490 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [May 9, 



rock here has a great affinity to the grey rocks of Cornah, which 

 have no distinct stratification. Here, however, black shales occur in 

 the quartz-rock, which dip at a high angle to the north-west. 



The hills immediately south of Sulby, four miles and a half west 

 of Eamsey, have a distinct slaty nature, and the slates have been 

 worked for roofing-purposes. Here also the Skiddaw slates dip 

 towards the north-west. Along Sulby Glen, a narrow valley which 

 leads to the highest land in the island, good exposures of rocks occur ; 

 and here, too, the Skiddaw slates dip north-west. Over the col which 

 separates the Sulby River from the river jSTib, rocks of the same age 

 occur; and among them the north-west inclinations obtain. These 

 rocks, with the same dip, continue to the river Peel. 



From Peel the Skiddaw slates form the coast to Port Erin, and 

 have also north-west inclinations. At Glen May, about four miles 

 south of Peel, these Skiddaw slates have a conglomerate in them ; 

 and south of Glen May they abound in quartz veins. At Port Erin 

 the anticlinal axis which was seen as occurring at Porth Moar and 

 extending inland again appears ; and on the south-east side of this 

 axis the strata assume the inclination shown among the Skiddaw 

 slates to the south of Porth Moar, namely towards the south-east. 

 The district around Castletown is principally occupied by Carboni- 

 ferous Limestone, which has been described by the Eev. J. S. Cum- 

 ming. About two miles east of Castletown, at Lang Ness, the 

 Skiddaw slates are again seen, being overlain on their edge by Old 

 Eed Conglomerate. From Lang Ness north-eastward Carboniferous 

 Limestone again occurs, and forms the coast from Derby Haven to a 

 small stream about a mile and a half north-east, called the Santon 

 River. The Skiddaw slates reappear on the east side of this stream, 

 having south-east dips ; and with these dips they continue along the 

 coast to Greenwick, where they become coarser in their nature and 

 have a well-developed conglomerate in them like that of Glen May. 

 The Skiddaw slates continue onwards, forming the coast, somewhat 

 contorted but with predominant south-east dips, until Douglas Head 

 is reached. At Douglas Head a change takes place in the rocks, 

 green ash -beds making their appearance and conformably overlying 

 the Skiddaw slates. These ash-beds strike across Douglas Bay, and 

 include within them the Coniston Rocks, upon which the Tower of 

 Refuge is built ; and this strike connects the green rocks of Douglas 

 Head with those of Bank How. We consider the Lower Silurian 

 rocks of the Isle of Man to belong to the Skiddaw slates, the lower 

 portion of the green ash-beds and porphyries of the Lake-district 

 and the Lower Silurian rocks of this island being on the exact hue 

 of strike of the Skiddaw slates of the Skiddaw country and of their 

 overlying green rocks. 



The foregoing section, taken through the centre of the Isle of 

 Man, shows the position of the anticUnal axis which traverses the 

 island in a north-east and south-west direction, as it occurs near 

 the road leading from Douglas to Peel. The more mountainous 

 portion of the island lies on the north-west side of this axis. The 

 section also shows at its south-east end the ash-beds of Douglas 



