GENERAL PROPERTIES OF BODIES. 29 



surface, which might be separated, if we had instruments 

 fine enough for the purpose. A grain of gold may be ham- 

 mered by the gold-beaters to such a degree of fineness, that 

 the two millionth part of it may be seen by the naked eye ; 

 and by the help of a microscope the fifty millionth part will 

 be visible. There are animals, it is said, so small that a 

 single grain of sand is larger than four millions of them. 

 But the natural divisions of matter are still more wonderful. 

 The fragrance of a body is a part of the body itself, and is 

 produced by very minute particles or exhalations which 

 escape from it. How inconceivably small must be the odo- 

 riferous particles of a carnation, which diffuse themselves 

 through a whole garden, so that, in every part of it, its fra- 

 grance is perceptible ! 



The word inertness expresses the resistance which inac- 

 tive matter makes to a change of state. It requires some 

 external force to put a body which is at rest in motion ; and 

 an exertion of strength is also requisite to stop a body which 

 is already in motion. If a ball were fired from a cannon with 

 a certain velocity, and there were no resistance from the air, 

 it would circulate round the earth perpetually, and never 

 come to a state of rest. In this manner the moon goes 

 round the earth. 



By attraction is meant the tendency that bodies have to 

 approach each other, whatever be the cause of such tenden- 

 cy. All bodies are composed of infinitely small particles 

 of matter, each of which possesses the power of attracting 

 or drawing towards itself any other particle, and of uniting 

 with it, when sufficiently near to be within the influence of 

 its attraction ; but in minute particles this power extends t® 

 so very small a distance around them that its eflfect is not 

 sensible, unless they are, or at least appear to be, in contact. 

 It then makes them adhere together, and is hence called the 

 attraction of cohesion. It is by this principle that bodies 

 preserve their forms, and are prevented from falling to 

 pieces. The cohesive attraction of solids is much greater 

 than that of fluids ; and in elastic fluids, such as air, there 

 is no cohesive attraction among the particles, and the utmost 

 efforts of human art have proved ineffectual in the attempt 

 to compress them, so as to bring them within the sphere of 

 each other's attraction, and make them cohere. If two po- 

 lished plates of marble, or of brass be but together with a 

 3* 



