96 MOLECULAR FORCES. SBCT. XIV. 



SECTION XIV. 



Repulsive Force Interstices or Pores Elasticity Mossotti's Theory 

 Gravitation brought under the same law with Molecular Attraction and 

 Repulsion Gases reduced to Liquids by Pressure Intensity of the Co- 

 hesive Force Effects of Gravitation Effects of Cohesion Minuteness 

 of the ultimate Atoms of Matter Limited Height of the Atmosphere 

 Theory of Definite Proportions and Relative Weight of Atoms Dr. Far- 

 aday's Discoveries with regard to Affinity Composition of Water by a 

 Plate of Platina Crystallization Cleavage Isomorphism Matter con- 

 sists of Atoms of Definite Form Capillary Attraction. 



THE oscillations of the atmosphere and its action 

 upon rays of light coming from the heavenly bodies, 

 connect the science of astronomy with the equilibrium 

 and movements of fluids, and the laws of molecular 

 attraction. Hitherto that force has been under consid- 

 eration which acts upon masses of matter at sensible 

 distances ; but now the effects of such forces are to be 

 considered as act at inappreciable distances upon the 

 ultimate atoms of material bodies. 



All substances consist of an assemblage of material 

 particles, which are far too small to be visible by any 

 means human ingenuity has yet been able to devise, 

 and which are much beyond the limits of our percep- 

 tions. Since every known substance may be reduced 

 in bulk by pressure, it follows that the particles of mat- 

 ter are not in actual contact, but are separated by inter- 

 stices, owing to the repulsive principle that maintains 

 them at extremely minute distances from one another. 

 It is evident that the smaller the interstitial spaces 

 the greater the density. These spaces appear in 

 some cases to be filled with air, as may be infer- 

 red from certain semi-opaque minerals and other sub- 

 stances becoming transparent when plunged into water ; 

 sometimes they may possibly contain some unknown 

 and highly elastic fluid, such as Sir David Brews ter has 

 discovered in the minute cavities of various minerals, 

 which occasionally causes these substances to explode 

 with violence when under the hands of the lapidary, 

 but in general they seem to our senses to be void ; yet 

 as it is inconceivable that the particles of matter should 

 vet upon one another without some means of commu- 



