S26 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



as to appear like a contemporaneous formation poured forth upon 

 the sea- bottom at the time of the deposition of the schists, while the 

 trap was erupted in a more fluid state and under great pressure, and 

 mixed with the limestone formations of the same basin, having in- 

 sinuated itself, like a fine mud, into very small crevices in the lime- 

 stone, adapting itself to the crevices between boulders of the Old 

 red conglomerate, and having often greatlj^ altered all the beds, 

 including the schists. Though there are many spots where the green- 

 stone and trap must intersect, these are always either covered up with 

 recent deposits, or too much confused to be readily made out. The 

 intersection at this extremity of Langness is the best developed, 

 and even here they are so much buried in sand, that it becomes 

 doubtful whether they cross or merge into each other. 



Proceeding onwards, we meet with the drift capping the highest 

 portion of the ridge ; and as we proceed more to the east, it forms an 

 extended platform at the height of thirty feet above the sea. At 

 the bend or hollow of the promontory we find under the drift the 

 Old red conglomerate, which lies in a depression of the schist, but 

 dips north on the north side of the ridge, and south on the south 

 side, thus giving evidence that the slight elevation of these schists 

 along the line running nearly east and west is of a more recent date 

 than the formation of the conglomerate and the older dark limestone. 

 My present impression is, that this elevation cannot be looked upon 

 as older than that convulsion of the Stack of Scarlet in a north- 

 western direction which contorted all the beds prior to the last 

 eruption of trap-tufi", as I think that otherwise this ridge would have 

 formed a basin to the north of which we should have some indica- 

 tion in the thinning out of the limestone. But so far from this 

 being the case, the different beds of limestone at the Stack on the op- 

 posite side of Castletown Bay are the thickest anywhere developed. 



As we pass up the north-western side of Langness, we still keep 

 on the Old red conglomerate, which here attains the greatest thick- 

 ness noticed in the basin. The base of it appears resting on the 

 schist at the water-worn caves and excavations, and the uppermost 

 beds of it can be readily traced down as they pass under the neigh- 

 bouring limestone. 



A remarkable fault or line of disturbance, which runs from the 

 southern extremity of Langness through Derby Haven, Ronalds- 

 way, Coshnahawin, and up the Santon river, begins to show itself 

 near the caves just alluded to. At this point the Old red sand- 

 stone, dipping at an angle of 5° in a direction N. 65° W. mag., is 

 suddenly broken off' on the south-western side by the upheaval of 

 the promontory of Langness : the broken and upheaved beds of the 

 Old red sandstone and limestone, which were once continuous over 

 Langness, have since suffered entire denudation, most likely from 

 the north-east, the remaining beds lying in hollows on the south- 

 western side, protected by the ridge of schists from any action upon 

 them to the north-east. 



At the same caves we find a dike of amygdaloidal trap running 

 70° west of magnetic south, which cuts through the Old red conglo- 



