CONTENTS. 



PAGE 



V. Observations on the Petrifaction of Shells in the Me- 



diterranean. By MM. Marcel de Serres and 



L. FiGUIER, ...... 50 



I. On the mode in which Organic Bodies became Petri- 

 fied in Historical and Geological Eras, . 50 



TI. Facts which prove that Petrifactions are now forming 

 in the bosom of existing seas, analogous to those of 

 Geological times, ..... 53 



III. On the progress and different degrees of the Petrifac- 



tion of Shells, ...... 55 



IV. On the Chemical Composition of Shells, considered in 



a fresh and also in a petrified state, during Histo- 

 rical and Geological times, .... 58 



Table of Analyses of Living Shells, and of such as 

 have been petrified in Geological and Historical 

 eras, ....... 59 



Of the Shelly Sandstones now forming in the Medi- 

 terranean, . . . . . .61 



Y. Have the Physical Phenomena of the Ancient World 



any Analogy with the Phenomena now taking place ? 63 



Conclusions, ...... g4 



VI. On the Silurian Rocks of Bohemia, with a few Re- 



marks on the Devonian Rocks of Moravia, in a 

 Letter to Professor Leonhard from Sir Roderick 

 I. MuRCHisoN. With a Plate. Communicated 

 in Manuscript by the Author, through M. Leon- 

 hard, for the Edinburgh New Philosophical 

 Journal, ....... 66 



VIL On the Height of the Aurora Borealis, By G. A. 



Rowell, ....... 79 



VIIL On the Auroi a Borealis. By G. A. Rowell, . 89 



IX. Biographical Sketch of the celebrated Alexander 



Brongniart, ...... 92 



