FACTS AND INFERENCES. 307 



20. The basaltic dyke bears such strong marks of having been 

 eomposed of fused matter, thrust upwards through a fissure in the 

 strata, by volcanic agency, or something akin to it, that we may 

 reasonably presume, that such agency may have been employed 

 in raising the strata, out of the ocean in which they were deposited. 

 — Some may think, that we should have placed this observation 

 among our conjectures, rather than among facts and inferences : but 

 the appearances of igneous origin presented by our whinstone 

 dyke, and other similar dykes, are so strong, as nearly to reduce 

 the matter to absolute certainty.* Had the fissure occupied by the 

 whin dyke been filled from above, as some suppose, whence were 

 the materials derived ? There are no strata above capable of filling 

 it; and if we could suppose that all the higher members of the 

 series once extended over the space through which the dyke runs, 

 which of these strata could supply the requisite materials? Why are 

 the numerous cracks and fissureSj in the oolite and other strata, not 

 filled with the same substance? And, since so many of the upper beds 

 consist of limestone, why does the dyke contain so small a portion 

 of calcareous matter? If the fissure was filled from above, by secre- 

 tions from beds that have been washed away; why does it not every 

 where reach the surface? Or rather, as it is harder than the strata- 

 washed away from it, why does it not every where stand up above the 

 surface like a wall, as it does at Langbargh and some other places ? 

 Besides, why are its contents disposed in large oblong blocks, lying- 



* The Rev. A. Sedgwick, Woodwartlian Professor, Trinity College, Cambridge, examined 

 the rocks of this coast a few months ago, and having paid particular attention to our basaltic 

 dyke, and to some trap dykes near Newcastle, and in High Teesdale, was fully convinced, that 

 the evidence for their igneous origin appears quite complete. Near Caldron Snout, he found 

 the limestone, where it comes in contact with the trap, converted into a granular mass, in which 

 you lose all trace of organic remains; but gradually recovering its usual texture at the distance 

 of a few feet. The coal shale, under the same circumstances, is so indurated as to resemble a 

 piece of Lydian stone. 



