CORNWALL.~ DJRECfOBY .) 13

GEOLOGY OF CORNWALL. -

NATURAL HISTORY AND ScrENTIFIO SocrETIEs.-Comwall The ordinary description of the rocks of Cornwall-••' Four Royal Polytechnic Society; Falmouth ~ Annual :Report.- or five islands of granite rising from a sea of clay-slate "-is Royal Institution of Cornwall; Truro: Journal. Miners' sufficiently true to be taken as a starting puint. A bare and .Association of Cornwall and Devonshire ; Truro: Papers and wind-swept peninsula, the wealth of Cornwall lies under and Proceedings. Plymouth Institution and Devon and Corn- not on the soil and in the seas that lave her shores, as -wall Natural History Society; Plymouth: Annual Report witness the old Cornish toast-" Fish, tin and copper." a:tl Transactions. Royal Geological Soeiety of Cornwall; In describing the rocks of Cornwall, we shall begin with Pen7.ance: Transactions and Reports. Penmnce Natural the oldest or first-formed; and at first sight the task might lfi:~tory and Antiquarian Society. seem to be an easy one. The fact, however, is that the Mcru:uMs.-Falmouth Museum ; Natural History and stratified rocks of this district have been so interfered witb, .A.,ti:1narian Society's Museum, Penzance; Museum of the llpheaved,. dislocated and altered by the presence and intru­ J:oyLooe, Plymouth ; tions and order of successwn are far from being thoroughly 2j, L•mnce3ton, Tavistock, Callington, Dartmoor ; 26, determined or worked out. The geological map of the county lJUlalord, Holsworthy, Hatherleigh; 29, Coast from Hart- was executed by De la Beche forty or fifty years ago, befoi'e land Point to Cambeak ; 30, Camelford, St. Columb.. Bodmin; the establishment of the Geological Survey; and although it 3r, St. Austell, Camborne, Redruth; 32, Lizard Head; 33, is a surprising work of skill for the time and as the result of Land's End, Penzance. Books.-Report on the Geology of one man's labour, yet it does not exhibit the detail which we •Cornwall, Devon and West Somerset, by De la Beche, q.s. now consider necessary. When maps of the region on the l'J.l;eoiOic Fossils of Cornwall, Devon and West Somerset, scale of six inches to a mile shall have been completed by the l>y Prof. Phillips. Ordnance Survey, then our Government Geological Survey IMPORTANT WORII:S OR PAPERS ON LocAL GEOLOGY.- will take the matter in hand, and we shall have minute and Li~t by Mr. Whitaker of 654 works by 237 authors in No. accurate coloured maps showing the extent and position of :x\'"i. of. the Journal of the Royal Institution of Cornwall. every bed of rock. · 1875· 1868. Roll, Dr. H. B.-Older Rocks of East Corn- SILURIAN FoRM.&.TION.-On the south coast from Chapel "all. Joum. Geol. Soc., vol. xxiv. p. 400. I8]o. Peach, Point past the Dodman and round Veryan Bay to Gerrnu slates by a Jl. 9· 1873- Collins, J. H.-Mining District of Cornwall and fault. or (as Sedgwick believed) the strata may be inve1·ted We:1t Devon. Proc. Inst. Mechan. Eng. for 1873, p. Bg. 1875. by the great disturbances to which the country has been sub­ Pilillips, J. A.-The :Mining Districts of Cornwall. Journ. jected and thus rna.dfl to rest upon tbe Devonians instead of (ieol. Soc., vol. xxxi. p. 319. 1876. Belt, T.-The Drift of lying beneath them as they naturally would do. CtJrnwall. Journ. Geol. Soc., vol. xxxii. p. So. 18]6. Phillips, DEVONIAN FoRMATION.-The beds Qf this age consist J. A.-The so-called "Greenstones" of Western Cornwall. largely of clay-slate, locally known as killas or shillet; near Jonrn. Geol. Soc., vol. xx:x:.ii. p. 155. 1878. Phillips, J. A.- the granite this is usually of a green or \·iolet hue, changing .. 'Greenstones" of Central and Eastern Cornwall. Joum. as the distance from the igneous rocks increases, to grer. -Gool. Soc., vol. xxxiv. p. 471. 1878. Foster, Dr. C. Le Neve. blue, or bufi; beds of red or grey gtit and sandstone alo:.•l -Great Flat Lode south of Redmth and Camborne. Journ. occur, with irregular impure limestones and interbedd~tl 6eoL Soc., vol. xxxiv. p. 64o. x8718. Collins, J. H.-The volcanic lavas and ashes. Although these slat.y rocks nm,t llensbarrow Granite District. Lake, Tmro, 2s. 6d. 1879· be some thousands of feet in thickness, yet we are not suro Ussher, W. A. E.-Hitltorical Geology of Cornwall. Gool. of the exact order of their superposition, or ru; to which are :Mag., vol. xvi. p. 27, &c. x88o. Phillips, J. A.-Concre- the older and which the newer beds. The difficulties, in tionary Patches, &c. in Granite. Journ. Gaol. Soc., vol. fact, in the way of making out their order of succession are ::nxvi. p. I. very great; to ~n with, they are much broken up, dislo- WHEN the rocks of any country are known to be rich in cated, faulted and altered by th'1 disturbances to which they $Ubstances which are valuable to man, it is plain that they have been subjected since their formation : the thrusting-up ~re likely to attract considerable attention and study, while of enormous masses of igneous rock (granite &c.) through tile mines, or works necessary to obtain the ores, will the slates. together with the heated waters and vaponrR themselves teach us much concerning the relations, struc- which have since traversed the strata, has greatly interferel "tnre and modificatiob.S of the strata, which we could never with and changed them. In the south part of the county, ~therwise have learnt. fossils-upon which we rely so greatly in classification- In Mr; Whitaker's list, published in No. xvi. of the seem entirely wanting, while those which occur in the .Journal of the Royal Iastitution of Cornwall, we find the eastern and northern divisions are generally in a wretched 'titles of 654 books, papers and maps, by 237 authors, which state of preservation. .-elate to tb.e geology of Cornwall and were written between L,ower Devonian.-The red grits and slates at St. Veep, I6o2 and 1873 ; the great mass of.these. however ( 633 out of Polruan, Fowey and Polperro ure well seen in cliffs along ~54), have been written during the present century, for the the coast; they dip northwards or inland and seem to be the -8Cientific study of rocks is cl. very recent origin. lowest rocks of the district. At Lantirit and Polperro scalel Among the early workers we may name Borlase, W. of such fist.es as &aphaspi.Jand Pteraspu occur; these were l'ryce, J. Came, W. Phillips, J. J. Conybeare and Professor long thought to be the remains of fossil sponges, and were -~wick; Messrs. Henwood, R. W. Fox, C. W. Peach and named Stega7Wdictyum Cornubicunl by ProfesSor M'Coy, bnt R. Hunt connect the old school of geologists with the men of their real natnre there is now no doubt ; spines of fisheAt 'Collins1 hofessor Bonney1 S. Allport and Dr. C. le Nc-;-e- coast, from St. Agnes Head to Padstow and thence inland, l'oster. , by Bodmin and Liskeard to ~t. Germans and Plymouthi" ii