2 EXPLANATION OF PLATE 1. 



full order of succession here represented, no fact is inserted 

 for which authority cannotbe found. The near approximation 

 of this synoptic representation by Mr. Webster to the facts 

 exhibited by an actual section, may be estimated by com- 

 paring it with the admirable section across Europe, pub- 

 lished by Mr. Conybeare in the Report of the Proceedings 

 of the British Association for the Advancement of Science 

 1832, and with his sections of England, in Phillips and 

 Conybeare's Geology of England and Wales. 



For facility of reference, I have numbered the princi- 

 pal groups of stratified rocks represented in the section, 

 according to their most usual order of succession ; and 

 have designated by letters the crystalline or unstratified 

 rocks, and the injected masses and dykes, as well as the 

 metallic veins, and lines of fracture, producing dislocations 

 or faults. The crowded condition in which all the Pheno- 

 mena represented in this section, are set together, does 

 not admit of the use of accurate relative proportions 

 between the stratified rocks, and the intruded masses, veins, 

 and dykes by which they are intersected. The adoption 

 of false proportions is, however, unavoidable in these cases, 

 because the veins and dykes would be invisible, unless 

 expressed on a highly exaggerated scale. The scale of 

 height throughout the whole section is also infinitely greater 

 than that of breadth. The plants and animals also are 

 figured on no uniform scale. 



The extent of the different formations represented in this 

 section, taking their average width as they occur in Europe, 

 would occupy a breadth of five or six hundred miles. A 

 scale of heights, at all approaching to this scale of breadth, 

 would render the whole almost invisible. The same cause 

 makes it also impossible to express correctly the effect of 

 vallies of denudatioriy which are often excavated through 

 strata of one formation into those of another subjacent 

 formation. 



