Geological Society. 49 



when in contact with trappaean rocks ; and when they also found 

 these latter rocks possessing all the intrusive characters assigned to 

 them in Europe, — they became satisfied of the insufficiency of the 

 aqueous system, and upon conviction, embraced the igneous theory 

 as affording the only satisfactory solution of such phenomena. 



The student who seeks for further evidence upon this subject, 

 may advantageously consult the Synopsis lately published by Profes- 

 sor Leonhardt of Heidelberg, in which many of the well-authenticated 

 phenomena attesting the effects of igneous action have been grouped 

 in so clear a manner as to leave no escape from the inferences upon 

 which I have been insisting. 



Colonel Sykes, after a long residence in Hindostan, has presented 

 us with a circumstantial account of the structure of the Deccan or 

 hilly region of the Peninsula to the east of Bombay. This tract, 

 it appears, is very similar to the other extremity of the vast trap 

 region which was described by Major Franklin, being exclusively 

 composed of trappaean rocks, which offer many varieties in mineral 

 composition. These rocks rise in tabular forms from low terraces 

 upon the coast, until they attain heights from 4000 to 6000 feet in 

 the interior : the profound chasms by which they are fissured are 

 occupied by the rivers, and their hardest and loftiest protuberances 

 afford those strong natural defences of the natives, known to Euro- 

 peans under the name of Hill Forts. In these step-like table-lands 

 are the remnants of volcanic outbursts of successive periods, pre- 

 senting further analogies to known igneous productions in dykes of 

 columnar basalt which have been injected vertically through the ho- 

 rizontal currents. According to the observations of Colonel Sykes 

 and of his precursors Capt. Dangerfield and Dr. Voysey, these igneous 

 phenomena extend over 250,000 square miles $ so that the mind is 

 almost lost in the contemplation of their grandeur : unfortunately, the 

 relative age of these eruptions must remain for the present undeter- 

 mined, no vestiges of secondary or tertiary formations having been 

 detected within the region described. 



Although that interesting small tract of extinct volcanos the 

 w Eifel," had been partially made known to the English reader by Dr. 

 Daubeny and Mr. Poulett Scrope, an adequate knowledge of it could 

 be obtained only by consulting the works of several German writers*. 

 Our learned associate Dr. Hibbert has now presented us with an 

 account of the same district, under the title of" History of the Ex- 

 tinct Volcanoes of the Basin of Neuwied," to complete which he has 

 devoted two years of assiduous, personal exertion. In recommending 

 this volume to your study, I may express my regret that the author 

 should not have first distinctly laid before us a clear view of the 

 mineral constitution and physical features of the district, and after- 



* While these pages are passing through the press, I learn that Professor 

 Hoffmann, having, on his return from Sicily, studied the relations of the 

 marble of Carrara, has communicated to the Academy at Berlin his opinion, 

 that this marble is of the age of the oolitic series (Jura or Alpine lime- 

 stone), and has been changed by igneous operations similar to those 

 which altered the chalk of Antrim, the lias limestone of Skye, &c. &c. 

 Third Series. Vol. 3. No. 13. July 1833. H 



