TRANSACTIONS OF THE GEOLOGICAL SOCIETY OF LONDON. SECOND SERIES. VOLUME V.- PART THE SECOND. Quod si cui mortalium cordi et curse sit, non tantum inventis hserere, atque iis uti, sed ad ulteriora penetrare; atque non disputando adversarium, sed opere naturam vincere; denique non belle et probabiliter opinari, sed certo et ostensive scire; tales, tanquam veri scientiarura filii, nobis (si videbitur) se adjungant. Novum Organum, Preefatio. LONDON: PRINTED BY R. AND J. E. TAYLOR, RED LION COURT, FLEET STREET. SOLD AT THE APARTMENTS OF THE GEOLOGICAL SOCIETY, SOMERSET HOUSE. 1840. OFFICERS AND COUNCIL OF THE GEOLOGICAL SOCIETY OF LONDON. 1839- PRESIDENT. Rev. WILILAM BUCKLAND, D.D., Professor of Geology and Mineralogy in the University of Oxford. VICE-PRESIDENTS. GEORGE BELLAS GREENOUGH, Esq. F.R.S. Rev. ADAM SEDGWICK, M.A., F.R.S. F.L.S., F.L.S. Woodwardian Professor in the University of LEONARD HORNER, Esq. F.R.S. L. & E. Cambridge. CHARLES LYELL, Jun., Esq. M.A. F.R.S. & F.L.S. SECRETARIES. CHARLES DARWIN, Esq. B.A. F.R.S. | WILLIAM JOHN HAMILTON, Esq. FOREIGN SECRETARY. HENRY THOMAS DE LA BECHE, Esq. F.R.S. F.L.S. TREASURER. JOHN TAYLOR, Esq. F.R.S. COUNCIL. CHARLES GILES BRIDLE DAUBENY,M.D. WILLIAM HALLOWS MILLER, Esq. M.A. F. R. S. & F.L. S., Regius Professor of Botany, and F.R.S., Professor of Chemistry in the University Aldrich's Professor of Chemistry in the University of Cambridge. of Oxford. RODERICK IMPEY MURCHISON, Esq. Sir PHILIP DE MALPAS GREY EGERTON, F.R.S. & F.L.S. Bart. M.P. F.R.S. RICHARD OWEN, Esq. F.R.S.& F.L.S., Hun- WILLIAM HENRY FITTON, M.D. F.R.S. terian Professor of Anatomy in the College of & F.L.S. Surgeons. ROBERT EDMUND GRANT, M.D. F.R.S. L. Sir WOODBINE PARISH, K.C.H. F.R.S. and & E. & F.L.S., Professor of Comparative Ana­ F.S.A. tomy and Zoology, University College, London. GEORGE RENNIE, Esq. F.R.S. WILLIAM HOPKINS, Esq. M.A. F.R.S. Rev. WILLIAM WHEWELL, B.D., F.R.S., ROBERT HUTTON, Esq. M.P. M.R.I.A. Professor of Casuistry in the University of Cam­ Sir CHARLES LEMON, Bart., M.P. F.R.S. bridge. CURATOR AND LIBRARIAN. WILLIAM LONSDALE, Esq. ADVERTISEMENT. THE Editors of the Transactions of the Geological Society are directed to make it known to the Public, that the Authors alone are respon­ sible for the facts and opinions, contained in their respective papers. It is requested that all letters and communications to the Secretaries, and presents to the Society, may be addressed to the Apartments of the Geological Society, Somerset House, London. .