S32 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



in those places where it encloses a mass of limestone betwixt two of 

 its branches. In this crystallized and altered limestone we meet with 

 thin strings of galena. I may also mention, that along the side of 

 the dike cutting the southern point of Langness, and in a narrow 

 gully, I have met with fine veins of copper in the schist. In the 

 dike at the caves in Langness, we have sulphuret of iron. 



From Castletown pier-head to Scarlet House several trap-dikes 

 occur, generally at right angles to the anticlinal just alluded to, and 

 following its slight curvatures. There is however one remarkable 

 exception in the dike which runs from under Knockrushen in the 

 direction of the southern end of Derby Haven in a direction S. 70° E. 

 This dike seems to be more compact than any of the others, 

 and its width in solid trap is twenty-one feet. I think it possible 

 that this dike is identical with that running in the same direction 

 from Copenhagen. If it should continue north-eastward in the 

 same direction, it will cut the isthmus of Langness at a point which 

 is buried under sand; but it is not altogether improbable that, 

 making a slight curve, it may also be the same as the more southerly 

 branching dike on Langness, and that the dike at Castletown pier 

 is the more northerly of the two which cut through the promontory. 

 Thirty yards to the south-west of this is a small dike one foot wide 

 running parallel to that which branches from the great Knock- 

 rushen dike; and sixty yards still further south-west, a dike one 

 and a half foot wide, running S. 25° E. mag. ; and again very near 

 to it, under the limekiln, is a smaller one running S. 20° W., and 

 soon terminating. 



All these last three dikes appear to be mere branches of the 

 greater Knockrushen dike, shooting out from it at a point a little 

 above the limekiln at the centre of a semicircular boss. The lime- 

 stone is here traversed by a number of joints and intersecting cracks, 

 and has been considerably altered. 



Passing by Scarlet House we find another boss where the shore 

 turns westward, and continuing in that direction towards the Stack, 

 very sudden and repeated contortions of the strata appear; the 

 strike of the beds, which has hitherto been pretty uniformly W.S.W., 

 trending round towards the south. The cause of this very soon 

 appears in the protrusion of the basaltic mass of the Stack, and the 

 great fault or disturbance running about N. 30° W. mag. from this 

 point (PL XVIL fig. 3). 



At this point there is a series of plutonic rocks of every character 

 and description, containing commingled masses of altered or trap- 

 paceous limestone, whose original order of deposition it is almost 

 impossible to speak of with confidence. The passage from the most 

 decided trap-rock into the most decided limestone is so gradual 

 that it seems hopeless to attempt a classification ; and we are forced 

 to the conclusion, that either under great pressure and under the 

 action of great heat, some of the elements of trap-rocks were made 

 to incorporate themselves with the proximate limestone, or as T have 

 rather concluded, that a deposition of carbonaceous sediment at the 

 bottom of the ancient sea in this locality was going on contempo- 



