88 Lectures on the Geology, Botany, fyc., of the 
and parallel to the Mitchell, very large and deep nymphaea ponds 
existed, around which the pasture was particularly rich. 
The rivers within the tropics are almost all remarkable for the 
immense width of their beds, which are filled with sand, with the 
exception of those spots in which the naked rock cropped out. 
They were overgrown with small trees, and the number and size 
of the latter depends upon the frequency and strength of those 
rushes of water which occasionally sweep down. The Upper 
Lynd was, for instance, covered with trees, whilst the bed of the 
Mitchell was entirely free from them. We observed water marks 
fifteen and eighteen feet above the level of the bed—evidently 
showing that a large body of water flows down to the sea in, 
perhaps, unusually rainy seasons. 
In finding these large channels, whether dry or with tiny 
streams, occasionally lost in the loose sands, are we then to sup¬ 
pose that the power of the floods which formed them was formerly 
greater than at present, and that the decrease of moisture, which 
has been remarked by the old inhabitants of the colony, has 
equally taken place in the tropics? Analogy certainly justifies 
such a conclusion. 
Large tracts of country on the east coast of the Gulf were 
covered with box (a species of eucalyptus,) and with a small tea- 
tree with broad lanceolate leaves. These trees generally indicated 
a stiff soil, which in the level country was never free from shallow 
holes, such as are called melon-holes by the squatters, formed, 
no doubt, by the infiltrating rain and standing water. In many 
of these holes we found dead crabs, and even fresh-water turtles 
and many shells, which also proved that long drought had pre¬ 
vailed and destroyed these animals. 
Another feature of the country are slight undulations, on which 
grew a few scattered rather stunted trees, amongst which a species 
of grevillia (gr. mimosoides R. Br.) with long, narrow, drooping, 
silvery leaves, particularly attracted our attention. 
The finest and most available country was along the creeks and 
rivers. Here the soil was much lighter, and the bloodwood, the 
leguminous iron-bark, and the pandanus, grew well on it, forming 
an open forest. 
