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 SCOTLAND. 
 
 THK 
 
 GEOLOGY OF COWAL 
 
 INCLUDING THE PART OF 
 
 ARGYLLSHIRE BETWEEN THE CLYDE AND LOCH FINE. 
 
 By W. GUNN, F.G.S., C. T. CLOTJGH, M.A., F.G.S. 
 AND J. B. HILL, R.N. 
 
 (WiTH PETROLOGICAL NOTES BY J. J. H. TEALL, M.A., F.R.S. 
 SEC. G.S., AND DR HATCH, PH.D., F.G.S.) 
 
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 PREFACE. 
 
 The district described in the present memoir includes that part of 
 Argyllshire, generally known as Cowal, which lies between Loch Fyne and 
 the Firth of Clyde. It embraces the south-western extension of the 
 various bands of rnetamorphic rocks which form the southern edge of the 
 Highlands. Bounded on three sides by coast-lines and penetrated by a 
 number of sea-lochs it affords better and more continuous sections of these 
 rocks than are generally to be met with in the interior of the country. 
 Advantage has been taken of these exceptional features to describe the 
 rocks in much greater detail than would otherwise be desirable. 
 
 From the detailed study of this part of the Highlands much information 
 has been obtained by the Geological Survey regarding the structures of 
 the schists and the successive movements by which these structures have 
 been produced. Originally most of the rocks described in the following 
 chapters formed a thick series of sedimentary deposits, the geological age 
 of which still remains to be determiued. These strata have been found 
 to have undergone a remarkable series of repeated movements. After 
 being thrown into folds and having been cleaved so as to acquire a first 
 system of deformation, they have again suffered a repetition of the process 
 more than once. They consequently present secondary and tertiary 
 perhaps even quaternary structures, probably due to mechanical move- 
 ment with accompanying re-crystallisation. The regional metamorphism 
 thus produced is not uniformly distributed, but seems to increase in 
 intensity both from the south-east and north-west towards a nearly 
 central line, ranging about north-east and south-west, which is an anti- 
 cline of the foliation. It has not been traced to any intrusion of igneous 
 rock, and is so general and diffused that it can hardly be regarded as in 
 any sense a contact phenomenon. Where intrusive masses occur in the 
 district they have given rise to their own accompanying alteration, quite 
 apart from the general metamorphism of the whole area. These interest- 
 ing and complicated structures, so well displayed in Cowal, are fully 
 discussed in the present Memoir. 
 
 The extreme south-western part of the promontory south of an east 
 
 325152 
 
IV 
 
 and west line drawn at Kilfinan was surveyed by Mr Gunn. The region 
 lying to the east of Loch Hidden and Glendaruel and thence northward 
 to Loch Fyne was mapped by Mr Clough, while the rest of the ground 
 lying along the east side of Loch Fyne was the work of Mr J. B. Hill. 
 Each officer describes in the Memoir the tract which he himself has 
 surveyed, their several contributions being indicated by their initials. 
 Mr Clough having mapped by far the largest part of the whole district 
 has had general charge of the Memoir, which is mainly written by him. 
 
 The petrographical notes whether embodied in the text or placed in the 
 Appendix have been chiefly supplied by Mr J. J. H. Teall, but some 
 were furnished by D. F. H. Hatch, when he was attached to the Staff of 
 the Survey. In the Appendix will be found a list of all the microscopic 
 slides in the collection of the Survey, which have been prepared from 
 rocks in Cowal ; likewise a list of fossils from the ".Clyde Beds " of the 
 region arid a Bibliography of the chief literature relating to the geology 
 of this part of Argyllshire. 
 
 ARCH. GEIKIE, 
 Director General, 
 
 GEOLOGICAL SURVEY OFFICE, 
 
 JERMYN STREET, LONDON, 
 
 5th April 18S7. 
 
CONTENTS. 
 
 PREFACE, ......... iii 
 
 CHAPTER I. INTRODUCTION. With Tabular View of the Rocks and 
 
 Summary of Literature, ....... 1 
 
 CHAPTER II. INTRODUCTION TO THE SCHISTS. DESCRIPTION OF VARIOUS 
 SECTIONS. Sections S. of Duiioon ; on the W. side of Loch Long, S. of 
 Ardentinny ; on the E. shore of the Kyles of Bute, ... 7 
 
 CHAPTER III. SCHISTS OF PROBABLE SEDIMENTARY ORIGIN. Schists S.E. 
 of the Bull Rock Grey wacke Schist. The Bull Rock Grey wacke Schist. 
 The Dunoon Phyllite Series. The "Green Beds" Schists between the 
 S.E. group of "Green Beds" and the Albite Schists. Albite Schists 
 and other schists that occur with these near "the anticline," . . 29 
 
 CHAPTER IV. SCHISTS OF PROBABLE SEDIMENTARY ORIGIN (continued). 
 The Loch Tay Limestone. The Garnetiferous Mica Schist. The 
 Graphitic Schists. The Ardrishaig Phyllite Series, ... 45 
 
 CHAPTER V. EPIDIORITES, HORNBLENDE SCHISTS AND RELATED CHLORITE 
 
 SCHISTS, 60 
 
 CHAPTER VI. SERPENTINE. Serpentine of Inellan and Toward, of Glen- 
 
 daruel, 72 
 
 CHAPTER VII. MINERALS IN THE SCHISTS. DIRECTIONS OF STRETCHING, 76 
 
 CHAPTER VIII. GENERAL PHYSICAL STRUCTURE OF THE SCHISTS. RE- 
 MARKS ON THE MKTAMOBFHISM, ...... 82 
 
 CHAPTER IX. UPPER OLD RED SANDSTONE. With account of the Geo- 
 logical Structure, ........ 92 
 
 CHAPTER X. THE IGNEOUS ROCKS. THE MARGIN OF THE GRANITE NEAR 
 
 CRUACH TUIRC. HORNBLENDE-PPKPHYRITE AND FELSITE. HYPERITE, 96 
 
 CHAPTER XL THE IGNEOUS ROCKS (continued). LAMPRUPHYKES AND 
 
 MICA TRAPS, including the foliated Camptonites, . . . 106 
 
 CHAPTER XII. THK IGNEOUS ROCKS (continued). BASALTIC DYKES. 
 
 GENERAL DESCRIPTION, ....... 126 
 
 CHAPTER XIII. THE IGNEOUS ROCKS (continued). DESCRIPTION OF 
 BASALTIC DYKES in PARTICULAR DISTRICTS. Districts ofTighna- 
 bruaich, Kilfinan and Stralachlan. Strachur and Lochgoilhead, . . 150 
 
VI 
 
 I'AOK 
 
 CHAPTER XIV. THE IGNEOUS ROCKS (continued). INTRUSIVE ANDESITE (?). 
 
 THE SITH AN T-SLUAIN DOLERITE. TRACHYTIC DYKES, . . 162 
 
 CHAPTER XV. GENEKAL GEOLOGICAL STRUCTURE OF PARTICULAR DIS- 
 
 TRICTS. Districts of Dunoon, Blairmore, Glen Massan, Colin traive, . 171 
 
 CHAPTER XVI. GENERAL GEOLOGICAL STRUCTURE OF PARTICULAR DIS- 
 TRICTS (continued). Districts of Tighnabruaich, Kilfinan and Stra- 
 lachlan, ......... 188 
 
 CHAPTER XVII. GENERAL GEOLOGICAL STRUCTURE UF PARTICULAR DIS- 
 TRICTS (continued). Districts of Carrick Castle, Beinn Mhor, St 
 Catherine's, Lochgoilhead, Cairndow, ..... 200 
 
 CHAPTER XVIII. GLACIAL DEPOSITS. GENEUAL DESCRIPTION, . . 235 
 
 CHAPTER XIX. GLACIAL DEPOSITS (continued). DESCRIPTION OF PARTI- 
 CULAR DISTRICTS. Districts of Tighnabruaich, Kilfinan and Stralachlan, 
 Strachur and Lochgoilhead, ...... 249 
 
 CHAPTER XX. MARINE AND FRESHWATER ALLUVIA, . . . 262 
 
 CHAPTER XXL PEAT. LANDSLIPS. BLOWN SAND. PREHISTORIC RE- 
 
 MAINS, ......... 273 
 
 CHAPTER XXIL GEOLOGICAL ASPECTS OF THE SCENERY, . . . 279 
 
 CHAPTER XXIIL ECONOMIC KESOURCES, . . . . .287 
 
 APPENDIX. 
 
 I.- GENERAL REMARKS ON THE PETROGRAPHY OF THE CUWAL DISTRICT, 
 
 RY MR TEALL, ....... 295 
 
 II. DESCRIPTION OF AN ALBITE SCHIST NEAR ARD A' CHAPUILL, BY 
 
 MR TEALL, ...... . 299 
 
 III. LIST OF MICROSCOPE SLIDES, . . . . . 300 
 
 IV. LIST OF GLACIAL FOSSILS, .... 304 
 
 V. BIBLIOGRAPHY, ....... 308 
 
 ........ 310 
 
 PLATES (see end of the volume). 
 
LIST OF ILLUSTRATIONS. 
 
 PAGE 
 
 Fig. 1. Fold in banded phyllite. Shore south of Dunoon, 1 . 10 
 
 , , 2. Banded phyllite with one set of foliation planes throwing an earlier 
 
 set. Shore south of Dunoon, . . . . .11 
 
 ,, 3. Phyllite with small faults accompanying an early set of foliation 
 
 planes. Shore -mile south of Glen Morag, Dunoon, . -^ 12 
 ,, 4. Diagram to show the laws of folding and thinning of limbs in the 
 
 Dunoon section, . . . . . . * 13 
 
 ,, 5. Pebble in the Bull Rock greywacke, . . . ,.,. . 16 
 
 ,, 6. Pebbles out of a greywacke schist near Lephinkill, . . .16 
 
 ,, 7. Polished section of a pebble from a boulder in Glen Lean, . r 16 
 
 , , 8. Quartzose schist bands overlying phyllitic schist. Near Gairletter 
 
 Point, . 19 
 
 ,, 9. Puckered "strain bands." Near Gairletter Point, . . .19 
 
 ,,10. Strain slip foliation crossing earlier planes. Near Gairletter Point 
 
 and Gartnamhuinn, ...... 20 
 
 ,,11. Folded calcareous bed with foliation oblique to its sides. Near 
 
 Gairletter Point, ....... 21 
 
 ,,12. Folded "strain bands." Fearna Bagh, . . . .23 
 
 ,, 13. Folded "strain bands." Beinn Bheag, .... 24 
 
 ,, 14. Folded "strain bands." Near Coirantee, .... 24 
 
 .,15. Strain slip foliations in a greywacke schist near Glenmassan, . 25 
 
 ,, 16. Strain slip foliations near Fearna Bngh, . . . ,25 
 
 17. Diagram to show the form of, and law of thinning of limbs in, 
 
 the prominent " anticline folds,". . . . . .26 
 
 ,, 18. Diagram to show the direction of " pre-anticline " folds, etc., in 
 
 different parts, ....... 28 
 
 ,, 19. Section in Garvie burn, ...... 38 
 
 ,, 20. Plan of a surface of a foliation plane of albite schist near Drimsynie- 
 
 beg, . . .41 
 
 ., 21. Plan of a section of an albite schist at right angles to the foliation. 
 
 One mile W. of Drimsyniebeg, ..... 42 
 ,, 22. Surface of a foliation plane of garnetiferous mica schist. Near 
 
 Bathaich ban Cottage, ...... 50 
 
 ,, 23. Cracked garnets from near Cruach nan Capull (133), . . 50 
 
 ,, 24. Chloride pseudomorphs after actinolite. Near Ardno, . . 51 
 
 ,, 25. Plan of folded phyllite and quartzite schist near Newton Bay, . 58 
 
 ,, 26. Plan of folded phyllite and quartzite schist near Strachur, . .59 
 
 ,, 27. Stretched pegmatite. Near Cruach na Cioba, . . .76 
 
 ,, 28. Slide of mica schist with mica flakes crossing the foliation. Inver- 
 
 chapel Burn, ..... .77 
 
 ,, 29. Bent and cracked tourmaline needles. A' Ch roach (182), . . 77 
 
 ,, 30. Sheafs of tourmaline in a quartz vein. Loose block near the foot of 
 
 the Cab, 78 
 
 ,, 31. " Trains " of magnetite grains in a schist near Strachur House, . 79 
 ,,32. Section in Kinglas Water, ...... 88 
 
viii 
 
 PAOK 
 
 Fig. 33. Horizontal section across the Upper Old Red Sandstone near To- 
 ward, ........ 95 
 
 34. Plan of portion of the glassy centre of the Cruach Mh6r dyke, . 134 
 
 ,,35. Plan of part of a glassy band in a dyke near Craigendaive, . . 135 
 
 ,, 36. Irregular strings in a dyke near Stronchullin, . . . 136 
 ,, 37. Diagram to illustrate the behaviour of dykes when they come to 
 
 pre-existing faults which run at right angles, . . .143 
 
 ,, 38. Diagram to illustrate the behaviour of north-west dykes wh^en they 
 
 meet pre-existing north and south faults, . . .144 
 
 ,, 39. Polygonal spherulites in a trachyte dyke near Craigendaive, . 168 
 
 ,, 40. Rows of spherulites in a trachyte dyke near Cruach Mhor, . . 169 
 ,,41. Horizontal section from Clyde View to Sandbank, . . .173 
 ,,42. Horizontal section from Inellan Perch to In verchaolin, . .175 
 
 ., 43. Horizontal section from Strone Point (174) to Stronchullin Hill, . ISO 
 
 ,, 44. Horizontal section from Lephinkill to An Socach, . . . 184 
 
 ,,45. Contorted schist near Lochan nan Cnaimh, .... 202 
 
 46. Folded schist near Carrick Castle, ..... 203 
 
 ,, 47. Horizontal section between Toll a' Bhuic and Lochan nan Cnaimh,. 204 
 
 ,, 48. Folded pebbly schist near Ardnahein, .... 207 
 
 ,, 49. Quartzose band broken through by foliation-faults. Near Mullach 
 
 a Chuirn, ........ 208 
 
 ,, 50. Horizontal section from near Lochgoilhead to St Catherine's, . 219 
 
 ,, 61. Contorted graphite schist in Eas Dubh, .... 220 
 
 ,, 52. Horizontal section from the Saddle to the foot of Hell's Glen, . 226 
 
 ,, 53. Contorted sand and gravel near Ardacheranbeg, . . . 240 
 
 ,, 54. Granulitic biotite gneiss. Fearna Bagh, .... 296 
 
 PLATES (all at end of Volume). 
 Plate I. Schistose limestone with folding of the prominent foliation planes. 
 
 Near Dunoon. 
 
 ,, II. Folded phyllite with quartz veins. East Bay of Dunoon. 
 ,, III. Contorted mica schist. Near Colintraive. 
 ,, IV. Folded strain slips. Near Colintraive. 
 ,,. V. Contorted mica schist. Near Coy let, Loch Eck. 
 ,, VI. Fig. 1. Slide of albite schist from near Ard a' Ghapuill. 
 ,, ., 2. Slide of albite schist from Beinn Tharsuinn (142). 
 ,, VII. ,, 3. Slide of albite schist from head of Stuck Burn. 
 ,, ,, ,, 4. Slide of "green bed" with albite and epidote'. Near 
 
 Dunderave Castle. 
 
 ,VIII. Sketch Map of the Geology of Cowal. 
 
 ,, IX. Sketch Map of Glacial and Post-glacial Geology of Cowal. 
 ,, X. Diagram to represent the possible structure of the " anticline." 
 
THE GEOLOGY OF COWAL. 
 
 CHAPTER I. 
 
 INTRODUCTION. 
 
 The district of Cowal includes that part of Argyllshire which is almost 
 isolated from the rest of Scotland by Loch Fine, the Kyles of Bute, and 
 Loch Long. The boundary on the north-east side is not clearly defined 
 physically, and we were for some time in doubt as to the limit of the dis- 
 trict in this direction. It appears from our inquiries * that at the present 
 time the north-east boundary is generally understood to extend to the head 
 of Loch Long, and then to keep along the boundaries between Argyllshire 
 on the one side and Dumbartonshire and Perthshire on the other side 
 as far as the parish of Dalmally. It then coincides with the boundary 
 between the parishes of Dalmally and Kilmorich until it meets Loch Fine 
 | mile east of Dunderave Castle. The area north-west of Loch Fine and 
 Glen Fine is said to have been added to the parish of Kilmorich and the 
 district of Cowal at a comparatively late period, about the year 1700, 
 in consequence of the change of ownership from the MacNaughtons of 
 Dunderave to the Campbells of Ardkinglas. The area then added is 
 separated from the rest by the well-marked physical boundary of Loch 
 Fine and Glen Fine, and we have not described it in the following pages. 
 Nor have we described the extreme north-east portion of Cowal as above 
 denned, as this portion was surveyed by other officers, and there seems no 
 physical reason for describing it with the rest. The north-east boundary 
 of the area described by us runs approximately along Coilessan Glen 
 (1-inch Map 38), and thence almost along the boundary between 1-inch 
 Maps 37 and 38 up to the margin of the granite by Meall Beag, then 
 along the granite margin to Glen Fine and down this glen to Loch Fine. 
 This area is comprised in 1-inch Maps 29, 37, and 38, the portion in 
 the latter Map being, however, only a few square miles in extent. In the 
 Appendix we have added the list of glacial shells collected by Mr Bennie 
 in Balnakailly Bay, which is in the island of Bute, and outside of Cowal. 
 
 The extreme length of the district described by us, from Ardlamont 
 Poiut on the south-west to the granite edge near Cruach Tuirc on the 
 north-east, is about 44 miles. The breadth, from Toward Point on the 
 south-east to Otter Beacon on the north-west, is about 18 miles. Owing 
 to the irregularity of outline, and the way in which the sea lochs, Loch 
 Riddon, Loch Striven, the Holy Loch, and Loch Goil, run up into the 
 land, it is not easy to estimate the superficial area of the district. It is 
 certainly somewhat less than 432 square miles, the area of the 1-inch Maps 
 of Scotland. 
 
 * We have specially to thank Mr Daniel Anderson of Dunoon, and Mr Duncan 
 Whyte of Glasgow, for information on this matter. 
 
 A 
 
4 GEOLOGY OF COWAL. 
 
 The combined town of Dunoon and Kirn is much the largest in the 
 district. All along the shore from Toward Point to Blairmore, there is an 
 almost continuous fringe of villas connecting Toward, Inellan, Sandbank, 
 Dunoon and Kirn, Kilmun, and Strone. These places, being so easily 
 reached from Glasgow, form a favourite holiday resort for the people of 
 this and the other large towns adjacent. The chief towns or villages 
 outside the fringe mentioned are Carrick Castle, Lochgoilhead, Strachur, 
 arid Tighnabruaich. All these are on the coast, and owe most of their 
 growth and prosperity to tourists and summer visitors : in the winter they 
 are half deserted. There are no large fishing or crofter communities. 
 
 The trees and the neat appearance of most of the cottage dwellings add 
 a feeling of comfort and home to the landscape which is wanting in many 
 of the more outlying parts of the Highlands. The far-stretching arms of 
 the sea give a charm to the country, and at the same time add immensely 
 to the facilities of travelling. In summer there is a general rush of 
 holiday makers to these erstwhile quiet shores. The sea lochs are then 
 dotted over with fast and well-appointed steamers and the " white wings" 
 of yachts. 
 
 There is a beautiful description of Argyllshire scenery which seems to 
 date back to the year 1238, and may be much earlier. It occurs in the 
 lament of Deirdre over Alban, and is thus described by Dr W. F. Skene 
 in his Introduction to the Book of the Dean of Lismore, p. Ixxxvii. : 
 " One of the poems in the tale of the Children of Uisneach contains such 
 a tender recollection of and touching allusion to Highland scenery that 
 it is hardly possible to suppose that it was not originally composed by a 
 genuine son of Alban." There are nine quatrains in Dr Skene's trans- 
 lation, of which we quote 1st, 5th, 8th, and 9th. 
 
 " Beloved land that Eastern land, 
 Alba, with its wonders. 
 O that I might not depart from it, 
 But that I go with Naise. 
 
 11 Glenmasan ! Glenmasan : 
 High its herbs, fair its boughs. 
 Solitary was the place of our repose 
 On grassy Invermasan. 
 
 " Glendaruadh ! O Glendaruadh ! 
 My love each man of its inheritance. 
 Sweet the voice of the cuckoo on bending bough, 
 On the hill above Glendaruadh. 
 
 " Beloved is Draighen and its sounding shore ; 
 Beloved the water o'er pure sand : 
 that I might not depart from the east, 
 But that I go with my beloved." 
 
 The scenery is all in Argyllshire, and Glenmasan and Glendaruadh will 
 be easily recognised as being in this district. The MS. of the original 
 Gaelic is in the Advocates' Library, Edinburgh, and is believed to have been 
 written in Glen Massan in 1238. Alba or Scotland is Eastern land, in 
 relation to Ireland. 
 
 In descriptions of localities the names referred to are those which occur 
 in the 1-inch Maps. The spelling of the names on the Maps has been 
 strictly adhered to, whether this is supposed to be correct or not, in 
 order to help in their identification. With the same view the numbers, 
 and sometimes the quarters, of the 6-inch Maps in which the localities 
 occur, have been given, excepting where the localities are likely to be 
 readily found. On the lower margin of each 1-inch Map there is a 
 
TABULAR VIEW OF THE ROCKS. 5 
 
 small index Map of the 6-inch Maps therein, and by referring to it any 
 one may ascertain in what part of the 1-inch Map the places that are 
 mentioned occur. 
 
 The numbers attached to the rock slides referred to are their numbers 
 in the collection of the Geological Survey of Scotland, kept at Jermyn 
 Street, London. 
 
 Tabular View of the Bocks. 
 
 The following is a list of the different superficial deposits and rocks 
 noticed in the area : 
 
 RECENT AND POST-TERTIARY 
 
 Blown sand. 
 
 Peat, in well-defined basin-shaped hollows or on the hills. 
 
 Freshwater alluvia. 
 
 Marine alluvia. 
 
 GLACIAL 
 
 Glacial shell beds. 
 Moraines. 
 Sands and gravels. 
 Boulder clay. 
 
 UPPER OLD RED SANDSTONE 
 
 Cornstones and magnesian limestones. 
 
 Red sandstones, breccias, and conglomerates. 
 
 METAMORPHIC ROCKS* 
 
 Schists probably of sedimentary origin. 
 
 Phyllites, including the two series of Dunoon and Ardrishaig, 
 
 which consist of phyllites and thin limestones, mixed in the 
 
 first series with schistose grits and in the second with quart- 
 
 zite schists. 
 
 Schistose grits and greywackes. 
 Quartzite schist or Quartz schist.* 
 Albite schist. 
 Garnetiferous mica schist. 
 Graphite schist. 
 Schistose limestones, on various horizons, including the Loch 
 
 Tay limestone. 
 Mica schist. Areas coloured thus in the Maps may also include 
 
 unseparated albite schists, sheared grits, and grey wackes, and 
 
 phyllites. 
 Green beds chlorite-epidote schists. The group lines may 
 
 include some mica schists and schistose greywackes. 
 Igneous rocks 
 
 Epidiorites, hornblende and chlorite schists. 
 
 Serpentine. 
 
 * The order in this list is not a stratigraphical one. 
 
 t The term quartzite schist has been already applied to these rocks in the pub- 
 lished 1-inch Map 29, and has, therefore, been also generally used in the subsequent 
 descriptions in this Memoir. The rocks in question are thoroughly granulitic in 
 structure. There seems no doubt about their sedimentary origin, but perhaps in 
 strictness it would be better to call them quartz schist or quartz granulite rather 
 than quartzite schist. 
 
6 GEOLOGY OF COWAL. 
 
 UNFOLIATED IGNEOUS KOCKS 
 
 Intrusive 
 
 Basalt and tachylite, including dolerite and augite andesite. 
 Trachyte. 
 
 Andesite ( ? intrusive). 
 
 Lamprophyre group, including camptonite and mica traps. 
 Hornblende-porphyrite and felsite. 
 Hyperite. 
 Granite. 
 
 The glacial deposits were separated from the other rocks, but are not 
 shown in the 1-inch Maps, except occasionally by writing. 
 
 Excepting for about 1 square mile, near Inellan and Toward, the whole 
 district is composed of schists or rocks intrusive in them. The intrusive 
 rocks generally occur in dykes and thin sheets, and are in places closely 
 crowded together. W.G., C.T.C. 
 
 Summary of Literature. 
 
 Very little has hitherto been written about the geology of the district. 
 A list of the works referring to it is added in an Appendix, but we also 
 give below a short statement of the more important conclusions arrived 
 at from time to time by earlier workers. 
 
 A hundred years ago the schists of this area were always spoken of by 
 geologists as primary or primitive strata. 
 
 Macculloch, in his Description of the Western Isles (1819), does not 
 directly describe any part of this district, but he gives in vol. iii. a 
 general Geological Map of the Western Isles which indicates the greater 
 part of the area of Cowal as made up of micaceous schist, with a narrow 
 band of his chlorite series along the upper part of Loch Fine, and a 
 pretty broad band of argillaceous schist near the Clyde. His Geological 
 Map of Scotland (1840), as far as this district is concerned, is a repetition 
 of that of 1819, except that the micaceous schist is now called mica slate, 
 including chlorite slate, and he gives a patch of limestone in the phyllites 
 at Cove on the eastern side of Loch Long. In neither Map does he show 
 any limestone, either at Durioon, Kilfman, Otter, or at Toward, though 
 he gives a strip of red sandstone at the latter place. In the small 
 Geological Map prefixed to Ami Boues Essai Geologique sur UEcosse 
 (1820), Macculloch's argillaceous band is shown as running from Bute to 
 Stonehaven, but is coloured as rocks chloriteuses and quartzeuses.* The 
 rest is all mica schist, except a small patch at the head of Loch Fine, which 
 seems intended for the Garabal Hill and Meall Breac granite. 
 
