2ft GENERAL PROPERTIES OF BODIES. 



to exist without certain properties, such as impenetrability, 

 extension, figure, divisibility, inertness, and attraction, these, 

 therefore, are called the general properties of bodies. 



By impenetrability , is meant the property which bodies 

 have of occupying a certain space, so that, where one body 

 is, another cannot be, without displacing the former ; for two 

 bodies cannot exist in the same place at the same time. A 

 liquid may be more easily removed than a solid body ; yet it 

 is not the less substantial, since it i? as impossible for a 

 liquid and a solid to occupy the same space at the same time, 

 as for two solid bodies to do so. If some water be put into 

 a tube closed at one end, and a piece of wood be inserted 

 that accurately fits the inside of the tube, it will be impos- 

 sible to force the wood to the bottom, unless the water is 

 first taken away. The air is a fluid differing in its nature 

 from liquids, but not less impenetrable. If you endeavour 

 to fill a phial by immersing it in water, the air will rush out 

 in bubbles in order to make way for the water ; and if you 

 reverse the phial, and plunge it perpendicularly into the wa- 

 ter, so that the air will not be able to escape, the water will 

 not fill it, though it will rise a little, because it compresses 

 the air into a smaller space in the upper part of the glass. 



A body which occupies a certain space must necessarily 

 have extension ; that is to say, length, breadth, and depth. 

 These are called the dimensions of extension, and we can- 

 not form ail idea of any body without them. The limits of 

 extension are called figure or shape. A body having length, 

 breadth, and depth, cannot be without form, either symme- 

 trical or irregular ; and this property admits of almost an in- 

 finite variety. The natural form of mineral substances is 

 that of crystals ; many of them are very beautiful, and not 

 less remarkable for their transparency and colour, than for 

 their perfect regularity, as may be seen in the various mu- 

 seums and collections of natural history. The vegetable 

 and animal creation appears less symmetrical, but is still 

 more diversified in figure than the mineral kiji^dpm. Mfc^^ 

 nufactured substances assume the various arbitrary f<^ms . 

 which the art of man designs for them. 



Divisibility is that property of matter, by which its parts 

 may be divided and separated from each other ; and of this 

 division there can be no end. We can never conceive of a 

 particle of matter so small as not to have an upper and under 



