OF NATURAL PHILOSOPHY. ' 235 



ther investigation seems necessary before we can 

 be said distinctly to understand it. 



(254-.) As the capillarity and cohesion of the parts 

 of liquids shows them to possess the power of 

 mutual attraction, so their elasticity demonstrates 

 that they also possess that of repulsion when for- 

 cibly brought nearer than their natural state. From 

 the extremely small extent to which the compres- 

 sion of liquids can be carried by any force we can 

 employ, compared with that of air, we must con- 

 clude that this repulsion is much more violent in 

 the former than in the latter, but counteracted also 

 by a more powerful force of attraction. So much 

 more powerful, indeed, is the resistance of liquids 

 to compression, that they were usually regarded as 

 incompressible ; an opinion corroborated by a cele- 

 brated experiment made at Florence, in which 

 water was forced through the pores (as it was said) 

 of a golden ball. More recent experiments by Canton, 

 and since by Perkins, Oersted, and others, have 

 demonstrated however the contrary, and assigned 

 the amount of compression. 



(255.) The consideration of the motions of fluids, 

 whether liquid or expansible, is infinitely more com- 

 plicated than that of their equilibrium. When their 

 motions are slow, it is reasonable to suppose that 

 the law of the equable distribution of pressure ob- 

 tains; but in very rapid displacements of their 

 parts one among the other, it is not easy to see how 

 such an equable distribution can be accomplished, 

 and some phenomena exist which seem to indicate 

 a contrary conclusion. 



(256.) Independent of this, there are difficulties 



