A dissertation on the sources of malignant bilious, or yellow fever, and means of preventing it : submitted to the examination of the Rev. John Ewing, S.T.P. provost; the trustees & medical faculty, of the University of Pennsylvania, on the sixth day of June, 1799, for th degree of Doctor of Medicine. By William G. Chalwill, of Tortola, member of the Philadelphia Medical and Chemical Societies.