Dr Boue*'s Geological Observations. 91 



These ideas afford a clear explanation of those mixtures of ve- 

 getables and animals of the temperate and torrid zone, that seem 

 at first unintelligible ; they also afford us the key to those centres 

 of creation which have been perceived on the globe, and account 

 for the intimate relations which seem to be established between 

 the geological structure of the earth''s crust, and the geographi- 

 cal distribution of plants and animals, and particularly the acci- 

 dental isolated state of some of them. The fossil conchologist 

 will conclude, a priori, from these propositions, that the more 

 we approach the poles from the equator, the more will the fossil 

 remains be similar or analogous in genera or species, to those at 

 present existing between the tropics. The more recent the for- 

 mations are, the more hope may we have of still finding the ana- 

 logous, or even identical, species of their fossils. But, on the 

 contrary, the more ancient the deposit is, the less reason will we 

 have to expect to find identical, or even analogous, species in the 

 sea or fresh water of the torrid zone ; for this zone perhaps no 

 longer presents all the circumstances necessary for the exis- 

 tence of such beings^ notwithstanding the actual heat of that 

 part of the earth. Lastly, the more recent the formations ob- 

 served in different continents, or in a particular continent, are, 

 the more must their fossils differ from one continent to another, 

 or rather from one zone to another, and also, at the same time, 

 from one basin to another. But the fossils of these various coun- 

 tries will always be in the same relation with respect to the num- 

 ber of the analogous or similar species, with the animals still 

 living in these various localities. These last propositions, de- 

 duced a priori, are conformable to experience, and have been, 

 and will still probably be, ably elucidated by Baron de Ferussac. 



Thus far does geology conduct us. We see with some pride 

 on our side, a Ferussac (see his Geological Ideas on Tertiary 

 Basins, in the Journal de Physique, and his article on the Geo- 

 graphical Distribution of the Mollusca in the Dictionnaire Clas- 

 sique d'Histoire Naturelle, 1825), a Humboldt, (see his Nou- 

 velle Recherches sur la Distribution des Vegetaux, in the Dic- 

 tionnaire des Sciences Naturelles, and his Discours sur les Vol- 

 cans), a Fourier, (Memoires sur la Chaleur Terrestre), a Von 

 Buch, (see his beautiful Memoirs on Trap Porphyries, and those 

 on the Tyrol and Germany, in Leonard's Taschenbuch, 1824), 



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