 The Rev. M. Mackay, in his account of the united parishes of Duuoon 
 and Kilmun, New Statistical Account of Argyllshire, p. 581, notices 
 serpentine 4 miles west (south) of Dunoon and a limestone on the 
 lands of Castle Toward near the western extremity of the parish which 
 judges had pronounced to be good marble. This must be one of the 
 limestones in the Dunoon phyllites. He notices other limestones in the 
 sandstones of Toward, p. 580, and the alteration produced by the Dunoon 
 Castle dyke on the surrounding beds, p. 581. 
 
 Dr James Bryce, in his Geology of Clydesdale, 1859, first called 
 attention to a band of intrusive greenstones, 60 to 100 yards wide, in the 
 country north of Dunoon, ranging from near Hunter's Quay to Dunloskin 
 Hill, as being different from the ordinary intrusive dykes of the coast, its 
 structure being slaty and with hornblende in excess ; and in a subsequent 
 
 * See, however, his description, pp. 72-78, where he includes schiste argileux under 
 this head. 
 
SUMMARY OF LITERATURE. 7 
 
 edition in 1865, he gives a small sketch Map showing the position of this 
 greenstone and of the Castle dyke. He also describes the limestone at 
 Cove previously noted by Macculloch. 
 
 Mr T. F. Jarnieson and Professor James Nicol are the two who have 
 hitherto principally contributed to our knowledge of the structure of the 
 district. The former, in his paper in 1861 ("On the Structure of the South- 
 West Highlands of Scotland," Quart. Jown. Geol. Soc., vol. xvil p. 133), 
 notices the Otter limestones, etc., and the epidiorites which accompany 
 them are described as greenstones, and rightly regarded as intrusive. 
 He describes the course of the anticlinal, which, however, he regards as a 
 true anticline in the beds, and hence he identifies the Dunoon phyllites 
 with those of Ardrishaig. He seems generally to take the foliation planes 
 for true bedding. The greater metamorphism of the beds with produc- 
 tion of felspar near the centre of the anticline was noticed by him. 
 
 Professor Nicol (Quart. Journ. Geol. Soc., vol. xix. pp. 197-199) 
 showed that the order of the beds on the south side of the anticlinal in 
 Cowal was the reverse of that in the more central districts about Loch Earn 
 and Dunkeld, and he was inclined to think the order in Cowal, of clay slate 
 over mica schist, was the true one, and that the beds had been reversed in 
 the central district with the production of overfolds by a force acting later- 
 ally and not vertically. The greater metamorphism of the mica slate in 
 comparison to that of the clay slate he seems to ascribe to its being taken 
 down further into the " interior regions of the earth's crust where the chief 
 laboratories of metamorphic action are situated." 
 
 In the first sketch of a New Geological Map of Scotland by Sir R. 
 Murchison and A. Geikie in 1862, an attempt was made to identify the 
 Highland rocks with certain portions of the Southern Uplands, and this 
 
 " b'l for the Dunoon phyllites, etc. (clay 
 and mica slates). 
 
 area is coloured and lettered as , b/1 * for a11 l , he , rest ? f - 
 
 division which embraced quartzose 
 
 flagstones, quartz rock, and associated 
 limestones. 
 
 The New Geological Map of Scotland by Sir A. Geikie in 1892 contains 
 much of the Survey work of this district in a reduced form. 
 
 In Sir A. Geikie's paper on " The History of Volcanic Action during 
 the Tertiary Period in the British Isles " (Trans. Roy. Soc. Edin., vol. 
 xxxv. 21, 1890) there is a Sketch Map showing the numerous dykes in 
 part of this area, with observations on them, from notes supplied by Mr 
 C. T. Clough. W.G. 
 
 CHAPTER II. 
 
 INTRODUCTION TO THE SCHISTS. DESCRIPTION OF 
 VARIOUS SECTIONS. 
 
 The schistose rocks make up much the largest part of the district, 
 occupying perhaps thirty times the area of all the other rocks combined. 
 Our ignorance of them is, in many respects, still exceedingly great : yet 
 it is worth while to set forth the knowledge at present possessed, in hope 
 that this may serve as a stepping stone in the path of future progress. 
 
 No organic structures have been observed in any of the schists, and the 
 geological age of these rocks is at present unknown : as regards most of 
 them, even their age in relation to one another is not certainly known, 
 
8 GEOLOGY OF COWAL. 
 
 so that, in making a traverse in any particular direction, we cannot say 
 whether we are going from older rocks to newer, or vice versa. 
 
 A glance at the Maps shows that the different schist bands traverse the 
 region in a north-east and south-west direction. Starting from the schist 
 boundary fault near Toward and proceeding in a north-west direction we 
 first pass over a group of phyllites and schistose pebbly grits with an 
 average breadth of outcrop of 1 mile. Further north-west we come to the 
 Bull Rock greywacke schist with a breadth varying from a little over 
 J mile to a little under J mile. Then comes the Dunoon phyllite series 
 with subordinate schistose grits and limestones : the average breadth of 
 this series is about 1J miles, but there are some subordinate outcrops 
 further north-west, which owe their existence to folding. Next we find 
 a series of " green beds " (chlorite-epidote schists, generally pebbly), mixed 
 with schistose grits and greywackes and phyllites. North-west of this 
 there is a zone, not less than 7 miles broad, of schistose greywackes, 
 phyllites or phyllitic mica schists, and albite schists. In this zone the 
 rocks are much more highly metamorphosed, brown mica is abundant and 
 a general change takes place in the direction of the dip of the foliation : 
 in the schist bands, already mentioned in this paragraph, and in the south- 
 east part of the zone the foliation dip is almost constantly south-east ; in 
 the north-west part of the zone and in the schist groups to be subse- 
 quently mentioned in this paragraph the foliation dip is north-west. The 
 axis of this great anticline of foliation traverses the whole of Cowal and 
 strikes north-east and south-west through Loch Riddon. After this wide 
 zone comes another set of "green beds," mixed with schistose greywackes 
 and albite and phyllitic mica schists. Next north-west of this is the Loch 
 Tay limestone, a bed which probably does not exceed 40 or 50 feet in 
 original thickness, but is the most definite of all the sedimentary schists 
 of the district. After this we get alternations of thin-banded mica schists, 
 generally garnetiferous, with some limestones and " green beds." Then a 
 set of graphitic schists, interbedded with dark graphitic limestones, 
 quartzose schists, and phyllitic mica schists. Finally, in the most north- 
 west part of the area, and composing the greater part of the shores of 
 upper Loch Fine, comes the broad Ardrishaig phyllite series with sub- 
 ordinate quartzose schists and limestones. The characters and positions of 
 these different schist groups are described in detail in subsequent chapters. 
 
 The different bands of limestone and of epidiorite or allied rock have, 
 as far as possible, been mapped out, but we have only rarely been able to 
 show the other rocks in the same detailed way, as it is found that they 
 both graduate into one another and alternate with one another in the 
 most minute way. The face of the Maps might, we fear, convey the 
 impression that the phyllites and schistose greywackes, etc., are less 
 mixed with one another than is the fact. There are two large zones 
 separated as phyllite those of the Dunoon and Ardrishaig phyllites 
 respectively but it must not be supposed that these consist wholly of 
 phyllite. As a matter of fact, the Dunoon phyllites contain a very con- 
 siderable admixture of quartzose pebbly grits, and the Ardrishaig phyllites 
 of quartzite schist. Still there is on these horizons a distinctly greater 
 proportion of phyllite than we usually find, and we have mapped them 
 out as groups in order to trace the broad physical structure of the district. 
 So, again, the groups of " green beds " may, particularly the wide one in 
 the north-west half of the district, contain a considerable proportion of 
 schistose greywacke or other mica schist like that outside them. 
 
 Numerous sea lochs intersect the area across the strike of the schists, and 
 afford excellent sections of the different horizons. Some of these sections 
 we will now describe in detail, with the aim, as we proceed, of explaining 
 
SECTION SOUTH OF DUNOON. 9 
 
 the characters of the different rock groups met with and the minute 
 structures in them. On the south-east side of the great anticline of folia- 
 tion which runs north-east and south-west through Loch Kiddon (which, 
 for brevity, we shall in future speak of as " the anticline ") the characters 
 and structures of the different rock groups are found to vary somewhat 
 in proportion to their distance from the centre of it. We shall therefore 
 describe sections which are representative of zones at different distances. 
 
 It will be shown from sections examined that there have been various 
 periods of folding and foliation production. The earliest foliation observ- 
 able either agrees in direction with the bedding or with the axial planes 
 of the first folds which affect the bedding. In certain areas and beds 
 this earliest foliation has been folded again and crossed by " strain slip " 
 foliations. These strain slip foliations are by no means all of the same 
 age. One set agrees roughly in hade with that of the first foliation where 
 this foliation is not itself contorted by the movements which gave rise to 
 the strain slipping. Another later set is only found in strength near the 
 centre of the " anticline," and is supposed to have been developed in con- 
 nection with the ridging up of it. This later set, and the folds which 
 gave rise to it, can frequently be seen in clear section to affect the strain 
 slips of earlier age. The later or anticline strain slips differ from the 
 earlier ones in hardly ever having quartz veins along them. The earlier 
 foliations, on the other hand, are often accompanied by quartz veins, and 
 in the region of the " anticline " the numerous folded quartz veins are a 
 ready indication of the folding of the earlier foliations also. Some pheno- 
 mena of " stretching " or elongation of particles in the schists will also be 
 described in this chapter, but further particulars of this subject are re- 
 served for chapter VII. 
 
 1. Section South of Dunoon. 
 
 A Section representative of the most distant zone occurs on the west 
 coast of the Clyde, a little south of Dunoon, between Glen Morag and 
 Clyde View. The rocks here belong to the south-east part of the Dunoon 
 phyllite series and to the schistose greywacke, which we may call the 
 Bull Rock greywacke, on the south-east side of this series. The former 
 includes, besides the bands of phyllite of different colour pale grey, 
 grey-green, buff, purple or black many exposures of schistose grit and 
 schistose limestone. 
 
 The black phyllites are probably somewhat carbonaceous, but they do 
 not stain the fingers : in places they contain a considerable abundance of 
 small crystals and nodules of iron pyrites, and, more rarely, thin films of the 
 same mineral running between the foliation planes of the rock. Pyrites 
 crystals may also occur in the phyilite of other colour, but not so 
 commonly. The purple bands are seen in several places to change to 
 pale buff : the change may clearly take place across the strike, and seems 
 connected with the proximity of small crush lines. Xear basalt dykes 
 the grey-green phyllites are often altered to dark grey or purple, and the 
 schists are evidently hardened, so as to stick up in rims by the dyke side. 
 The colours most nearly akin may occur in such thin stripes, e.g., of J 
 inch or so, that the rock has generally a finely ribboned appearance, 
 which in clean tide-washed exposures is very beautiful. These slight 
 differences of colour are often associated with slight differences of texture 
 also, one band being rather less of a true phyllite than another, or even 
 containing occasional pebbles of quartz, etc. These differences of texture 
 indicate that the colour striping is itself also essentially an original 
 structure, but they do not stand alone as a proof of this. Repeatedly 
 
10 
 
 GEOLOGY OF COWAL. 
 
 throughout the whole section, secondary planes of schistosity are seen 
 crossing these earlier stripes at marked angles. It is along these secondary 
 planes that the rock now splits. There is often in this section more 
 than one set of secondary planes, and the most prominent, which cor- 
 responds to the chief foliation planes of the district generally, may at 
 times run with the bedding of the rock, but we can never go more than a 
 few yards without seeing instances where this is not so : over and over 
 again the bedding is disposed in folds, and the foliation crosses the folds 
 parallel to the axes of fold * : and even when no distinct folding is 
 visible the foliation planes may strike and dip rather differently to the 
 bedding planes the dip of the former in these cases is generally rather 
 steeper, and the strike rather nearer east and west than that of the latter. 
 
 FIG. 1. xl. Shore S. of Dunoon. Fold in banded phyllite, as seen on a surface 
 sloping gently E. The direction of shading indicates that of the foliation. 
 
 These splitting planes are distinctly lustrous, and can therefore be with 
 accuracy called foliation planes, there having been a mineral rearrange- 
 ment in the rock which has led to the growth along them of minute 
 flakes of secondary sericitic mica, generally too small to be picked out by 
 the unaided eye. They are also characterised by a set of fine streaks 
 "rodding" or "stretching" lines. One may not be always able to dis- 
 cern these in the phyllite itself, but they are always conspicuous in 
 the thin quartz veins and pegmatites which occur so abundantly in it, 
 roughly parallel to the foliation. They are also more generally prominent 
 in the grits and greywackes associated with the phyllites. We shall 
 
 * There are cases, though, in which it is not quite parallel. In this and subsequent 
 passages the word axis is used to denote the section of the axial plane at right 
 angles to the axes, the axial plane being the plane which contains the axes or lines 
 along which the sharp twists of successive bands take place. This double use of the 
 word axis cannot be justified ; but in describing rock exposures and writing field notes 
 the section above referred to has so often to be mentioned that it is advisable to get 
 some brief term to express it, and the word " axis " has thus slipped into use. 
 
SECTION SOUTH OF DUNOON. 11 
 
 shortly (pp. 16, 17) have to mention details of structure in these veins, 
 grits, etc., which are intimately connected with such lines. 
 
 The direction of these stretching lines is not always the same : even on 
 one plane they may be occasionally seen to be slightly waved, now in one 
 direction and now in another, and in planes only a few inches separated 
 from one another the general direction may be different. They are but 
 rarely quite at right angles to the strike of the foliation : perhaps most 
 generally they run some 10 or 11 nearer east and west than the foliation 
 dip. 
 
 It has already been said that sometimes we may see more than one set 
 of foliation planes in the section. Some subordinate planes especially pro- 
 minent strike at a considerable angle, often about 80, to the chief foliation, 
 and hade nearly vertically. The general strike is perhaps 30 to 45 west 
 of north. They are of variable prominence in different localities, and make 
 little or no show in the more massive beds associated with the phyllites. 
 Their surfaces are distinctly lustrous and coated with a minute him of 
 sericite. In one of the best exposures such planes occur at intervals of 
 
 N.E.. 
 
 FIG. 2. xl. Shore S. of Duiioon. Banded phyl lite scar dipping from observer 
 Many, nearly vertical, late foliation planes throw the earlier foliation and bedding. 
 
 every ^ inch or so, and in between these there may be minute lines of 
 contortion with axes running parallel. 
 
 In age this subordinate foliation is clearly later than the main one, for 
 one often sees that it is accompanied with slight throws which affect 
 the main one and the thin quartz veins which run with it. As far as 
 examination goes it would seem that the throws and contortions 
 accompanying them have a constant tendency to shift the north-east side 
 of any band slightly to the south-east. 
 
 The planes of the earlier foliation are also frequently accompanied 
 by distinct throws. Sometimes the amount of this can be estimated by 
 the help of the bands cut, and we find that shifts of several inches are 
 not uncommon : one was observed of not less than 15 inches, and there 
 are others which may exceed even this. These little faults occur along the 
 thinnest lines running parallel to the other foliation planes, and seem of 
 quite the same character as these planes, except that the amount of throw is 
 large enough to be readily observed. In some places they occur so abun- 
 dantly that the bands representing original bedding are cut up into thin 
 
12 GEOLOGY OF COWAL. 
 
 lenticular strips which cannot be satisfactorily correlated with the others 
 near, and so help, together with the folding, to confuse the appearance 
 of the section. The throws are not always in the same direction, and 
 there may be both direct and reversed faults close together crossing the 
 same limb of a fold ; it seems impossible to say which of the two kinds 
 is generally the more common. 
 
 ' IflBHi 
 
 IW 
 
 C. r.c. 
 
 FIG. 3. x \. Shore -mile S. of Glen Morag, Dunoon. Sketches from rock slopes 
 inclining gently E. The dark bands are purple phyllite ; the paler bands are 
 pale grey rather harder phyllite. The shading shows the foliation direction ; 
 the darker lines are accompanied with throws. 
 
 These foliation faults must not be confused with some later crushes, which 
 also strike and hade almost with the main foliation. These crushes make 
 little nicks or gulleys along the shore line, which may be filled with thin 
 streaks of crushed phyllite, and have clearly been instrumental in destroy- 
 ing the phyllite character, not accompaniments of its production. 
 
 In the phyllites the tendency to split along the foliation direction is of 
 the closest possible character, but in the more siliceous and pebbly beds 
 it is not so close, the splitting planes having, for one thing, to go round 
 the pebbles, unless where they occasionally succeed in breaking through 
 one. Hence, in pebbly beds, the distance between the planes may 
 be as much as \ inch or even more. Where phyllites and pebbly grits 
 are folded together in clear section, it is seen at once that the number of 
 foliation planes in the former is very much greater than in the same 
 breadth of the latter : it is also observed that the angle of dip of the 
 foliation in the latter is not usually quite the same, being often rather 
 less steep. 
 
 Almost universally in this section where the bedding is folded the 
 prominent foliation still keeps straight, with an average strike of about 
 30 north of east, and a dip to south-east of about 53 ; hence the 
 rocks split along straight lines, and the phyllites admit of being used as 
 slates. But some cases occur where this foliation has itself been folded ; 
 it may be quite gently, it may be so sharply that " strainslip " or 
 " ausweichung " foliation has been developed along the axes of the folds. 
 The direction of hade of these axes is not always the same : in many 
 cases both limbs of the fold hade south-east, but close to this may be 
 others with axes hading slightly north-west : on the whole, however, it 
 seems as if the sharpest and most prominent of these later folds have 
 axes hading south-east. These strain slips always seem to have some 
 
SECTION SOUTH OF DUNOON. 13 
 
 throw, and to have been developed from a series of corresponding limbs 
 of folded bands overlying one another, along which actual breaks have 
 occurred. Neither here nor in other parts of the schist area have quartz 
 veins been commonly developed along strain slips of this age, though 
 such are so common along the earlier foliation. Hence, in this section, 
 one sees but rarely folded veins, whereas in " the anticline " country they 
 are excessively common ; and lying on the shore here are some large 
 boulders of " anticline " schists, which testify at once to the difference 
 between themselves and the rocks they rest on, both in this and other 
 respects. 
 
 The first foliation is exceedingly uniform in strike and hade, with the 
 exceptions due to the subsequent folding just referred to. It is, as 
 already stated, parallel, or all but parallel, to the axes of the early folds 
 in the section, and we suppose it may be regarded as having been pro- 
 duced at the same time with, and as a direct consequence of, these folds. 
 
 It is a general law here, and throughout the south-east side of " the 
 anticline," that in these early folds the longer limbs of anticlines are the 
 south-east limbs. The effect of this structure is to make the general dip of 
 the beds less steep than that of foliation. It is noticeable, too, that the 
 original bands of bedding vary in thickness in different parts of the folds 
 according to a general law. Looking, indeed, at some of the small folds 
 
 Sf. W 
 
 FIG. 4. Diagram Vertical Section. To illustrate the laws of folding and thinning 
 of limbs in the Dunoon horizon. 
 
 that we may chance to see, it may be sometimes the south-east limbs 
 that are the most thinned, and sometimes the north-west, or there may be 
 no difference. But if we examine the parts adjacent to such folds we shall 
 find that the area in which there is no evident law of thinning forms but 
 a small part, in which the limbs are all comparatively short, coming in 
 between longer and generally much more thinned limbs, each hading 
 south-east. If we regard the series of short limbs as representing to- 
 gether one limb, with a hade in the contrary direction to that of the 
 longer limbs, we may say that the most thinned limbs are the south-east 
 limbs of anticlines. The most thinned limbs are the parts which, if 
 further pressure had been applied, would ultimately have thinned away 
 to nothing in one part, and have given rise to " thrust " lines analogous 
 to those in the Durness and Torridon rocks of the north-west of Scotland ; 
 and, from analogy, we should expect them to be on the underlying sides 
 of isoclinal anticlines, and to have been produced by pressure origin- 
 ating in a locality lying in a direction pointed to by the dip of the axes 
 of fold. How, then, has it come about that in this Dunoon section it is 
 the uppermost limbs of anticlines that are the most thinned, and is it 
 likely that the pressure which produced the early foliation was produced 
 by earth movements in a locality lying south-east from the present High- 
 land frontier 1 Both questions seein to receive an answer if we bear in 
 mind the fact that all these beds on the south-east side of "the anticline" 
 
14 GEOLOGY OF COWAL. 
 
 have, by the agency of this plication, been given an inclination which was 
 not originally theirs. The upper limbs of anticlines at Dunoon must 
 once have been under limbs, and the dip direction of their axes of fold 
 must once have been north-west and not south east. 
 
 Three specimens of the phyllites have been examined by Mr Teall 
 (slides 3825, 3826, 3827). Of these the first, of pale grey colour, was 
 found to consist essentially of quartz and sericite, with certain portions 
 crowded with rutile needles. 3826, a dark leaden colour, was also very 
 rich in these needles. 3827, greenish-grey in colour, is composed of quartz, 
 sericite and chlorite, and contains rutile needles in much less abundance. 
 
 The limestone outcrops have not in general a greater apparent thickness 
 than 5 or 6 feet. It is rash at present to speculate on the extent to 
 which different bands may have their outcrops thickened by folding, or 
 repeated in other parts of the section. In our 6-inch Field Map no less 
 than 17 different exposures are shown in a length, diagonal to the strike, 
 of f mile. They generally weather a rusty colour, but the fresh 
 fracture is dark grey, and the grain fine. The foliation planes are coated 
 with a micaceous lustre, but these planes are not so close or so regular as 
 in the phyllites, and not uncommonly two can be seen to run into one 
 another at a gentle angle. 
 
 The limestones seem to have suffered from folding more than any of 
 the other rocks in the section, the first foliation in them being more 
 frequently waved or twisted. A striking instance of this occurs in a broad 
 exposure a little over J mile north of the Bull Rock : here not only 
 is the most prominent foliation folded and sharply twisted, and crossed 
 by strain slip foliation, but it ssems as if this foliation was itself preceded 
 by another, by the contortion of which it was developed as a strain slip 
 foliation : the earlier thinner foliation is indicated by an alternation of pale 
 grey purer limestone streaks with other darker more micaceous bands. 
 The latest folding in this section may be of " anticline " age, like much of 
 that described in subsequent pages, but it cannot be stated for certain 
 that this is so, Dunoon being so far from the region where the anticline 
 folding occurs in force. At all events this latest* Dunoon folding agrees 
 with the anticline folding in being later than the early foliation and 
 strain slips of the district. In another exposure the prominent foliation 
 planes, clearly corresponding to that in the phyllites, occur at intervals 
 of every \ inch or so, and, besides the mica in these planes, there is a 
 distinctly lustrous surface along a folded bedding plane which is crossed 
 by the prominent foliation. This suggests that there was an earlier 
 foliation here again, which agreed with the bedding, before the develop- 
 ment of the prominent foliation.! But perhaps during the production 
 of foliation the formation of new mica may take place along the old 
 bedding planes, as well as the new foliation planes, in cases of hard beds 
 in which new splitting planes are not readily formed. This might be 
 supposed to be more likely to happen if the angle between bedding and 
 foliation is only a small one. In the phyllites, however, we have not 
 noticed any limit to the angle at which bedding and foliation may lie 
 without actually coinciding: it can certainly be as little as 10. The 
 prominent foliation in the exposure last mentioned does not look like 
 the later " anticline " strain slip foliation : it is quite parallel to the 
 prominent phyllite foliation, and has quartz veins parallel to it : that it 
 
 * Latest with the probable exception of the minute contortions accompanying the 
 foliation which strikes 30 to 45 west of north (see p. 11). 
 
 1 It is not impossible that this may have been the case in the Dtiuoon phyllites 
 generally. The earlier structures in such micaceous beds as these seem to be com- 
 paratively readily obliterated (see p. 21). 
 
SECTION SOUTH OF DUNOON. 15 
 
 is not so close as in the phyllites is only in accordance with the law 
 that prevails in all hard beds, and should we see a phyllite parting in a 
 folded limestone the parting is sure to be crossed by the closest foliation 
 planes, parallel to the rarer ones in the limestone. 
 
 In the part of the section included in the phyllite group the pebbly 
 beds are generally distinguished by a considerable abundance of opaque 
 white quartz pebbles, which may attain the size of a sparrow's egg. In 
 the thick band south of this group the more prominent pebbles are of 
 felspar, generally pink, and it is hence called a greywacke the "Bull 
 Rock " greywacke rather than a grit. In the same band there are also 
 pebbles of quartz, white and granulitic, or else free from granulitisation, 
 and with an opalescent appearance. In those of the last character a 
 pale shade of blue may often be observed. There are also patches 
 up to over au inch in breadth, of purplish-red hard clayslate, and thin 
 streaks of the same. These streaks are often so long in proportion 
 to their breadth, perhaps 1 foot by less than 1 inch, that we consider 
 them to be essentially cotemporaneous deposits, or derived from such. 
 
 The opalescent quartz is like that of many of the quartz streaks 
 in the Lewisian Gneiss, and of pebbles in the Torridonian rocks derived 
 from this. But it must be stated that similar quartz also occurs not 
 uncommonly in the epidiorites of St Catherine's and of the central 
 Highlands. The felspars of the pebbles have not been examined in 
 detail, either in this or the other pebbly schists of the Map. In the grits 
 which occur some distance further north-east, outside of Cowal, along 
 the foliation strike, it has been determined by Mr Teall that they are 
 generally a soda felspar, oligoclase. The felspar of the felspar pebbles 
 in the chocolate and red Torridon sandstones of north-west Scotland is 
 a potash felspar, but in the grey Lower Torridonian rocks of Skye 
 oligoclase is about as abundant as the potash felspar. 
 
 We do not think any pebble was noticed in this greywacke which could 
 not be referred to quartz or felspar or clayslate. Pebbles of composite 
 rocks are indeed exceedingly rare throughout the schists of this area. 
 Sometimes, however, compounds of quartz and felspar, much like those 
 of many pegmatites, have been noticed : and some pulled-out streaks of 
 chloritic rock occur in a schist ^ mile east of Inellan Hill (194 south-east), 
 for the description of which see p. 30. There are also some pieces of 
 green-grey hornstone-like rock in the band mapped south of Gairletter 
 (174). 
 
