50 PHYSICAL CO]S"SEIlVATIO]S" ATTD EESTOEATIOI?'. 



I determine how far one set of effects is neutralized by another, or 

 compensated by unknown agencies. This question scientific re- 

 search is inadequate to solve, for want of the necessary data ; but 

 well-conducted observation in regions now first brought under 

 the occupation of man, combined with such historical evidence 

 as still exists, may be expected at no distant period to throw 

 much light on this subject. 



Australia and ISTew Zealand are, perhaps, the countries from 

 which we have a right to expect the fullest elucidation of these 

 difficult and disputable problems. Their colonization did not 

 commence until the physical sciences had become matter of al- 

 most universal attention, and is, indeed, so recent that the memory 

 of living men embraces the principal epochs of their history ; the 

 peculiarities of their fauna, their flora, and their geology are such 

 as to have excited for them the livehest interest of the votaries of 

 natural science ; their mines have given their people the neces- 

 sary 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 rapidly pass- 

 ing under the control of civilized man. Here, then, exist greater 

 f acihties 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 artificial 

 condition of terrestrial surface began about the period when the 

 most important instruments of meteorological observation were 

 invented. The first settlers in the territory now constituting the 

 United States and the British American provinces had other 

 things to do than to tabulate barometrical and thermometrical 

 readings, but there remain some interesting physical records from 

 the early days of the colonies,* and there is stiU an immense ex- 



* The Travels of Dr. Dwight, president of Tale College, which embody the 

 results of his personal observations, and of his inquiries among the early set- 

 tlers, in his vacation excursions in the Northern States of the American Union, 

 though presenting few instrumental measurements or tabulated results, are of 

 value for the powers of observation they exhibit, and for the sound common 

 sense with which many natural phenomena, such for instance as the formation 

 of the river meadows, called "intervales," in New England, are explained. 

 They present a true and interesting picture of physical conditions, many of 



