GUMMING ON THE ISLE OF MAN. 331 



fault, combined with tlie axis, already mentioned as having elevated 

 the schists, has raised the Old red conglomerate to the surface on 

 the hill to the south-west above Athol Bridge (sometimes called 

 Silverburn Bridge). It appears here in considerable force on the 

 Peel road, which has in part been cut through it, and forms an in- 

 teresting section. 



A little above Athol Bridge, near the mill, there is some evidence 

 of a disturbance and fault at right angles to that which I have men- 

 tioned, which is continued apparently quite into the mountain range 

 of South Barrule. The rise side of this fault appears to be to the 

 north. 



I have never seen or heard of any indication of limestone to the 

 north of a line drawn hence to Port-le-Murray. The whole distance 

 however to the sea is covered up by diluvium and estuary deposits, 

 and if the beds are not cut off by a fault, we must conclude that a 

 line nearly in this direction formed the ancient limit to the basin on 

 the north-west (see Map, PI. XV.). 



Directing our course again southward along the Peel road, we 

 come upon the large development of limestone forming the Ballahot 

 quarries and supplying the limekilns of this neighbourhood. The 

 beds dip gently, but on a saddle, towards Poolvash and the Carrig, 

 and soon attain a considerable thickness. The base of these beds 

 is not seen in the quarries. On the road however which crosses 

 from the Peel road to Rushen Abbey, just by Ballahot farmhouse, 

 we find ourselves upon the underlying Old red conglomerate, which 

 is here observable in its upper beds as white quartz gravel in a lime- 

 stone paste. The dip is here 10° west of south. Following this 

 road down to the Abbey, we find this same bed of the Old red con- 

 glomerate on the side of the road which leads by the west wall of 

 the Abbey gardens, and the north Abbey cottage to Crossag Bridge. 

 The fault however along the course of which the Silverburn runs, 

 and which may be observed in the river at Crossag Bridge, must 

 have turned the direction of the basset edge of the Old red conglo- 

 merate to the southward, and it is covered up by the diluvial gravel 

 in the low ground in the neighbourhood of the Abbey. 



If we follow the Silverburn towards Castletown from Ballasalla, 

 we find it presently passing through some broken limestone ground, 

 but the nature and extent of the disturbances are not well-developed. 

 My impression is, that the river runs along the line of a crack on 

 the ridge of the limestone in a direction 4-0° west of south ; and 

 there is a cross fault at right angles, perhaps connected with that 

 which runs in this direction from Coshnahawin. It is only in a few 

 places that we can obtain an angle of dip, and the beds have sufi'ered 

 considerably by denudation. 



At the mouth of the river in Castletown harbour we find the lime-- 

 stone again presented in an anticlinal axis running 70° west of south 

 from imder Government House towards Scarlet Head. This axis is 

 cut through nearly at right angles by a trap-dike which makes its 

 appearance on the south side of the old pier in the new harbour. 

 This dike has greatly altered the limestone, and more particularly 



