GUMMING ON THE ISLE OF MAN. 327 



merates, and probably also through the limestone series (see Map, 

 PI. XV.). This dike seems to have been affected by the dislocation 

 before noticed. A series of parallel dikes occurs, penetrating the 

 schist a little further to the north, generally conforming to the strike 

 of the schist, and not intersecting the Old red conglomerate. These 

 might be taken for grauwacke beds in the plane of the schists, but the 

 wall of one of them is very well exhibited, and shows the well-known 

 tessellated appearance marking the surface of trap-rocks. Proceed- 

 ing still northwards, we find coming out from under the drift a trap- 

 dike, which winds about and ramifies amongst the Old red conglo- 

 merate with a general northerly direction, till it meets and merges 

 into the great dike intersecting the middle of Langness in a direc- 

 tion N. 15" W. mag. It will be seen that this dike presents on the 

 ground-plan numerous branches, several of which terminate in a 

 north-westerly direction. If we now cross over to the south-eastern 

 side of Langness, we find the same dike running out into the sea, 

 having the same general direction (S. 15° E. mag.), and including 

 altered masses of the schist. The total width of this dike, with its 

 included masses, is here forty-five feet. 



On the summit of the ridge of Langness, about 200 yards to the 

 north of the land-mark, we find the greenstone dike before de- 

 scribed running here N. 65° W. mag. This dike is intersected by 

 the trap we have just noticed, but the intersection is covered up by 

 the drift. It is afterwards seen running out in a mass into the sea 

 on the north-eastern side of Langness, where its structure may be 

 well examined. In passing up the same side of the peninsula north- 

 wards from this point, we fall in with several masses of greenstone 

 amongst the schists (see Map, PI. XV.). 



About 500 yards north-eastward of the former trap-dike, a second 

 is seen, thirteen feet Avide, running in a direction N. 25° W., and 

 this re-appears on the western side of Langness, with the same 

 direction, but soon divides into two main branches, one of which 

 runs at right angles to this direction along the saddle where the Old 

 red sandstone is brought up, and then returns to that former course 

 for a short distance and terminates ; the other turns a few degrees 

 westward, and is shortly lost sight of under the sea-weed. 



If we cross over the narrow neck uniting Langness with the main 

 island into Derby Haven, a continuation of the before-named 

 saddle again brings the Old red conglomerate lor a short distance to 

 the surface ; but crossing a synclinal to the southern corner of the 

 bay, we find this rock coming up again regularly from under the 

 limestone and resting unconformably upon the schists, which are 

 here contorted by a mass of greenstone, apparently continued in a 

 somewhat irregular dike to the northern extremity of the little 

 island upon which stands the fort and ruined church. At the 

 southern extremity of the bridge uniting this island with Lang- 

 ness, we meet with another trap-dike, three feet wide, running 

 N. 20° W. magnetic ; and at the northern end of the bridge near 

 the church, another running N. 15° W. : these dikes arc continued, 

 ill directions generally parallel to each other, across the bay to the 



