4 INTRODUCTION. 
being, not only with regard to itself but to its surrounding 
relations. The analysis of these conditions frequently con- 
ducts us to general laws, as certain as those that are derived 
from calculation or experiment. . 
It is only when all the laws of general physies and those 
which result from the conditions of existence are exhausted, 
that we are reduced to the simple laws of observation. 
The most effectual method of obtaining these, is that of 
comparison. ‘This consists in successively observing the same 
bodies in the different positions in which nature places them, or 
in a mutual comparison of different bodies; until we have 
ascertained invariable relations between their structures and 
the phenomena they exhibit. These various bodies are kinds 
of experiments ready prepared by nature, who adds to or de- , 
ducts from each of them different parts, just as we might wish 
to do in our laboratories ; showing us, herself, at the same mig 
their various results. 
In this way we finally succeed in establishing certain laws 
by which these relations are governed, and which are ind 
ployed like those that are determined by the general sciences. 
The incorporation of these laws of observation with the 
general laws, either directly or by the principle of the con- 
ditions of existence, would complete the system of the natural 
sciences, in rendering sensible in all its parts the mutual in- 
fluence of ev ery being. ‘To this end, should those who culti- 
vate these sciences direct all their efforts. 
All researches of this nature, however, pre-suppose means 
of distinguishing clearly, and causing others to distinguish, the _ 
bodies they are occupied with; otherwise we should be con- 
tinually confounding them. Natural history thenshould be 
based on what is called a system of nature; or a great cata- 
logue in which all created beings have suitable names, may be 
recognised by distinctive characters, and be arranged in divi- 
sions and subdivisions, themselves named and characterised, 
im which they may be found. 
In order that each being may be recognised in this catalogue, 
it must be accompanied by its character: habits or properties 
‘ 
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v 
