186 

 GEOLOGICAL COLLECTIONS, 



INCLUDING MINERALOGY. 



Value of Fossil Shells in indicating the relative Geological Epochs of different 



Strata A dispute has arisen between Monsieur Boue and Messrs 



Murchison and Sedgwick, respecting the age of certain deposits at Gossau, 

 which the former classes with the newer secondary, while the latter, from a 

 consideration of their " relations, structures, and fossils," assign them to the 

 tertiary rocks. From the shells, according to Monsieur Boue, it is impossible 

 to determine any thing, since many of them appear to belong to genera 

 hitherto found only in the chalk, and many more to those considered peculiar 

 to the tertiary beds. He confirms his opinion by the result of the researches 

 of Monsieur Dufresnoy into the geology of the South of France and the 

 Pyrenees, who, " after a careful study of all the fossils from the chalk 

 formation of the countries under examination, concludes, that, out of 240 

 species, 40 are species that, until now, were considered as tertiary — a case 

 similar to that of Gossau." The opinion of Monsieur de France, esteemed 

 the most learned conchologist now living, is also quoted by him, and is well 

 deserving the attention of geologists : — " I have collected fossils for a long 

 time," said this excellent man to me, " and hence you would conceive, that 

 the species in my cabinet would increase ; but this is not the case. On the 

 contrary, the more individuals I receive, the more transitions of one species 

 into another I observe ; and, consequently, the number of species become 

 less and less. Each locality appears to possess, not so much its own species, 

 as more frequently its own varieties of every where nearly the same species. 

 This circumstance, too much neglected, makes the best works on fossils 

 only applicable to certain localities. If, on the other hand, we could get 

 together from all parts of the earth all the series of fossils, we would see a 

 great many species from one locality, identify themselves with those of 

 others, because the connecting links would be present. In short, concho- 

 logists do not possess the means of fixing the specific characters, and some- 

 times not even those of the genera ; this can only be done by the study of 

 the animals, without which no one can trace a strict line of separation 

 between the accidental and specific characters of the species of fossils or of 

 shells." — See Dr Boue's paper in Edin. New Phil. Journ. Jan. 1831, p. 

 14—34. 



Heights of Table Lands. 



Toises above the sea. 

 The table land of Iran in Persia, . . 650 



Table land in which Moscow is situated, . 67 



The plain of Lombardy, .... 80 



Table land of Swabia, 

 Auvergne, 

 Schweitz, 

 Bavaria, 

 Spain, 



150 

 174 

 220 

 260 

 350 



These table lands are not longitudinal valleys between ranges of moun- 

 tains. The bottom of a longitudinal valley, which is from 1500 to 2000 

 toises above the sea, as is the case in the Andes, is caused by the elevation 

 of a whole mountain chain. True table lands, such as those of Spain and 

 Bavaria, were probably formed by the upraising of a whole continental mass. 

 Both epochs are geognostically considered different. — Humboldt, — Edin. 

 New Phil. Journ. Jan. 1831. 



