554 GEOLOGY. 



overbalance it, which is 6.9 miles per second; e.g. a body shot away 

 from the surface at a speed exceeding 6.9 miles per second, would escape 

 from the control of the earth if the influence of the atmosphere and 

 other bodies is neglected; while a body shot away at less than this speed 

 would return to the earth. 



Molecular and sub-molecular attractions. — In addition to gravity^ 

 there are at least three additional classes of attractive agencies whose 

 laws appear to differ from those of gravity, viz. cohesion, chemical 

 affinity, and sub-atomic attraction, using these terms in their compre- 

 hensive generic senses. The thought has been entertained that these 

 might be reducible to forms of gravity in ulterior analysis, but it does 

 not appear from existing evidence that the laws of their attractions are 

 conformable to the Newtonian law of the inverse square of the distance, 

 to which gravity conforms. Apparently the forces of the molecular, 

 atomic, and sub-atomic attractions increase at higher rates, and have 

 individual peculiarities of action quite different from gravity. II would 

 be of the utmost service to geological philosophy if these laws of molec- 

 ular and sub-molecular attractions were firmly established, and could be 

 applied to the conditions of heat and pressure under which the matter 

 of the interior of the earth exists. In the absence of such determina- 

 tions, we can do little more than recognize that the matter of the interior 

 of the earth tends to condense itself by the aid of molecular and sub- 

 molecular attractions, supplemental to the attraction of gravity. 



Cohesion and crystallization. — The force of gravity between small 

 bodies is exceedingly feeble, but it is cumulative, every particle in a 

 mass attracting every other particle, so that in great masses the force 

 becomes enormous. In cohesion, and probably in the other molecular 

 and sub-molecular attractions, the particles attract very strongly the 

 particles with which they are in close relations, but beyond minute dis- 

 tances their effects are insensible. The force of crystallization is felt 

 for a very short distance from the crystal, and ''mass action" is prob- 

 ably dependent on a function of similar kind, acting at a very small dis- 

 tance, but the range of these forces is very limited in comparison ^vitll 

 that of gravity. 



Rock matter, as a rule, tends to become crystalline b}^ the assembling 

 of like molecules in systematic order. The general effect is condensa- 

 tion, though this is not universally the case, for in some instances the 

 crystalline arrangement results in expansion. The crystallizing force 



