INTRODUCTION. 



AS correct ideas respecting natural history are not very generally 

 formed, it appears necessary to begin by defining its peculiar ob- 

 ject, and establishing rigorous limits between it and neighbouring 

 sciences. 



In our language and in most others, the word NATUEE is vari- 

 ously employed. At one time it is used to express the qualities a 

 being derives from birth, in opposition to those it may 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 phy- 

 sics 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 proceeding 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 bo- 

 dies whose motions it examines. Optics considers the particular 

 motions of light, whose phenomena, which, hitherto, nothing but ex- 

 periment 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 other; the 

 combinations or separations which result from the general tendency 

 of these molecules to re-unite; and the modifications which the va- 

 rious circumstances capable of separating or approximating them 

 B 



