36 



" sedimentary ?J rocks used here, are to be considered in the same 

 sense, having no reference whatever to the time of their forma- 

 tion. With regard to the interior of the globe below the ee pri- 

 mary base," nothing can be determined from immediate observa- 

 tion, nor is the question essential to our inquiry. Were we to 

 speculate on this subject, we should consider it filled with hy- 

 drogen gas, from the fact of its surface being principally com- 

 posed of water : be this as it may, there is no reason to suppose 

 it to consist of an igneous fluid ; we cannot conceive the exist- 

 ence of such an element in a quiescent state. This point can- 

 not be too much insisted upon, as geologists have assumed 

 such an agent, and consequently all crystalline rocks are called 

 igneous. 



In our investigation of phenomena dependent on natural 

 causes, certain laws of reasoning should inviolably be adhered 

 to. First, no cause should be adduced whose existence is not 

 proved either by its effects or by a true process of induction. 

 Secondly, no effect should be attributed to a cause whose known 

 powers are inadequate to its production. Thirdly, no powers 

 should be ascribed to an assumed cause but those that it is known 

 to possess according to the laws of terrestrial physics. To these 

 rules we mean strictly to conform, in which conformity rest the 

 merits of our argument in support of the effects of terrestrial 

 magnetism to account for all geological phenomena. 



In the first place, we have no proof of the existence of an ig- 

 neous element. Granting its existence, it could not produce a 

 solid, but merely the melting of a substance already formed; 

 therefore there is nothing gained by such an assumed agent. 

 Besides, it is extremely difficult to produce crystals from fusion, 

 and those which are imperfectly formed are produced when in 

 the act of sublimation. Siliceous and calcareous crystals have 

 often been formed by art in the moist way, but never by igneous 

 fusion. The crystals forming the primary base could never be 

 imitated by fusion, even though every other necessary circum- 

 stance should concur, especially those with or without an inter- 

 mediate prism, terminating with pointed pyramids at both ends, 

 as those of quartz and calcareous spar. Even those rocks called 

 ancient lava, such as basalt, trap, &c, are of the same aqueous 

 composition as any other rock, their pores being always filled 



