﻿Vol. 6 1.] ORDER OF SUCCESSION OF THE MANX SLATES. 361 



of fine laminae. It is a very distinct rock, though it may become 

 less so in places. It may be seen, however, in its true form on 

 both sides of the upper part of Glen Laxey, that is, in the tram-line 

 cuttings on the opposite side of the valley from Laggan Agneash, 

 and on the same side as Laggan Agneash in various exposures (the 

 beds always dipping at various angles in a westerly direction), 

 and may be traced thence over the slopes above. No other grit is 

 comparable to this, in its altered form and laminated structure ; and 

 it is essential to distinguish it by those constant characters from 

 those other less-altered, but unlaminated grits to which the same 

 name has been applied. It is the lowest stratum, according to my 

 observations, anywhere exposed on the surface of the island, at 

 least in the northern part, unless some crystalline quartzite, also 

 without lamination, seen near Slieau Ouyr, represent something- 

 lower. 



With this stratum ends on the surface the typical triad of the 

 older Manx Slates, exhibiting a steady north-westerly dip, though at 

 various angles, with which any indications of folding do not interfere 

 on a large scale. The order of their succession is the same as that 

 adopted by Mr. Lamplugh, but there is nothing among them at all 

 resembling a schistose breccia. To see this and its relations to the 

 other strata, we must pass to the north-western side of the axis. 

 Here, along a stream running a little to the north of the road which 

 leads from Snaefell to Sulby, and enters the glen by the waterfall 

 at Tholt-e-will, we get in the upper reaches a ' reappearance of the 

 striped slates, with gritty alternations like those seen higher up/ 

 These are accounted for by Mr. Lamplugh as an upturn of the same 

 strata, but there is no evidence of any change of dip ; they continue 

 the same dip as before,' and are followed by the Barrule Slates as 

 before ; in other words, there is a repetition of the upper part of the 

 typical series, which was left behind when the Snaefell range was 

 uplifted along a strike-fault. We are, therefore, on an ascending- 

 series l as we descend the gorge of Tholt-e-will, and at the end we 

 find a series of slates of an ordinary appearance, but on breaking 

 them up we find them full of fragments. We are thus introduced 

 to the Schistose Breccia. 2 It is associated with the Barrule Slate, 

 of which it appears as forming a part ; but we must seek for this 

 more certain proof, for in this part of the island there are many 

 places where rocks are marked as ' crush-conglomerate,' in which 

 no sign of a fragment is seen, included, we must suppose, in the 

 ' certain bands in which the bedding-planes are only partially 

 disrupted' (op. cit. p. 65). 



(4) The Schistose Breccia. 

 Glen Auldyn.— In the upper part of Glen Auldyn, a mass of 

 Barrule Slate occupies the lower ground, and a stream descending 



1 See 1-inch Geol. Surv. Map, Sheet 100. 



2 See Mem. Geol. Surv. ' Geology of the Isle of Man' 1903, pp. 133-34. 



