1884.] in part of the Guernsey Gneiss. 155 



the foliation was visible, and the positions of the outcrops which 

 resembled each other harmonized with this strike. Pursuing the 

 investigation I found that there was evidence of a complete and 

 conformable succession over a considerable distance. I think that 

 it may be interesting to briefly note this, and to remark upon one 

 or two conclusions which follow from it. 



The nature of the succession and the evidence for it need not 

 be given very fully. All the beds are gneiss of the very oldest 

 type. The strike of the foliation can usually be detected, and is 

 always in the region dealt with N. and S. The dip is sometimes 

 nearly vertical, but generally more or less steeply inclined, invari- 

 ably to the W. Five successive distinct series can be clearly 

 recognized, the first along Vazon Bay and at several points to the 

 S., the second along Perelle Bay, the third around the L'Eree 

 Hotel, the fourth on the L'Eree peninsula and across the sound of 

 Libou, the fifth in the island of Lihou. I have not seen any 

 passage of the first into the second, but the second can be traced 

 continuously in the shore at low water, and seen to change into the 

 third along the ridge extending out into the sea to the islet called 

 Chapelle Domhue. The third can be seen passing into the fourth 

 on the L'Eree shore, and also in the outermost rocks of the islet 

 just mentioned. The fourth is seen within 10 feet of the fifth on 

 the shore of Lihou, separated only by one of the greenstone dykes 

 which are so numerous. 



Now were the beds of this series of rocks repeated either by 

 faults or by plications and over-fold, then as we made traverses in 

 directions across their strike we should from time to time often 

 find repetitions of particular beds. But in the succession above 

 described nothing of the kind is seen. Each division of the series 

 is perfectly distinct from the rest, lasts for a certain space, is suc- 

 ceeded by another, and does not, in the area described at least, reap- 

 pear. It would be possible that any one of these divisions separately 

 might owe its thickness to plication, but I cannot conceive this 

 process going on in more than one without an obvious repetition 

 of alternating divisions. We may conclude that the thickness of 

 the series as estimated by this area is a real thickness free from 

 the errors introduced by plications. There may perhaps be an 

 error due to irregular thickness or lenticular arrangement, but I 

 am not now considering these. Moreover I have identified series 

 II. and III. for more than two miles along their strikes, and I. at 

 extreme points separated by three miles. 



The breadth of this succession measured across the strikes is 

 over two and a half miles. Allowing for the inclination of the 

 beds this must represent a thickness of nearly two miles. 



Another conclusion I should draw is that the nature of gneiss 

 must depend not so much on metamorphosing agents as on the 



