1 62 THE NATURALIST IN AUSTRALIA. 



secondary, crowned in many places with sheets and caps of 

 basalt and lava. Since this period a general elevation of the 

 whole land has taken place ; and, although much of the old 

 ground has disappeared and Tasmania is now cut off, the 

 shallow tertiary sea has dried up, and Australia is again one 

 continent. 



To this geological tradition we owe the peculiar charm of 

 Australian plant and animal life. We really have before us a 

 great game preserve of Mesozoic times. Cut off by breadths of 

 deep sea from Asiatic lands, its denizens were exempt from 

 interference on the part of rival claimants in the struggle for 

 existence, whilst, during the subsidences and submersion of the 

 Cretaceous period so fatal in the similar case of the British 

 Isles they had a safe asylum to the westward in which a large 

 proportion of existing forms of vegetable and animal life 

 survived. Thus Australia preserves the types of Mesozoic 

 vegetation and animals which Britain has lost and replaced by 

 more recent forms it is, in fact, an " Ark." Its flora and fauna 

 have had simply to settle accounts amongst themselves and 

 develope any modifications rendered necessary by a few gentle 

 terrestrial changes. There have been, of course, occasional 

 immigrations of birds, reptiles, fishes, bats, such small rodents 

 as might come in ships or on driftwood, and at some fairly 

 recent period there was the introduction of the "Dingo;" but 

 nothing has occurred to greatly disturb the balance of power in 

 the possession of " Secondary " types. 



The interior for many months in the year largely presents the 

 aspect of arid and waterless desert, many thousands of square 

 miles having no permanent water supply. When it does rain (at 

 very uncertain intervals) the land responds bountifully, and 

 clothes itself with grass waving breast high. Rivers roll through 

 the plains, large areas are flooded ; but soon the water sinks out 

 of sight, the grasses are bleached, then break off, and are blown 

 away, leaving the land a desert again. Here an interesting 

 geological fact enables the colonist to struggle successfully 

 through rainless seasons. 



