216 Prof. Hennessy — On the Internal Fluidity of the Earth. 



Jaw of a Fish (? Enchodus), in flint, Ann. Nat. Hist. vol. 19, p. 7. Chalk, Kent. 

 Remains of a Large Fish, undescribed, L. G. J. p. 21, Woodcuts. Chalk, Kent. 



LIST OF WORKS REFERRED TO. 



Baker, Hist. Northampt. History and Antiquities of the County of Northampton, 



by George Baker. 

 Dixon, F. S. Fossils of the Tertiary and Cretaceous Formations of Sussex, by 



Frederick Dixon. 

 D. and M. Pal. Palseontographica. Beitrage zur Naturgeschichte der Vorwelt, 



herausgegeben von Wilhelm Dunker und Hermann von Meyer. 

 F. O. R. S. Palaeontographical Society, Monograph of the Fishes of the Old 



Red Sandstone, by James Powrie and E. Ray Lankester. 

 Geol. Mag. Geological Magazine. 

 Geol. The Geologist. 



Icon. F. S. Icones Fossilium Sectiles, by Charles Konig, 1825. 

 J. G. S. Quarterly Journal of the Geological Society of London. 

 King, Perm. Foss. Palseontographical Society, Monograph of the Permian 



Fossils of England, by William King. 

 Kon. A. F, Description des Animaux Fossiles qui se trouvant dans le terrain 



Carbonifere de Belgique, par L. de Koninck. 

 L. and B. Jahrb. Neues Jahrbuch fiir Mineralogie, Geology, und Petrefakten- 



Kunde, herausgegeben von K. C. von Leonhard und H. G. Bronn. 

 L. G. J. The London Geological Journal, 1846, 7. 

 Mant. F. T. F. Illustrations of the Geology of Sussex, the Fossils of Tilgate 



Forest, by Gideon A. Mantell. 

 Mant. G. S. The Fossils of the South Downs, or Illustrations of the Geology of 



Sussex, by Gideon A. Mantell. 

 M. G. S. Memoirs of the Geological Survey of Great Britain. 

 Mag. Nat. Hist. The Annals and Magazine of Natural History. 

 Nat. Vert. IIoU. Wet. Naturkundige Verhandelingen van de Hollandsche Maat- 



schappij der Wetenschappen in Haarlem. 

 Pesch. Lab. Monografia dei Pharyngodopilidse studi Palseontologici del Del. 



Cav., Prof Igino Cocchi, 1864. 

 Phil. Trans. Philosophical Transactions of the Royal Society. 

 P. F. Recherches sur les Poissons Fossiles, par Louis Agassiz. 

 P. F. V. G. R. Poissons Fossiles du Vieux Gres Rouge, par Louis Agassiz. 

 P. F. d'Oen. Description de quelques nouvelles especes de Poissons Fossiles des 



Calcaires d'eau douce d'Oeningen, par T. C. Winkler. 



nsroTzoiES oip Dvcisnynoiias. 



I. — The Internal Fluidity or the Eauth.^ 



The following is a translation of a letter addressed by Professor 

 H. Hennessy, F.R.S., to tlie Secretary of the Academy of Sciences of 

 Paris, which has appeared in the Comptes Bendus for March the 6th : 



" On the 13th of July, 1868, M. Delaunay made a communication 

 to the Academy, in which he treats of the rotation of the earth con- 

 sidered as a hollow shell inclosing a nucleus of fluid matter. By a 

 simple train of reasoning he was led to conclude that the very slow 

 motions of rotation which produce the phenomena of precession and 

 nutation of the earth's axis would take place as if the whole earth 

 were absolutely solid, and therefore that the phenomena of preces- 

 sion and nutation could not afford any foundation for an estimate of 

 the thickness of the solid crust of the globe. When 1 read M. 

 Delaunay's paper in the Comptes Bendus, I was much pleased to find 

 1 Communicated by Prof. E. Hull, F.E.S., etc. 



