CHI ST 01' THE EARTH. 333 



deficient in power is made up in time, and effects arc 

 produced during myriads of ages, by powers far too weak 

 to give satisfactory results by any experiments which 

 inii; lit be extended even over a century. 



If, with the eye of a geologist, we take but a cursory 

 glance over the Earth, we shall discover that countless 

 ages must have passed during the progress of this planet 

 to its present state. This is a fact written by the finger 

 of nature, in unmistakeable characters, upon the mighty 

 tablets of her mountains. 



The superficial crust of the earth, by which is meant 

 only that film, compared with its diameter, which is 

 represented by a few miles in depth is composed of dis- 

 tinct mineral masses, exhibiting peculiar physical con- 

 ditions and a certain order of arrangement. These rocks 

 appear to have resulted from two dissimilar causes ; in 

 one class the action of heat is evident, and in the other 

 we have either the slow deposition of matter suspended 

 in water, or crystallization from solution ; an aqueous 

 origin is indicated by peculiarities of formation in all the 

 more recent rocks. 



There are few branches of science which admit of 

 speculation to the extent to which we find it carried in 

 geology. The consequences of this are shown in the 

 popular character of the science. A few observations 

 arc made over a limited area, and certain structural con- 

 ditions are ascertained, and at once the mind, ' ' fancy 

 free," penetrates the profound depths of the earth, and 

 imagination, having " ample room and verge enough/' 

 creates causes by which every effect is to be interpreted. 

 Such students, generally ignorant of the first principles 

 of physics, knowing little of mineralogy, and less of 

 chemistry, to say nothing of palaeontology, having none 

 of the requisites for an observer, boldly assume premises 

 which are untenable, and think they have explained a 

 phenomenon, given to the world a truth, when they 

 have merely promulgated an unsubstantiated specula- 



