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178 A. G. HAMILTON. 
On THE EFFECT wuicno SETTLEMENT in AUSTRALIA Has 
PRODUCED UPON INDIGENOUS VEGETATION, 
By Auex. G. Hamirron. 
[Read before the Royal Society of N.S. Wales, September 7, 1892.] 
In considering this object, the first point to be noted is the state 
of the indigenous vegetation at the time of first settlement. This 
we can only arrive at by analogy. Australia being for so long a 
period practically isolated from the other continents, and the con- 
ditions of the animal and vegetable life having been for so long a 
time constant and uniform, the vegetation then must have been 
in a state of balance, or, if any changes were taking place, they 
were very small in amount and slow in action. 
The balance above spoken of was then, and is still being, dis- 
turbed in the following ways by settlement : 
Division I.—By the direct action in destroying forests and herbage 
by clearing the land for cultivation and settlement ; in clear- 
ing roads, railways and telegraph-lines ; procuring timber for 
building, fencing and fuel, and for mining purposes ; and 
ringbarking tracts of land to improve the grazing capacity. 
Under this head too, comes the checking of bushfires, although 
as will be seen when this subject is treated of, this has per- 
haps only an indirect action. 
Division II.—The introduction of a new fauna altering the flora; 
and the destruction of the native fauna modifying it. 
Division III.—The introduction of a new flora, and consequent. 
modification of the indigenous flora through competition. 
It is necessary to examine each of these causes in detail, to” 
arrive at an understanding as to how, and to what amount each: 
of them acts. 
