AUSTRALIA AS A FIELD OF OBSERVATION. 
51 
clearing and cultivating of the ground, and of other rural 
operations, upon climate. It is disputed whether either the 
mean or the extremes of temperature, the periods of the 
seasons, or the amount or distribution of precipitation and of 
evaporation, in any country whose annals are known, have 
undergone any change during the historical period. It is, 
indeed, impossible to doubt that many of the operations of the 
pioneer settler tend to produce great modifications in atmo¬ 
spheric humidity, temperature, and electricity ; but we are at 
present unable to determine how far one set of effects is neu¬ 
tralized by another, or compensated by unknown agencies. 
This question scientific research is inadequate to solve, for 
want of the necessary data; hut well conducted observation, 
in regions now first brought under the occupation of man, 
combined with such historical evidence as still exists, may he 
expected at no distant period to throw much light on this 
subj ect. 
Australia is, perhaps, the country from which we have a 
right to expect the fullest elucidation of these difficult and 
disputable problems. Its colonization did not commence 'until 
the physical sciences had become matter of almost universal 
attention, and is, indeed, so recent that the memory of living 
men embraces the principal epochs of its history; the pecu¬ 
liarities of its fauna, its flora, and its geology are such as to 
have excited for it the liveliest interest of the votaries of 
natural science ; its mines have given its people the necessary 
wealth for procuring the means of instrumental observation, 
and the leisure required for the pursuit of scientific research ; 
and large tracts of virgin forest and natural meadow are rap¬ 
idly passing under the control of civilized man. Here, then, 
exist greater facilities and stronger motives for the careful study 
of the topics in question than have ever been found combined 
in any other theatre of European colonization. 
In North America, the change from the natural to the arti¬ 
ficial condition of terrestrial surface began about the period 
when the most important instruments of meteorological obser¬ 
vation were invented. The first settlers in the territory now 
