242 ME. H. H. ARNOLD-BEMEOSE ON A SILL AI7D [May 1 899, 



small lava-flow, which may be on the same horizon as one of tliose 

 near the southern fault. 



Minor faults trending roughly east and west are seen in the 

 limestone along the middle road nearly opposite the marble-quarry. 

 They have a small throw of 3 feet and less, and the walls of the 

 joints have sometimes a slickenside surface. 



The limestone between the middle and lower roads immediately 

 north of the southern fault is broken by fissures. 



III. The Lavas and Inteusive Doleeite oe the Inliee. 



It will be seen from the map (PI. XIX) and horizontal section 

 (fig. 1, p. 244) that the compact dolerite is sometimes found resting 

 on the limestone, and at others is separated from it by clay (not 

 shown in the map) or by a varying thickness of vesicular lava. 

 This lava is seen resting on the limestone in the gully leading up 

 to Meadow Farm, and probably attains its greatest thickness 

 there, or a short distance north on the upper portion of the hill on 

 the western side of the dale. It is not seen at this point on the 

 opposite side, being carried down under the road by a south-easterly 

 dip. In the quarry, about 2 feet of it was seen at the base of the 

 compact dolerite by the Rev. J. M. Mello and the late Mr. Wilson ;^ 

 though this I have not seen, owing to its having been covered up 

 for several years by debris from the quarry-workings. Eesting 

 upon the compact dolerite is a vesicular lava, which can be traced on 

 the eastern side of the valley from the northern to the southern 

 fault. 



The lower road to Tideswell passes along the bottom of Tideswell 

 Dale. Although the beds near the southern fault show signs of 

 disturbance, the limestones seen below the compact dolerite of the 

 quarry soon dip nearly due north. As the road ascends the valley, it 

 passes successively through higher beds of limestone, enters the 

 compact dolerite above them, and continues in it as far as the 

 northern fault. The horizontal section (fig. 1, p. 244) was made in 

 a direction nearly at right angles to the strike of the beds at the 

 western and eastern extremities, close to, and nearly parallel with, 

 the small valley which runs up to Meadow Earm. At the western 

 end of the section the limestone is seen dipping under the vesicular 

 toad stone on the southern slope of the small valley. The compact 

 dolerite above it is seen in this valley, and also on the hillside along 

 which the section was made. The section crosses the middle and 

 lower Tideswell roads at a point about 800 feet north of the 

 quarry : the limestone below the dolerite is seen in both roads. It 

 dips nearly due north, and the beds in the direction of the line of 

 section are almost horizontal. Below the compact dolerite, about 

 50 feet of limestone is seen, the upper jjortion on the eastern side 

 of Tideswell Dale being marmorized. The limestones below the 



^ Quart. Journ. Geol. Soc. toI. xxvi (1870) pp. 701-702; Geol. Mag. 1870, 

 p. 522. 



