PHYSICAL GEOGRAPHY, 291 



completely separated from one another. There is a great 

 similarity 'in South America and Australia between still living 

 and extinct species of animals. In New Holland fossil 

 remains of the kangaroo have been found, and in New Zea- 

 land the semi-fossilised bones of an enormous bird, resembling 

 the ostrich, the dinornis of Owen,* which is nearly allied to 

 the present apteryx, and but little so to the recently extinct 

 dronte (dodo), of the Island of Rodriguez. 



The form of the continental portions of the earth may, 

 perhaps, in a great measure, owe their elevation above the 

 surrounding level of the water to the eruption of quartzose 

 porphyry, which overthrew with violence the first great vege- 

 tation, from which the material of our present coal measures 

 was formed. The portions of the earth's surface which we 

 term plains are nothing more than the broad summits of hills 

 and mountains, whose bases rest on the bottom of the ocean. 

 Every plain is, therefore, when considered according to its 

 submarine relations, an elevated plateau, whose inequalities 

 have been covered over by horizontal deposition of new sedi- 

 mentary formations, and by the accumulation of alluvium. 



Among the general subjects of contemplation appertaining 

 to a work of this nature, a prominent place must be given, 

 first to the consideration of the quantity of the land raised 

 above the level of the sea, and next to the individual configu- 

 ration of each part, either in relation to horizontal extension 

 (relations of form), or to vertical elevation, (hypsometrical 

 relations of mountain- chains.) Our planet has two envelopes, 

 of which one, which is general the atmosphere is composed 

 of an elastic fluid, and the other the sea is only locally dis- 

 tributed, surrounding, and therefore modifying, the form of the 

 land. These two envelopes of air and sea constitute a natural 

 whole, on which depend the difference of climate on the earth's 

 surface, according to the relative extension of the aqueous and 

 solid parts, the form and aspect of the land, and the direction 

 and elevation of mountain chains. A knowledge of the reci- 

 procal action of air, sea, and land, teaches us that great 

 meteorological phenomena cannot be comprehended when 

 considered independently of geognostic relations. Meteor- 



* [See American Journal of Science, vol. xlv. p 187; and Medal* 

 of Creation, vol. ii. p. 817 ; Trans. Zoolog. Society of London, voL ii * 

 Wonders ?/ Geology, vol. i. p. 129.] Tr. 



