404 REV. E. HILL ON THE ROCKS OF GUERNSEY. 
30. The Rocks of Gurrnsey. By Rev. E. Hit, M.A., F.GS., 
Fellow and Tutor of St. John’s College, Cambridge. With 
an APPENDIX on the Rocks referred to, by Prof. T. G. Bonney, 
D.Sc., F.R.S., Pres.G.S8. (Read April 2, 1884.) 
[Puate XX.] 
ConTENTS. 
1. Introduction. 5. The Granites. 
2. The Gneiss. 6. The Dykes and Veins. 
3. The Diorites and Syenites. 7. General Remarks. 
4, The Hornblende-Gabbro. 
1. Lyrropuction. 
Ar the opening of this paper I desire to acknowledge my great 
obligations to Professor Bonney for his assistance throughout my 
investigations. I must also thank J. R. Cousins, Esq., of St. John’s 
College, Cambridge, for valuable help. 
Little has hitherto been written on the geology of Guernsey which 
would be of much use to a visitor. Macculloch contributed a brief 
account to one of the earliest publications of this Society. Ansted’s 
book on the Channel Islands contains some remarks on its general 
features. There are two papers by Professor Liveig, with which 
in many respects I cannot agree, in the Cambr. Phil. Soc. Proce. 
vols. iii. and iv., and one by Mr. J. A. Birds in the Geol. Mag. for 
1878, which contains some accurate observations. A few interesting 
but short papers on raised beaches and the like complete the litera- 
ture of the subject. How scanty is the information furnished thereby 
may be imagined from the fact that not one of these publications 
contains a geological map; and the sketch map (Pl. XX.) which 
accompanies this paper is, so far as I know, the first which has ever 
been published. 
Any map shows clearly enough the triangular shape of Guernsey, 
and with a glance at the scale of miles its dimensions can be easily 
estimated. But most maps do not even attempt to indicate the 
remarkable physical difference between the northern and southern 
parts. A spectator on the deck of a steamer approaching St. Peter’s 
Port sees on the right a long low coast rising into a series of hum- 
mocks (each bearing the local name of Hougue), the highest crowned 
by an obelisk, the monument to Admiral Saumarez. On the left he 
sees a range of noble cliffs, with the Doyle column at one extremity 
and the ramparts of Fort George at the other ; while in the centre 
of the picture the cliffs fall back into an amphitheatre lined by the 
quaint and striking town. Could the spectator hover above as a 
bird, or survey the island from a balloon, he would see that these 
cliffs are the edge of a table-land, whose northern face is a scarp 
which sweeps across from east to west. He would see the table- 
land a cultivated plateau, cut by a few deep valleys mostly running 
north-west. The low ground beyond the scarp he would see to be an 
alluvial centre surrounded along the coast by a horse-shoe ring of 
