PHYSICAL GEOGRAPHY. 287 



size.* Ill the silurian epoch, as well as in that in which the Cy- 

 cadeee flourished in such abundance, and gigantic saurians were 

 living, the dry land, from pole to pole, was probably less than it 

 now is in the South Pacific and the Indian Ocean. We shall 

 see, in a subsequent part of this work, how this prepondera- 

 ting quantity of water, combined with other causes, must have 

 contributed to raise the temperature and induce a greater uni- 

 formity of climate. Here we would only remark, in consider- 

 ing the gradual extension of the dry land, that, shortly before 

 the disturbances which at longer or shorter intervals caused 

 the sudden destruction of so great a number of colossal verte- 

 brata in the diluvial 'period, some parts of the present conti- 

 nental masses must have been 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 Zealand the semi-fossilized bones of an enor- 

 mous bird, resembling the ostrich, the dinornis of Owen, f which 

 is nearly allied to the present apteryx, and but little so to the re- 

 cently extinct dronte (dodo) of the island of Rodriguez. 



The form of the continental portions of the earth may, per- 

 haps, in a great measure, owe their elevation above the sur- 

 rounding level of the water to the eruption of quartzose por- 

 phyry, which overthrew with violence the first great vegeta- 

 tion from which the material of our present coal measures was 

 formed. The portions of the earth's surface which v»'e 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 inequahties have been 

 covered over by horizontal deposition of new sedimentary for- 

 mations and by the accumulation of alluvium. 



* [These movements, described in so few words, were doubtless go 

 ing on tor many thousands and tens of thousands of revolutions of our 

 planet. They were accompanied, also, by vast but slow changes of other 

 kinds. The expansive force employed in lifting up, by mighty move- 

 ments, the northern portion of the continent of Asia, found partial vent ; 

 and from partial subaqueous fissures there were poured out the tabular 

 masses of basalt occurring in Central India, while an extensive area of 

 depression in the Indian Ocean, marked by the coral islands of the Lac- 

 cadives, the Maldives, the great Chagos Bank, and some others, were 

 in the course of depression by a counteracting movement. — Ansted'a 

 Ancient World, p. 346, &c.]— Tr. 



+ [See American Journal of Science, vol. xlv., j). 187 ; nnd Medals 

 of Creation, vol. ii., ]i. 817 ; Trans. Zoolog. Society of London, vol. ii. : 

 Wonders of Geolcry, vol. i., p. rJ9.]— Tv. 



