of the Cumbrian Mountains. 55 



assume that similar effects have been produced by similar causes acting within 

 a very limited region. And, if this hypothesis be admitted,, we can advance 

 a step further^ and point to the probable origin of these great diverging 

 fissures : for the valleys start from a central region, which is violently broken, 

 where the dip and range of the stratified masses is unsymmetrical, and which 

 is marked by protruding mountains of granite and syenite. 



Secondly. Notwithstanding the great dislocations of the masses of green 

 slate and porphyry, forming the support of the limestone, there is hardly any 

 instance in w hich they are bent and contorted. After seeing the violent contor- 

 tions of some portions of the other slate systems of the region, this fact might 

 appear inexplicable ; but we find a solution of our difficulty in the enormous 

 irregular masses of hard unbending felspathic and porphyritic rocks, ini- 

 bedded in, and so intimately mixed with, the green quartzose slate, that we 

 in vain seek to separate the formations from each other. If, then, we 

 admit the igneous origin of the porphyries, in what way can we account for 

 the accompanying, and apparently almost contemporaneous, deposits of stra- 

 tified chloritic slate ? I know no explanation so probable as that which sup- 

 poses igneous and aqueous causes to have acted together — the porphyries 

 to have been produced by some modification of submarine igneous action — 

 and the chloritic slates to have been deposited from the waters in the same 

 region, and in the same periods of time : the first operation supplying, at 

 least in part, the materials for the second, and similar operations being many 

 times repeated. 



Thirdly. The previous details enable us clearly to determine the mean line 

 of bearing of the whole system of stratified rocks associated with the lime- 

 stone ; and this line makes the schistose masses, one after the other, to abut 

 against the carboniferous zone. This fact alone proves that the older and 

 newer systems are entirely unconformable — a conclusion confirmed by all the 

 sections which connect the slate rocks with the calcareous zone. 



Again : There is no gradation between the two systems ; their position is 

 not only unconformable, but the transition from one system to the other is 

 instantaneous. Masses of red conglomerate are found here and there, near 

 the base of the older mountains, resting upon the edges, and filling up the 

 inequalities of the component strata, and upon these conglomerates are depo- 

 sited the lower beds of the carboniferous limestone. These facts seem to 

 prove, that the elevation of the cluster of mountains of Cumberland was sud- 

 den (which seems to be almost implied by the great faults and dislocations 

 above described, as well as by the regularity of the lines of bearing), and that 

 all those causes which produced the elevation of the older strata, and deter- 



