212 E. HILL AND T. G. BONNET ON THE 



of its earlier history has been destroyed, there is no reason why it 

 should not be called an igneous rock. We speak of a pig of iron as 

 cast iron equally whether it has been just melted from the ore or 

 from the fragments of an ancient railing. If, then, the term igneous 

 rock be used to denote a rock which has been either poured out on 

 the surface, like a lava-stream, or injected among other rocks (the 

 only intelligible sense, as we contend), it has always appeared to us 

 there was never any real ground for doubting the igneous origin 

 of these Charnwood rocks. The evidence adduced against it was of 

 the slightest kind — little more than a supposed transition from these 

 rocks to the adjacent metamorphic sedimentary rocks, and an appear- 

 ance of bedded structure. The supposed " transition " has always 

 turned out on examination to be merely superficial resemblance; 

 the "bedded structure" is only that tendency to parallel jointing 

 which is not rare in large masses of igneous rock. Finally, the 

 discovery of actual intrusive junctions, as already described, may be 

 regarded as setting the question at rest. Owing to the character of 

 the ground these are rare ; but there are three good instances at 

 least in the southern area, and three not quite so easily recognized 

 in the northern. 



The Southern Syenites. — A considerable area (see Map, PI. X.) is 

 occupied by these rocks in the vicinity of Groby, where they also form 

 the southernmost exposures of the Pre-Triassic rocks of the Porest. 

 Here they occur in insular masses, the summits of an ancient undu- 

 lating district on which the Trias was deposited. Excellent sections 

 of the irregular junctions of the two rocks, of the old weather-worn 

 surface of the former, of the sloping stratification and included 

 syenite boulders of the latter, are obtained in the great stone- 

 quarries. There is little doubt that all these syenite masses are 

 continuous beneath the surface, and that there is a tract extending 

 from the village of Groby, for full two miles at least, in a north- 

 west direction, the breadth generally being nearly three quarters of 

 a mile. The presence, however, of slate and grit near Steward's 

 Hay, on the east side of the Ashby road, shows that the south-western 

 boundary of this patch is greatly incurved. Separated by a broad 

 plateau of Trias is the great massif of Bradgate Park, which ends 

 in the immediate vicinity of the ruins. We think this may fairly 

 be regarded as continuous with the former, though the position of 

 the slate north-east of Bradgate House shows that the north-western 

 boundary is also incurved considerably. How far these massifs may 

 extend to the south-east we have no means of knowing, except that 

 the position of the Stable-Quarry Grit in Bradgate Park seems to 

 indicate that we are there upon its eastern limit. North-west of 

 the end of the Groby massif, separated by about three quarters of a 

 mile of upland Trias, comes the Markfield exposure, a circular patch 

 of syenite forming a commanding hill, and limited on the northern 

 side by the slaty, on the southern by the Triassic rocks. Still in 

 in the same direction, and across a broad, rather deep valley, appa- 

 rently in the Trias, comes the Cliff-Hill syenite, forming also a 

 conspicuous rugged ridge, probably a continuation of the former. 



