CHAP. XXII THE FLORA OF NEW ZEALAND 



495 



extensive and more isolated portion of the continent in 

 which the peculiar Australian flora was principally 

 developed. The existence there of a very large area of 

 granite — 800 miles in length by nearly 500 in maximum 

 width with detached masses 200 miles to the north and 

 500 miles to the east — indicates such an extension; for these 

 granitic masses were certainly once buried under piles of 

 stratified rock, since denuded, and then formed the nucleus 

 of the old Western Australian continent. If we take the 

 1,000-fathom line around the southern part of Australia to 

 represent the probable extension of this old land we shall see 

 that it would give a wide additional area south of the Great 

 Australian Bight, and form a continent which, even if the 

 greater part of tropical Australia were submerged, would be 

 sufficient for the development of a peculiar and abundant 

 flora. We must also remember that an elevation of 6,000 

 feet, added to the vast amount which has been taken away 

 by denudation, would change the whole country, including 

 what are now the deserts of the interior, into a mountain- 

 ous and well-watered region. 



But while this rich and peculiar flora was in process of 

 formation, the eastern portion of the continent must either 

 have been widely separated from the western or had 

 perhaps not yet risen from the ocean. The whole of this 

 part of the country consists of Palaeozoic and Secondary 

 formations with granite and metamorphic rocks, the 

 Secondary deposits being largely developed on both sides 

 of the central range, extending the whole length of the 

 continent from Tasmania to Cape York, and constituting 

 the greater part of the plateau of the Blue Mountains and 

 other lofty ranges. During some portion of the Secondary 

 and Tertiary periods therefore, this side of Australia must 

 have been almost wholly submerged beneath the ocean ; 

 and if we suppose that during this time the western part 

 of the continent was at nearly its maximum extent and 

 elevation, we shall have a sufficient explanation of the 

 great difference between the flora of Western and Eastern 

 Australia, since the latter would only have been able to 

 receive immigrants from the former, at a later period, and 

 in a more or less fragmentary manner. 



If we examine the geological map of Australia (given in 



