INTRODUCTION. 9 



only with plants and animals, but with certain mi- 

 neral and chemical productions called Crystals, usu- 

 ally bounded by plain surfaces. 



20. Motion, of which all bodies are susceptible, 

 is the continued change of place. 



21. It is a general law in the material world, 

 that no body loses motion in any direction, without 

 communicating an equal quantity to other bodies in 

 that same direction ; and conversely, that no body 

 acquires motion in any direction, without diminish- 

 ing the motion of other bodies by an equal quanti- 

 ty in that same direction. 



What relates to the motion of bodies, will be consi- 

 dered more fully hereafter ; it is mentioned here 

 merely for the sake of order, as being part of the 

 definition of Body. 



22. The force with which the parts of bodies re- 

 sist any endeavour to separate them is called cohe- 

 sion. 



Q. We may conceive a body to be made up of an as- 

 semblage of small indivisible particles or corpuscles 

 adhering to one another, with forces that are greater 

 as the distance of the particles is less. These cor- 

 puscles are called the elements of body. 



b. Hardness, softness, tenacity, fluidity, ductility, are 

 modifications of cohesion. 



c. Smooth 



