788 E. HILL AND T. G. BONNEY ON THE 



is not quite so marked a contrast as is usual between the two when 

 weathered and decomposed ; and both rocks near the junction are 

 much cut up by small quartz veins. The rock also is much masked 

 by turf and furze. Hence, though we could in one place see that 

 the junction lay somewhere in about half a square yard of a small 

 outcrop, we could not hit it with absolute certainty. At the same 

 time we do not consider that there is the slightest evidence of a 

 passage from the sedimentary rock to the syenite; we have no 

 doubt whatever that the latter is intrusive ; but in ordnr to demon- 

 strate this by the evidence of specimens, it would be necessary to 

 blast away a few cubic feet of the more rotten rock. 



On LongclifF, at the southern end, the syenite forms the foot of a 

 hill, the crest of which is of banded slates ; and the appearance of the 

 rock suggests that it is approaching a junction. At the northern 

 end of the wood there is a small hill of banded slate, at the foot of 

 which is a little outcrop of syenite. The two rocks can be traced to 

 within three or four yards of each other ; and the slate is highly 

 altered ; but the two cannot be seen in contact, though this could 

 be exposed by a very small excavation. Mr. Hill, however, picked 

 up in the vicinity a loose fragment which clearly shows an intrusive 

 junction between the syenite and a rather coarse quartzose grit, a 

 bed of which occurs in another part of the hill. 



The contorted condition of the Brazil- Wood gneiss was long ago 

 noticed. The granite also of the opposite knoll assumes a very 

 different aspect in the portions of it which are nearest to the gneiss. 

 Here also, we think, there can be no doubt that the granite is in- 

 trusive. Still, as there is also a mass of diorite not far off, and a 

 dyke of similar rock (to be described hereafter) in the granite itself 

 at a very short distance, one cannot, without excavation, absolutely 

 determine to which agent the disturbance is due. 



On the whole, then, we feel justified in asserting that all the 

 Charnwood syenites are intrusive. The quarzite which they disturb 

 at Bradgate and Groby forms almost our highest horizon. The 

 overlying workable slates are thrown by them at Groby into great 

 rolls. Hence they are posterior in time to the whole of the Charn- 

 wood series. Their lines of junction with the surrounding strata, 

 when clearly exposed, are sharp and unmistakable. Hence there is 

 no evidence of transition from sedimentary to igneous rock any- 

 where in this region ; for even in the northern district ; that of the 

 " felstone porphyries," there is rarely any thing more in these rocks 

 than the most superficial resemblance to a true felstone. Charn- 

 wood Forest therefore must be removed from the number of localities 

 which can be adduced as affording evidence of such transition. 



In the second part of this memoir we purpose touching upon the 

 dislocations of the strata, and describing in detail the igneous masses 

 mentioned above, together with certain dykes more or less associ- 

 ated with them. Besides these, the group of igneous rocks protru- 

 ding from the Trias in the vicinity of Narborough will be described*. 



* Since this paper was read we have been fortunate enough to obtain evidence 



