ORIGIN OF ERUPTIVE AND PRIMARY ROCK8. 471 



lave been instantaneously evaporated. This rapid condensation 

 and evaporation must have continued through long ages before 

 any considerable accumulation of water could have taken place. 

 Even then such accumulations must have possessed for a long 

 time a boiling temperature, and long ages must again have been 

 necessary before it cooled down to such an extent as to enable ani- 

 mated creatures to exist within it. If to these considerations we 

 add the following,namely that the water condensing upon the heated 

 rocks must have been charged with muriatic and carbonic acids, 

 (the latter at a later slage than the former), it is very plain that 

 the products of the action of the atmospheric influences then, must 

 have been of a character widely different from those produced by 

 the same agencies at the present day. The action of such acid- 

 ulated water aided by heat must have been much more energetic 

 then than now. This has been already fully recognized by Dr. 

 Hunt. "The solid crust," he remarks, "would afterwards be at- 

 tacked by the acids, precipitated, with water, under the pressure 

 of a high atmospheric column, and at an elevated temperature ; 

 from which would result the separation of a great amount of silica, 

 and the formation of an ocean, whose waters would contain in the 

 state of chlorides and sulphates not only alkalies, but also large 

 portions of lime and magnesia. At a later period, the decompo- 

 sition of exposed portions under the influence of water and carbon- 

 ic acid would give rise, on the one hand to clays, and on the other 

 to carbonate of soda. This latter reaction upon the calcareous 

 salts of the seawater must produce chloride of sodium and carbon- 

 ate of lime. We have here a theory of the source of the quartz, 

 the carbonate of lime and the argillaceous matters of the earth's 

 crust explaining at the same time, the origin of the chloride of 

 sodium of the sea, and the fixation of the carbonic acid of the at- 

 mosphere in the form of carbonate of lime."* I may be permit- 

 ted to remark, that no theory accounts more completely and satis- 

 factorily for the origin of the so-called Primitive Slate formation, 

 than does this. It is surely not too much to assume, that the 

 crystalline character of its rocks has been caused by the nature of 

 the agents then- at work, and the influence of the higher tempera- 

 ture and greater atmospheric pressure then prevailing. It is evi- 

 dent that the action of the muriatic acid of the atmosphere 

 must have long preceded the action of carbonic acid, since we 

 are almost unable to conceive that, the latter gas could exist in 



•Canadian Naturalist, vol. vii., p. 202. 