 On the shore there is a continuous section of the greywacke for a length, 
 not quite at right angles to the strike, of over ^ mile, and a little of the 
 north-west end of it is probably covered under drift. Throughout this, 
 bands, of phyllite are rare, and never exceed 4 or 5 feet in breadth, 
 so that it hardly seems likely that they are folded up inliers of the mapped 
 phyllite series. There are frequent alternations in the size of the pebbles 
 in different bands, and the original bedding is not generally hard to make 
 out. There are not so many prominent folds as in the phyllites, and 
 perhaps the greywacke, being so massive, may to some extent have 
 escaped the folding to which the softer beds yielded, as is often seen to 
 be the case in the later foldings of " anticline " age. 
 
 The colour of the greywacke is often somewhat greenish. This is pro- 
 bably due to the chlorite which the microscope shows to occur in it in 
 association with the sericite. Mr Teall describes the microscopic character 
 of a specimen as follows (slide 3823) : " Micaceous (silvery) lustre on 
 cleavage planes. Relics of clastic grains of quartz and felspar very 
 conspicuous. These lie in a fine-grained granulitic matrix containing 
 wavy strings of chlorite and sericite. Iron ores and small opaque white 
 
16 
 
 GEOLOGY OF COWAL. 
 
 grains (? leucoxene) sparingly represented. Structure microflaser. It 
 seems probable that this is the type of rock termed sericite gneiss on the 
 continent." On either side of the quartz or felspar pebbles in the 
 direction of " stretching," there are often special accumulations, or tails, of 
 granulitic quartz, and it is suggested that these have been formed by the 
 breaking down and recrystallising of the original 
 edges. The felspar pebbles often show cleavage 
 faces across their whole breadth, and on the 
 average have perhaps suffered less from granu- 
 litisation than those of quartz. In some bands 
 of greywacke schist, e.g., in the thin band 
 mapped 1 mile E.S.E. of Lephinkill (172 
 south), the felspar substance (slide 3828) has 
 FIG. 5. x 2. Shore S. of a dusty aspect near the centre of the pebbles, 
 Dunoon. Surface of pebble but it is clear at the outside . this clear part 
 
 ^LTfnB^Vcfgr 1 ;;. Fobably a product of recrystallisation, 
 
 wacke. The felspar sub- but it is in optical continuity with the centre. 
 
 stance is shaded ; the clear The sericite flakes are perhaps larger and 
 
 parts are grannlitic quartz. more conspicuous than in the phyllites, but 
 
 to counterbalance this there are fewer of them, there being fewer 
 
 foliation planes. 
 
 The direction of " stretching " is shown in many places by the parallel 
 elongation of the pebbles, but particularly well at a spot just below the 
 quarry in the greywacke. The direction runs a few degrees nearer east 
 and west than the direction of dip of the foliation. The pebbles are 
 often stretched to a length of over J inch, while the breadth does 
 not amount to J inch, and they are repeatedly cracked and the 
 
 FIG. 6. x 1. Pebbles out of greywacke schist 
 i-mile N.E. of the "k" of "Dalleik," 
 1 mile E.S.E. of Lephinkill (172). The 
 felspar substance is crossed by lines of 
 grauulitic quartz in a direction at right 
 angles to their length. In the right hand 
 pebble the cleavage of the felspar is distinct. 
 
 FIG. 7. y 2. From a boulder in Glen 
 Lean. Polished section of lenticular 
 pebble - form patch in greywacke 
 schist, cut at right angles to foliation 
 and in the direction of stretching. 
 The shaded areas are felspar ; the 
 rest granulitic quartz. 
 
 cracks filled with granulitic quartz. In one pebble, not over \ inch 
 long, ten such cracks were counted. Similar cracks are also to be 
 observed in the opalescent quartz, but these are not so conspicuous, 
 probably from the want of sufficient colour contrast. The cracks do 
 not usually run quite at right angles to the length of the pebbles or the 
 dip of the foliation : we could not satisfy ourselves that there was a law 
 guiding their directions : sometimes they incline more steeply than the 
 
SECTION SOUTH OF DUNOON. 17 
 
 plane at right angles to the foliation, and sometimes less so. Besides the 
 cracks nearly at right angles to the lengths of the pebbles, there are 
 sometimes other thinner ones roughly parallel to the lengths, and these 
 last may slightly throw the former. 
 
 In the Bull Rock greywacke, and also in some grit bands near the 
 north end of it, one sees in places that the prominent foliation is crossing 
 another less continuous set of planes. There are certainly films of 
 sericite lying along the less continuous planes as well as along the 
 others. By the dyke side J mile S.S.E. of Glen Morag it seems clear 
 that there must have been an earlier foliation preceding that which 
 is usually the most prominent, the pebbles in a quartzose pebbly 
 band being distinctly elongated along planes which are cut by the 
 prominent foliation. 
 
 The stretching of these pebbles is supposed to have taken place at the 
 time of the production of the rodding or streakiness seen on the foliation 
 planes of the adjoining phyllites, and, probably, both were accompaniments 
 of the production of foliation. The rock was not only rendered fissile and 
 to some extent mineralogically changed along these foliation planes, but 
 the particles on these planes were elongated or stretched in a definite 
 direction along it. This elongation seems quite comparable to the well- 
 known distortion of fossils on the cleavage planes of slate.* In no part 
 of Cowal have we been able to distinguish on foliation surfaces an elong- 
 ation due to the "anticline" movements apart from that due to the 
 movements of earlier date. Sometimes, though, one sees in vertical 
 sections that the pebble-like specks in pebbly schists are more elongated 
 in the limbs of folds of " anticline " age than in their centres, so that 
 some stretching or elongation must have taken place at the time of the 
 formation of these folds. At Dunoon the schists are, with the possible 
 exception of some small exposures (chiefly of limestone, see p. 14), un- 
 affected by the anticline movements, and the stretching noticed there 
 must consequently be essentially of pre-anticline date. 
 
 The veins and pegmatites in the section rarely exceed a few inches in 
 breadth, and occur much more commonly in the phyllites, etc., than the 
 more massive beds. The felspar in them is generally pink, and in small 
 proportion to the quartz. Lumps and strings of green chlorite are common 
 in them, or at their sides, and flakes of it are often enclosed in the outer 
 parts of quartz bands, giving them a green colour. Thin strings and 
 lenticles composed almost entirely of chlorite are also common. In 
 general, the veins run roughly with the foliation, and show on their sides 
 prominent " stretching " or " rodding " structure, the quartz and felspar 
 running in rod forms in a definite direction, that of the stretching of the 
 pebbles in the pebbly beds : in some cases the rod structure extends 
 through the thickness of a vein several inches wide. Many of the veins 
 have been cracked across, and the cracks filled with a new growth of 
 quartz : such later growths are very prominent in the polished face of a 
 specimen obtained from 50 yards south of the Bull Rock, and on examining 
 a slide of it under the microscope we see that the new quartz is much 
 clearer than the old, being much more free from minute dust-like en- 
 closures : probably these enclosures are of secondary origin, and their 
 greater abundance in the older quartz depends on the greater number of 
 strains to which it has been subjected. A ferriferous carbonate is 
 frequently associated with the veins, and may occur in masses several 
 inches across : in some places this mineral is certainly of earlier date than 
 some of the quartz, for strings of the latter may be seen breaking across 
 
 * See, for instance, Daniel Sharpe, "On Slaty Cleavage," Quarterly Journal, 
 Geol. Soc. London, vol. 3, p. 74. 
 
 B 
 
18 GEOLOGY OF COWAL. 
 
 its cleavage planes. When veins of quartz and carbonate run across the 
 foliation their edges frequently show casts of its planes, and also a close 
 alternation internally of quartz and carbonate layers, which may approxi- 
 mately agree in direction with the foliation planes. Among the veins 
 which run neither with the foliation nor at right angles to it there seems 
 a tendency to an inclination rather more steep than that of the foliation, 
 and to a strike less near east and west. The veins of this class are at times 
 affected by the vertical foliation already described, and so must be very 
 old. They are often accompanied by slight throws : the up-throw side is 
 often the south-east, but not always. Some of the veins which run at 
 right angles to the prominent foliation are full of minute twists, the axes 
 of which are roughly parallel to it. It might be supposed at first that these 
 veins are of earlier date than the foliation, and have been contorted at the 
 time of its production. On this supposition, the total length of the vein, 
 calculated through all the twists, would indicate the original thickness of 
 the rock traversed by it, and thus afford a means of finding the amount of 
 compression subsequently undergone. But it is doubtful whether the 
 supposition is a safe one : perhaps the pre-existence of foliation may itself 
 be a cause for a later formed vein to alter its course in directions which 
 have reference to it. 
 
 A thin slice (7314) of the pegmatite about 50 yards south of the Bull 
 Rock has been examined microscopically by Mr Teall. The specimen sliced 
 seemed quite the same in character as the other thin pegmatites which 
 occur on the shore both in the grey wackes and phyllites. Mr Teall states 
 that the slice is composed of quartz, albite, and a little carbonate, and 
 shows signs of crushing. He continues : " This is no doubt a segregation 
 vein, and is therefore different from the quartz-microcline pegmatites 
 which are often associated with granites. Similar quartz-albite veins 
 occur in the schists near Start Point in Devonshire and in an area of 
 dynamic metamorphism in the Hartz as described by Lossen." The albite 
 of these Dunoon pegmatites differs from the albite of the albite schists 
 (pp. 39, 40), and of the pegmatites in these schists, in being pink 
 macroscopically and in showing distinct roddiug. The albite in the Start 
 Point pegmatites is also pink. In another pegmatite (slide 4198) 
 obtained from a schistose greywacke J mile north-east of Mark (153) the 
 felspar has also been determined as albite by Mr Teall : the colour is 
 quite the same as that of the albite in the Dunoon pegmatites, but the 
 specimen does not show whether it is rodded or not. We are also 
 informed by our colleague Mr Barrow that he has sent from twenty to 
 thirty specimens of pegmatite from the greywacke schist of the Stonehaven 
 district to Mr W. M. Hutchings, who has determined the felspar to be 
 albite in all cases. 
 
 2. Section on the West Side of Loch Long, South of Ardentinny. 
 
 The next Section we will describe lies on a horizon 3 or 4 miles nearer 
 " the anticline " than that south of Dunoon. This occurs on the west side 
 of Loch Long, from J mile north of Gairletter Point to about J mile south 
 of Ardentinny. Here there is a much less proportion of phyllite, or of soft 
 phyllitic mica-schist, than there is at Dunoon, and nothing we can call 
 limestone. A great portion consists of schist in which granulitic quartz 
 and sericitic mica occur in thin distinct folia, but this schist is mixed with 
 more massive greywackes and hard quartzose bands, which are much less 
 perfectedly foliated, and there are also many calcareous, ochreous weather- 
 ing, bands and lenticles, rarely exceeding a few inches in breadth and a few 
 
SECTION SOUTH OF ARDENTINNY. 
 
 19 
 
 yards in length, which show no clear foliation at all. These calcareous 
 bands are great helps in making out the original bedding. 
 
 As compared with the Dunoon section the number of foliation planes 
 in a similar breadth of exposure is less, these planes being generally 
 further apart than at Dunoon. This is not due to a diminution in the 
 strength of the force that produced foliation, but to original differences in 
 the rocks acted on, to the fact that the rocks here are generally harder, 
 more quartzose and massive than at Dunoon. For in places we can see 
 hard quartzose bands folded with more micaceous schists or phyllites, the 
 
 
 FIG. 8. Rather more than -mile N.W. of Gairletter Point. Hard quartzose schist, 
 with hardly any cross foliation, overlying finely foliated green-grey phyllitic 
 schist. The shading in the latter shows the direction of foliation. 
 
 latter being foliated in the finest possible way, while the former are only 
 affected by strain slip foliation at intervals of \ inch, or even occasionally 
 of 1 inch : these strain slips run parallel to the fine foliation of the phyl- 
 lites and to the axes of fold in the exposure. One very massive quartzose 
 band, for a distance of more than 3 feet across the axis of fold, shows no 
 strain slips, except 3 or 4 short discontinuous lines. Yet just below it, in 
 more micaceous schists, the very finest foliation is seen. Such inter- 
 stratification of readily and less readily foliated beds may give rise to 
 appearances closely simulating false-bedding. Not uncommonly the 
 foliation is so poorly developed that the rock splits more readily along the 
 
 original bedding, now repeatedly folded, than 
 along the foliation, and for this reason the 
 possibilities of acquiring roofing slates are less 
 than at Dunoou. 
 
 The chief system of fold is the same as at 
 Dunoon, and the same law regulates the 
 length and the thinning of the different limbs 
 of anticlines. The chief foliation planes are 
 parallel to the axes of fold, and correspond 
 roughly in strike and dip with those at 
 
 Dunoon. They are on the whole, too, about 
 FIG. 9. xl. Shore N. of Gair- , J ,, , ., ,1 
 
 letter Point, Loch Long. as steady and unfolded as these, the apparent 
 Shaded parts are the more less regularity of splitting planes being due, 
 micaceous. Direction of not to an extra folding of the foliation, but to 
 
 f acfc tnat some O f tae roc k s sp li t by pre- 
 
 along their beddiag planes, which may 
 
 foliation plane are folded, be folded to any extent. But as we traverse 
 though folding cannot be the section from south to north the waving 
 discerned in the more quart- O f tae prominent foliation becomes gradually 
 more pronounced : in most of it this waving 
 noticed in the more micaceous schists, as a succession of 
 minute folds, probably averaging hardly |- inch in breadth, or of 
 strain slips parallel to the axes of these folds. But near the north 
 end such folding is common even in massive quartzose schists, and is 
 also of one predominant type, with axes hading north-west : still, how- 
 
 shading shows the lie of 
 
 zose parts, 
 can only be 
 
20 GEOLOGY OF COWAL. 
 
 ever, the folding has not, in quartzose rocks, been strong enough to 
 give rise to strain slips. Pretty hand specimens can be acquired which 
 show the late folding and strain slips in micaceous layers which are 
 themselves of secondary origin and lie along the lines of earlier strain slip. 
 The folia of mica in the earlier strain slips are arranged in the same 
 general direction as the strain slips, and so, too, are often those of the 
 micaceous layers cut through by the slips. At times there are indications 
 of an arrangement in the same direction even in the quartzose layers : this 
 is shown by the elongation of small ferriferous carbonate specks within 
 them. But if examined more minutely it is seen that, independently of 
 the later folding, the mica in the slips is not always quite parallel to the 
 sides of the slips, but lies at a small angle, approximately that at which 
 the earlier banding approaches the slips. For this reason as one moves 
 one's finger along the surface of a slip one feels a slight roughness when 
 
 FIG. 10. x 1. Coast N. of Gairletter Point. Burn -mile E. of Gortnamhuinn 
 (173). " Ausweichung " or "strain-slip " foliation crossing earlier planes. The 
 shaded parts are the more micaceous : the direction of shading indicates the 
 general direction of the mica flakes. The black spots represent hollows left 
 by the weathering out of a ferriferous carbonate. 
 
 the direction of movement is contrary to the direction of inclination of 
 these earlier bands. 
 
 The micaceous layers developed along the early strain slips sometimes 
 attain a breadth of J inch or more, and hence secondary alternations of 
 mineral character of such a marked degree are acquired that they may 
 rival or exceed in prominence those along the bedding, or along an earlier 
 foliation. The last words are added, because it is clear in some part of 
 the section that, besides the foliation which corresponds with the prominent 
 one at Dunoon, there is also a mineral rearrangement along the bedding 
 or other planes cut by it. For instance, about J mile north of Gairletter 
 Point, a hard quartzose schist is seen folded over phyllitic schist : the 
 phyllitic schist has a foliation like that at Dunoon, but the quartzose band 
 is hardly affected by this foliation, and breaks more readily along the bed- 
 ding, and the curved surfaces thus obtained are covered with secondary mica. 
 Again, at the north end of the section, there is a schist with many pebbles, 
 both of quartz and of white and pink felspar. The bedding is shown by 
 the line between this schist and a much more micaceous dark grey schist, and 
 crossing this bedding and the whole exposure, a set of foliation planes, 
 
SECTION SOUTH OF ARDENTINNY. 
 
 21 
 
 runs closely together in the more micaceous and less so in the pebbly 
 schist. But in addition there is in the pebbly schist another set of 
 planes, which are cut by the more prominent ones. These last mentioned 
 planes agree in direction approximately with the bedding : but they do 
 not represent bedding alone, for the pebbles are distinctly elongated 
 along them. There are other sections indicating the existence of a 
 foliation, which did not agree with bedding, prior to the production of 
 a prominent set of strain slips hading south-east and striking the same as 
 the prominent foliation of the district. In some of these sections the 
 angle at which the bedding is cut by the earlier foliation is much the 
 same at all points of the fold, and it is therefore probable that it was 
 lying evenly at the time the first foliation was set up, and has been 
 subsequently crumpled together with it. But in other cases the angle 
 between the bedding and the earlier foliation is not constant, and we 
 may conclude that the bedding was folded before, or at the same time 
 with, the production of the foliation, as is so constantly the case at 
 Dunoon. 
 
 S.VY. 
 
 S. . 
 
 N.W. 
 
 FIG. 11. Not quite ^-mile N.N.W. of Gairletter Point. Plan of a rock surface 
 sloping E. The spotted band is an ochreous weathering bed which shows 
 hardly any foliation. Rest of rock is a well-foliated quartzose schist : the fine 
 lines in it represent first foliation : the darker lines crossing these are strain-slip 
 foliation. At points over the letter " a " the angle between the first foliation 
 and the bedding is approximately the same in each case. 
 
 It seems clear that in alternations of phyllitic and quartzose schists, 
 the old structures of the former may be so obscured by renewed movement 
 and strain slipping as to be no longer recognisable, though the corres- 
 ponding structures in the quartzose schists may remain quite distinct. In 
 some of the sections mentioned in the preceding paragraph, we suppose 
 there was at one time a distinct foliation in the more micaceous schist 
 running parallel to the bedding or to the foliation still seen in the quart- 
 zose beds, but that by a renewal of folding the particles of the former 
 schist have got their directions rearranged parallel to the axes of the new 
 folds. In the crags J mile N.N.W. of Glenmassan (163), in alternations 
 of more and less micaceous schists, one sees that in the former the strain 
 slips may sometimes be exceedingly close within -^ or even ^ inch of 
 one another so close that had it not been for the more quartzose bands 
 of the section we should certainly have carried away the idea that the 
 strain-slip foliation was the only foliation present, though, as a matter of 
 fact, there was an earlier one during the contortion of which the strain- 
 slip foliation was produced. The folds in connection with which the above 
 strain-slip foliation was produced are not very acute, and it is probable 
 that by a little more intensity of movement the earlier structures would be 
 
22 GEOLOGY OF COWAL. 
 
 still more obscured, until in certain bands they could not be recognised. 
 This last result seems to have been arrived at in parts of the Ardentinny 
 section. 
 
 In places where bedding and foliation do not coincide, the pebbles in 
 pebbly beds are elongated along the foliation planes, their greater lengths 
 sticking up at times at right angles to the original planes on which they 
 were deposited. 
 
 Quartz veins are common both along the main foliation and the bed- 
 ding: they seem more common along the latter than they are at Dunoon. 
 
 If we compare the amount of mineral change in this section with 
 that at Dunoon we are struck by the occurrence here of brown mica 
 occasionally along the foliation planes, besides sericite ; whereas at 
 Dunoon brown mica does not occur. The sericite also commonly occurs in 
 larger and more distinct flakes.* Brown mica has not been noticed at the 
 south end of the section : as we proceed from south to north it is first seen 
 in a quartzose band a little over ^ mile from the south end. In this band 
 it is not conspicuous : it occurs only in small flakes, and on many foliation 
 surfaces of some extent it could not be found at all, in spite of close 
 search. North from this, brown mica becomes gradually more prominent, 
 and in the massive grey wacke lying east of the word " Driseig " is fairly 
 abundant. Even yet the amount of change is not so great as in the 
 schists lying a mile or two further north-west, for, among other things, 
 the number and size of the brown and black mica flakes in these last are 
 greater, and the quartz veins along the bedding or earlier foliation are 
 more prominent : this can be seen from the boulders of these rocks which 
 lie scattered about on the shore. In this section, then, we seem to have 
 an intermediate stage between the types of greatest and least alteration of 
 the district. The amount of folding, as has been said, is not appreciably 
 different from that at Dunoon ; we have not yet advanced far enough 
 north-west to be within range of the more prominent movements connected 
 with the development of "the anticline." Therefore it does not seem 
 likely that folding or physical movement, to be seen in the section itself, 
 can be the cause of the greater metamorphism. 
 
 Still it is clear that folding does effect a metamorphism, or, at all 
 events, that greater metamorphism is shown along lines which have been 
 specially subject to mechanical disturbance. There is hardly a space of a 
 yard length that does not show the metamorphism to vary locally and 
 sharply, according to the lie of the rocks and the amount of physical strain 
 they have undergone. Again and again we see broad bands, whether of 
 bedding or early foliation need not here concern us, which are lying 
 nearly flat in the centres of small folds, and in this position they are, 
 on the average, two or three times as thick as they are in the limbs. On 
 the other hand, the more micaceous layers are, at least, as thick in the 
 limbs as in the centres, so that the bands are, as a group, of much darker 
 appearance, and more micaceous than in the centres. This difference 
 must imply a molecular change throughout. The new mica which occurs 
 along the strain slips is also an example of the appearance of mechanical 
 movement and metamorphism together. We may look upon a strain slip 
 as a limb thinned to the utmost extent, and the presence of new mica 
 along it as due to an extension of the law that in thinned limbs the 
 quartzose parts of bands diminish in quantity, while the micaceous 
 remain the same or increase. 
 
 * We had the great advantage of Mr Teall's company in going over the section. 
 
SECTION IN KYLES OF BUTE. 
 
 23 
 
 3. Section along East Shore of the Kyles of Bute. 
 
 The next Section we will describe extends along the east shore of the 
 Kyles of Bute, from J mile north-east of Colintraive to Port an Eilein. 
 The rocks here consist of an alternating series of schistose grey wackes, and 
 more thinly foliated very micaceous or chloritic schists, in many of which 
 small specks of albite are abundant. Near the north-west end of the 
 section the grey wackes form a larger proportion of the rock than usual, 
 and have been mapped out as a zone. 
 
 The south-east end of the section lies about 1J mile nearer "the 
 anticline " than the north end of the section last described does, and there 
 is a difference in the amount of mineral change in the rocks of the two 
 localities : the brown and black mica in the Colintraive greywackes form- 
 ing larger flakes, and a generally more uniform layer along foliation surfaces. 
 But the mechanical movements to which the rocks have been subjected 
 are still essentially the same, the evidence for the later movements con- 
 nected with "the anticline" not becoming pronounced until we advance 
 north some little way in the section. The first distinct albite crystals that 
 we noticed in traversing the section from the south-east occur about 100 
 yards south-east of the foot of Allt Glac na maill, in bands of very 
 micaceous schist which alternate with other quartzose bands, which seem 
 free from albite. The albites here are so small that they could easily be 
 overlooked, and it is probable that similar crystals in bands further south- 
 east have escaped notice. North-west from this locality almost any exposure 
 of the more micaceous or chloritic layers will, on careful search, disclose 
 albites, becoming, as a rule, larger and more prominent the further north- 
 west we go. Further details about these albite schists will be given on 
 p. 39. They are possibly a further indication of the greater mineral meta- 
 morphism of the rocks. 
 
 FIG. 12. x 1. Fearna Bagh. Sketches from specimens of quartzose mica schist. 
 Folded " pre-anticline " strain slips in " Pre-anticline " strain slips, slightly 
 
 middle of sketch. The black spots re- 
 present hollows left by the weathering 
 out of a ferriferous carbonate. Nothing 
 to indicate bedding. 
 
 waved, in left part of sketch. The 
 earlier foliation approaches these at a 
 distinct angle and is cut by them. In 
 right hand of sketch weakly developed 
 strain slips of ' ' anticline " age are 
 crossing the first foliation. 
 
 As we proceed north-west the evidence for the movements connected with 
 " the anticline " becomes stronger, and is particularly well seen at the point 
 north of the Burnt Islands, and that north-west of Fearna Bagh. Every 
 few yards we see places where an early foliation has been crossed by 
 early strain slips, of the type of the prominent ones in the Ardentinny 
 section, but these again are crumpled most variously by later "-S"i''n" 
 
 anticline 
 
24 
 
 GEOLOGY OF COWAL. 
 
 movements. Plate IV., near the end of the volume, shows a natural rock 
 exposure on the north side of Fearna Bagh. In this the strain slips are 
 seen distinctly folded by the later anticline folds. Plate III., also from 
 the north side of Fearna Bagh, and Plate V., from the south side of Coylet 
 Inn, Loch Eck, show folds, which also are probably of anticline age, in 
 still greater intensity. 
 
 Sufi 
 
 FIG. 13. x 1. From a vertical section of pebbly schist near the top of Beinn Bheag 
 (152). The parts drawn are placed in their natural relation. The lines all 
 indicate foliations. Folded strain-slip foliation planes, crossing the earlier 
 planes, are seen in the top portion, and at left hand of bottom portion. At the 
 right hand of bottom portion there is an attempt to develop strain slips along 
 axis of same fold which folds the early strain slips in top portion. 
 
 The strain slips of anticline or pre-anticline age may be only a few 
 yards or less in length, passing into lines of sharp contortion from which 
 they have been developed, and these lines of contortion may grow much 
 less conspicuous, or die out altogether, in the massive beds which have 
 been less readily crumpled. 
 
 S.E. 
 
 H.W 
 
 Fir*. 14. x T V Vertical section in quartzose schist 250 yards S. of Coiraiitee (163). 
 Strain bands hading N.W. have been subsequently folded along an axis inclin- 
 ing steeply S.E. All the lines indicate foliations. Nothing to show the 
 bedding. 
 
 The narrow rock strips lying between two closely adjacent strain slips 
 we will for convenience call " strain bands." The earlier foliation crossing 
 these bands is often almost obliterated by the development of numerous 
 small spots of ferriferous carbonate weathering into hollows, the greatest 
 lengths of which He parallel to the strain slips. It was originally, too, pro- 
 bably not so much developed as in the rock at the sides of the strain bands, 
 
SECTION IN KYLES OF BUTE. 
 
