9 9 



CHAPTER III. 



GEOGRAPHY OF THE GLOBE SINCE THE SECONDARY EPOC:H SUBSIDENCE IN SOUTHERN AND ELEVATION IN 



NORTHERN HEMISPHERE CORAL REEFS BANDS OF ELEVATION AND DEPRESSION. 



It TviU save the reader as well as myself much subsequent digression if I lay before bim at the outset 

 a general view of what I conceive to bave been the past geograpby of tbe globe during the successive 

 epochs which have elapsed since mammals first appeared, or rather, were first established — in other 

 words, since the close of the secondarj'' epoch. 



My theory, that change in the forms of organic life is the result of alteration on the physical 

 conditions of the earth, requires that some important change on the condition of the globe should have 

 occurred at the close of the secondary and commencement of the tertiaiy epoch ; for at that time 

 there was a great start given to the development of species, and new forms and new tj-pes came then 

 into beipg. 



What the change consisted ia we do not know ; but it may have been some great change in 

 the relative proportions of land and water : a change from a world almost covered with water to one 

 with less sea and more dry land. The fact that no remains of land-animals have been found during 

 the cretaceous epoch, and very few of terrestrial plants, while soon afterwards they become jslentifid, 

 suggests the possibility of this having been the nature of the change. 



Whatever it was, however, the fact seems certain that a great change did then occur, and, inter 

 alia, that terrestrial life for the first time assumed an important place among created beings. 



The first stage was the eocene epoch. Remains of this period occur in Europe, Asia, and 

 America ; also in North Africa ; but none have been found in Africa south of the Sahara, nor in 

 Australia. 



Of Australia, Mr. Jidces says, " Above the pala;ozoic series there is an absolute gap, a total 

 deficiency of all other stratified rocks whatsoever, so far as .is at present known, except those be- 

 longing to a tertiary formation which, from the verj^ recent aspect of its fossils and their resem- 

 blance to existing forms I believe to be a very modern one."* Some of the \-iews entertained at 

 the time Mr. Jukes wrote have since been modified, but it remains uncontroverted that a portion of 

 Australia w'as above the sea in the secondary and eocene epochs, and has continued always above 

 it until now. 



As the characters of the early eocene flora and fauna of Europe bear great resemblance to 

 those stUl existing in Australia, geologists have concluded that these two countries were formerly 

 in some way imited, and that a continuous stretch of dry land existed between them. It has 

 been supposed that never having since been wholly submerged, AustraKa had preserved the general 

 type of this eocene life down to the present day ; and although Professor M'Coy has latterly 

 taken exception to the correctness of this in its full extent, the comparative lists of plants 

 found in the eocene deposits of Europe contrasted with those now living in Australia, given by 



* Ju;;es, "Sketch of the Physical Structure of Australia,'' London, 1850, p. 89. 



