12 WELLS'S NATUKAL PHILOSOPHY. 



i 



7. These substances are not all equally < 

 ^"'ate^df'^^' distributed over the surface of the earth : 



most of them are exceedingly rare, and only 

 known to chemists. Some ten or twelve qnly make up 

 the great bulk or mass of all the objects we see around 

 us. 



All the different forms and varieties of matter are in some respects alike 

 — that is, they all possess certain general properties. Some of these prop- 

 erties are essential to the very existence of a body; others are non- 

 essential, or a body may exist -without them. Thus it is essential to the 

 existence of a body that it should occupy a certain amount of space, and 

 that no other body should occupy the same space at the same time ; but* it is 

 not necessary for its existence that it should possess color, hardness, elas- 

 ticity, malleability, and the like non-essential properties. 



8. The following are the most important of 

 molt import* tlic gcucral propcrtics of matter — Magnitude 

 ofufauer?''^" or Extension, Impenetrability, Divisibil- 

 ity, Porosity, Inertia, Attraction, and In- 

 destructibility. 



9. By Magnitude we mean the property 

 ^^nuudo?''^' of occupying space. We can not conceive that 



a portion of matter should exist so minute as 

 to have no magnitude, or, in other words, to occupy no 

 space. 



The SURFACES of a body are the external limits of its magnitude; the 

 SIZE of a bod}"- is the quantity of space it occupies ; the area of a body 

 is its quantity, or extent of surface. 



The FIGURE of a body is its form or shape, as expressed by its bound- 

 aries or 'terminating extremities. The volume of a body is the quantity of 

 space included within its external surfaces. The figure and volume of a 

 body are entirely independent of each other. Bodies having very different 

 figures may have the same volume, or bodies of the same figure may have 

 very different volumes. Thus a globe may have ten times the volume 

 of another globe and yet have the same figure, or a globe and a cylinder 

 may have the same volume, that is, may contain the same amount of matter 

 within their surfaces, but possess very different figures. 



10. By Impenetrability we mean that 

 i^etrJbiuty? property or quality of matter, which renders it 



impossible for two separate bodies to occupy • 

 the same space at the same time. 



