OF THE PROPERTIES OF MATTER. 9 



\Vliere the sphere of attraction ends, a repulsive force LECT. 

 begins ; thus, water repels most bodies till they are wet ; ^-^~*^ 

 and hence it is, that a small needle, if dry, swims upon Repulsion, 

 water, and flies walk upon it without wetting their feet. 8 



The repelling force of the particles of a fluid is but 

 small ; and therefore, if a fluid be divided, it easily unites 

 again. But if glass, or any other hard substance, be 

 broken into small parts, they cannot be made to stick 

 together again without being first wetted ; the repulsion 

 being too great to admit of a re-union. 



The repelling force between water and oil is so great, 

 that we find it almost impossible to mix them so as not 

 to separate again. If a ball of light wood be dipped in oil, 

 and then put into water, the water will recede so as to 

 form a channel of some depth all around the ball. 



The repulsive force of the particles of air is so great, 

 that they can never be brought so near together by con- 

 densation as to make them stick, or cohere. Hence it 

 is, that when the weight of the incumbent atmosphere is 

 taken off from any small quantity of air, that quantity 

 will diffuse itself so as to occupy (in comparison,) an in- 

 finitely greater portion of space than it did before. 



Attraction of gravitation is that power by which Gravita- 

 tion. 

 Xo/e 8. Although steel has a greater specific gravity than water, 



and, as such, being bulk for bulk heavier, must, under ordinary cir- 

 cumstances, sink in the fluid in which it is immersed, yet we find a 

 variety of exceptions to this apparently self-evident law. By taking 

 the two instances cited by our author, we may, however, sufficiently 

 illustrate the matter. The floating of a steel wire is alluded to, as a 

 proof of some repulsive force in the needle : that, however, is not the 

 fact, as the phenomenon may readily be accounted for by reference to 

 the cohesion existing between the particles of the water ; which, 

 being greater than the gravitating force of so light a body, admits of 

 a partial hollow being formed without allowing the needle to sink. 

 In the latter case cited, two causes appear to operate in supporting 

 the various aquatic insects, which are seen passing upon the surface of 

 the water without being actually immersed in it. The first will be 

 found similar to that alluded to with reference to the needle ; and the 

 second is a very remarkable provision made by nature, apparently 

 for the express purpose of supporting them upon their native element. 



