37 



with mineral salts. There is not a single case to support an 

 igneous doctrine ; whereas by means of the natural solutions and 

 the polar current, we can, not only account for, but imitate the 

 natural productions. There is scarcely a substance known but 

 what is either found naturally in solution, or may be dissolved 

 in an aqueous menstruum. The apparent insolubility of quartz 

 has given rise to some of the difficulties which have embarrassed 

 geologists ; but as silica is found in that state in the primary 

 base, we need not trouble ourselves with the question how quartz 

 may be redissolved. 



We shall consider the ocean as the primary menstruum from 

 pole to pole, — a compound of all the elements in solution 

 through which the magnetic currents circulate. From analogy 

 and by experiment, crystallization would commence at the ne- 

 gative pole, and would continue to form until its growth would 

 extend to the positive pole in meridional lines, thus producing 

 the polar grain or lamination explained in the previous chapter. 

 In the primary rocks we recognise in every crystal the action of 

 the constant and undeviating laws of the polar force and che- 

 mical affinity, giving to the mass a regular grain, and to every 

 crystal a definite form and composition. Hence the above may 

 be considered an experimental and natural truth. 



The elementary substances entering into the composition of the 

 primary rocks may on an average be considered the following : — 

 Silica, Iron, 



Aluminum, Manganese, 



Magnesia, Fluoric acid, 



Potash, Carbonic acid, 



Soda, Water. 



Lime, 

 These are united with variable proportions of the gases, hydro- 

 gen, oxygen, chlorine, &c. The compound consists of the above 

 in a state of fluids, semifluids and solids, being an aggregation 

 of the separate elements in different states of crystallization. 



Silica forms Quartz. 



Silica, alumina, lime and potash . . . Felspar. 

 Silica, alumina, potash and iron .... Mica. 



Silica, magnesia and potash Talc. 



vSilica, alumina, magnesia and iron . . . Chlorite. 