 25 
 
 owing to the strain slips having usually occurred near the centres of folds, 
 and so in areas somewhat protected from the drag and thinning experienced 
 in the limbs. From these causes the earliest foliation layers may have 
 less distinct differences between them than the strain bands and the rock 
 at their sides. Hence, in a first traverse, one is apt to miss the earliest 
 foliation altogether, and take strain bands as indication of bedding; 
 whereas, in fact, these bands only occur crossing, and contorting or breaking, 
 
 N.W. 
 
 FIG. 15. Half a mile N.N.E. of Glenmassan (163). Folded pebbly greywacke 
 schist. The lines across the bedding show the directions of two sets of strain- 
 slip foliations : the relations of these are not known, the more vertical and 
 weaker set dying away before the other is reached. 
 
 an earlier foliation, and even this earlier foliation need not coincide with 
 bedding. The want of parallelism between the early strain slips and the 
 earlier foliation is often so slight that it may, at first, be taken as merely 
 a sign of slight false-bedding, and it may, too, be less readily noticed 
 owing to the later folds and strain slips which affect them both. We 
 cannot help thinking that many of the supposed instances of false-bedding 
 
 S. E 
 
 C.T.C 
 
 FIG. 16. x \. Headland S. of Fearna Bagh (182). Appearance in a vertical section 
 in thin alternating schists. The crumpled line represents a foliation plane. The 
 lines converging towards right hand of sketch are strain slips and axes of folds : 
 these probably belong to some of the last " anticline" movements. 
 
 in mica schists which have been mentioned by early observers are really 
 due to structures of this kind. 
 
 The later folds and strain slips are not all of one type, nor of one 
 age, but they are only found in strength near " the anticline," and were 
 no doubt produced in connection with it. The axes of one set of these 
 folds, and the direction of the strain slips produced with them, hade north- 
 west, and these are generally the most prominent, even if not the most 
 abundant, through the angles of fold being the most acute, and their 
 strain slips most abundant. But there are also other late folds with axes 
 
26 GEOLOGY OF COWAL. 
 
 hading south-east or vertical. The relation in age of these with the others 
 whose axes hade north-west cannot always be determined, but some- 
 times they are both seen in one section, together with strain lines of 
 " pre-anticline " age. In some cases the late folds with axes hading south- 
 east must be later than those with axes hading north-west, the strain slips 
 belonging to the latter being folded by the former. In others, folds with 
 axes of very varying hades may have been produced together. 
 
 It is possible to get specimens which show four different systems of 
 fold or foliation. In order of age these are : 
 
 1. Folding previous to, or accompanying the development of the first 
 
 foliation. 
 
 2. Folding of the above first foliation, accompanied with early strain 
 
 slip foliation. 
 
 3. Folding and strain slipping of " anticline " age, with axes hading 
 
 north-west. 
 
 4. Folding still later than 3, with axes hading south-east. 
 
 1 and 2 are both of " pre-anticline " age. 4 was probably produced 
 near the close of the ridging up of " the anticline," when the resistance 
 
 N W 
 
 s.f- 
 
 C T.C 
 
 FIG. 17. Diagram Vertical Section to illustrate the form of, and law of thinning of 
 limbs in, the most prominent set of " anticline " folds. The folded lines repre- 
 sent an early foliation merely, not necessarily bedding. Compare fig. 4. 
 
 on its south-east side was becoming equal in strength to the pressure 
 producing the anticline. 
 
 " The anticline " itself, in those areas where folds of type 3 are observed 
 in strength, may be regarded as a very great enlargement of these folds, 
 for its axis too hades north-west, the foliation dip on the north-west 
 side being generally low, perhaps 20 to 30, compared to that on the 
 south-east side.* 
 
 The connection between movements 1 and 2 and the amounts of 
 alteration is the same as that already described in the Ardentinny 
 section. Similarly, movements of types 3 and 4 are connected with a 
 further alteration in the rocks affected by them. Where affected strongly, 
 the average thickness of the earliest foliation lamina? in the quartzose 
 bands is perhaps ^ inch (though in some very much more), which is 
 distinctly less than the average thickness in unaffected rocks. The amount 
 of mica in the former is also greater. This is connected with the fact 
 that when "anticline" foldings are abundant there are but few of the 
 earlier laminae of the rock that can remain unaffected by folding, nearly all 
 having been further stretched and thinned, and, with this thinning, made 
 more micaceous. In this section one sees but few wide centres of folds 
 of comparatively unaltered rocks, like those near Ardentinny, and one 
 
 * West of Loch Riddon there is no marked difference. 
 
SECTION IN KYLES OF BUTE. 27 
 
 reason for this is, that any portions that were so left by the " pre-anticline " 
 movements have been further affected by "the anticline" movements at 
 a later time. Some bands in the limbs of " anticline " folds are hardly 
 half the thickness they are in the centres. 
 
 The strain bands and the centres of folds generally show the rock in 
 its least altered character. If we want to make out what the unaltered 
 rock was like, whether, for instance, it is likely to have been igneous 
 or sedimentary, it is to the examination of these parts that we have 
 to turn. If, in comparing them with the more thinned parts, we find 
 a more sedimentary aspect in the former, more numerous distinct pebbles, 
 etc., we may conclude that the rocks in question represent sediments. 
 This conclusion seems confirmed by the frequent alternation, in some 
 parts of the section, of bands of slightly different character, as regards 
 size and abundance of pebbles, just as we should expect in pebbly sedi- 
 ments. In the headland on the north-west of Fearna Bagh it is surpris- 
 ing to see how many of the felspar pebbles have escaped granulitisation : 
 frequently we can see such pebbles, generally pink in colour, with cleavage 
 planes occupying the whole area of section. Opalescent quartz pebbles 
 are also often seen, and without any evident distortion. The microscopical 
 structure of these rocks is described fully by Mr Teall on p. 296. 
 
 The same parts of the rock that are the least affected by the " pre- 
 anticline" movements have a tendency to continue the least altered 
 through the subsequent movements also, for, being more massive parts, 
 they have not been so readily broken through by subsequent strains, or so 
 much altered in internal character. Still even these parts, the early strain 
 bands, are often distinctly thinned along the limbs of later folds, are 
 broken across by strain slips parallel to the axes of these folds, and may 
 have the minerals in them for a little distance arranged parallel to these 
 strains. The breadth of mica introduced along " the anticline " strain 
 slips has sometimes been observed to exceed J inch. "Eodding" or 
 " stretching " indications may appear on the surfaces of the "anticline" 
 strain slips, as on those of "pre-anticline" age, but we observed no, or 
 only exceedingly few, quartz veins running with them. In this respect 
 there is undoubtedly an important difference between the strain slips of 
 " anticline " and " pre-anticline " age. 
 
 The "anticline" strain bands are not so likely to be mistaken for 
 bedding as the " pre-anticline " bands, for the first foliation lying at an 
 angle to the former is sure, in some part or other, to have been further 
 accentuated by extra drag and thinning, and so forms more fissile 
 conspicuous laminae. 
 
 South-east of Port an Eilein the general dip of the prominent 
 " pre-anticline " foliation is still south-east. Half a mile or so further 
 north we begin to observe this foliation flat in places, when looked 
 cat on a large scale, though it is full of small folds, the axes of which 
 strike north-east and south-west and hade usually north-west. A 
 little further on, the general dip is south-east again ; further still, flat 
 on the large scale ; and so we may proceed with alternations of this kind 
 for some distance. There is no distinct line which we can say is the 
 centre of "the anticline." So, too, on the north-west side of "the 
 anticline " there are alternating areas of north-west dipping and 
 essentially flat foliation. It is not until a mile or more north-west of 
 Port an Eileiu that the general dip of foliation is to the north-west, 
 and, for several miles beyond, exposures are not uncommon in which it is 
 again south-east. This arrangement is seen well in the crags on the hill- 
 side north-east of Upper Stronafian, and between here and Lephinkill. 
 
 In the same locality it is evident that " the anticline " folding of type 
 
28 GEOLOGY OF COWAL. 
 
 3 with axes hading north-west, is more prominently developed than 
 it is south of Port an Eilein. Here the closeness of the new strain 
 bands, and the differences developed on either side of the sharp twists 
 accompanying them, are quite comparable to those of the " pre-anticline " 
 movements, excepting that quartz veins running along the strains are 
 rare, though one or two have been noted. We think, too, that the 
 beds are generally more thinned and altered than they are south of 
 Port an Eilein. One notices less commonly, and less distinctly, than in 
 the last mentioned locality, evidence of those "pre-anticline" strain 
 bands which have existed previously to, and been folded by, the later 
 folds with north-west axes. Why is this ? Can it be that the greater 
 thinning, etc., effected during the later movements, has now almost 
 entirely obscured the earlier structures, or were these latter never so 
 strong in this locality ? We incline to the former supposition. We 
 know that even south of Port an Eilein the early strain bands are often 
 markedly thinned by the folds of later date. On this hillside, "the 
 anticline" movements being stronger, the general thinning and drag 
 
 W 
 
 FIG. 18. Diagram to illustrate the direction of "pre-anticline" folds and strain 
 slips in different parts of the anticline, and their appearance compared with 
 those of "anticline " age. The single dotted line represents roughly, neglecting 
 earlier folds, the position of a " pre-anticline " foliation plane as it is traced 
 across the anticline. The coupled dotted lines represent the strain slips and 
 axes of fold of "anticline" age. The single continuous lines may represent 
 either bedding or foliation planes folded by the prominent type of " pre- 
 anticline " folds. The coupled continuous lines are the strain slips of "pre- 
 anticline " age. 
 
 should be still greater, and the earliest foliation planes, those lying across 
 the early strain bands, might be made to cross these bands at such a 
 small angle that it would with difficulty be perceived. Bands which 
 may represent such extremely pulled out strain bands are not uncommon, 
 They appear in many cases almost like thin quartz veins, but differ from 
 these in not standing out in relief on weathered faces, and in being 
 granulitis.ed, and so not in possession of such even surfaces : there are 
 indications, too, of flakes of mica lying somewhat frequently within them, 
 and of spots of ferriferous carbonate, like those so commonly noticed in 
 the strain bands of other districts. In some parts of the hillside, too, 
 there are early strain bands of " pre-anticline " age, which still remain 
 perfectly clear, themselves sharply folded with axes of fold hading 
 north-west. 
 
 In parts where the main foliation is now dipping north-west, these 
 early strain bands may either incline north-west also, but at a dis- 
 tinctly lower angle than the strain bands connected with the later 
 " anticline " folding, or they may be approximately horizontal, or even 
 incline south-east at a gentle angle. Which of these positions is found 
 depends on the present dip of early foliation ; the angle made by the 
 
SCHISTS S.E. OF THE BULL ROCK GREYWACKE. 29 
 
 early strain bands to the general dip of the early foliation remaining 
 nearly the same. The strain bands are supposed to be parallel to the 
 axes of fold accompanying them, as all those observed in clearer sections 
 are, and therefore they testify to the existence of a set of early folds 
 with axes hading less steeply to the north-west, or, what comes to the 
 same thing, more steeply to the south-east, than the early foliation, 
 which they affect, did. These early folds are in fact of the same 
 type as those near Dunoon and Ardentinny, etc. Their axes on 
 either side of " the anticline " now lie differently with respect to the 
 horizon, because this " anticline " has given to those on one side of it 
 a direction of inclination which they did not originally possess. The 
 same law respecting the amount of thinning in the different limbs is 
 observed in the early folds on either side of "the anticline." At 
 Dunoon it will be remembered it was the upper limbs of anticlines that 
 were the most thinned. Here it is the under limbs, these corresponding 
 with the upper series on the south-east side of " the anticline." 
 
 In " the anticline " folds with axes hading north-west, it is the under 
 limbs of anticlines that have a tendency to be the most thinned, whether 
 we are on the south-east or north-west side of the centre of the anticline. 
 Hence, if we regard the early " pre-anticline " folds as having originally had 
 axes hading north-west, the same law of the greater thinning of under 
 limbs of anticlines prevails in both : and we may conclude that the source 
 of the pressure which produced them both, lay to the north-west of the area 
 being described, and that the pressure was outwards from the Highlands 
 in a south-east direction. The evidence in the north-west of Scotland 
 is now well known to show that there were there, partly at all events in 
 post-Cambrian times, mountain-making forces pressing outwards from 
 the Highlands in a "NV.X.AV. direction. Hence, the central Highlands 
 represent an area from which earth moving forces have pressed outwards, 
 on the one side in a west-north-westerly and on the other side in a south- 
 easterly direction. C.T.C. 
 
 CHAPTER III. 
 
 SCHISTS PROBABLY OF SEDIMENTARY ORIGIX. 
 
 We shall describe the different groups of sedimentary schist as nearly 
 as possible in the order in which they are mentioned on p. 8, at the 
 beginning of chapter II. 
 
 Schists South-East of the Bull Rock Greywacke Schist. 
 
 The most south-easterly zone of schists in Cowal, between the Bull Rock 
 greywacke and the schist boundary fault, consists of a series of phyllites 
 and schistose pebbly grits. The average breadth of outcrop is 1 mile. 
 The pebbles in the grits differ from those in the Bull Rock greywacke in 
 being chiefly of white opaque quartz with comparatively few of felspar. 
 The proportion of phyllite is less than in the Dunoon phyllite series, 
 and there are fewer limestone outcrops. The different bands of grit 
 and phyllite have not been separated out, except for short distances. 
 The best sections are those on the shore at and east of Toward Quay and 
 between Inellan Pier and Glenacre. 
 
 The characters and structures of most of the types of schist are 
 
30 GEOLOGY OF COWAL. 
 
 like those of corresponding types iti the Dunoon series, as seen in the 
 coast section south of the West Bay of Dunoon, described on p. 9. 
 The phyllites make as good slates as those of the Dunoon horizon, or 
 perhaps slightly better. They have been worked on the west side of 
 the Tom, near Inellan : the colour here is black and purple. There are 
 also large old quarries in purple and green phyllite on the east side 
 of the burn to the north of the "a " of "Chapelton " * : a little below the 
 band quarried, comes another in which the colour is purple and black. 
 
 A good example of the massive pebbly schists with pebbles of quartz, 
 prominent both in size and number, occurs on the north side of the Tom 
 and runs from the "a" of " Glenacre" for rather over J mile W.S.W. 
 
 Only three or four limestone outcrops have been seen, and these are 
 thin and of poor quality. Various thin bands and lumps occur in black 
 phyllite on the Clyde shore -J mile south-east of the last " e " of " Glen- 
 acre." Some calcareous bands are seen in a peculiar gritty phyllite on 
 the coast west of Toward Point, and in a black phyllite still further 
 west. Oil the coast close to and 100 yards east of Toward Quay there 
 are thin calcareous stripes in black phyllite. 
 
 In a few places near the south-east margin of the zone there are expos- 
 ures of a peculiar schist which deserves special mention. This schist is 
 characterised by the association of very fine and very coarse sediment. 
 In the Map the exposures have been coloured the same as the schistose 
 grits and greywackes, but this is rather misleading. The most northerly 
 exposure of such beds occurs in a little burn i mile south-west of the 
 top of the Tom : it contains pebble-like lumps of quartzose pebbly schist 
 in a phyllite matrix : the lumps are sometimes 1 inch in length. A little 
 further south-west, south of the word "Free," two other much clearer 
 exposures of peculiar pebbly beds occur. These have at first sight a very 
 ashy aspect. They are of a green or purple tint, effervesce freely in 
 many parts with dilute hydrochloric acid, and show on fresh fracture many 
 small specks of ferriferous carbonate, up to the size of a pea. The cal- 
 careous character causes the pebbly portions to stick out on weathered 
 surfaces, and gives a rough appearance to the rock. There are many small 
 roundish specks of water-clear quartz contained in the rock : also narrow 
 lenticular wedges of black and purple phyllite, which do not always 
 continue as much as 1 inch in the direction of the stretching lines, and 
 small chloritic patches. The phyllite patches are distinctly lustrous, and 
 like the phyllite seen at the sides of the exposures : we suppose them to 
 be " galls," portions derived from essentially cotemporaneous beds. The 
 specks of carbonate often occur at the sides of quartz pebbles, and may 
 have originated in the way described on p. 80. A specimen from one 
 of the outcrops was sliced (slide 4840), and is thus described by Mr Teall : 
 " Dark greenish fine grained schistose grit. Quartz grains, green patches 
 mainly composed of chlorite. Matrix in places opaque in consequence 
 of minute grains or particles of iron ores or carbonaceous material. 
 Schistose chloritic grit." The chloritic patches appear to represent 
 pebbles of some old igneous rock or elongated lenticles which may have 
 been formed by the pulling out of pebbles. The splitting planes of the 
 rock are not chloritic except where these chloritic patches occur. 
 
 On the shore about 1J mile west of Toward Point we get a black 
 phyllite which contains many pebble-like lumps of quartzose pebbly grit, 
 and other lumps, fewer in number, of a calcareous rock or limestone. The 
 exposure is crossed by many north-east crushes, and is probably repeat- 
 edly folded, but it hardly seems that the pebble-like shape of the lumps 
 * In describing localities it has often been found convenient to mention their 
 distances from certain letters or words engraved on the 1-inch Maps. 
 
PUXOON PHYLLITE SERIES. 31 
 
 can have been acquired by crushing and folding only : we see sharply out- 
 lined pieces of grit again and again and can hammer them out, and thus 
 ascertain that they sometimes end sharply in all directions. But there are 
 other pieces which seem more like galls than true pebbles, for they have 
 thin streaks of phyllite penetrating into them for some distance. The 
 phyllite matrix of the rock is as lustrous as that of the Dunoon phyllites. 
 The grit patches contain abundant pebbles of water-clear quartz, which 
 are about the size of small shot: these are not noticeably pulled out 
 and no mica is seen in the matrix of these patches, so that they have a less 
 altered aspect than the associated phyllite. Such massive portions would 
 naturally suffer the least during mechanical movements of the rock. A 
 specimen from this bed was sliced (slide 4841), and is thus described by 
 Mr Teall: "Phyllite and grit (1 interfolded). Irregular grains and 
 patches of quartz in a fine-grained matrix essentially composed of the 
 same substance. The outlines of the original grains are now only pre- 
 served in a few cases. Crushed grit." 
 
 Two exposures of much the same character are seen in the little burn 
 near the " a " and " p " of " Chapelton." In the section on the south side 
 of Toward Quay also, there are beds with an approximation to the same 
 appearance, massive pebbly schists being irregularly mixed with bands 
 and irregular pieces of green-grey phyllite : some of the pieces are nearly 
 as broad as long. 
 
 The Bull Eock Greywacke Schist. 
 
 The character of the Bull Rock greywacke schist is described on p. 15. 
 Besides the coast section there described, there are other goad exposures 
 of the bed on the Gantcocks, in the burn going through the " r " of " Tor 
 Aluinn," in the wood f mile "W.S.W. of Inellan Hill, and in various 
 places isolated within the raised beach deposits north-east of Ardyne Point. 
 The bed is largely quarried for building stone near the coast a little north 
 of the Bull Rock. The outcrop varies in breadth from a little over J 
 to a little under J mile. Hillside exposures generally give one the 
 impression that the band is nearly free from phyllite. In the section 
 south of Dunoon there are no bands of phyllite within it which exceed 
 4 to 5 feet in breadth. There are no clear sections of the margins except 
 one, of the south-east margin, 200 yards south-east of the Bull Rock : here 
 there is a fairly sharp line between the greywacke and the purple and 
 green phyllite on the south-east side. 
 
 The Dunoon Phyllite Series. 
 
 The section of the Dunoon phyllites on the coast south of Dunoon is 
 already described, p. 9, together with their minute structures. This 
 may be taken as representative of the series generally. Fortunately we 
 have on either side of it, through most of the area, well characterised 
 bands of schist, a green bed on the north-west, and the Bull Rock grey- 
 wacke on the south-east. Were it not for these bands it would not be so 
 easy to separate the series from the adjacent rocks, for on either side of 
 it, beyond the green bed and the greywacke respectively, phyllites of 
 the same character are found, excepting that the purple tint very rarely 
 appears on the north-west side; and there are pebbly grits in fair 
 abundance within it. Still the horizon between the green bed and the 
 greywacke contains a distinctly larger proportion of phyllite and a 
 greater number of limestone outcrops than we find on the other sides 
 of them. The pebbles in the schistose grits within the phyllite zone 
 
32 GEOLOGY OF COWAL. 
 
 are also more frequently of quartz than is the case in the schists on the 
 north-west of it ; but this character is common also in the schists south- 
 east of the Bull Kock greyvvacke. 
 
 Examples of black phyllites, indistinguishable from some of those 
 within the phyllite series, occur just above the top of the most north- 
 westerly "green bed" in the burn J mile N.N.E. of the "o" of "Bishop's 
 Seat," on the east side of the west of the two faults that run north 
 to south by the "K" of "Giant's Knowe," in outcrops between the 
 top of the north-west green bed and the south-east band of hornblende 
 schist. A little on the north-west side of the above green bed black 
 phyllite also commonly occurs, e.g., in the burn J- mile south- 
 west of the " G " of " Giant's Knowe," f mile E.S.E. of the last " n " of 
 " Inverchaolain Glen," and in the burn that enters this glen by the 
 second " n " of " Inverchaolain." Other good exposures are seen in the 
 bum 200 yards south of the " 1 " of " Tighnuiit," J mile south of the " h " 
 of the same word, on the shore of Loch Striven 1 mile and J mile north of 
 Strone Point (194), and on the west side of the fault f mile north of the 
 "8" of "Strone Point "(194). 
 
 The green-grey phyllites are still more abundant outside the Dunoon 
 phyllite series, and it is unnecessary to mention particular exposures. 
 
 Besides the section south of Dunoon, there are other good sections of 
 the phyllite series on the south side of the East Bay of Dunoon, from 
 | mile south-west of Kirn pier to J mile south of Hunter's Quay, and 
 for some distance on either side of Creag na Cailliche (194). There are 
 also good sections in the different burns that run into the West Bay 
 of Dunoon, in Glen Fyne burn (194) between Knockdow and the "F" 
 of "Fyne," and many other places. Many outcrops of limestone are 
 seen in all the coast sections mentioned. There is an unusually broad 
 exposure of limestone J mile south of the "C" of "Corlarach Hill" 
 (183). In only one locality does limestone appear to have been quarried, 
 and this is on a small scale, by the junction of the little burns J mile 
 W.N.W. of the "D " of "Dunoon " (town). Most of the bands have a 
 dark grey fracture, but some are buff or creamy. Examples of the last 
 occur immediately north of Dunoon Pier, J mile N.N.E. of this pier, 
 and J mile north of Kirn Pier. 
 
 Near both margins of the zone the purple phyllites are conspicuous, but 
 especially so near the south-east margin. In some places, near thin 
 crushes, and where there are indications of faulting, the purple tint 
 changes along the strike into buff or yellow with streaks of red. This is 
 seen on the shore 100 yards S.S.E., and not quite J mile south, of 
 Ardfillayne. 
 
 The phyllites are not now quarried for slates, but some bands were 
 worked in former times : e.g., at the edge of the 100 foot beach by 
 the first " o " of " Dunoon " (town), in the deep ravine of the burn J 
 mile W.S.W. of this letter, at the burn side a little over ^ mile E.S.E. 
 of Corlarach, and on the hillside J mile north-east of Corlarach. 
 None of these workings are on a large scale, perhaps not even so large 
 as the old quarries in the phyllite on the south-east side of the Bull Rock 
 greywacke. The colours of the phyllites so used are dark grey, black, 
 and purple. There are many other quarries withiu the phyllite series, 
 particularly in the close neighbourhood of Dunoon, but the rock quarried 
 is pebbly schist in most cases, and is used for building stone. 
 
 Schistose grits included within the phyllite zone occur, among other 
 places, at Creag na Cailliche (194), f mile north of Creag na Cailliche, J 
 mile north of Kirn Pier, at the foot of the burn that runs into the East Bay 
 of Dunoon, various places between Ardfillayne and the second " 1 " of 
 
THE GREEN BEDS. 33 
 
 " Bull Wood," on the south side of the Dunoon reservoir, and on the hill- 
 side J mile south-west of Ardtillayne. 
 
 On the shore a little north of Ardfillayne there are a few lenticular 
 bands, only an inch or so thick, of a heavy dark grey hard rock which 
 is only slightly schistose. Dilute hydrochloric acid does not cause effer- 
 vescence, but after digesiing with this acid and then adding ammonia 
 to the liquid, a considerable quantity of ferrous oxide is precipitated. 
 
 The "Green Beds." 
 
 The " green beds " are, as implied by the name, a set of more or less 
 green coloured schists. They are often intersected, too, by thin quartzose 
 veins coloured green by epidote. Some of them are of such fine grain 
 that, microscopically, very little could be learnt of their true character, 
 but these are always mixed with others in which conspicuous grains 
 of quartz and felspar occur, often in bands running parallel to one 
 another and to the pebbly bauds in the adjoining greywackes, so that the 
 iirst presumption is that the green beds, like the greywackes, are also 
 -sediments, but of an especial kind. This presumption seems confirmed 
 by the quite insensible gradations by which we may pass from a green 
 bed into a greywacke. A typical green bed, whether pebbly or uot, can 
 be id en titied at once, but there is no sharp line between such a green bed 
 and one of the schistose grits or greywackes with a grey matrix, the green 
 tint passing into grey quite insensibly. Also, green beds with a. green 
 matrix may alternate so repeatedly with other beds with a grey matrix that 
 it has nut been practicable to map them all out separately. Instead of this 
 the green beds have been mapped as groups, each group representing 
 typical green beds mixed with a certain proportion of others. On the 
 north-west side of " the anticline " it is estimated that about half of the 
 green bed group consists of other schists : on the south-east side the different 
 outcrops mapped are comparatively unmixed. 
 
 The green beds are usually tough to the hammer, and give rise to a 
 number of scars which weather into blocks that are often rather rounded 
 at the edges. Smooth hill slopes, when free of drift, have a slightly 
 greener and drier appearance than slopes composed of the quartzose 
 schists and phyllite. This colour is noticeable on the hill south-east of 
 Ardkiuglas woods, and near Cairndow and Upper Clasheoiu (126). 
 
 During the processes of folding to which the district has been subjected 
 the green beds seem to have behaved in a similar way to the other 
 massive beds, the schistose greywackes, etc., for they have evidently not 
 been crumpled so much as the phyllitic mica schists. 
 
