LAWS OF ANIMAL DISPERSION. 
275 
animal kingdom is arranged or distributed over the 
surface of the globe; it being opposed to reason 
and at variance with all scientific considerations, 
to suppose that living beings have been placed on 
the earth promiscuously, indiscriminately, and with¬ 
out regard of order and adaptation. 
Since the greatest benefits and most important 
uses of natural science depend upon the determina¬ 
tion of principles and of general conclusions, the 
labour bestowed on the study should centre on this 
great object; and in the enumeration of facts we 
should be careful to inquire as we proceed, what 
effect that detail has on admitted doctrines, or 
what influence it might have in establishing or dis¬ 
closing new views and theories. In accordance 
with this idea I shall combine a recognition of laws 
with a statement of facts in the present chapter ; 
first mentioning the primary and secondary laws 
by which the distribution of animals is governed 
and then entering upon the detail of zoological 
geography as observed in the south of Devon, 
availing myself in this second part of the subject, 
of every occasion to advance the knowledge of the 
higher department of principles and general results. 
It will be needful to remember that this subject of 
the Geography of Animals is intimately associated 
with several others of great interest, and more par¬ 
ticularly with migration and the “ polity of nature,” 
and these have, equally with the present question, 
law's and general considerations connected with 
them, which are by no means to be confounded 
■with those we are now about to state. 
On enquiring how far the dispersion of animals 
is affected by, or connected wfith the relative tem¬ 
perature of the earth according to distance from 
the extreme points of heat and cold, w r e find that the 
animal creation is greatly accumulated w ithin the 
tropics and that it gradually diminishes in extent 
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