Baden Powell — Igneous Rocks of Charnwood Forest, 117 



in the Survey as altered slate or feldspathic porphyry, of which there 

 are specimens in the Museum, justly described as exhibiting great 

 action of heat. But these characters are by no means confined to 

 one spot, but are exhibited by various rocks about different parts of 

 the hill, especially in a large mass of rock on that part immediately 

 above Holgate, marked picturesquely by a gnarled oak growing out 

 of the crevices. 



These appearances of igneous action become more numerous as we 

 approach the syenite of Bradgate. 



Syenite of Old John-hill. — Besides a remarkable isolated mass of 

 syenite, near the base of Old John-hill, close to one of the plantations 

 of Bradgate Park, which, I believe, has not been described, there is, 

 on the shoulder of the same hill, just over the village of Newtown, 

 under a clump of trees, a remarkable collection of blocks of syenite. 

 Some of these seem deeply imbedded. Are these merely transported 

 and heaped on that one spot ? or, is it not an analogous case to that 

 of Black-hill — a true manifestation of syenite in situ ? 



Igneous action. — It is, theoretically, quite conceivable that a true 

 igneous eruption might have vented itself with so little force as 

 merely to break off, as the erupted matter cooled, in detached lumps, 

 especially when under the sea, and be scattered over a small sur- 

 face immediately adjacent, as in these instances ; while it might 

 have been only the same kind of action, in higher intensity, which 

 protruded the heaps and knolls of rock at several other localities, and 

 the larger and loftier hills in other places. 



Following the indications of igneous action in this central region, 

 as we approach its S.E. boundary, towards the syenite of Bradgate, 

 we are naturally led to connect them, and to imagine that the igneous 

 force, after expending itself while pent up, in elevating the slate by 

 a regular fracture, producing the axial valley, with opposing dips 

 along its sides, — in some cases altering the slate into porphyry when 

 it came into closer contact, and even in one or two places itself find- 

 ing a vent, — at the commencement of this intermediate region began 

 to force up new matter, filling up the fracture with elevations, through 

 which in some places the fused matter protruded, and at length ter- 

 minated in exuding through a wider space about Bradgate and its 

 neighbourhood. 



It has been argued by some that rocks adjacent to igneous erupted 

 matter, not altered or upheaved by it, must have been subsequently 

 deposited. I do not see the force of this conclusion ; for if we sup- 

 pose the elevating, dislocating, and altering force to be that of the 

 igneous action, so long as it was pent up beneath the superincumbent 

 mass, then as soon as it found a vent the fused matter- would be 

 ejected quietly without injury to the adjacent rocks, like steam when 

 the valve is opened. 



Extension of axis. — The line of the axis has been traced to extend 

 to the limestone region at Breedon, beyond the N.W. end of the 

 slate region, and is nearly parallel to the great fault which abruptly 

 bounds the coal-field of Ashby on the W. side towards Charnwood, 

 as well as to other faults which traverse it. 



