6 EXPLANATION OF PLATE 1. 



if they had been injected, either at the time of, or after the 

 elevation of all the strata, and had produced but little 

 disturbance in the rocks through which they are protruded. 

 It should however be understood, distinctly, that some In- 

 jections may have preceded the elevation of Strata to their 

 present height, and that numerous and successive eleva- 

 tions and injections, attended by various degrees of frac- 

 ture and disturbance, have prevailed in various localities 

 during all periods, and throughout all formations ; from the 

 first upraising of the earliest Primary rocks, to the most 

 recent movements produced by existing Volcanoes. M. 

 Elie de Beaumont has discovered probable evidence of no 

 less than twelve periods of elevation, affecting the strata of 

 Europe. 



Examples of the fractures and dislocations attending 

 these movements, and producing faults, are represented in 

 our Section by the lines designated by the letter 1. Some of 

 these fractures do not reach to the present surface, as they 

 affected the lower beds at periods anterior to the deposi- 

 tion of more recent strata, which cover unconformably the 

 summits of the earlier fractures. (See 1. P. R P. R F.) 



Basalt. 



A third series of Igneous Rocks is that which has formed 

 dykes, and masses of Basalt and Trap, intruded into, and 

 overlying formations of all ages, from the earliest Granites 

 to the most recent Tertiary Strata. These basaltic rocks 

 sometimes occur as Beds, nearly parallel to the strata, into 

 which they are protruded, after the manner represented in 

 the carboniferous Limestone of our Section, f. 2. More fre- 

 quently they overspread the surface like expanded sheets 

 of Lava. Our Section gives examples of Trap under all 

 these circumstances. At f. 1. it intersects and overlies 

 Primary strata ; at f. 2. f. 3. f. 4. f. 5. it stands in similar 



