INTRODUCTION. 



As correct ideas respecting natural history are not very 

 generally formed, it appears necessary to begin by defining 

 its peculiar object, and establishing rigorous limits between it 

 and neighbouring sciences. 



In our language and in most others, the word nature is 

 variously employed. At one time it is used to express the 

 qualities a being derives from birth, in opposition to those it 

 inay owe to art ; at another, the entire mass of beings which 

 compose the universe ; and at a third, the laws which govern 

 those beings. It is in this latter sense particularly that we 

 usually personify nature, and, through respect, use its name 

 for that of its Creator. 



Physics, or Natural Philosophy, treats of the nature of these 

 three relations, and is either general or particular. General 

 physics examines abstractedly each of the properties of those 

 movable and extended beings we call bodies. That branch 

 of them styled Dynamics, considers bodies in mass ; and pro- 

 ceeding from a very small number of experiments, determines 

 mathematically the laws of equilibrium, and those of motion 

 and of its communication. Its different divisions are termed 

 Statics, Hydrostatics, Hydrodynamics, Mechanics, &c. &c., 

 according to the nature of the particular bodies whose motions 

 it examines. Optics considers the particular motions of light, 

 whose phenomena, which hitherto nothing but experiment has 

 been able to determine, are becoming more numerous. 



Chemistry, another branch of general physics, exposes the 

 laws by which the elementary molecules of bodies act on each 

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