460 



PROOFS OF INTRUSION OF TRAP. 



all the phenomena. The case near Long's Quarry is equally subversive of the notion of 

 contemporaneous deposit, as may be seen in the irregular dome of trap which has been 

 recently exposed near the banks of the Avon. 



If, however, we quit the pigmy dykes of Charfield Green, which are necessarily 

 obscure in parts of their course, owing to the flat surface of the ground which they 

 traverse, and examine any of the chief trappean rocks north or south of the Avon, near 

 Damory Mill, we meet with the most unanswerable evidence of their intrusive character. 

 If, for example, we inspect the mass extending from Avening Green to Crockley Wood, 

 we see that it is not parallel to the strata for twenty yards together ; for although not 

 exceeding the width of 100 paces at Avening Green, where it is an irregular boss 

 with altered rocks upon its sides, before reaching Crockley 's it diminishes to a few 

 yards, and passing by that farm house with a broken and irregular outline, it suddenly 

 bulges out into a great mass, not less than a quarter of a mile in width, and oc- 

 cupying Crockley's Wood, throws off, in opposite directions, the strata in contact with 

 its flanks. Wherever this rock does not rise to the surface, its course is well known 

 to the farmer by the dry and absorbent nature of the soil above it, which is strongly 

 contrasted with the heavy clays of the Caradoc Sandstone, through which the trap has 

 forced its devious course. At Horsley Mill, where it appears to have burst out from 

 north to south, the trap is composed of great globular concretions, partially enveloped 

 by broken pellicles of sandstone, limestone and shale, all more or less altered and oc- 

 casionally containing fossils. On tracing this trap to the edge of the Caradoc Sand- 

 stone, east of Woodford Green, the latter appears fractured and distorted in every 

 imaginable direction, points of the former protruding here and there through the 

 broken and indurated strata, which are thrown off towards Woodford Hill. All the 

 evidences in Michaelwood Chace are equally decisive of the intrusive character of the 

 trap, but especially at the extensive quarries opposite Damory Mill, where a short and 

 very uneven ridge of the rock rises up through the sandstone, and produces the pic- 

 turesque and rocky outline in the gorge of the Avon. In their central portion, where 

 deeply cut into, these fine quarries present nothing but reddish and greenish trap, 

 usually arranged in large concretions' which exfoliate concentrically, and in them we 

 find passages from varieties of tuf and amygdaloid, to beautifully compact, crystalline 

 greenstone. Not a trace of sedimentary deposits or of fragments containing fossils, is. 

 detectable in the central part of this mass of volcanic matter, but as we ascend to the 

 surface and flanks of the quarries, coatings of serpentine appear on the joints of the 

 rock, and finally beds of purple and green shale, with bands of sandstone full of fossils 

 (including the small ornamented trilobite Trinucleus), are tilted off from the sides of the 

 protruding mass, dipping in different directions, some of them to the south, others 

 particularly on the left bank of the river to the south-west, indicating a force acting 



1 A single concretion which I observed in the Damory quarries measured twelve feet by six. 



