4 THE WONDERS OF GEOLOGY. 



respect geology is, therefore, not alone. Its ascertained facts are 

 numerous ; they are correctly observed and reported ; they are 

 skilfully classed, and a sufficient number of general as well as par- 

 ticular conclusions has been drawn from them to furnish the basis 

 of a noble science. Its boundaries are daily extending, and will 

 be extended without limit, by continued observations — its evidence 

 will constantly accumulate, and although its theoretical speculations 

 may change, nothing can occur to subvert the grand conclusion, 

 that the earth has a regular structure, and that its materials have 

 been arranged under the operation of general laws of great energy 

 and duration, the physical expression of omniscient intelligence 

 and omnipotent sway, guided by benevolent design, which becomes 

 more and more apparent and convincing with every new and suc- 

 cessful research in geology. 



4. Sources of its evidence. — If the inquirer ask for the 

 source of geological evidence, it may be answered that it is 

 derived from diligent and careful examination of the structure of 

 the earth; and for this object our means are more ample than 

 might at first appear. 



Every artificial excavation — every well and cellar — every cut for 

 a fort, for a common road, a railway, or a canal — every stone quarry 

 — every tunnel through a mountain — and every pit and gallery of a 

 mine bored into the solid earth, furnish means of perusing its 

 interior structure. Still more do the inland precipices, and the 

 rocky promontories and headlands along the rivers, lakes, seas, and 

 oceans ; the naked mountain-sides ribbed with strata, that bound 

 the defiles, gorges, and valleys ; the ruins accumulated at the feet 

 of lofty pinnacles and barriers, and those that have been transported 

 and scattered, far and wide, over the earth, present us with striking 

 features of the internal structure of our planet. 



Most of all, do the inclined strata push up their hard edges, in 

 varied succession, and thus faithfully disclose the form and sub- 

 stance of the deep interior, as it exists, many miles beneath the 

 observer's feet. 



Volcanic eruptions throw up into daylight the foundations of the 

 fathomless deep below, in the form of ejected or molten masses, or 

 in rivers of ignited and fluid rocks, which congeal on the surface 

 of the ground, either inflated like the scorirc of furnaces, or in solid 

 m asses, with no visible impress of heat ; and often containing very 

 perfect and beautiful minerals, elaborated in the volcano, or dis- 



