Little is known of Burton's activities between 1825 and 1834: he disappeared into the Egyptian desert for nine years until his father stopped his allowance and he was compelled to return to London in 1834. None of his explorations from this period have been published, but the papers of his Egyptologist companion George Greenough, which are kept at University College, London, provide information about Burton's life: ""Besides his black slaves before mentioned he has a young Greek purchased by a Scotch renegade by the name of Osman"", wrote Sheffield, another Egyptologist. At a birthday celebration for Charles Humphrey, Burton drank 'till he fell off his chair'. Burton was described as having 'a superb French bed with a long looking glass' and spending almost all of his time in 'coffee, smoking and drinking spiritous mixtures' in 'his divan - his harem'. Burton contracted ophthalmia, lumbago, liver problems, and a scorbutic infection, and consumed opium 'to so great a degree' that his friends feared his 'speedy madness or death'. Burton lost weight and expected to live no longer than five years: one of his friends wrote of him, 'He is reduced to a mere skeleton'.