212 Messrs. Buckland's and Conyeeare's Observations on the 



All these formations which have here been simply enumerated, will be de- 

 fined and fully described in the course of the present Memoir. 



On comparing the strata of the two great series of rocks, the first circum- 

 stance that forces itself on our attention, is their difference of inclination to the 

 horizon. Those of the first series are generally highly incHned, and exhibit 

 marks of disturbance in every form of fracture and irregular position. Those 

 of the second series, on the contrary, are either perfectly level, or inclined im- 

 perceptibly to the horizon : they seldom show traces of internal derangement, 

 and they rest transversely on the truncated edges of the strata of the former 

 series. The horizontal formations, throughout the greater part of our district, 

 are confined to lower levels than the inclined, and form upfiUings (as they are 

 termed) between the loftier ridges, into which the inclined strata ascend on 

 emerging from the horizontal deposits thus partially spread over them. 



Such being the covering by which these older formations are invested, and 

 such the irregularities of their stratification, it is only by multiplied observa- 

 tions on the character and dip of the strata, as displayed in their scattered 

 and seemingly independent masses, and by a comprehensive study of those 

 observations, that the geologist will be able to ascertain that a determinate 

 succession prevails in the order of the inclined strata; and thence that he will 

 be able to infer the former or actual continuity of those masses, and trace from 

 one part of the district to another their relative bearings and connexion. 



The order of super-position in the inclined strata being very regular, 

 scarcely less so than in the overlying, it seems probable that they were formed 

 originally in a nearly horizontal position, and that they owe their present frac- 

 tures, curvature, and elevation, to convulsions long subsequent to their being 

 formed ; and since the internal derangements which affect the inclined strata 

 very rarely extend to the overlying ones, the disturbing causes, it should ap- 

 pear, were of high antiquity, and anterior to the deposition of the overlying 

 beds. 



The entire want of conformity between the two series of rocks causes the 

 lowest of the overlying strata to come into contact indifferently with any one 

 of the inclined beds. It is impossible, therefore, at a given spot, without in- 



Buch, we have substituted the term " dolomite " for magnesian limestone. That definite triple 

 salt, the carbonate of lime and magnesia, when found native in a state of purity, and associated 

 with primitive rocks, has received the name of dolomite; and it is the same chemical salt, ren- 

 dered impure by iron or bitumen, or by carbonate of lime, intimately but mechanically blended 

 with it, which occurs in our first and second series of rock-formations, and has there been called 

 magnesian limestone. It appears to us desirable to use but one appellation for substances not 

 essentially differing in chemical constitution. 