 The green beds on the south-east side of " the anticline " are not exposed 
 in any satisfactory coast section, but burn and hill-side sections are 
 numerous. Among the best are those in the burns south of the Badd 
 (184), and in the burns 1 mile north of the Badd (184), and on the 
 raised beach margin a little, north of Strone Point (194). The green beds 
 on the north-west side of " the anticline " are exposed in Kiuglas Water, 
 from a point J mile E.N.E. of Ardkinglas House for a little over J 
 mile up the burn, the burns that run north-east from Stob an Eas, the 
 river Cur above its junction with the Cab, and Strath nan Lub below 
 ths " S." In all these sections from the north-west side of " the anti- 
 cline," bauds of grey pebbly schist and phyllitic schist alternate with the 
 green beds proper, as already mentioned. 
 
 In some of the coarser pebbly green beds, e.<y., in those in the wood 200 
 yards south-east of Ardnadam Farm (174 south-west), it can be seen that 
 many of the pebble-like pieces, in fact nearly all of them which do not con- 
 
 C 
 
34 GEOLOGY OF COWAL. 
 
 sist of quartz (which here is usually opalescent), have a pale yellowish- 
 green tint, and that the abundance of these pieces gives the rock its 
 colour. These green pieces are seen on microscopical examination (slide 
 3793) to be very rich in grains of epidote, and it is these grains that give 
 the colour. In all probability these pieces represent altered felspar, for 
 in a slide of somewhat similar rock (slide 3791) from 150 yards west 
 of Conchra (162 south-east), there are signs of the development of epidote 
 in the felspar fragments. The evidence to be obtained in this area does 
 not enable one to decide whether the epidote of the fragments was 
 formed before or after their inclusion in the bed as pebbles. 
 
 The green tint of this Ardnadam rock is clearly due to these epidotised 
 fragments, but in others of the green beds, perhaps we should say most 
 of them, the shade of green is much darker, and is chiefly due to chlorite. 
 Two of these on the south-east side of "the anticline" have been 
 examined by Mr Teall, and their microscopical appearance is described 
 belo\v. Slide 3793, from -J mile south of Ardnadam Farm (174 south- 
 west) : " Dark green, fine-grained slightly schistose rock. Composed of 
 chlorite, felspar, quartz, white mica, iron-ores. Chlorite-mica schist." 
 Slide 3795, from Tighnuilt, Inverchaolain (183): "A green schistose 
 chloritic grit. Contains large fragments of quartz and felspar more or less 
 granulitised, embedded in a schistose matrix composed of epidote, chlorite, 
 white mica, sphene, quartz, and felspar." Dr Hatch has also described 
 two from the same area. His notes run as follows : Slide 2830, from 
 1 mile south-west of Ardnadam Farm : " Epidote-chlorite schist. 
 Marked parallel structure produced by the mechanical extension of 
 the constituents. Chlorite in rudely parallel lamellar bands, between 
 which are lenticular grains (eyes) of quartz and felspar, the latter 
 slightly turbid in the central portions of the crystal, always clear at the 
 periphery, with here and there included spicules and arrow-headed twins 
 of rutile. Scattered abundantly through the section are grains of 
 epidote some of considerable size showing the characteristic high 
 double refraction and pleochroism (in yellow tints). Here and there 
 lie isolated plates of a green strongly absorptive mica. Iron ore 
 (magnetite or ilmenite) in isolated grains." Slide 2831, from the burn 
 J- mile north of Bishop's Seat (183 north-east) : " Chlorite-mica schist. 
 Marked eye-structure, the lenticles consisting mostly of quartz, some- 
 times a mosaic of differently orientated granules, sometimes one crystalline 
 individual. A few of the smaller eyes are turbid felspar. Chlorite in 
 scales and lamellae. Mica in strongly absorptive plates. Epidote in 
 small granules nut so abundant as in 2831." 
 
 In the green beds on the north- west side of " the anticline," chlorite 
 and black mica associated, with it are, however, much more abundant, 
 and in larger flakes. There is, too, a great prominence of albite, both 
 as isolated individuals throughout the mass of a bed, and collected into 
 pegmatite veins like those of the albite schist. For the description of 
 the albites refer to p. 39. In the green beds on the south-east side of 
 "the anticline," such albite is hardly ever observed. In slide 3794, 
 from a green bed near the top of Blar Buidhe (183), a mineral referred 
 doubtfully to albite occurs, and we have also seen a few thin pegmatites, 
 about 250 yards south-west of Kilmariiock Hill (194 north), which 
 .seemed like those of the albite schist. These occurrences, though so rare, 
 are perhaps an indication that on this horizon albite of this kind is more 
 common than in the other schists. The felspar in the pegmatites of the 
 Dunoon shore section (p. 18) is also albite, but these pegmatites usually 
 show distinct rodding, and we are not inclined to connect them in age 
 with the albites of the albite schist. 
 
THE GREEN BEDS. 35 
 
 Small magnetite grains and crystals, up to a small pea in size, are very 
 abundant in some of the green beds on both sides of "the anticline," 
 though the beds associated with the green beds on the south-east side 
 do not usually show them in any prominence. These magnetites are 
 referred to again, p. 80. Spots, up to J inch in length, of ferriferous 
 carbonate giving rise to rusty-coated hollows, are also common on both 
 sides of "the anticline." Not uncommonly it may be seen, e.g., on the 
 east side of Glendaruel near Lephinkill (172 west), that the spots have 
 their greater lengths orientated in one direction that of the stretching 
 common in the neighbourhood. In slide 4726, from J mile north-west of 
 Mullach Clioire a' Chuir (142), the spots of carbonate contain inclusions 
 which show that the rock was a foliated rock before the time of their 
 development : in spite of this, they are developed with their greatest 
 lengths in one direction. Veins which consist largely of ferriferous 
 carbonate are also unusually abundant in the green beds, particularly, we 
 think, on the north-west side of "the anticline." 
 
 In the north-west bank of Strath nan Lub (163), mile south-west of 
 the letter " S," there is a band, 1 to 6 inches thick, of white coarsely 
 crystalline limestone, in which the calcite crystals reach -^ inch in 
 diameter. This is in tough pebbly green beds. Just at the side of the 
 band the rock is rather calcareous. The band is repeatedly folded with 
 both limbs hading north-west. We know of no other such band in the 
 green beds, and it is perhaps possible that the one described may represent 
 an early segregation vein. 
 
 As stated elsewhere, p. 149, the green beds have a habit of chang- 
 ing colour to dark grey or black near basalt dykes. Instances and 
 particulars of the change are given in the reference. 
 
 Many microscopic sections of the beds on the north-west side of "the 
 anticline" have been examined. Slide 3831, from about f mile slightly 
 north of east of Lephinkill (172), is thus described by Mr Teall : "Dark 
 green schist, with brilliant lustre on the cleavage surfaces. Albite, 
 chlorite, white mica, rutile, and dark narrow lath-shaped sections, probably 
 pseudomorphs after some other mineral, also tourmaline. The albite 
 occurs in idiomorphic crystals and crystalline groups. It contains single 
 prisms and knee-formed twins of rutile as inclusions. Sometimes a 
 distinct fluxional arrangement of inclusions may be seen in the albite. 
 The matrix of the rock in which the albite crystals occur as porphyritic 
 constituents is essentially composed of chlorite and white mica, probably 
 paragonite. The tourmaline is present as beautifully formed prismatic 
 crystals, often showing perfect rhombohedral terminations : E pale brown, 
 opaque. In addition to the constituents above mentioned, a yellow 
 mineral occurring in flat square tables, and giving a negative uniaxial 
 figure, may be observed in the tailings formed by vanning the powder of 
 the rock. The double refraction of this mineral appears too low for 
 anatase, and there are no indications of the pyramidal faces which bound 
 the square tables of that mineral." 
 
 In some quartz veins in the green beds not quite J mile W.S.W. of 
 An Socach (162 south-east) there are needles of black "tourmaline attain- 
 ing a length of over 1 inch ; they form sheath-like aggregates, sometimes 
 with a breadth of J inch. 
 
 We suppose that the green beds on both sides of " the anticline " were 
 essentially of the same original character : and that the differences now 
 seen in them result from the greater metamorphisin experienced by 
 those on the north-west. These differences are only of the same kind as those 
 exhibited by the other groups of rocks in the respective areas. It does 
 not, of course, follow from this that the green beds on either side of " the 
 anticline " are stratigraphically equivalent. This is a question which we 
 
36 GEOLOGY OF COWAL. 
 
 discuss elsewhere, p. 86. What is their original character likely to 
 have been 1 During our early examination of the district we supposed 
 them to have been formed by an admixture of volcanic and normal sedi- 
 ments to be beds in the formation of which submarine volcanoes had prob- 
 ably a share. The abundant chlorite might be supposed to be an alteration 
 product, derived from original hornbleudic rocks, and the magnetite 
 indicated that these rocks were of basic character. But we have never 
 found, in any green bed, pebbles which could be referred to a cotempor- 
 aneous igneous rock, either ashy or vesicular, nor are there any bands 
 which could with probability be attributed to interbedrled lava flows. 
 Where schistose igneous rocks are associated with them these are always 
 of the same class as those found in the schist areas adjoining epidiorites, 
 hornblende or chlorite schists bands which, indeed, have a habit of 
 running as sills with the bedding, but most probably represent old 
 intrusions, not cotemporaneous rocks. 
 
 It has been known for some years that the old surfaces of the Lewisian 
 Gneiss in the north-west of Scotland, where they underlie the Torridon 
 rocks, are often largely epidotised, and quite lately thick beds of green grit 
 of Lower Torridon age have been found, which have clearly been formed 
 by the detritus from such gneiss surfaces. Grits of this kind are well 
 shown, among other places, on the west side of the Sound of Skye, 
 between Isle Ornsay and Kylerhea. These grits have a striking resem- 
 blance to the green beds now being described, though they are not so 
 highly altered. The resemblance extends to the microscopic appearances. 
 Epidote grains occur abundantly, mixed with others of quartz and felspar, 
 and pebbles occur which seem to have had their epidotic character 
 before inclusion in the rock. Small flakes of secondary sericitic mica 
 and chlorite also occur, and small grains of iron ore. It is curious, too, 
 that these green rocks of Skye often change their tint to dark grey or 
 black near basalt dykes, just as these Argyllshire green beds do. We 
 cannot say that the two groups of rock are to be correlated in time, but 
 their resemblance is certainly to be insisted on. 
 
 In no part of Cowal have hornblende needles, either macroscopically or 
 under the microscope, been noticed in the green beds. In this respect 
 they are noticeably different from the green beds which occur further north- 
 east. In the glens of Forfarshire examined by Mr Barrow, the occur- 
 rence of hornblende within the green beds is usual, and there are rocks in 
 which parallel black hornblende needles occur in abundance, together 
 with pebble-like specks of quartz and felspar, as large as a pea : Mr 
 Barrow considers these needles to have been formed by thermal meta- 
 morphism in beds which were previously chloritic. Mr Hill finds that 
 hornblende begins to appear in some of the green beds near the north-east 
 corner of 1-inch Map 37, and that it rapidly increases in prominence to 
 the north-east. In the exposures south of Achadunan we looked for signs 
 of hornblende, but saw none. 
 
 In a little scar J mile south-east of Cruach narn Mult (134) a pebbly band 
 of the green beds contains a number of small oval or round shapes from the 
 size of a marble up to that of a duck's egg. They are slightly harder than 
 the rock in which they occur, and separate from it more or less readily 
 on hammering. They seem also more epidotic than the inclosing rock, 
 and contain larger and less thinned pebbles, which consist in part of 
 opalescent quartz. The shearing or foliation goes through the shapes to. 
 >ome extent, but they also act as " eyes," the tine foliation of the matrix 
 curving round them : at the sides they merge, in some places, insensibly 
 into the surrounding more foliated rock. Both the shapes and the rest 
 of the rock contain abundance of black mica. Some of the shapes show 
 
THE GREEN BEDS. 37 
 
 indications of concentric structure : on the weathered face we may see an 
 outer shell projecting, then a zone which weathers in depression, then an 
 inner projecting shell, arid lastly a hollow central core. 
 
 It is probable that these shapes were in existence before the foliation 
 of the rock was produced, and that the less sheared character of the 
 pebbles in them is clue to the protection afforded by the hardness of the 
 shapes. Some of the shapes are distinctly longer in the direction of the 
 foliation than across it, so it is clear they have not wholly escaped the 
 shearing action. Slides 4728 and 47*29 are cut from these shapes. Mr 
 Teall describes the microscopic aspect of the former as follows : " Clear 
 patches of quartz, either formed of simple individuals or of granular 
 aggregates. These may represent original clastic grains. The green 
 matrix is an aggregate of epidote, calcite, and quartz. The epidote occurs 
 in small granules closely crowded together : the calcite, which is often 
 closely associated with the epidote, extinguishes uniformly over large 
 areas. A few scattered grains of iron-ore, partially changed to leucoxene, 
 are scattered through the slide." 
 
 The south-east margin of the green beds on the north-west side of 
 " the anticline " is not a well-delined line. For a little space below the 
 line taken for the base of the main zone there are in many places thin 
 bauds of the same character. These are mentioned in the detailed 
 account of each area. Such bands may possibly be due to infolds of the 
 higher lying bed, but this has not been made out with certainty in any 
 case. In the north part of Cowal we have taken the north-west margin of 
 the zone some distance below the Loch Tay limestone. Between it and 
 the limestone comes usually a considerable thickness of massive quartzose 
 schist. But green beds do not stop at this line. In several places, e.g. t 
 1 mile S.S.W. of "h " of " Creag Dhubh," and J mile north-east of the 
 same letter, a thin band rests directly on the main outcrop of limestone, 
 and there are two other bands which have often been mapped in the space 
 between this limestone and the graphitic schists. As the limestone does 
 not make a double outcrop in this area it is not possible to regard the 
 green beds north-west of the limestone as repetitions by folding of the 
 green beds on the south-east. The bands in question occur within a 
 broad zone of garnetiferous mica schist, and garnets may occur in the 
 green bands also within this zone, e.g., on the shore J mile south of " R " 
 of " Rudha Bathaich Bhain" (133). Still further north-west, on the shore 
 of Loch Fine on either side of Mid Letter, green beds occur again. This 
 is within the Ardrishaig phyllite series. 
 
 In a few places there has been noticed within the green beds a 
 structure not easy of explanation. We do not think the structure is 
 confined to these beds ; in fact, neither of the beds in which the best 
 examples occur is a typical green bed, though both are within the green 
 beds zone. The impression received on first seeing the structure is, that 
 we are dealing with a case in which the foliation is folded, while the 
 bedding keeps straight. It is seen best of all in a greenish albite-bearing 
 bed in the north bank of Garvie burn (162) J mile south of "S" of 
 " Strondavain." The section is not easily accessible, and cannot be 
 examined properly without wading. There is a distinct alternation of 
 more or less pebbly beds dipping W.N.W. at 43', and there are 
 thin quartz veins running parallel to them : albites are common in 
 some of the bands. Crossing the bedding are more or less intermittent 
 lines which are specially rich in biotite, and appear darker than the 
 rest of the rock. These run parallel to one another : they are in some 
 places straight, in others they have the appearance of sharp folds with the 
 axes parallel to the bedding. When these dark lines are examined more 
 
38 
 
 GEOLOGY OF COWAL. 
 
 FIG. 19. x tV. North bank of Gar vie 
 burn. Section in alternating pebbly 
 green beds and more micaceous schists. 
 The direction of shading shows the 
 
 carefully they are seen to be made up of flakes of biotite, the flat sides 
 of which lie across the general direction of their lines of occurrence, 
 but parallel to the bedding. Also in the greener rock at the sides of 
 the dark lines, the greenish flakes are lying approximately parallel to the 
 bedding. The dark lines are not accompanied with any throw. They 
 are most conspicuous in the soft more micaceous schists, and are not 
 noticed in some of the pebbly bands at all. Where a pebbly band 
 comes against one that is more micaceous, the dark lines come up at 
 
 a more or less marked angle to the 
 junction of the bands, and then 
 suddenly stop. Indications of 
 some structure running in the same 
 directions as the dark lines are also 
 sometimes seen in the quartz veins. 
 On the bedding planes of the more 
 micaceous bands it is often seen 
 that the surface is slightly waved, 
 and that the lines of black mica 
 have the individual flakes lying at 
 a slightly different angle to the 
 flakes of mica or chlorite in the 
 adjoining area. Of the bedding 
 there is no doubt. The parallelism 
 of the mica flakes to the bedding 
 is doubtless an instance of the 
 
 X lit! UirUU U1U11 Ul SHclUlII" SliUWS tllC 11 i t j_1 1 V A. ' 
 
 direction of foliation and the lie of the parallelism of the early foliation 
 mica flakes. Where the shading is dark and the bedding. The dark lines 
 the mica is chiefly black. o f biotite may perhaps be con- 
 
 sidered to accompany small strains 
 
 of later date (perhaps of the same age as the later anticline movements 
 described on p. 26), along which strains the pale micas, etc., have been 
 altered to biotite. But what about the folding of these lines ? Has 
 there been a later movement along the bedding and foliation planes, 
 which has had the effect of contorting them ? 
 
 Schists between the South-East group of " Green Beds " and 
 the Albite Schists, etc. 
 
 The schists that come north-west of the green beds on the south-east side 
 of " the anticline " are well represented in the Loch Striven coast section 
 between the Couston high terrace and a point J mile north of the second 
 " o " of " Strone Point " (194), on the east side of this loch between Finnart 
 Point and Inverchaolain, and on the south-west side of the Holy Loch 
 near Hunter's Quay. The proportion of quartzose schists in these 
 sections is considerable, and massive pebbly bands are not uncommon. 
 Good examples of these last are seen 100 yards S.S.E. and 170 yards 
 N.N.W. of Hunter's Quay. 
 
 The general colour of the phyllites is green-grey, but black bands are 
 also common, particularly near the base of the green beds zone. For 
 the localities of some of the exposures, refer to p. 32. 
 
 Thin ochreous-weathering calcareous bands and lenticles are common. 
 These are like those described, p. 18, in the section on the west side of 
 Loch Long from l mile north of Gairletter Point to about J mile south of 
 Ardentinny. The thickness very rarely exceeds an inch or two. Good 
 examples occur on the coast | mile N.N.E. of Inverchaolain Church, 
 and in Inverchaolain burn mile north of the " n " of " Glen." 
 
ALBITE SCHISTS. &9 
 
 South-east of the horizon of the Loch Long section just alluded to, we 
 have noticed no black or brown mica, no albites excepting the few in- 
 stances in the green beds mentioned on p. 34, and those in the rodded 
 pegmatites (p. 18), nor any tourmaline. It is not likely, however (see 
 p. 35), that the absence of these minerals implies any original difference 
 between these beds and the others a little nearer the anticline. We take 
 it rather to indicate that the metamorphism was less intense. 
 
 The Albite Schists and other Schists that occur with these 
 near " the Anticline." 
 
 The albite schists of the Kyles of Bute, and " the anticline area," etc., 
 appear to play the same role in the section as the phyllites, and other 
 schists which are mainly made up of mica and chlorite, in the districts 
 lying further to the south-east of "the anticline." But whether they were 
 originally of quite the same character as these is not clear. If they were, 
 it must be admitted that a considerable chemical change, and a large 
 impregnation with soda, have subsequently taken place in them, arid they 
 might be quoted as additional evidence of the greater metamorphism of 
 the areas in which they occur. Two chemical analyses have been made 
 by Mr Teall to illustrate this point : one (I.) of green phyllite from 100 
 yards north of Blairaiore pier, which we think may be taken as representa- 
 tive of the phyllites generally : and another (II.) of albite schist from the 
 head of Stuck burn (152 south-east). The following are the analyses : 
 
 i. ii. 
 
 Silica, .... 43-3 634 
 
 Titanic acid, . . . . 1-2 trace 
 
 Alumina, .... 26'2 18'1 
 
 Ferric oxide, . . . . 13 -6 67 
 
 Lime, . . . . 0'5 0'9 
 
 Magnesia, . . . 3*8 1-9 
 
 Potash, .... 4-6 3-2 
 
 Soda, .... 1-8 3-2 
 
 Loss on ignition, . . .4*5 2*8 
 
 99-5 100-2 
 
 Mr Teall adds : " If the whole of the soua in n. were used to form albite 
 it would make 28 per cent. ; that is, 28 per cent, of the rock would be 
 formed of this mineral." It is curious that the potash and soda taken 
 together form the same percentage in both rocks. 
 
 The albite spots are almost confined to the more micaceous or chloritic 
 beds : it is doubtful whether they occur at all in the quartzose pebbly beds. 
 Even in the former rocks they are of very variable occurrence : in some 
 parts of a band they hardly appear, while in others they may form the 
 chief constituent. They seem generally of fairly equal dimensions in all 
 directions, rarely exceeding ^ inch in length, and occasionally they show 
 an approach to idiomorphic outlines. The usual colour is pale brown : 
 this colour is probably due to the inclusions, which we know from micro- 
 scopical examination are so common in them. In rock exposures they 
 generally project somewhat from the micaceous matrix. 
 
 They never show any appearance of stretching or clear deformation, 
 and are. thus easily distinguished microscopically from original pebbles. 
 From this fact it might be inferred that they are of later age than th< 
 mass of the movements which affect the rocks in which they occur, 
 
40 GEOLOGY OF COWAL. 
 
 There is abundant further evidence to the same effect. In field sections 
 we notice that they have a habit of occurring in greatest abundance 
 in the more micaceous layers which have been developed in strain 
 slips : they may occur in these layers even when the rock traversed by 
 them is a quartzose grit, and shows no albites. Many of the strain slips 
 along which the albites occur cau be made out to be of " anticline " age, 
 of types both 3 and 4 (see p. 26), by the fact that they affect the 
 abundant early quartz veins of a section, and the earlier strain bands of 
 " pre-anticline " age. It is therefore clear that they have been developed, 
 either simultaneously with or subsequently to " the anticline " movements. 
 They occur, too, in the micaceous layers along the " pre-anticline" strain*, 
 and, as these earlier strains are more abundant than the later, the albites 
 are more often seen in them. 
 
 The microscope affords still more conclusive evidence of the movements 
 being earlier in age than the albites, the puckered foliation planes of the 
 rock being traceable through the albites by the help of frequent inclusions 
 of magnetite, quartz, and some nearly colourless prismatic microlites.* 
 Inclusions of white mica never occur. On the other hand, the magnetite 
 specks may form a larger proportion of the albite space than they do of 
 the schist outside it. Mr Teal! has made a detailed microscopical exam- 
 ination of a specimen of the albite schist on the hillside \ mile E.N.K. 
 of Ard a' Chapuill (182 north-east), and his full description is given in 
 Appendix. Mr Teall has also taken photographs from this slide and from 
 slides of albite schiste of two other localities, viz., slide 4733 from Beinn 
 Tbarsuhm (142), and slide 5215 from near the head of Stuck Barn (152). 
 Reproductions of these photographs are given in Plates VI. and VII., at 
 the end of the volume. 
 
 In these schists it is usual to find veins or pegmatites which consist of 
 albite, or albite and chlorite, mixed with quartz. Occasionally such veins 
 traverse the grits associated with these schists, but this is not very 
 common. In the veins albite crystals occasionally attain a large size, 
 cleavage faces sometimes exceeding J inch in breadth. One-sixth of a 
 mile N.N.E. of G'raigendaive, head of Loch Striven, the veins reach a 
 breadth of several feet, and are traceable several yard*, but more usually 
 a breadth of several inches is tbe most that is seen. On the hillside east 
 of Upper Stronafian (182 north-east) there are albite pegmatites, as much 
 as 2 feet broad and several yards long, which contain black tourmaline 
 needles 1 inch in length. Smaller tourmalines are common in the matrix 
 of the albite schists generally. Good examples of them occur in the /.. 
 by the road side \ mile north-east of Ard a' Chapuill, and on A' Chrnach 
 (182 north-east). These tourmalines are referred to again, p. 
 Tourmaline prisms are included within albite in slide 5215, from near the 
 nead of Stock burn (152), and so must be of earlier date than the al 
 The albite pegmatites of the albite schists never show rodding or zW. 
 ing at their sides, and thus differ markedly from those with pink or opaque 
 white albite, which are common in some of the schists, e.y., in tr 
 already described at Dunoon, 
 
 The alhite schists have not been mapped hi any part of 1-meh M 
 and their character as albite schists escaped observation for some time after 
 the commencement of the surrey. As a result, however, of various sub- 
 
 * It seems to follow from this that these included minerals are of earlier forma- 
 tion than the albites. Tbe albite sehitts of the Hoosae and Greyloek Moantatn*, 
 described by Messrs Wolff and Bale ("On the Geology of tbe Green Mountain*," 
 ToL xmi. of the MoMgrapk* <tf ike U.S. Geological Survey), seem in many ways 
 comparable to those of Cowal, but the albite. ate eonsidmd by these oteerrers to 
 nave "evidently crystallised contemporaneoosly with the other mineral* in tbe 
 rock." See p. 297 for farther reference to these and other albite sebist*. 
 
ALETTE SCHIBTB. 
 
 41 
 
 iT:fcy r:'VV r t'itt L. :* I not 
 
 of a line drawn between Ardentinuy and 
 Only two or thuec Qearrexice*- bare been noticed soutb-ea#t 
 and all tbee vere in ^ green beds." On the nortb-irest of ibis 
 are a/bundant, up to nearly as far as tbe Glendaruel or Loeb Tar 
 and : certain liandfc on tbe nortb-wet side of tide HID^- 
 
 . HM ^nKtiCemH D ica - -; DQH^ - : , - M gbtly jw rti 
 fid Lettea HI) milt QOrtb-east, ai . -"",- - w oi - bl 
 
 tonei cd a bite -::> oa : iciiri i 
 rery abundant, bare been traced. Hiey 
 quartzow pebblj Bchiiite. anc Beem, L> >.: 
 same part in tbe section as tbe pbyllite^ 
 
 Near "tbe anticline " centre at Ladt- 
 , . . ._, . B ., te, . v,- D :. 
 
 f a be* tibey *re rare, and may escape olfBerration : in otbers caJy a little 
 may lie Tesy abundant. Tbk i not surprising wbeu one 
 
 t . j'. 
 
