1.14 MOLECULAR FOECES. [SECT. xiv. 



SECTION XIV. 



Repulsive Force Interstices or Pores Elasticity Mossotti's Theory Gravi- 

 tation brought under the same Law with Molecular Attraction and Repul- 

 sion Gases reduced to Liquids by Pressure Intensity of the Cohesive 

 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. Faraday's Dis- 

 coveries with regard to Affinity Composition of Water by a Plate of Platina 

 Crystallisation Cleavage Isomorphism Matter consists of Atoms of de- 

 finite 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 consideration 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 parti- 

 cles, 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 perceptions. Since every 

 known substance may be reduced in bulk by pressure, it fol- 

 lows that the particles of matter are not in actual contact, 

 but are separated by interstices, owing to the repulsive prin- 

 ciple that maintains them at extremely minute distances 

 from one another. It is evident that, the smaller the in- 

 terstitial spaces, the greater the density. These spaces appear 

 in some cases to be filled with air, as may be inferred from 

 certain semi-opaque minerals and other substances becoming 

 transparent when plunged into water ; sometimes they may 

 possibly contain some unknown and highly elastic fluid, such 



