of the Parallelism of Contcmporaneom Lines of Elevation. 123 



Exmoor, which, when the eye glances over the map, appear 

 to be its prolongation, and yet are really anterior to the age 

 of the new red sandstone*. 



III. A third parallel anticlinal line traverses the Vale of 

 Pewsey, another valley of elevation on the greensand, sepa- 

 rating the chalky ranges of Salisbury Plain and Marlborough 

 Downs. — The protrusion of the greensand, in the prolongation 

 of this line at Ham and Kingsclere, (see Buckiand's paper f, 

 Geol. Trans. 2nd series, vol. ii.) within the western angle of 

 the London basin, may be referred to the same line of ele- 

 vation, which will give it an extent of about 30 miles, I am 

 not aware that its eifect on the contiguous tertiary strata has 

 been noticed, and can therefore only conjecture that it will 

 probably, on examination, prove exactly contemporaneous 

 with that of :he Isle of Wight. 



The above elevations, that of the Isle of Wight certainly, 

 and those of the Weald and Vale of Pewsey, by the most pro- 

 bable analogy appear to have taken place subsequently to the 

 formation of the inferior tertiary strata, and before the more 

 recent beds. Elie de Beaumont assigns only the systems of 

 Corsica and Sardinia to this epoch, and characterizes them 

 as having a north and south direction ; whereas our examples 

 uniformly range E. and W. 



Supplement to I. — Although in the northern portion of our 

 Island the absence of cretaceous and tertiary formations de- 

 prive us of this direct test of the aera of the disturbances which 

 have there affected the sti-ata, yet the association of many of 

 these disturbances with apparently the newest varieties of the 

 trap formation, and their intimate analogies, in general direc- 

 tion and in most of their geological circumstances, with those 

 which we trace on the opposite side of a narrow channel, in 

 the basaltic area of Ireland, must at once induce us to refer 

 them to a similar age ; and in Ireland this is shown, by the 

 presence of the chalk through which the basaltic eruptions 

 have burst and ovei'flowed, to be posterior to that of the cre- 

 taceous formation. On the Scotch coast, in Skye and Mull, 

 we only see the basalt in contact with the oolites and lias, 

 which, as at Portrush, &c. in Ireland, are dislocated, altered, 

 and overflowed by it. But to consider the case more generally, 

 we shall find the general bearing of all the strata in Scotland, 

 as in England, N.E. and S.W., and the same line is pro-, 

 tracted into Ireland: this is the general bearing of the southern 



• See Geol. Trans, vol. ii. 2nd scries, for Dr. Fitton's Hastings Section, 

 and those of the Western Weald, where the anticlinal line ranges through 

 Hastings, and comes north of Petersfield. 



t An alistract of this paper will be found in Phil. Mag. vol.ixv. p.214.— Eu. 

 11 2 



