1881.] Prof. Liveing, On the rocks of the Channel Islands. 127 



sembles that at similar spots in the Guernsey syenite. An in- 

 stance of this kind of segregation is seen at the boss forming 

 Le Nez Point on the W. side of St Clement's Bay. 



I have before called attention to the curious metamorphism by 

 which a stratified rock has taken a columnar jointing like basalt 

 at La Crete Point in St Catharine's Bay. A similar columnar 

 jointing in the same rock is also seen inland in the valley leading 

 from St Martin's towards St Catharine's Bay only a few hundred 

 yards from the Church. These and all the stratified rocks of 

 the island I believe to be volcanic ashes. In some places they 

 are quite slatey, and in my former communication I mentioned 

 them as shales and slates. In the N.E. of the island these ashes 

 are of a peculiar reddish-purple colour, compact, and in many 

 places regularly stratified, and in different spots shew varying 

 degrees of crystallization. At some spots the stratified structure 

 seems quite effaced while in the same mass at a very short 

 distance the stratification is still quite plainly seen. In some 

 places there has been an approach to a porphyritic segregation 

 of materials, and in others the rock has acquired completely 

 the porphyritic character and looks like a trap rock, but the 

 continuity and gradual sequence in crystalline character leave 

 no doubt in my mind that the whole is metamorphosed ash. 

 In the central part of the island the purple colour gives way 

 to a grey, but the same gradual segregation of the felspar in 

 crystals may be traced in it in some parts, as in the valley leading 

 down to the town mills in St Saviour's parish. In some places 

 the felspar crystals are of two colours, red and green. This I take 

 to be due to some difference in the chemical composition of 

 fragments in the original ashes which have served as nuclei 

 for the crystallization and supplied some of the substance of the 

 crystals. There are however masses of trap amongst the ashes in 

 some places. Under Gallows hill, where is now the People's Park, 

 such a mass has been largely quarried. 



At the junction between the granitic and volcanic rocks on 

 the N. side of the island between Cotil and Fremont Points 

 the granite is of a bright red colour and appears at first sight 

 to have sent branching veins of a similar red colour into the 

 adjacent rock, looking very much as if the granite had been forced 

 into cracks in a fused state. Any such inference would in this 

 case be very rash. It would imply that the granite is a newer 

 formation than the volcanic rock into which it is intruded, which 

 cannot be the case for the following reasons. In the first place 

 the granite at the junction is highly quartzose and must have 

 a far higher fusing point than the highly felspathic rock adjoining, 

 so that if the fused granite had been brought in contact with 

 the felspathic rock the latter must have been more or less fused up 