 'Adding and early foliation, and 
 MHMHflvi jiflK > W strain in tbe 
 
 iciasit MB tzbe west side of Leeb 
 
 --ii 1 mile to tbe 
 
 ev Mack, Most of tbe bill- 
 
 a Bhniel 
 OK Our in 
 *iri*,ttnd, 
 OK UM^j ilhito H^ : bg H Ml 
 
 ;V"- ..,;,.; . ..,.;: ./ ; : 
 . ..- 
 
42 
 
 GEOLOGY OF COWAL. 
 
 we have suddenly come across them in abundance in another exposure 
 of the same band at no great distance. Probably more prolonged search 
 would show albites in all the more micaceous schists from " the anticline " 
 centre up to the base of the green beds on the north-west side. 
 
 In the albite schist 1 mile west of Drimsyniebeg (142) the little ridges 
 caused by the puckering of the early foliation planes by " the anticline " 
 movements are very conspicuous, arid, crossing these ridges almost at right 
 angles, are obscure indications of rodding or stretching. Crossing both 
 the puckering and the stretching at a marked angle are short discontinuous 
 vein-like outcrops of schist in which albites are very abundant, while 
 the rock at the sides of these outcrops is almost free from albites. 
 Sections nearly at right angles to the foliation planes show the lines rich 
 in albite crossing a succession of foliation planes : the planes may be quite 
 even, and yet the lines of albite may show an appearance as of sharp con- 
 tortion. Sometimes the axes of the apparent contortions show no clear 
 relation to the direction of the foliation, but in other cases they are 
 approximately parallel to it. In the last cases it might at first sight be 
 supposed that the lines of albites had been folded, but this idea is 
 negatived by the occasional presence of other albite lines which cross 
 the foliation without any twisting. 
 
 FIG. 21. x 3. One mile W. of Drimsyniebeg, Lochgoilhead. Section of albite 
 schist at right angles to foliation. Shading shows the direction of foliation. 
 The black lines are lines of special occurrence of albite. 
 
 There are good hillside sections of albite schist on the west side of 
 the glen between Lochgoilhead and Drimsyniebeg. This is at a lower 
 level than the Cruach a' Bhuic band, but we cannot be certain that it is 
 not the same band repeated by folds with approximately horizontal axes. 
 The best burn sections are in Allt Glinne Mhoir, above the word " Mhoir," 
 and in Kinglas Water from 200 yards west to f mile west of Butterbridge. 
 Perhaps both these sections are in the same band as the one between 
 Lochgoilhead and Drimsyniebeg. The section in Kinglas Water shows 
 various interstratified quartzose pebbly schists in its east part, and there 
 are many thin bands of albite schist still further east. It rather seems 
 as if in the albite schists of these sections beds which at the time 
 of the formation of " the anticline," must have been among the lowest 
 beds of the district, whatever their position originally albites are more 
 abundant and in larger shape than in the higher lying beds. In a burn 
 J mile north-east of Butterbridge the bigger ones attain the size of peas. 
 In the higher beds near the base of the green beds the average size is 
 about that of small shot. It is certain that as we go along the west 
 side of Loch Goil from near Woodside Lodge to the mouth of Glen 
 Finart, the albites become gradually smaller, until in sections south of 
 Rudha nan Eoin we cannot, without the aid of the microscope, feel 
 
ALBITE SCHISTS. 43 
 
 certain of their existence. The albite pegmatites also get rarer as we 
 go south along this coast. A special examination for albite on the coast 
 south of Rudha nan Eoin was made in company with Mr J. B. Hill : we 
 saw no albite pegmatites, and no schists that we could be quite certain 
 with the naked eye were albite bearing. But frequently we met with 
 thin chloritic bands, generally only a few inches thick, which we sus- 
 pected might contain albites of exceedingly small size so small that we 
 could not be sure of their character. A specimen of such a doubtful 
 albite schist, close by the lamprophyre dyke, ^ mile north of "11" of 
 " Toll a' Bhuic," was sliced and proved to be an albite schist. Similar 
 bands with minute albites certainly extend as far south as the foot of 
 Knap burn, and probably further. Now, in walking on the side of Loch 
 Goil from Woodside Lodge south, we are advancing from beds which at 
 the time of the formation of " the anticline " were lower on to beds which 
 were higher . The lower beds contain the larger albites, and in the 
 higher beds the albites gradually decrease in size. 
 
 Proceeding north-east along "the anticline," it seems, too, that the 
 albites increase in size. We do not think that in the Kyles of Bute district 
 such large albites occur as in Kinglas Water. 
 
 It has already been stated that the albites are of later age than the 
 mass of the movements which affect the schists in which they occur, and 
 various proofs of this have been given. It is not, certain, however, 
 that they are later than all these movements. It is not uncommon for 
 the rows of inclusions in the albites to run in a different direction from 
 the foliation of the rock enclosing them. The inclusions show the direc- 
 tion of foliation at the time of formation of the albites, but there is a 
 suggestion that since then the albites may have received a twist, and that 
 thus a discordance in direction has been brought about between the 
 foliation preserved in them and the foliation now seen at their sides. 
 In slide 4733, from near the side of the east to west basalt dyke on 
 Beinn Tharsuinn (142), the rows of inclusions in the albites are at times 
 at right angles to the foliation at their sides. Albites have, as already 
 stated, a habit of occurring along lines of special strain or twist, but it 
 hardly seems as if this were an adequate explanation of all that is observed 
 in the slide : at the sides of, and in the part between, two adjacent albites 
 placed diagonally to the foliation, the foliation may be quite even, and yet 
 the rows of inclusions are inclined 45 to this. In various places on the 
 south-west side of Glen Fine albites are frequently bordered by quartz grains 
 of larger size than any seen elsewhere in the specimen. It is uncertain 
 whether this is due to the incipient formation of an albite pegmatite, or 
 whether the quartz may not be of later age than the albites, and developed 
 at their sides after the rock matrix has partly been dragged away in the 
 course of earth movements, in the same way as it has from the sides 
 of magnetite crystals, etc. (p. 80). Slide 6102, from Garbh Allt Mor, 
 -i mile south-east of Achadunan, is cut from a rock of this type. The 
 appearance under a hand lens rather suggested that the albites had been 
 granulitised, but the opaque white aspect is in reality due to the quartz 
 grains at their sides. 
 
 It is not clear that the albites are absolutely the last of the constituents 
 formed in the schists. In slide 3416 (described fully in Appendix II.) 
 Mr Teall states that the white mica ends off abruptly when it comes against 
 the albite, and never occurs as inclusions in it. Large white mica flakes 
 cross the foliation of the albite schists not unfrequently, e.g., at the head 
 of Stuck burn (152), and there are sometimes bands, about | inch 
 thick, in these schists, which are almost entirely made of mica flakes 
 of this kind. Mr Teall describes the microscopic character of one 
 
44 GEOLOGY OF COWAL. 
 
 of these bands from a little over J mile N.N.E. of Beinn Lochain 
 (141), as seen in slide 4732, as follows : " The substratum of this rock 
 is an aggregate of well-crystallised white mica. The different individuals 
 interlock with each other just as the grains of quartz in a quartzite, and 
 there is no orientation of the plates parallel with the general foliation. 
 Embedded in the groundmass of mica are numerous minute opaque grains 
 which are black by reflected light and not attracted by a magnetite needle. 
 These are therefore probably ilmeiiite. They define by their arrangement 
 the foliation of the rock. The other constituents which can be identified 
 are prisms of tourmaline, plates of chlorite and biotite, and possibly a few 
 grains of quartz. There are also small hexagonal prisms of a nearly 
 colourless mineral having a much lower double refraction than tourmaline. 
 These may be apatite. The crystallisation of the mica has obviously 
 taken place after all movements had ceased, as this mineral forms the 
 matrix in which the other minerals are uniformly distributed." The 
 biotite flakes are arranged parallel to the ilmenite. The biotite is not 
 usually included in the white mica : it often ends suddenly at the sides 
 of this mica, as if, perhaps, it had been used up in making the latter 
 mineral. The tourmaline prisms sometimes have their long axes parallel 
 to the foliation, and sometimes across. 
 
 In other places brown mica flakes occur lying across the foliation of the 
 albite schists, e.g., on the hill top f mile slightly east of north of Binnein 
 an Fhidleir (134). 
 
 The matrix of the albite schists may be either green, pale greenish- 
 grey, or leaden coloured. Kear the head of Stuck burn the two last 
 colours are in close association. The pale greenish-grey occurs on 
 the outside of the numerous little quartz veins in the schist, in the 
 flakes enclosed in these veins, and in thin bands mixed with the harder 
 quartzose schists. The leaden coloured rock is very fine in grain, and no 
 separable flakes can be made out by the eye or hand lens : it breaks up 
 less readily under the hammer than the greenish-grey type. Besides a 
 close interbanding of the two types, there is also apparently a gradual 
 passage 1 between them: it is often uncertain to which type a particular 
 specimen belongs. In the Stuck burn, albites seem most abundant in 
 the leaden coloured variety. 
 
 The alteration of albite schists by various of the unfoliated intrusive rocks 
 is described on pp. 98, 106, 114, 149. 
 
 Bands of typical albite schists are included within the green bed zone 
 on the north-west side of " the anticline." Besides these, there are other 
 beds which, from their toughness and richness in epidote, we should prefer 
 to class with the green beds, which yet contain albite of the same kind as 
 the typical albite schists. A green bed, the next below the base of the 
 main zone of green beds, J mile north-west of Mullach Choire a' Chuir 
 (142), may be mentioned as an example. Slide 4726 is cut from a 
 specimen of this. Probably there is no distinct line between these rocks and 
 typical albite schists, any more than there is between pebbly green beds 
 and pebbly quartzose schists. On the shore 1 mile slightly south of 
 east of Dundarave Castle there is a green bed with abundant epidote 
 both in grains and prisms, and chlorite and biotite in equal abundance ; 
 this also contains albite specks, but the specks are hardly like those of 
 the typical albite schists : some are very free from inclusions.* This 
 occurrence is within the garnetiferous schist zone. Another outcrop of 
 green beds with albites is seen in the same zone, \ mile slightly north 
 of west of Meall Reamhar (141). 
 
 * A reproduction of a photograph taken by Mr Teall from the slide (4725) of this 
 rock is given in Plate VII. near the end of the volume. 
 
LOCH TAY LIMESTONE. 45 
 
 Quartz veins of irregular occurrence and thickness, but not generally 
 more than an inch or two thick, are abundant in the albite and phyllitic 
 mica schists. They are certainly more numerous in these schists than in 
 the more quartzose schists. 
 
 The quartzose and pebbly schists associated with the albite schists in 
 " the anticline " district, generally do not differ in any marked way from 
 the corresponding schists in the Kyles of Bute section (see pp. 23-27, 296). 
 A relative abundance of black and brown mica is characteristic of them when 
 compared with the less altered grits to the south-east, in the area where 
 there are no visible albites. Some portions of bands are much more full 
 of pebbles than others, and when seen in good sections the alternations 
 from more to less pebbly portions closely resemble alternations due to 
 original deposition. The shapes of the pebbles are generally more de- 
 formed in the limbs of folds than in the axes (see pp. 27, 296), but there is 
 no area where it is probable that the absence of pebbles is due to complete 
 destr action of them in a band that was coarsely pebbly at first. It is 
 more likely that the finer-grained quartzose schists free from pebbly specks 
 were from the beginning marked by a comparative absence of large 
 pebbles. There are also many bands of schist which are neither genuine 
 phyllitic schists, nor yet very quartzose. Their original representatives 
 may have been sandy shales. 
 
 Tourmaline prisms a-re more common in the albite and more niicacaous 
 schists than in the quartzose, but they do occasionally occur in the latter. 
 A quartzite-like schist from a burn 1 mile N.N.W. of Ben Donich shows 
 on the foliation planes a set of closely parallel rods, which are made up 
 of small prisms of tourmaline, each running parallel to the direction of 
 the rods. Slide 4731 is cut from a specimen of this rock. 
 
 Ochreous weathering lenticles and short bauds of calcareous schistose 
 grit, 1 or 2 inches thick, are common, just as they are among the 
 schistose grits further south-east (see p. 38), in areas where no albites 
 have been recognised. Good examples occur on A' Chruach(182), on the 
 south-west side of Tom nan Con (164), and on the hillside east of Clunie 
 Wood (164). 
 
 C.T.C. 
 
 CHAPTER IV. 
 
 SCHISTS PROBABLY OF SEDIMENTARY ORIGIN (continued} 
 The Loch Tay Limestone. 
 
 The Gleudaruel or Loch Tay limestone is perhaps the most readily 
 mapped and best denned schist in the district. It does not usually make 
 swallow holes, though here and there, e.g., on the watershed a little more 
 than | mile slightly south of east of Cruach nan Capull (133), and f mile 
 north of Cruach an Lochain (151), such do occur, but there is a distinctness 
 of character in it, and the associated beds, which usually enables it to be 
 recognised in the different outcrops. It is also probably thicker than any 
 other limestone in the district in its unfolded state. It is seldom seen 
 without a band of hornblende schist either in or just at the sides of it, or 
 in both positions. 
 
 Among the best sections are those in the burn ^ mile north-east of the 
 " g "of " Creag Dhubh " (141), the nearest burn south-east of this stream, 
 
46 GEOLOGY OF COWAL. 
 
 the burns J mile south-east, and | mil S.S.E., of the same letter, at Glen- 
 sluan, various burns on the south-east side of Sith an t-Sluain (152), Kil- 
 bridemore burn (162), and various burns on the west side of Glendaruel 
 as far south as Glendaruel House. 
 
 In the north part of Cowal the part of the limestone above the included 
 hornblende schist is commonly about 20 to 30 feet thick ; and below the 
 hornblende schist limestone or calcareous quartzite schist occurs again 
 with an average thickness of about 20 feet. There may in some places be 
 greater thicknesses than these, owing to folding. Both parts of the lime- 
 stone, but especially the lower part, are sometimes mixed with bauds and 
 lenticles of calcareous quartzite. Below the limestone comes often a few 
 feet of leaden coloured phyllitic schist, and below this a considerable 
 thickness of massive quartzose schist. Above the limestone is soft 
 phyllitic schist which may contain small garnets, and above this often 
 another outcrop of limestone, usually about 6 to 7 feet thick, and above 
 this again is soft garnetiferous schist. The interval between the upper 
 and the main limestone is in places 30 feet, in other places only 12 feet, 
 and in others, again, we see nothing of the upper outcrop. Perhaps this 
 upper limestone is only a repetition of part of the lower one by folding. 
 Further details of the section in different localities are given on pp. 98, 
 106, 114, 149. 
 
 The calcite crystals which make up the mass of the limestone show 
 cleavage faces varying in size from a small mustard seed up to \ inch in 
 length : perhaps the average length is about ~ inch, but it may vary 
 rapidly. In some bands the general colour is nearly black, in others pale 
 grey, and in others there is a mottled appearance due to the mixing of 
 these colours. In the mottled bands the black parts are formed of calcite 
 crystals of larger size than those in the pale grey parts. The black 
 crystals, either in combination or singly, form island-like areas which are 
 separated by narrower portions made up of smaller pale grey or white 
 crystals. Both black and white parts effervesce freely with dilute hydro- 
 chloric acid. The outlines of the black parts are sometimes markedly 
 angular, and the white parts may penetrate into them along bays or thin 
 crack-like lines, and then suddenly end. In sections across the foliation 
 it is seen that the black parts have often a greater length parallel to the 
 foliation than across it. It is suggested that the white parts have been 
 formed by a kind of crushing, and recrystallisation in smaller crystals, of 
 the black parts. The section in the burn below the road 1 mile W.S.W. 
 of Cruach nan Capull (151 ami 152) shows in one place a succession of 
 dip slopes of mottled limestone, and it is clear that the longer axes of the 
 black crystals are parallel to one another. This is so whatever the 
 size of the black areas : sometimes they are 2 or 3 inches long. The 
 direction of elongation is the same as that of the stretching or rodding 
 in the neighbourhood, as seen in some surfaces of calcareous quartzite 
 schist in the same burn. 
 
 It is not clear what is the cause of the colour in the black calcite. In 
 slide 5136, from black limestone riot quite J mile south of Cruach nan 
 Capull (141), the calcite is often dusty, with minute inclusions, and possibly 
 it is these that give the colour. 
 
 The section at the quarry at Glerisluan is described by Mr W. Ivison 
 Macadam ("On the Chemical Composition of certain Limestone Kocks 
 from Ballimore, Argyllshire," Trans. Edin. Geol. Soc., vol. iv. 1883, 
 p. 101), who gives a series of chemical analyses of the limestone and of 
 vein arid crush rocks which occur in it. Analysis No. 3, of blue limestone 
 of the common type of the quarry, is as follows : 
 
LOCH TAY LIMESTONE. 47 
 
 Ferric oxide, Fe. 2 3 , . . . .^^. I'U 
 
 Aluminic oxide, A1 2 O 3 , . . . . 0*18 
 
 Calcic oxide, CaO, . . . . . 37'21 
 
 Magnesic oxide, MgO, . . . . 0'35 
 
 Silica aud silicates, SiO 2 , . . . 29*52 
 
 Carbonic anhydride, CO 2 , . . . 29'63 
 
 Sulphuric anhydride, SO 3 , . . . 1*56 
 
 Organic matter and moisture, . . . 0'41 
 
 100-00 
 
 This corresponds to a percentage of 66*44 of carbonate of lime, and 0'75 
 of carbonate of magnesia. 
 
 Analysis Xo. 7, of a red coloured baud, shows a considerably higher 
 percentage, viz., 84 '86, of carbonate of lime. The details of this analysis 
 are as follows : 
 
 Ferric oxide, Fe 2 O 3 , .... 1'24 
 
 Aluminic oxide, ~A1 2 O 3 , .... 0'42 
 
 Calcic oxide, CaO, 47'51 
 
 Magnesic oxide, MgO, .... 0*25 
 
 Silica and silicates, 12*28 
 
 Carbonic anhydride, C0 2 , . . . 37'64 
 
 Sulphuric anhydride, SOg, . . . 23 
 
 Organic matter and moisture, . . . 0'43 
 
 100-00 
 
 We have not elsewhere noticed any red coloured baud in the limestone, and 
 perhaps this colour is confined to the proximity of a crush line or vein. 
 
 C.T.C. 
 
 Small pale coloured micas are sometimes seen, but in no great abundance, 
 lying flat on the foliation planes. Weathered faces frequently show 
 small specks of quartz, about the size of small shot. These are often 
 opalescent, e.g., in the burn J mile south-west of Glensluan, and probably 
 represent pebbles. They are not generally elongated in any particular 
 direction, but perhaps the calcareous parts of the rock, being readily 
 soluble, would, during the shearing, flow easily from the sides of the 
 pebbles, and allow them to remain undistorted. They are often some- 
 what rusty coloured on the outside, but this may be owing to residues 
 left from the weathered limestone. In the limestone quarry at Otter 
 Ferry pebbles may be seen as large as peas. Some of these are of clear 
 glassy felspar with partially rounded outline, some are of a dull pink 
 coloured felspar, and others are clear blue quartz. C.T.C. , J.B.EL 
 
 Weathered faces of some of the impure limestone bands also show in 
 certain places crowds of minute pale straw coloured or white needles, often 
 about -Q inch in length. These needles have a general parallelism of 
 direction. Slide 5547 is from a band of this kind from the limestone just 
 above the hornblende schist in the burn j mile south-west of the "g" of 
 "Creag Dliubh" (141). Mr Teall identifies the needles as idocrase. : he 
 says, " The prisms of idocrase are seen to be eight-sided, due to the forms 
 (100) and (101). Terminal faces appear to be rare, but a combination of 
 the pyramid (111) and basal plane (001) has been observed." There are 
 also small hemispherical knots, about the size of peas, projecting on 
 some of the weathered surfaces, aud somewhat resembling the tops of 
 worm tubes. These spots are distinct in the slide, and are finer grained 
 than the rest of the rock : the calcite in each spot may extinguish simul- 
 taneously : the foliation has a tendency to go round the spots. The purer 
 
48 GEOLOGY OF COWAL. 
 
 limestone from the same locality also shows slender prisms of idocrase 
 projecting on the weathered face. Mr Teall says there is probably also a 
 mineral of the^epidote zoisite group present. 
 
 A calcareous quartzite schist from the limestone below the hornblende 
 schist J mile E.N.E. of Bathaich ban Cottage (134) contains hemispherical 
 projections which seem to the unaided eye very like those in specimen 
 5547. This was sliced (slides 4730 and 5133), and disclosed a great 
 number of minute colourless garnets, forming in some parts more than 
 half the bulk of the rock. They are occasionally collected into spots and 
 streaks, and the spots probably form the projections noticed on the 
 weathered face. There are abundant small pyrites specks in the same 
 rock. 
 
 In the calcareous quartzite below the hornblende schist, \ mile south- west 
 of Glensluan, there are bedding surfaces which show oval projections some- 
 times more than 1 inch in length, but these have not teen examined 
 microscopically. 
 
 The Garnetiferous Mica Schist. 
 
 North-west of the Loch Tay limestone conies a broad zone wherein nearly 
 all the rocks, whether green beds, epidiorites, thin fissile mica schists, or 
 quartzose schists, may contain garnets, often in great abundance. This 
 zone is not supposed to represent a stratigraphical horizon, but in a rough 
 description of the boundaries, or in an attempt to represent them graphi- 
 cally, it is convenient to take the Loch Tay limestone as the south-east 
 margin, and the most north-west of the graphite schists, which often runs 
 at a distance of about 1 mile north-west of this limestone, as the north- 
 west margin. But, as stated already, white garnets are in places 
 abundant within the Loch Tay limestone itself. A band of hornblende 
 schist within the limestone in the burn f mile south-east of Ardno also 
 contains small pink garnets (see p. 63) ; and garnets of the same size and 
 colour as those in the defined zone, and many of which have undergone 
 the same changes occur also in places outside the zone. There seems 
 to be a tendency for these occurrences gradually to increase in number, 
 and to lie at a further distance south-east of the Loch Tay limestone, the 
 further we go north-east, so that a little way up Glen Fine it is doubtful 
 whether the limestone continues to be the best boundary for the main 
 zone. In the river Cur, \ mile west of Creag Dhubh, garnets occur in 
 a green bed some distance below the north-west boundary of the green 
 beds zone : at the junction of the Cur and the Cab they are also seen in a 
 green bed : in the Cab, \ mile above its foot, they are in a thin fissile 
 mica schist near the base of the green beds : in Leamhanin they are in 
 quartzose schist and phyllite east of the letter " m," near the base of the 
 green beds. Further north-east still, garnets are common in the albite 
 schists below the green beds. The first we noticed occur in small outcrops, 
 and their size is but small perhaps T ^ inch in diameter. This is on 
 the high ground near Binneiri an Fhidleir ; there is one small outcrop 16 
 yards west of the Ordnance Station 2658, another 150 yards W.N.W. of 
 the same station, and another T 7 mile slight! jMiorth of east of it. Further 
 north they become more abundant. They are prominent in the crags \ 
 mile W.N.W. of Lochan Mill Bliig, and by the " Ri " of " Eas Riaeham," 
 and in a little burn running parallel to Eas Kiachain, on its north-east 
 side, at a distance of about 160 yards above the delta of the burn. 
 
 In the same way the occurrences of garnet do not stop sharply at the 
 graphite schist band mentioned, but here and there we find them on the 
 north-west side of it, e.g., in the schist at the edge of a hornblende schist T 5 ^ 
 
i 
 
 GARNETIFEROUS MICA SCHIST. 49 
 
 mile south-east of Newton, on the shore at the south side of Straohur Bay, 
 and in the branches of the burn that enters Loch Fine at St Catherine's. 
 
 In the burn south-east of Leawach (151) the garnets are about as pro- 
 minent and large as in the areas further along the strike to the north- 
 east, but south-west of the burn they seem gradually to decrease in size. 
 In the south part of Cowal near Kilfinau, the schists on the north-west 
 of the Loch Tay limestone were surveyed before those on the same 
 horizon further north-east, and it was not observed at the time of 
 the survey that garnets were specially characteristic of this horizon. 
 It has been subsequently noted, however, that small garnets, not ex- 
 ceeding the size of a pin's head, are not uncommon on or a little south- 
 east of this horizon, e.g., in the hornblende schist about 50 yards 
 north-west of the Loch Tay limestone on the north side of Auchalick Bay 
 (181), and in the green beds just west of Ballochandrain (172), and they 
 were noticed in slide 3830 from the green beds near Lephinkill (172). 
 
 Among the best sections within the main zone are these, on the shore 
 from J mile to T 7 ^ mile south-west of Rudha Bathaich Bhain (133), in the 
 different burns that run N.N.W. from Cruach nan Capull (133), in the 
 lower part of Eas Dubh (141), and in the burn south-east of Leanach 
 (151), up to a point \ mile south-west of the "n" of Leanach." The 
 most common type of rock within the zone is a thin fissile phyllitic mica 
 schist, on the foliation planes of which there is sometimes a good deal of 
 chlorite irregularly distributed. The rock breaks readily across the chief 
 foliation, and shows usually a great number of close folds with axes 
 parallel to this foliation, and the impression is conveyed that the folding 
 is generally more repeated than in the rock zones further south-east. 
 Intermixed with this type are more quartzose schists, with thin rusty- 
 weathering calcareous lenticles, and many thin quartz veins. The 
 quartzose bands and veins are comparatively free from garnets, but iu 
 one place, not quite \ mile south-west of Cruach nan Capull (133), there 
 are quartz veins which are nearly half composed of garnets. Frequently, 
 e.g., in Eas Dubh J mile east of Inverglen, the vein-quartz is in the 
 form of short rods which run parallel to one another and to the other 
 indications of stretching in the neighbourhood. Often, too, in the more 
 quartzose schists, there is a rod structure which is more prominent than 
 the foliation : the rock splits readily into a series of parallel rods, but 
 it is hard to get a large plane slab. This is shown well in the scars of 
 An Carr (141 and 142). There is a constant repetition of sharp folds 
 in the scars. It has been suggested by Mr G. Barrow, that in cases like 
 these, where the rodding is prominent but the foliation is not, the rock 
 may have been folded before the force which produced the rodding 
 commenced to act. 
 
