His reading over the summer of 1827, and his trouble with medical school, seem to have convinced Darwin that the life of a country parson was the life for him. He decided to go to the University of Cambridge to study for the clergy. There, unlike at Edinburgh, he was required to sign the "Thirty-Nine Articles," a statement of faith in the Anglican creed, which he did willingly albeit not without some doubts. Although his grandfather Erasmus had been a staunch dissenter and agnostic, a couple of generations of success had weakened the Darwin resolve against religion. Later in life Darwin's doubts would lead him to a fiercely atheistic position, but for now he was willing to make peace along with the prevailing faith.
At the beginning of 1828 Charles headed to Cambridge. He found a place to live on Sidney Street above a tobacconist's store. The summer of 1828 was spent in Barmouth, Wales, with classmates from Cambridge. Their goal was to study with private tutors for three months to allow Charles to focus on mathematics. But he soon found himself taking solitary walks and leading group expeditions out into the countryside and along the coast, showing his new friends at Cambridge all he know about insects and wildlife. Meanwhile, the math languished. He continued to correspond on the subject of beetles with his cousin William Darwin Fox, whom he visited towards the end of the summer. As usual, he also made stops at Woodhouse, Maer, and the Mount. His doubts about his willingness to commit himself to a religious life were increasing, but were not yet powerful to prevent him from returning the Cambridge in the fall of 1828 and devoting himself, with some success, to his studies. The year went uneventfully: he continued to study, to collect beetles, and to take the occasional holiday trip home to The Mount.
Darwin spent the summer of 1829 in Shrewsbury, but took a brief break to study insects in Wales. Unfortunately his lips became painfully inflamed, for some unknown reason, so his trip was cut short and he returned to The Mount to recuperate. He took brief trips to socialize and hunt at Woodhouse and Maer. At Woodhouse he was particularly happy to see Fanny Owen, with whom he'd had a long flirtation, but it was starting to become clear that what little fire there had been between them was slowing going out of their relationship. A year later, she would be happily engaged to someone else.
While Charles was at Cambridge, Erasmus, who had been working in London as a doctor, retired at the age of 25. He and his father agreed that his "delicate frame" was not suited to the hard work of medicine. Erasmus retired with a pension to a flat in London, where he established a wide circle of friends in the literary, scientific and medical communities.
At Cambridge in the fall of 1829, Charles enjoyed an increasingly close relationship with a professor of botany, John Henslow. He took Henslow's courses, went on long walks with him, and faithfully attended the Friday night soirees at Henslow's house where scientists and students gathered to chat about school and science. Under Henslow's direction, he began a microscopic study of pollen.
As at Edinburgh, Charles was happier collecting and exploring than studying. The first step towards a Bachelor of Arts degree was the "Little Go," a test of classical and theological knowledge. Charles had a poor background in both fields, but he studied Greek and Latin, and read texts such as Paley's Evidences of Christianity, which argued that the wonders of nature were clear evidence of an intelligent and benign Creator. On March 25, 1830, he was ecstatic to learn that he had passed the "Little Go." The summer of 1830 went much as the previous summers had. He spent time at The Mount hunting and collecting, visited his cousin William Darwin Fox, and fished and collected beetles.
At Cambridge in the fall, Charles dedicated himself to his work. He was intent on graduating in the spring and was slightly worried that he might not. His time spent outside of class with Henslow was educating and rewarding, but he would not be tested on botany or beetles; instead, he would have to write on Homer, Virgil, Locke, Paley, mathetmatics, and physics. He studied assiduously until the three-day test in January 1831, and passed with flying colors. He was ranked 10th out of 178 students. The major hurdle had been crossed, but he lingered in Cambridge until June in order to fulfill his residence requirement.
That spring and summer, he started dreaming about a trip to the tropics to study local geology and botany. He planned to visit Tenerife in the Canary Islands, and recruited Henslow and several students to accompany him. He even managed to convince his father to contribute 200 pounds towards the journey. But after an August spent doing geological research with Professor Adam Sedgwick in North Wales, he was shocked to learn that one of his would-be traveling companions had died unexpectedly, and his plans for the Canary Islands along with him. He returned to The Mount with no clear plans for the future, except for a vague desire to become a parson-naturalist in some country parish, where he could live quietly and continue his newfound passion for collecting and observing. Instead, he found upon his return a letter that changed his life. He had been invited to serve as the resident naturalist on board the HMS Beagle for a two-year journey to South America and around the world. His dream of seeing the tropics was coming true after all.