320 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



but hitherto without success ; the only indication of organic exist- 

 ence consisting of the fucoids which occur in some of the upper 

 beds. 



I have seen nothing in any of these schists which I could recog- 

 nize as true slate, or as exhibiting cleavage distinct from stratifica- 

 tion, the stratification seeming pretty clear, as well from the evidence 

 of the fucoids as from ripple-marks and various coloured layers. I 

 have observed at the northern extremity of Langness, in some parti- 

 cular lights, an appearance which is not unlike a contorted bedding, 

 in a direction entirely differing from the fissile planes of the schists 

 at this point ; yet it is here that the fucoids are most abundant, 

 and they lie in the plane of cleavage. All the schists are greatly 

 traversed with joints, and there is a general tendency to an imper- 

 fect rhomboidal structure, especially in the neighbourhood of tlie 

 greenstones. 



The schists immediately under the Old red conglomerate are 

 deeply claret-coloured, and at the southern extremity of Langness 

 contain as much as fifteen per cent, of pure iron. 



At Spanish Head there is a series of liglit blue beds, which at a 

 distance may be mistaken for limestone. This rock is used largely 

 for lintels and gate-posls, and is slightly elastic. It appears to be 

 nearly horizontal, but has been rent into deep chasms in conse- 

 quence of a land- slip. 



Between the schists and the Old red conglomerate there are no 

 formations visible ; and we have several sections both on the north- 

 west and south-east sides of the island where the unconformity of 

 the Old red sandstone to the schists is clearly exhibited. Perhaps 

 the most beautiful is that on the eastern side of Castletown Bay in 

 the Peninsulaof Langness, where the conglomerate forms the crown 

 of a fine natural arch, and the unconformable claret-coloured schists 

 (the layers of which are distinct and variegated) form the abut- 

 ments. 



The Old red sandstone appears in two districts ; first, on the north- 

 western side of the mountainous chain in the neighbourhood of Peel, 

 where it is of moderate thickness (not more than 300 feet), and co- 

 vers from one to two square miles*. It is here in the character of 

 a fine sandstone, used extensively for building purposes, flags and 

 tombstones. Its dip is north-west and at a high angle. The same 

 rock appears again in the south of the island in the neighbourhood 

 of Castletown, where it lines the whole of the limestone basin, and 

 may be observed at the basset edge, almost continuously from the 

 southern extremity of Langness, in a curved line by Ronaldsway, 

 Coshnahawin (at the Santon river mouth), Ballasalla, Ballahot, 

 buried under diluvio-glacial and pleistocene deposits in the neigh- 

 bourhood of Ballahick and Arbory, and overlapped by the linie- 

 stone at Port-le-Murray. In this southern basin the Old red exliibits 

 for the most part the character of a conglomerate, and in no place 

 where it can be observed is it more than fifty feet in thickness, 

 being often not more than four or five feet, and giving plain indi- 

 * The greater portion is covered up by the tertiary clays and gravels. 