 Two chemical analyses of mica schist which possibly belong to this zone 
 are given on p. 55. 
 
 The garnets are of a port-wine colour, and vary in size from large peas or 
 small marbles down to specks which are hardly visible. The small sizes 
 occur near the margins of the zone, or in areas outside it. The most 
 common is that of a small pea. Perhaps the largest noticed are those in 
 Eas Dubh (141) J mile S.S.E. of the letter "h" of "Creagan an Eich." 
 A first glance at some exposures may fail to show any clear distortion or 
 indication of movement since the formation of the garnets. But more 
 careful search nearly always shows distortion ; the angles of the garnets 
 are slightly rounded, or the shape elongated in one direction, or there is a 
 rim of chlorite around them. This rim usually extends along the foliation 
 to a greater distance in one direction than in others, or rather in two direc- 
 tions opposite to one another, forming two tail-like extensions. The ex- 
 
 D 
 
50 
 
 GEOLOQY OF COWAL. 
 
 tensions on the same foliation plane are parallel to one another, and also 
 to the rodding in the quartz veins. The direction on adjoining slabs is 
 not necessarily quite the same, but neither are the directions of rodding. 
 
 The most general direction is north- 
 west or N.N.W. As seen in sections 
 at right angles to the foliation, the 
 rim is extremely thin at right angles 
 to the stretching, or it may hardly 
 be observed at all. These are just 
 the directions that would show the 
 least thickness of any material 
 formed from the garnets by rubbing 
 or crushing along the foliation. Tf 
 the, larger garnets are examined they 
 are not uncommonly seen to be 
 traversed by strings of chlorite, and 
 to be distorted, or even broken into 
 
 ^^^ ===s====: ^ pieces. In the most westerly burn 
 
 FIG. 22. xlT^GametiferouTmica schist of two parallel burns nearly % mile 
 % mile S.W. of Bathaich ban Cottage, slightly east of south of Laglingarten 
 Surface of a foliation plane with patches / 133 \ fcae garnets are pulled out into 
 of dark green chlorite, supposed to be v 11-11 T n lUfl^ ana* 
 
 replacing or edging garnets. streaks i mch lon fr In a g 8(M ? 
 
 nearly J mile south-west of Cruach 
 
 nan Capull (133), J mile north of the "C" of "Creag Dhubh" (141), 
 and at a point 70 yards west of Meall Reamhar (HI), the garnets are 
 crossed by minute veins of quartz, running nearly at right angles to the 
 foliation, and accompanied with slight throws : there may be three such in 
 one garnet. In the most westerly of three neighbouring burns J mile 
 slightly south of west of Ardno, there are thin bands of leaden coloured 
 
 FIG. 23. x 2. 
 
 One quarter of a mile S.W. of Cruach nan Capull (133). 
 crossed by cracks filled with granulitic quartz. 
 
 Garnets 
 
 schist in which the garnets are sometimes surrounded by rims of quartz 
 which have a special extension in two opposite directions along the 
 foliation. No doubt these rims are of the same nature as those around 
 the magnetite crystals, etc., described on p. 80, and were formed in the 
 same way. Some of the garnets with quartz rims are distorted : round 
 those with rims of quartz we did not notice any chlorite, but others with 
 chlorite rims occur within 2 feet of them. 
 
 All stages seem to occur in the relative prominence of the chlorite rim 
 compared with the garnet centre, the latter getting smaller as the former 
 enlarges. In many localities we see no garnets at all, but many small 
 specks and streaks of chlorite which probably represent them. 
 
 On the shore J mile south-west of Rudha Bathaich Bhain there are, 
 besides the chlorite areas surrounding the garnets, spots and crystals of 
 black mica. We discerned no common orientation in these, arid no garnet 
 centres, and it is not probable they have any connection with the garnets. 
 
 In some places the garnet schists contain also distinct radiate 
 shapes, probably after actinolite. The best localities are the burn 
 mile slightly west of south of Ardno, and another burn (on either side 
 of a little east to west crush) nearly \ mile south-west of Ardno. 
 These two places are on much the same horizon. The rays of the 
 
GARNETIFEROUS MICA SCHIST. 51 
 
 shapes may attain a length of 3 to 4 inches. The substance composing 
 them is quite soft, and presumably chlorite. Spots of similar substance 
 occur on the same foliation planes replacing garnets. The faint stretch- 
 ing lines and wave lines on the foliation planes which contain the shapes, 
 cross the surfaces of the shapes also, without projecting beyond the general 
 level of the surface. Similar shapes also occur in the more micaceous 
 parts of some rather quartzose schist blocks tumbled from the west bank 
 
 FIG. 24. x 1. Chlorite pseudomorphs after actinolite, in the garnetiferous mica 
 schist mile slightly W. of S. of Ardno : as seen on a foliation plane. The fine 
 shading indicates the direction of the crests of the small waves affecting the 
 foliation plane. At a place vertically over "a" in the sketch these waves are 
 clearly seen to affect the pseudomorphs. 
 
 of the burn not quite J mile south of Ardno, in the burn 130 yards 
 south-east of the farm buildings at Ardno, in Eas Dubh J mile east of 
 the "h" of "Creagan an Eich" (141) in thin bands which are rather 
 more quartzose than the normal type of garnet schist ^ mile north-west 
 of Meall Reamhar (again in a rather quartzose schist), and in a scar ^ 
 mile south-west of An Carr in a greenish fissile schist. 
 
 Besides these, there are other places where the shape and arrangement 
 of many of the chlorite areas rather remind one of deformed actinolite 
 rays. It is possible that most of the irregular patches of chlorite may 
 have originated in this way, or from the occurrence of garnets and 
 actinolites in close association. 
 
 It is to be noted that the garnets in the albite schists of Glen Fine are 
 also at times surrounded with a distinct chlorite rim. This is seen in a 
 burn (not marked in the 1-inch Map) mile south-east of the 
 big "R" of "KILMORICH" (126), and in a little burn running parallel 
 to Eas Riachain on its north-east side, at a distance of 160 yards from 
 the delta of the burn. In slide 6103, from a specimen obtained % 
 mile slightly south of west of the Eagles Fall, the garnets are irregular 
 in shape, and chlorite veins cross them, and there are large chlorite flakes 
 at their sides. The garnets are sometimes partially or wholly replaced 
 by carbonates, and it is to this that the white rim noticed in the hand 
 specimen is due. 
 
 In a few places within the garnet schist area small white knots have 
 been observed, of about the same size and frequency as the garnets in 
 the adjoining schists. In slide 5054, from a dark slightly graphitic 
 schist mile slightly north of west of Cruach nan Capull (133), the 
 knots are composed of aggregates of quartz, mica, and an opaque 
 brown substance : in one of them the mica flakes are arranged some- 
 what radially, starting from a nearly opaque mass near the centre and 
 passing through the clearer quartz at the edge. In the same knot 
 there seemed to be minute specks of garnet. Possibly the knots are 
 pseudomorphs after garnets. White knots of an apparently similar kind 
 also occur in the burn J mile north-west of the "r" of "Creag 
 Dhubh"(141). 
 
52 GEOLOGY OF COWAL. 
 
 Though the garnets have suffered much alteration and physical dis- 
 tortion, It is not likely they have passed through the same amount of 
 movement and change as the schist in which they occur. Probably the 
 : rock was a schist before the formation of the garnets. In slide 4739, 
 from a specimen obtained from the shore J mile west of Bathaich ban 
 Cottage (133 and 134), the garnets contain inclusions, part of which 
 consist of some brightly polarising needle-shaped substance, and part 
 of some black opaque grains, probably ilmenite. These inclusions 
 run in rows across the garnet : the rows are slightly waved, and run 
 in much the same direction as the schist foliation. The same slide 
 shows two or three portions of vein quartz, the interiors of which are 
 nearly free from chlorite or garnet, but contain a good deal of white mica : 
 the chlorite is specially abundant at the sides of the garnets, but is riot 
 confined thereto it may also occur in small isolated flakes. 
 
 An albite schist on the hillside east of Mid Letter, from within the 
 garnet schist area, contains also elongated chloride streaks which prob- 
 ably represent garnets. A slide was prepared from this schist (slide 
 5432), but it failed to give any clear evidence of the relation in age of 
 the albite and chlorite. Considering how commonly the garnets are 
 deformed, while there is no satisfactory evidence of distortion in the 
 albites, it is probable that the metamorphism which produced the garnets 
 is of earlier date than that which produced the albites at all events it is 
 not of later date. 
 
 An instance of the presence of garnets in green beds in the garnet 
 schist zone is given on p. 37. Garnet bearing hornblende schists within 
 the same zone are seen J mile slightly north of west of the first " C " of 
 " Cruach nan Capull" (133), f mile north-west of the same letter, 
 and, as already mentioned (p. 48), in a band within the Loch Tay 
 limestone. 
 
 In a burn J mile north-east of Sith an t-Sluain (152) there are 
 large brown mica flakes in a phyllite of the garnet schist zone. The flat 
 sides of the flakes cross the foliation at a considerable angle, and are 
 evidently of later formation than it. 
 
 The north-west band of graphite schist may be considered as the north- 
 west boundary of the area of chief occurrence of garnets. Apart from the 
 presence of garnets the schist for some distance on the south-east side of 
 this band is in most respects very like that on the north-west side. There 
 is, however, one difference. Most of the quartzose bands intermixed with 
 the phyllites on the north-west side are fine grained, and very compact are, 
 in fact, a kind of quartzite schist while the harder bands within the garnet 
 schist zone are generally pebbly, and rarely so compact or purely siliceous. 
 For this reason, apart from others, it does not seem probable that the 
 mass of the garnet schist zone can be a repetition of the beds at the base 
 of the Ardrishaig phyllite series in a different state of alteration. 
 
 In the area between Strachur arid Ardno there is a limestone outcrop 
 a little south-east of the graphite schists. A band of hornblende schist 
 usually occurs in or below this, or there may be more than one band. 
 In the burn J mile S.S.W. of Arduo the upper exposure of limestone is 
 6 to 8 feet thick, and contains conspicuous quartz pebbles :, below this is 
 a hornblende schist about 6 feet thick : then limestone again, mixed with 
 a larger proportion of calcareous quartzite, the thickness of the two 
 together being perhaps 12 feet. Below this is about 6 feet of hornblende 
 schist resting on shivery garnet schist mixed with occasional quartzose 
 bands containing quartz pebbles. On the hillside J mile N.N.W. of the 
 "C" of "Creag Dhubh" the limestone is divided into four parts by 
 three bands of hornblende schist : the upper part is rather a calcareous 
 
GRAPHITIC SCHISTS. 53 
 
 quartzitc tliau limestone. In a little burn 1 mile W.S.W. of the 
 " C " of " Creag Dhubh " some parts are quite a coarsely crystalline pale 
 grey limestone, others are more a calcareous quartzite : the weathered 
 faces are a deep ochreous colour, deeper than those usual in the Loch Tay 
 limestone, and many of the splitting planes are black, as if partly graphitic : 
 we saw no mottled bands. There is no corresponding limestone outcrop 
 seen on the south-west of Strachur, excepting in a little burn J mile 
 north-west of the "n" of "An Carr" (141 and 152). 
 
 If this limestone be regarded as a repetition of the Loch Tay limestone 
 by folding, it must occur in a sharp syncline or anticline, both sides of 
 the outcrop representing the same margin of the bed, for the Loch Tay 
 limestone on the south-east side does not make a double outcrop. It is 
 difficult on this supposition to see why the hornblende schist seen close on 
 the south-east side in some of the sections, e.g., in the burns J mile S.S.W. 
 of Ardno, J mile south-east of Laglingarten, f mile north-west of the first 
 " C " of " Cruach nan Capull " (133), and other places, is not also repeated 
 on the north-west side. The hornblende schist is supposed to be intrusive 
 and not necessarily continuous, but we know of no reason why it should 
 die out more quickly across the strike than along it. 
 
 The Graphitic Schists. 
 
 In the north part of Cowal there are various parallel outcrops of 
 graphite schist, impure graphitic limestone, and calcareous quartzite, at a 
 distance of about 1 mile north-west of the Loch Tay limestone. As stated 
 on p. 48, the most north-westerly of these has been adopted as the 
 north-west boundary of the garnet schist zone. There are not always the 
 same number of outcrops in the different localities : in some places we can 
 only see one or two, in other places four or more, e.g., on the south-west 
 side of Strachur Bay. Probably these variations in number are due to 
 variations in the amount of folding in the different localities. Among 
 the best sections of these beds are these, at the head of Eas Dubh 
 (141), in the burn \ mile south-west of Laglingarten (133), in various 
 burns by the shore between Mid Letter and Strachur Bay, and in the burn 
 \ mile north-east of Leanach (151). 
 
 All the bands show a great amount of twisting and crushing, there 
 being special lines of disturbance running along with them in a general 
 N.JST.E. direction. These lines are of later date than the folding which 
 .accompanied the schist manufacture, for they twist this folding without 
 producing any further foliation, and the actual breakage lines are filled 
 with streaks of clay formed from the crushing of the crystalline schist. 
 But they are in part of earlier date than some of the lamprophyre 
 intrusions (see p. 109). 
 
 Owing to the movements it is hard to get good specimens of the softer 
 schists, and the blackening of the fingers on handling specimens is great, 
 owing to abundant thin streaks of crush rock. The bands of limestone 
 and calcareous quartzite mixed with the graphite schist are themselves dark, 
 graphitic, and thin bedded, and in most places they are so mixed with 
 the schist by contortions and crushes, that it is hard to separate them. 
 It is possible, too, that in the original succession the beds were closely 
 intermixed. At the head of Eas Dubh there is a moderately good lime- 
 stone at least 6 to 8 feet thick, dark grey in colour, and fine grained. 
 There is graphite schist on both sides of this outcrop, and other impure 
 calcareous bands : the graphitic horizon is probably not less than 50 yards 
 wide. In the burn \ mile north-east of Leanach (151) there is a graphitic 
 limestone ^with an apparent thickness of about 10 feet. 
 
54 GEOLOGY OF COWAL. 
 
 Slide 5053, from a rather quartzose variety of graphite schist 1J mile 
 south-east of St Catherine's pier, shows that the rock is composed of 
 micro-crystalline quartz, white mica, and much opaque dust. Many areas 
 are comparatively clear, consisting mainly of granulitic quartz with but 
 little opaque matter, while other areas are entirely opaque : the clear and 
 the opaque areas being roughly parallel to one another. The white mica 
 is conspicuous in the clear areas. Some of the micas seem to have 
 accumulated in themselves a good deal of the opaque matter. There are 
 indications of sharp folding in some layers : the folds may end at strain 
 or slide-like lines which are parallel with the foliation of the rock. In 
 slide 5054, of the dark knotted schist already mentioned on p. 51, the 
 opaque dust is not so abundant as in 5053 : in addition to the opaque 
 dust there are also opaque folia stained brown. 
 
 In the bend of the burn J mile north-west of the " C " of " Creag Dhubh " 
 a quartzite schist, under a dark limestone and graphite schist, contains 
 quartz pebbles as large as peas. In Eas Dubh, 1 mile south-east of 
 Ardnagowan Cottage, thin quartzite schists are intimately mixed with 
 leaden coloured garnetiferous schists and thin bands of graphite schist : 
 in one of the quartzite bands there are various black spots, about the size 
 of peas, with prominent cleavage planes. Microscopic examination (slide 
 5134) shows that the rock consists essentially of quartz, felspar, and white 
 mica. The felspars generally contain opaque particles, which Mr Teall 
 considers are probably carbonaceous, and it is these which form the black 
 spots in the hand specimen : some opaque matter commonly occurs also 
 on the foliation planes. 
 
 In the burn J mile north-east of Leanach the graphite schist appears 
 as dark as usual, and is associated with a graphitic limestone already 
 mentioned. Graphite schist is seen again on the south-east side of the 
 same burn, near the limekiln 200 yards north-east of Leanach. We cannot 
 say for certain that the graphite schist continues south-west of Leanach. 
 The district to the south-west was surveyed before that to the north-east, 
 and no graphite schist was noted in it. 
 
 The Ardrishaig Phyllite Series. 
 
 The Ardrishaig phyllites or " calcareous sericite schists " consist of 
 greenish-grey soft phyllitic mica schists, in many parts of which there are 
 abundant calcareous lenticles, often hardly \ inch thick. Intermixed with 
 these are occasional thicker outcrops of limestone which can be mapped, 
 and bands of hard compact quartzite schist or greywacke schist. The 
 greater part of the zone is extremely soft, and the rock, on hammering, 
 breaks almost as readily across the foliation as along it : for this reason 
 it cannot be used for slates, and the burns traversing the area are 
 unusually deep and narrow. Good sections occur on the shore between 
 Creag a' Phuill and a point J mile north-east, between Creggan's Point 
 and Aird Cottage, and between Mid Letter and a point J- mile south-west. 
 
 Only the south-east portion of this series comes into Cowal, and there is 
 a greater breadth of exposure, at right angles to the strike, on the north- 
 west side of upper Loch Fine than on the south-east side. In the part of 
 Cowal north-east of Strathlachlan (151) the most north-westerly band of 
 graphite schist has been adopted as the south-east margin of the series 
 (see p. 53), but the graphite schists have not been noticed in the area 
 south-west of Leanach, and there is therefore a possibility that the 
 margin adopted in this area is not exactly the same as that adopted to the 
 north-east. In the south-west area the bands of quartzite schist near the* 
 south-east margin gradually increase in prominence tb the south-west, 
 
ARDRISHAIG PHY LUTE SERIES. 55 
 
 and finally are in excess of the intermixed soft phyllitic mica schists. 
 In the north-east area, on the other hand, the more prominent quartzite 
 schists do not usually occur within J mile of the south-east margin. In 
 such a greatly folded series, a bed may have its apparent thickness greatly 
 altered in different localities owing to the varying relations of the ground 
 surface to the different parts of the folds. But it is found that not 
 only in Cowal but also on the west and north-west of this district, the 
 quartzose bands throughout the series, and not alone near the south east 
 margin, generally increase in prominence to the south-west : for example, 
 they make a great show on the west shore of Loch Fine near Erins and 
 Stronchullin, but away to the north-east, on the north-west side of Glen 
 Fine, they are very thin and inconspicuous. It seems possible that the 
 more quartzose parts of the series were originally thicker and more 
 numerous in the north-east area than they were to the south west. 
 
 In his " Preliminary Notice of a Clay Shell-bed between Newton and 
 Strachur, Loch Fynne, Argyllshire " (Trans. Edin. Geol. Soc., vol. iv. 1883, 
 p. 94), Mr W. Ivison Macadam gives a chemical analysis of the mica 
 slate of the district. It is not stated from what locality the specimen 
 analysed was obtained. If obtained from near the shell-bed, it must 
 belong either to the Ardrishaig phyllites or the garnetiferous mica schists. 
 The analysis is as follows : 
 
 Ferric oxide, Fe 2 O 3 , . . . . 16 "91 
 
 Aluminic oxide, A1 2 3 , . . . 22'12 
 
 Calcic oxide, CaO, .... 0'65 
 
 Magnesic oxide, MgO, . . . 1 '44 
 
 Silica, etc., Si0 2 , .... 58*88 
 
 100-00 
 
 In another paper, " Notice of Veins of Specular Iron Ore at Strachur, 
 Argyllshire" (Trans. Edin. Geol. Soc., vol. iv. 1883, p. 95), Mr 
 Macadam gives two analyses of mica schist near the veins described in 
 the paper. The exact locality is not given. The analysis of the schist 
 6 feet from the veins is as follows : 
 
 Fe. 2 3 , . . . 15-18 
 
 CaO, 0-36 
 
 MgO, 0-84 
 
 SO 3 , 0-09 
 
 Silicates, 83-53 
 
 100-00 
 
 The insoluble silicates, after being fused, yielded the following 
 results : 
 
 Fe 9 3 , . . . . 1-73 
 
 ALOjp .... 22-12 
 
 CaO, .... 0-19 
 
 MgO, . . . . 0-61 
 
 Si0 2 , .... 58-88 
 
 Soluble in acids, . . 16 -4 7 
 
 100-00 
 
 Here and there we get close alternations of colour in the phyllitic 
 schist. Such are seen on the south side of the quartzite at Creag a' Phuill, 
 and in the two burns, at 130 to 270 yards from high- water mark, 
 
56 GEOLOGY OF COWAL. 
 
 which run into Loch Fine on either side of St Catherine's pic>r. 
 These striped schists remind us of the striped phyllites of the Dunoori 
 series, but in the Ardrishaig phyllites there is not the same wide range of 
 colour, there being hardly any purple or black. The Ardrishaig phyllites 
 are also softer and more calcareous than those of Duuoon : many parts 
 in which the eye can distinguish no clear carbonate effervesce freely 
 with dilute hydrochloric acid. A specimen of the phyllite on the shore 
 J mile south-west of Aird Cottage (slide 5433) was found to consist 
 essentially of carbonates, quartz, sericite, and chlorite ; this is probably 
 more than usually calcareous. 
 
 The white mica on the foliation planes seems generally in smaller and 
 less distinct flakes than in the schists nearer " the anticline," and brown 
 mica is less common. The latter is, however, still seen in places. It is, e.g., 
 conspicuous in a pebbly schist within the phyllite zone J mile south-west 
 of Stucreach (151). It may be remembered that in the Dunoon phyllites 
 no brown mica has yet been observed (p. 22). Probably, too, the 
 white mica on the shore between Newton Bay and Strachur is in larger 
 flakes than at Dunoon. 
 
 The calcareous lenticles weather with an ochreous tint. Similar 
 lenticles also occur, but less frequently, in the bands of quartzite schist. 
 The weathered surfaces of the latter lenticles often show a number of 
 small projecting specks of opalescent quartz, even when none are observed 
 in the quartzite itself. There are all variations in the thickness of the 
 lenticles, from the thinnest streaks up to bands that can be mapped. In 
 the area north-east of Newton Bay there is no limestone outcrop which 
 exceeds 4 feet in thickness, and none have been traced except on the 
 shore ; the thickest occurs J mile north-east of Creag a' Phuill, but 
 it is not a good limestone. Most of the limestones are individually only 
 a few inches thick, but they come so near to one another that they form 
 a considerable proportion of the section. In an 18-inch band nearly J 
 mile north-east of Creag a' Phuill the calcite grains are clearly longer in 
 a particular direction along the foliation than in directions across it, and 
 this no doubt is generally so, the direction of elongation corresponding 
 to that of the other indications of stretching. The band referred to has 
 phyllite overlying it, but quartzite schist below. 
 
 The quartzites or quartzite schists mixed with the phyllites vary in 
 width from a few inches or less to J mile, as on the north-east side of 
 Ardchyline (133). In every section of intermixed phyllite and quartzite 
 repeated folding is seen, and there is no doubt that the thicknesses of 
 these rocks have been enormously increased in this way. Scars and 
 fresh fractures are of a pale buff or straw colour. The wider bands split 
 into fairly definite layers which are often from 3 to 4 inches to a foot in 
 thickness, and these layers are sometimes crossed by joints at right angles 
 to the strike. The grain of the rock is usually fine, and shows no indica- 
 tions of pebbles. 
 
 On the surfaces of many of the quartzite layers there are scattered small 
 depressions about the size of peas. These are of the same type as the 
 markings on the quartzites on the north-west side of Loch Fine, near 
 Inveraray, which the Duke of Argyll has called attention to ("On 
 certain Bodies, apparently of Organic Origin, from a Quartzite Bed near 
 Inveraray," Proc. Hoy. Soc. Edin., vol. xxi. p. 39). He supposes these 
 markings may represent the ends of worm tubes, such as those in the 
 pipe-rock or upper quartzite of Sutherland, etc. Good examples of such 
 markings may be seen in the burn a little over J mile south-east of St 
 Catherine's, on the shore a little over J mile north-east of Ard na Gailich, 
 and J mile north-east of Creag a' Phuill. In the last place there is a thin 
 
ARDRISHAIG PHYLLITE SERIES. 57 
 
 purplish phyllite between the different posts of quartzite, and the markings 
 weather with a rusty colour. This colour suggests the presence of weathered 
 pyrites, and we have often found either small specks of this mineral, or 
 its decomposition products, in or -close by the marks in other localities. 
 
 In the burn J mile south-west of St Catherine's some of the markings 
 on one of the planes of bedding project slightly, others form depressions 
 with slightly raised rims. It seems as if the rock substance composing 
 the marks was a little paler than that outside. We could see no pyrites 
 or ochre in this bed. On another bedding plane near the above there are 
 ochreous spots which weather into hollows : they are sometimes 1 inch 
 long in the direction of stretching, J inch in breadth, and rather less than 
 J inch in depth at right angles to the foliation planes. These last mark- 
 ings are certainly due to the weathering out of pyrites specks. C. T. C. 
 
 On the shore 1 mile west of Newton there are somewhat similar 
 bodies both in the quartzite schists and in the micaceous schists which 
 accompany them. They are very numerous, and are found along foliation 
 planes which are oblique to the dip. Most of them are ovate, without 
 any very clear outline. A few of them, however, are partially rectilinear, 
 and contain portions of crystallised pyrites. In others, where the material 
 is brown and rusty, the outline points to its having been derived from 
 pyrites. The shearing of beds containing pyrites has been responsible 
 for, at any rate, a large proportion of these markings. J. B. H. 
 
 The microscopic character of slide 5434, from a quart/.ite schist band 
 f mile S.S.E. of Aird Cottage, is described by Mr Teall as follows: 
 " Quartz, felspar (scarce), white mica, and chlorite. The last two in 
 detached scales and not very abundant. There are some small grains 
 of sphene." 
 
 Pebbly schists may be seen within the series on the shore, 150 yards 
 south-west, and ^ mile south-west, of Creag uam Faoilean ; T 6 mile north- 
 east of Stucreach ; at Stucreach, and extending thence for J mile south- 
 west along the shore. In the last exposure brown mica in moderately 
 large flakes is abundant on many of the foliation planes : some of the 
 quartz pebbles are nearly 2 inches long in the direction of stretching, 
 though only J inch broad. 
 
 As already mentioned on p. 37, green beds of the same type as those 
 further south-east may occur within this horizon, and garnets also are not 
 uncommon. The garnets may be clothed with a rim of chlorite, like those 
 in the adjoining garnet schist zone. 
 
