Unaware that disappointment was going to be a continuing feature of his life, Mantell continued hunting for fossils—he found another giant, the Hylaeosaurus, in 1833—and purchasing others from quarrymen and farmers until he had probably the largest fossil collection in Britain. Mantell was an excellent doctor and equally gifted bone hunter, but he was unable to support both his talents. As his collecting mania grew, he neglected his medical practice. Soon fossils filled nearly the whole of his house in Brighton and consumed much of his income. Much of the rest went to underwriting the publication of books that few cared to own. Illustrations of the Geology of Sussex , published in 1827, sold only fifty copies and left him 300 pounds out of pocket—an uncomfortably substantial sum for the times.
In some desperation Mantell hit on the idea of turning his house into a museum and charging admission, then belatedly realized that such a mercenary act would ruin his standing as a gentleman, not to mention as a scientist, and so he allowed people to visit the house for free. They came in their hundreds, week after week, disrupting both his practice and his home life. Eventually he was forced to sell most of his collection to pay off his debts. Soon after, his wife left him, taking their four children with her.
Remarkably, his troubles were only just beginning.