Mr. Hvtton on the Stratiform Basalt. 211 



injection of the Whin Sill might be even after that of the deposition of 

 the Lias, except so far as the evidence may go, afforded by the Dyke at 

 Quarrington Hill, already named. This is, to my mind, at variance 

 with the physical state of the country, for if the Basalt was intruded at 

 so comparatively late a period, it is clear the Metalliferous veins and 

 faults of the district are of still later date, the Basalt and all the other 

 beds being alike affected by them. 



The valleys also, even those of very small streams, running eastward, 

 which now cut down to the Whin, and which we cannot suppose to 

 have had an existence prior to the rising of Cross Fell, must all have 

 been formed since the period indicated, or surely the Basalt rising so 

 near the surface under an enormous pressure, would have found a vent 

 in such situations. 



Had the Basalt thus insinuated itself, we ought to find all the per- 

 pendicular partings, which are common to the Carboniferous, as to 

 other formations, full of the injected matter ; but this is certainly not 

 the case, and if this formation had any open veins existing in it, at 

 the time of the Basaltic irruption, then decidedly these should be 

 found filled with the Basalt ; but no such circumstance is known, and 

 this is perhaps the best examined, and the most extensively worked, 

 mining district in the world. 



My opinion is, that this bed of Basalt was produced by an over- 

 flowing of Lava during the deposition of the Mountain Limestone, after 

 those beds which are found below, and prior to those above it. 



It has been observed, that there are, in some instances, two or more 

 beds of Basalt : these are separated sometimes by a bed IS inches in 

 thickness ; at others, by many fathoms of regularly interposed Lime- 

 stones, Sandstones, and Shales, which would indicate a succession of 

 overflowings at different periods. 



The chemical action exhibited upon the rocks in contact with the 

 AVhin is highly interesting, and is in a greater or less degree, almost 

 always observable, the Limestone being often rendered crystalline ; but 

 it by no means follows that this is the case wherever it approaches 

 the Whin, instances occurring in many situations (as on Murton Fell) 



