered his former pupil's reputation by giving selected
naturalists access to the fossil specimens and printed copies of Darwin's geological writings. When the Beagle returned on
2 October 1836, Darwin was a celebrity in scientific circles. He visited his home in Shrewsbury and his father organised investments
so that Darwin could become a self-funded gentleman scientist. Darwin then went to Cambridge and persuaded Henslow to work
on botanical descriptions of modern plants he had collected. Afterwards Darwin went round the London institutions to find
the best naturalists available to describe his other collections for timely publication. An eager Charles Lyell met Darwin
on 29 October and introduced him to the up-and-coming anatomist Richard Owen. After working on Darwin's collection of fossil
bones at his Royal College of Surgeons, Owen caused great surprise by revealing that some were from gigantic extinct rodents
and sloths. This enhanced Darwin's reputation. With Lyell's enthusiastic backing, Darwin read his first paper to the Geological
Society of London on 4 January 1837, arguing that the South American landmass was slowly rising. On the same day Darwin presented
his mammal and bird specimens to the Zoological Society. The Mammalia were taken on by George R. Waterhouse. Though the birds
seemed almost an afterthought, the ornithologist John Gould revealed that what Darwin had taken to be wrens, blackbirds and
slightly differing finches from the Galįpagos were all finches, but each was a separate species. Others on the Beagle, including
FitzRoy, had also collected these birds and had been more careful with their notes, enabling Darwin to determine from which
island each species had come.
In London, Darwin stayed with his freethinking brother Erasmus and at dinner parties met inspiring savants who
thought that God preordained life by natural laws rather than ad hoc miraculous creations. His brother's lady friend Miss
Harriet Martineau was a writer whose stories promoted Malthusian Whig Poor Law reforms. Scientific circles were buzzing with
ideas of transmutation of species controversially associated with Radical unrest. Darwin preferred the respectability of his
friends the Cambridge Dons, even though his ideas were pushing beyond their belief that natural history must justify religion
and social order.
On 17 February 1837, Lyell used his presidential address at the Geographical Society to present Owen's findings
to date on Darwin's fossils, noting particularly the unexpected implication that extinct species were related to current species
in the same locality. At the same meeting Darwin was elected to the Council of the Society. He had already been invited by
FitzRoy to contribute a Journal based on his field notes as the natural history section of the captain's account of the Beagle's
voyage. He now plunged into writing a book on South American Geology. At the same time he speculated on transmutation in his
Red Notebook which he had begun on the Beagle. Another project he started was getting the expert reports on his collection
published as a multivolume Zoology of the Voyage of H.M.S. Beagle, and Henslow used his contacts to arrange a Treasury grant
of £1,000 to sponsor this. Darwin finished writing his Journal around 20 June when King William IV died and the Victorian
era began. In mid-July he began his secret "B" notebook on transmutation, and developed the hypothesis that where every island
in the Galįpagos Archipelago had its own kind of tortoise, these had originated from a single tortoise species and had adapted
to life on the different islands in different ways.
Under pressure with organising Zoology and correcting proofs of his Journal, Darwin's health suffered. On 20
September 1837 he suffered "palpitations of the heart" and left for a month of recuperation in the country. He visited Maer
Hall where his invalid aunt was being cared for by her spinster daughter Emma Wedgwood, and entertained his relatives with
tales of his travels. His uncle Jos pointed out an area of ground where cinders had disappeared under loam and suggested that
this might have been the work of earthworms. This led Darwin to the idea for a talk which he gave to the Geological Society
on 1 November, on the unusually mundane subject of worm casts. This work is considered to be the first scholarly treatment
of soil forming processes. He had avoided taking on official posts which would have taken up valuable time, but by March William
Whewell had recruited him as Secretary of the Geological Society. Illness prompted Darwin to take a break from the pressure
of work and he went "geologising" in Scotland. In glorious weather he visited Glen Roy to see the phenomenon known as "roads"
which he (incorrectly) identified as raised beaches.
Fully recuperated, he returned home to Shrewsbury. Scientifically pondering his career and prospects he drew
up a list with columns headed "Marry" and "Not Marry". Entries in the pro-marriage column included "constant companion and
a friend in old age ... better than a dog anyhow," while listed among the cons were "less money for books" and "terrible loss
of time." The pros won out. He discussed the prospect of marriage with his father then went to visit his cousin Emma on 29
July 1838. He did not get around to proposing, but against his father's advice he told her of his ideas on transmutation.
While his thoughts and work continued in London over the autumn he suffered repeated bouts of illness. On 11 November he returned
and proposed to Emma, once more telling her his ideas. She accepted, but later wrote beseeching him to read from the Gospel
of St. John a section on love and following the Way which also states that "If a man abide not in me...they are burned". He
sent a warm reply which eased her concern, but she would continue to worry that his lapses of faith could endanger her hope
that they would meet in afterlife.
Darwin considered Malthus's argument that human population increases more quickly than food production, leaving
people competing for food and making charity useless. He later formulated this in the terms of his biological theory as: "Man
tends to increase at a greater rate than his means of subsistence; consequently he is occasionally subjected to a severe struggle
for existence, and natural selection will have effected whatever lies within its scope." (Descent of Man, Ch.21) He related
this to the findings about species relating to localities, his enquiries into animal breeding, and ideas of Natural "laws
of harmony". Towards the end of November 1838 he compared breeders selecting traits to a Malthusian Nature selecting from
variants thrown up by "chance" so that "every part of newly acquired structure is fully practised and perfected", and thought
this "the most beautiful part of my theory" of how species originated. He went house-hunting and eventually found "Macaw Cottage"
in Gower Street, London, then moved his "museum" in over Christmas. He was showing the stress, and Emma wrote urging him to
get some rest, almost prophetically remarking "So don't be ill any more my dear Charley till I can be with you to nurse you."
On 24 January 1839 he was honoured by being elected as Fellow of the Royal Society and presented his paper on the Roads of