248 THE PHYSICAL GEOGRAPHY OF AUSTRALIA. 



truly continental proportions during the Mesozoic era. A narrow belt 

 of dry land; corresponding - to the position of the Great Dividing Itange, 

 extended along the whole seaboard of Australia, uniting Tasmania, 

 New Guinea, and Borneo. The whole western half of the continent 

 was likewise raised above the surface of the ocean, curving westward 

 to Java, Sumatra, and, effecting a junction with the eastern area at 

 Borneo, stretched northerly to the southeast portion of India. 1 Owing 

 to this remarkable process of evolution, an enormous gulf or inland 

 sea swept the whole central region of Australia, extending northerly 

 and westerly to the southern shores of Borneo. The climate during 

 this period was in like manner uniform, though less persistently marked 

 than in earlier times. In the dawn of Tertiary times, Australia had 

 become entirely continental or insulated. The connecting belts, which 

 formerly uited it with neighboring counties, were submerged, and the 

 inland "waters were confined to a tract of submerged country in the 

 neighborhood of the junction of the Murray and Darling rivers. Besides 

 this the sea encroached upon the coast districts of the Gulf of Carpen- 

 taria, also upon a portion of the coast fringe in Western Australia, 

 between Shark's Bay and Cape Leeuwyn, and a narrow section along 

 the head of the Great Australian Bight was also submerged, but in all 

 other respects the general conformation of our continent was almost 

 identical then with what it is now. Contemporaneous witli this physi- 

 cal change in the geographical aspect of the country a yjronounced 

 differentiation of climate occurred. Climatic zones possessing marked 

 and distinctive characteristics existed, and in these mild seasonal 

 changes prevailed. Although I have already remarked upon the uni- 

 formity of climate during the two preceding ages, still it seems reason- 

 able to suppose that the atmospheric air was then more highly charged 

 with moisture than we can at present conceive it to be, and that the 

 rainfall in tropical and extra-tropical regions must have been enormous, 

 owing to the widely distributed equatorial waters over vast areas of 

 the globe, and the extensive circulation of ocean currents. It is worthy 



1 It is not by any means improbable tbat during this age there was actually a land 

 connection between Australia, New Zealand, the Antarctic Continent, and Patagonia. 

 On a map accompanying a paper read before the Royal Geographical Society, and 

 published in the Geographical Journal, January, 1894, Dr. John Murray shows that 

 these lands are connected by a submerged plateau over which the soundings are 

 very shallow, compared with the enormous depth of the neighboring ocean bed. 

 The strongest evidence in support of this theory is, however, to be found among the 

 fragmentary remains of extinct animals recently discovered in these now widely 

 separated regions. In the Chatham Islands there have been found the remains of a 

 large ocydromine rail and the fossil bones of a coote, allied to other extinct families 

 that formerly inhabited Mauritius, and were probably distributed over a very wide 

 geographical range of the southern hemisphere. There is also the occurrence of 

 struthious birds in New Zealand, Queensland, Madagascar, and Patagonia, which 

 seems to indicate that they were scattered about at a time Avhen there were few 

 impediments to interfere with their migratory movements over immensely wide 

 areas, part of which is now occupied by the waters of the South Pacific Ocean. 