 Crystals and specks of pyrites and of magnetite are also not uncom- 
 monly seen, surrounded with chlorite rims, e.g., J mile south of the " y " 
 of " Strachur Bay," and 200 yards north-east of Tigh na Criche. In the 
 latter locality the rim is sometimes of chlorite and quartz combined, and 
 is prominently extended in two opposite directions along the foliation 
 plane. The magnetite streaks are in places 1 inch long and J inch broad, 
 but when as long as this we could discern no crystal form. On the shore 
 160 yards N.N.E. of Ardnagowan Cottage, pyrites crystals reaching the 
 size of a pea are abundant, forming nearly half the bulk of some rather 
 quartzose bands, and they seem specially abundant along lines parallel to 
 the direction of extension. The corners of some of them are slightly 
 rounded, and there are growths of quartz and chlorite extending from 
 them in parallel directions. 
 
 On the shore 70 yards N.X.W. of M'Phun's Cairn there is an ex- 
 posure of schist, generally quartzose, which is unusually rich in pyrites. 
 There are some bauds, occasionally 6 feet thick, which consist almost 
 entirely of pyrites mixed with some galena and blende. In other bands 
 
58 GEOLOGY OF COWAL. 
 
 extremely thin streaks of these minerals run parallel with the foliation, 
 or there are scattered specks of pyrites. The specks often give us the im- 
 pression of being deformed crystals : they reach the size of a large pea. 
 The bands specially rich in pyrites seem quite part of the schist, and are 
 sometimes folded with axes parallel to the strike of the schist foliation. 
 The total breadth of the pyritous rock on the foreshore is about 8 yards. 
 It is not seen in the little bank at high-water mark, and probably there 
 is a fault running north-west, between the exposure and this bank. We 
 saw nothing of this rock except on the shore. The exposure is in places 
 overlain by a hard surface-breccia, with a ferruginous cement derived 
 from the weathering of the pyrites ; and in other places it is covered by 
 a white soluble efflorescence, which has a strong taste of sulphate of iron. 
 A specimen of the ore that contained more than the average of galena and 
 blende was sent to South Kensington for analysis, and was reported on as 
 follows by Mr Ernest A. Smith. 
 
 ORE FROM ARGYLLSHIRE. 
 oz. dwts. grs. 
 I ST : : 1 ! ^} Per ton of 2240 ,b, 
 
 Insoluble residue, mainly silica with a little mica, 24*50% ; zinc 3*5% ; 
 iron 30'0% ; lead 3'0% ; sulphur 30'5%. Together with alumina and 
 oxygen. Sample in one lump. Total weight 13,700 grains. 
 
 Outcrops of pyritous schist also occur on the shore south-east of Creggans 
 Point, beyond the hornblende schists. These are much like that near 
 M'Phun's Cairn, but we noticed no galena or blende. The exposures 
 extend for about 100 yards along the shore to the south, but there are 
 barren intervals here and there. The rock containing the pyrites is 
 chiefly a quartzose schist, but in the phyllite also there are streaks and 
 nodules of pyrites as large as a pigeon's egg. The pyrites specks are often 
 elongated in the same direction, and there are sometimes quartz growths 
 extending from their sides in this direction. A smaller exposure of 
 similar rock is seen in the bank of the raised beach, along the strike of 
 the rock on the shore. 
 
 .r.C 
 
 FIG. 25. x gV Shore near Newton Bay, Loch Fine. Ground plan of folded 
 phyllite and quartzite schist. Shaded areas are phyllite : direction of shading 
 shows direction of foliation. 
 
 The great contrast in colour and hardness between the sericite schist 
 and the quartzite schist shows off the bedding in the sea-coast sections 
 distinctly, and enables one to follow it through many complicated folds. 
 The thickness of any quartzite band varies according to the part of the 
 fold in which it occurs. It is always thinnest in the limbs of folds. At 
 the axes a band may be 7 to 8 inches thick, and yet in part of the limb may 
 be less than 1 inch, or may even be pulled out to nothing. 
 
AKDRISHAIG PHYLLITE SERIES. 
 
 59 
 
 A peculiarity of the folds here as compared with those at Duiioon, 
 and near Gairletter Point, etc., is that the limbs have very little ex- 
 tension along the strike of foliation, the crests or axes (using the word 
 axis now in its strict sense see footnote on p. 10) being often steeply 
 inclined and almost parallel to the dip of the foliation. They strike and 
 dip much with the foliation of the sericite schist, but their extension 
 along the strike is so small that the outcrop of any particular baud is often 
 more at right angles to the foliation than along it. This is seen on rather 
 a large scale on the shore 100 yards west of Leak (151). The folds are so 
 close that a band only a few inches thick in one place may in another be 
 several feet. If it had not been for the quartzites most of the folds 
 would have escaped notice, as distinct bedding is rare in the phyllites. 
 In the neighbourhood of the folded quartzites there is a close foliation in 
 the phyllites mixed with them r parallel to the axes of the fold ; in the 
 quartzites themselves there is usually but little distinct foliation. The 
 close foliation in the phyllites to a large extent obscures original 
 differences of bedding, but on careful examination the phyllites them- 
 selves may show indications of folds ; sometimes there are slight differ- 
 ences of colour along the bedding, and these different colours cross the 
 foliation. It is possible that the prominent foliation is itself a strain slip 
 foliation, and the earlier colour banding may represent a still earlier 
 foliation running with the bedding. The limbs of folds are sometimes 
 so closely appressed that the soft phyllite is squeezed out from between 
 the quartzite limbs for nearly the whole depth of the fold. 
 
 N . vV. 
 
 N.E 
 
 S . E. 
 
 FIG. 26. Shore mile S.S.E. of Aird Cottage, Strachur. Ground plan of folded 
 phyllite and quartzite schist. Shaded areas are phyllite : direction of shading 
 shows direction of foliation. Shows the attenuation of the long limbs in 
 the quartzite, and how the phyllite may be squeezed away from between 
 quartzite limbs. 
 
 Many of the veins of quartz, or quartz mixed with carbonates, are 
 also repeatedly folded, e.g., on the shore T 5 T mile south of Aird 
 Cottage. 
 
 If we examine vertical sections as nearly at right angles to the foliation 
 strike as possible, we can often see that it is the under limbs of anticlines 
 with axes hading north-west that are the longest and most thinned. But 
 one cannot say that this is so universally, for sometimes the reverse is 
 the case. In a burn f mile E.S.E. of St Catherine's Pier there is a 
 good section at right angles to the foliation, in a deeper cut than we 
 usually see on the shore, which shows the under limbs to be the longest. 
 On the south side of Creag a' Phuill the well-striped green and grey 
 phyllites on the south side of the quartzite show clear folds with the 
 
//GO GEOLOGY OF COWAL. 
 
 finest foliation crossing the folds : there are often slight throws, of about 
 J inch, accompanying the foliation, in the same way as described in the 
 Dunoon section (pp. 11, 12). 
 
 Even near " the anticline " centre there is seldom any doubt which foli- 
 ations are of " pre-anticline " age, and these are generally much more 
 pronounced than the later ones. On Loch Fine we cannot doubt that 
 the prominent foliation, and the abundant folding which accompanies it, 
 are also of "pre-anticline" age. The folds and foliation of anticline age seem 
 gradually to get less strong in a north-west direction from the anticline 
 centre, just as they do in a south-east direction. Even at the base of the 
 green beds the sharper folds of "anticline " age are not very prominent. 
 
 The coast sections give one the idea that the folding is even more 
 repeated than at Dunoon, and the sudden ending of various bands when 
 traced along the foliation helps to confirm this idea. The hornblende 
 schists near Leak and the quartzite near Ardchylirie show good examples 
 of this. 
 
 Besides the folding of the same age as the prominent foliation, we not 
 uncommonly see sets of folds, of later date, of much less depth and ampli- 
 tude. These plicate the early foliation without effecting much change in it, 
 and they rarely exceed an inch or two in depth. Generally speaking, the 
 strike of their crests is not far off east to west, and the crests succeed one 
 another in very close succession. They da not seem to affect the more 
 massive beds, quartzites, etc. In the pebbly schist and phyllite on the 
 shore J mile or more north-east of Stucreach there is a set of close folds, 
 the crests of which strike rather nearer east to west than the foliation, 
 and the axes hade north-west more steeply. One- third mile north-west of 
 Leak there are small folds with axes hading north-west less steeply than 
 the foliation, and their under limbs are slightly thinned. Between and 
 J mile S.S.W. of Aird Cottage some close small folds strike 16 to 23 
 north of west, and have axes which are almost vertical, or hading S.S.W. 
 In the same locality there are other folds, with nearly vertical axes, which 
 cross the preceding set nearly at right angles : apparently the last men- 
 tioned set is the later. At the point J mile S.S.E. of Aird Cottage some 
 prominent small folds have crests striking 29 south of west, and axes 
 hading south-east. These are stronger than most of the later folds in the 
 neighbourhood, and are accompanied by strain slips and thinning of the 
 under limbs of anticlines. The axes hade south-east, but sometimes at so 
 low an angle that they are almost horizontal. 
 
 In the albite schists near Achadunan (126) it is also common to see 
 sets of small late folds with axes hading south-east, and generally strik- 
 ing nearer east and west than the strike of foliation. Perhaps these are 
 of approximately the same age as the late folds in the Ardrishaig phyllites. 
 They may both represent the latest "anticline" folds mentioned on 
 p. 26. C.T.C. 
 
 CHAPTER V. 
 
 EPIDIOEITES, HORNBLENDE SCHISTS, AND RELATED 
 CHLORITE SCHISTS. 
 
 The epidiorites, and hornblende and chlorite schists connected with 
 them, are much more abundant in the north-west third of the area than in 
 other parts. Even the most schistose of these rocks are generally harder 
 
EPIDIORITES AND RELATED SCHISTS. 61 
 
 than the other schists, and so often stick up in field exposures ; they are 
 traced with comparative facility and afford a great help iu working out 
 the physical structure. 
 
 They are never vesicular or scoriaceous, and seem iu places to have 
 given rise to a small but perceptible amount of contact metamorphism in the 
 schists at their sides. Hence it is believed that they represent old intru- 
 sions, and not lava flows. On the shore of Loch Fine J mile west of 
 Newton (151) the quartzite schist on either side of the hornblende schist 
 is baked and altered. A similar alteration is noticed J mile south-west of 
 Castle Lachlan in the schist next to a felspar-chlorite schist, J mile west of 
 Tom na h' lolaire (171) in a calcareous schist next to a hornblende schist, 
 and on the north side of Auchalick Bay (181). 
 
 We cannot in Cowal point to any clearly visible transgression of 
 bedding by these schists. The north extremity of the hornblende 
 schist on the north side of the burn that flows into Loch Loskin (184) is, 
 however, of a very irregular shape and strongly suggestive of an intrusive 
 rock. One of the hornblende schists both on the west and on the north 
 of the Bishop's Seat seems also gradually to change its stratigraphical 
 horizon (see p. 174). The hornblende schists are seen to be repeatedly 
 folded with the sedimentary schists (see, e.g., pp. 174, 176, 213), but it is 
 possible, notwithstanding this, that these sedimentary rocks were partly 
 folded and sheared before the intrusion of the rocks now represented by 
 the hornblende schists, etc. There is no evidence, however, to show that 
 this was the case. 
 
 They do, however, in the main, keep to the bedding of the schists of 
 sedimentary origin, and they have undergone the same foldings as these. 
 In the west and north-west parts of Cowal they occur on the horizons of 
 the Glendaruel or Loch Tay limestone, and of some other beds which lie 
 on the north-west side of this. Between this limestone and the green beds 
 on the south-east side of " the anticline " very few bauds of epidiorite, etc., 
 have been mapped, but it is believed that some may have escaped notice, 
 the thickness of the bands near Ardeiitiimy, and between there and Uig, 
 being generally not more than a few yards. W.G., C.T.C., J.B.H. 
 
 There is a special danger of confusing some of these old igneous rocks 
 with green beds. In both, chlorite may be a prominent constituent ; in 
 both, ferriferous carbonate spots, and quartz strings stained with epidote, 
 are common. In hand specimens and microscope slides it is sometimes 
 impossible to decide with confidence whether a certain rock is a green bed 
 or a schist derived from an originally massive igneous rock. Isolated 
 field sections may even leave one in doubt about this question, but after an 
 examination of all the exposures belonging to the doubtful bed it is 
 generally possible to give an answer with a fair amount of confidence. 
 We may, for instance, find indications of pebbles, or bands of pebbles, in 
 some of the exposures, or find the rock passing, especially as we proceed 
 inwards from the margins of the band, into one of which the original 
 igneous character cannot be doubted. Occasionally small specks and 
 streaks of opalescent quartz may occur in the epidiorites, but these specks 
 are, fortunately, in rocks which tell their own tale of igneous origin 
 clearly. The specks of carbonate in these old igneous rocks, and also those 
 in the green beds, are not confined to the surface of the rock, and they have 
 not originated as a consequence of weathering. They occur throughout 
 thick masses of rock, and are an essential part of the soundest varieties. 
 We suppose them to have been formed as a result of the alteration of 
 hornblende into chlorite or black mica. In some bands the specks of 
 carbonate are so numerous and large that the beds containing them acquire 
 
62 GEOLOGY OF COWAL. 
 
 the aspect of limestones. This is seen in the band | mile south-west of 
 Stronchullin Hill (163 south-west), and in that on the south side of Coire 
 Athaich (173 north-east). The last mentioned band was, indeed, originally 
 mapped as a limestone. 
 
 Opaque white patches of leucoxene (decomposition product after 
 ilmenite) are at times large enough to be distinguished by the unaided 
 eye, and may have ilmenite kernels. 
 
 In the bands which occur on the south-east side of " the anticline " the 
 hornblende is represented by pale green shreds of fibrous actinolite. 
 This can generally be made out with a hand lens. The felspar is repre- 
 sented by streaks and patches of saussurite, generally pale grey by 
 reflected but almost opaque to transmitted light. These streaks may 
 occur either closely parallel, or in a mesh, according as the rock is more 
 or less perfectly foliated : in either case, they are a help in distinguishing 
 these rocks from green beds. Slide 2832, from the band exposed on the 
 coast 230 yards N.N.W. of Hunter's Quay, is thus described by Dr Hatch : 
 "Flasers diabase or epidiorite (?). Well-marked flaser structure. 
 Lenticular masses and layers of green fibrous hornblende (actinolite) 
 alternating with dirty coloured almost opaque masses of very altered 
 felspar (probably saussurite), which show here and there a tendency 
 to the development of eyes. Leucoxene in isolated turbid grains. 
 Probably a sheared and metamorphosed diabase or epidiorite." We 
 noticed here and there in the coast section from which the rock described 
 above was procured, some squarish sections of saussuritized felspar, reach- 
 ing to | inch in length, but these are not common. In the exposure 
 west of Blairmore pier the hornblende, again pale green, occurs in some- 
 what stouter and more conspicuous forms, often about -^ inch in breadth. 
 
 The first hornblende schists noticed after passing north-west of " the 
 anticline " are some thin outcrops never apparently more than 16 feet 
 thick and not often so much which occur near the base of the green 
 beds, sometimes a few feet above and sometimes a little below. Such 
 are seen at the top of Creag Bhaoigh (152), on the north and east of Cruach 
 nam Mult (134), and on the west side of Birmein an Fhidleir (134). 
 These thin beds are, as we might expect, well foliated throughout. The 
 hornblende in them has not been replaced by chlorite in any marked 
 degree : it is dark green in hand specimens and less fibrous than the 
 variety which exists in some of the Cowal hornblende schists. The same 
 general type continues in the different bands of hornblende schist we meet 
 with further north-west as far as the graphite schists, and is seen best of 
 all in the sills which almost constantly accompany the Loch Tay lime- 
 stone. We may therefore speak of this type as the Loch Tay type. 
 
 In a wide band in the green beds J mile east of the " 1 " of 
 " Maol Odhar" (162) the foliation is sometimes less perfect. The horn- 
 blende appears in shapes up to ^ inch in breadth, which have a 
 general parallelism of direction, but do not coalesce together into lines. 
 Some scars of this exposure are very blocky. In the probable continua- 
 tion of this band south-west, yellow mica may occur in abundance, e.g., 
 f mile south of the "i" of " Strondavain" and J mile south of An 
 Cruachan. 
 
 The sill in the Loch Tay limestone in the burn a little more than J 
 mile south of the " u " of " Creag Dhubh " appears to be about 30 feet 
 thick. This is perhaps about the average thickness, but near Ardkinglas 
 it seems to be thicker, the outcrop being unusually wide even for the dip 
 slope. In the burn J mile south-west of Glensluan there are veins of 
 epidote, quartz, and a little carbonate between the hornblende schist and 
 the overlying portion of limestone. The epidote is in prisms of a pale 
 
EPIDIORITES AND RELATED SCHISTS. 63 
 
 yellowish-green colour ; these occasionally attain a length of 1 \ inches, and 
 are sometimes slightly bent. 
 
 In the burn J mile south-east of Arduo there is a sill a little below 
 the base of the Loch Tay limestone which has an apparently greater 
 thickness than the sill within the limestone ; but outcrops on this horizon 
 are not often seen in the north part of Cowal. C.T.C. 
 
 In the area west of Glendaruel the hornblende schist in association 
 with the Loch Tay limestone is sometimes found below the limestone and 
 at some distance from it, or it may be resting on the limestone, or it may 
 be at some distance above it. It must be borne in mind that the horn- 
 blende schist represents an intrusive rock, and that the region was 
 intensely folded after the intrusion. It is not surprising, therefore, to find 
 that sections along the line of strike show variations of character in the 
 relative numbers, sizes, and positions of the hornblende schist bands. In 
 some sections the hornblende schist does not appear at all, while in the 
 next burn, at a short distance, bands of various thicknesses may be found, 
 either in the limestone above, or in the limestone below it, or in both 
 of these positions. Along the steep west slope of Glendaruel, there are 
 numerous burn sections, crossing the strike of the beds, which exhibit 
 such differences ; it is clear that the hornblende schists are not necessarily 
 continuous, but that they represent a series of sills which have been 
 injected along slightly different horizons and then subsequently folded ; 
 they vary considerably in width of outcrop, and this variation is certainly 
 attributable in many cases to differences in the amount of folding. These 
 different sills are all composed essentially of hornblende and felspar. 
 Biotite is generally common. Garnets, epidote, magnetite, pyrites and 
 leucoxene occur as accessories. Chlorite and calcite are rare. The horn- 
 blende may be green, dark green, or nearly black; the dark varieties 
 are very common. In the finer grained specimens actinolite is often 
 the common hornblende, disposing itself in needles along the foliation 
 planes. In the coarser types the hornblende occurs in dark green stumpy 
 prisms. In these types the foliation is less perfect than in the finer 
 grained types, which are usually highly schistose throughout. The 
 coarser varieties, especially when they occur in big masses, sometimes show 
 very little foliation in their interior coarser portions, though they are finely 
 schistose in their upper and lower portions. Even the coarsest specimens 
 are finer in grain than some of the bands found to the north-west of 
 them, near Stralachlan. J.B.H. 
 
 As elsewhere mentioned (p. 48) garnets sometimes occur in the horn- 
 blende schists within or near the garnet schist zone. Some are seen in a 
 thin exposure within the limestone on the west side of Ardno burn J 
 mile south-east of Ardno, in a band under a limestone J mile slightly 
 north of west of the first "C" of " Cruach nan Capull" (133), and in a 
 locality | mile north-west of the same letter. 
 
 The hornblende schists that accompany the limestone which is a little 
 south-east of the graphite schists, are of the same type as those with tho 
 Loch Tay limestone. The bands f mile south-west of An Carr (152), 
 arid on the west side -of An Carr, near the top, are also of this character. 
 
 The bands on the north-west side of those mentioned in the last 
 paragraph are generally of a rather different character. Most of the horn- 
 blende is pale green in hand specimens and colourless in thin slices, 
 belonging to the variety called tremolite. In the more sheared varieties 
 chlorite is often abundant, and sometimes it prevails to the exclusion of 
 hornblende. In some bands certain portions are unusually poor in felspar, 
 and appear to be ultrabasic. We may call this type the St Catherine's 
 type, as it occurs in t\vo broad bands near this place. It is not probable 
 
64 GEOLOGY OF COWAL. 
 
 that there is any sharp line between this and the Loch Tay type, and 
 we may be in doubt as to which type a particular band should be referred, 
 but in the extreme forms the difference is readily discerned. 
 
 The two broad bands at St Catherine's are of much the same character. 
 The south-east band comes down to the sea-coast on the south-west side of 
 Ard na Gailich, between 140 and 370 yards from the point, and shows itself 
 in scars near the top of the wood between St Catherine's and Ardchyline. 
 The north-west baud is seen on the shore south-west of St Catherine's, 
 from nearly J mile to slightly over -^ mile from that place, also at the 
 back of the raised beach, and in the island-like knoll on which the chapel 
 of St Catherine stands. There are old quarries on an extensive scale 
 east of the knoll, and most of the stone used in building Inveraray 
 Castle, and in rebuilding it after the fire, is said to have been procured 
 from these. The stone is reputed an excellent building stone, extremely 
 durable, and yet comparatively easy to cut. It has long been known 
 under the name of " potstone." 
 
 A specimen of the chief variety obtained from the quarry 50 yards 
 north of St Catherine's Chapel has been sliced (slide 5058), and is thus 
 described by Mr Teal I : " The main mass of the rock is composed of 
 chlorite and white hornblende (tremolite). The tremolite forms irregular 
 patches consisting of individuals confusedly aggregated. The chlorite 
 also forms aggregates. It is faintly pleochroic in green and brown tints. 
 .... One patch looks like unaltered hypersthene. With this doubtful 
 exception, the whole rock must be looked upon as a pseudomorph. In 
 the process the original minerals have not only been replaced by others of 
 different composition, but their forms have also been destroyed. The 
 rock in its present state may be termed tremolite-chlorite rock." In the 
 hand specimen, the tremolite appears of a pale greenish tint. Some of it 
 forms stout lumps nearly ^ inch long. 
 
 Mr J. Wallace Young gives (" Miscellaneous Notes on Chemical Geo- 
 logy," Trans. GeoL Soc. Glasgow, vol. iii. p. 28) an analysis of foliated 
 chlorite from St Catherine's, Loch Fine, but he does not state the exact 
 locality from which he obtained the specimen. He describes the specimen 
 as follows : " Colour, blackish-green ; lustre, pearly ; consists of long, 
 narrow folise cohering together, rendering the mineral almost fibrous in 
 appearance. The thin leaves nearly transparent. When in a state of 
 very fine sub-division, it is entirely decomposed by sulphuric acid. 
 Sp. gr. 2-781 at 15-5 C. 
 
 Silicic Acid, .... 33*55 
 
 Alumina, 15 '00 
 
 Ferrous Oxide, .... 10'78 
 
 Magnesia, . . . . . 2 9 '7 3 
 
 Water (by difference), . . 10*94 
 
 100-00 
 
 " No chromium present. In one specimen the chlorite was associated 
 with a ferriferous dolomite in rhomboidal crystals. Its composition is 
 as follows : 
 
 Sp. gr. 2*935 at 15*5 C. 
 Carbonate of Lime, . . . '53*00 
 Iron, . . . 8-16 
 
 ,, Magnesia, . . 39*00 
 
 100*16 
 Trace of Manganese." 
 
EPIDIOKITES AND RELATED SCHISTS. 65 
 
 Part of the rock on the shore 260 yards south-west of the pier, is very 
 closely foliated and soft, and we could see no hornblende in it. But it did 
 not seem possible to separate it by any sharp line from the more massive 
 rock with clear hornblende on the north-west, and the soft rock itself con- 
 tains small eye-like pieces that are massive. Twenty yards further south- 
 west, the rock is very thinly foliated, and contains much black mica, and on 
 the foliation planes there are closely felted dark green actinolite needles. 
 The needles are as much as J inch in length, and they lie in different 
 directions on the foliation planes, but do not cross them. The main por- 
 tion of the rock near this is massive, and weathers with a brownish-orange 
 tint ; in some parts the white elements are more prominent than others ; 
 black hornblende in " eyes " of the size of a pea is occasionally seen, 
 as well as the tremolite. There are some veins, as much as 3 inches wide, 
 which contain epidote prisms, dark green chlorite, and some calcite. 
 The veins are often nearly vertical, and strike nearly east to west The 
 epidote prisms are sometimes seen penetrating into the calcite ; they 
 usually run across the vein from side to side, and sometimes attain a length 
 of 2 inches or more. In some places they are distinctly bent ; we see the 
 bending most pronounced when the long axes of the prisms are at right 
 angles to the foliation strike ; but when the long axes are parallel to the 
 strike, they may also be waved to some extent. Near them are also thin 
 bands which consist of asbestus and chlorite, with here and there small 
 eyes of hurnblende encircled by the asbestus fibres. 
 
 On the shore T V mile south-west of the pier, the part of the band next 
 to high-water mark is massive and hard and sharply jointed : blades of 
 hornblende are prominent on the weathered face. Near low-water mark, 
 and separable from the rock just described by a fairly definite line, is a 
 much darker variety, weathering in big blocks with rounded outlines. 
 This is much softer than the rock near high-water mark. In hand speci- 
 mens it shows pale green " eyes " of hornblende, attaining the size of peas, 
 embedded in a soft dark matrix in which brown mica is abundant. A 
 specimen of the paler rock was examined by Mr Teall (slide 5057), and 
 he sees in it " hornblende, chlorite, felspar, quartz, epidote, carbonates, 
 and brown mica (scarce). Indications of micropegmatitic structure in 
 places." The quartz specks are pale blue and opalescent in the hand 
 specimen ; the felspar is abundant and in moderately large pieces. The 
 softer ultrabasic-looking rock from the same locality was also sliced (slide 
 5059), and examined by Mr Teall. He calls it a tremolite mica schist, 
 and sees in it "tremolite, brown mica, a little green hornblende, and 
 some aggregates of sphene granules." The mica flakes lie parallel to one 
 another, and give rise to the foliated look of the rock ; they are closely 
 intermixed with the tremolite, not in separate layers. 
 
 Bluish opalescent quartz, like that in specimen 5057, is also seen in a 
 massive portion of the south-east band of epidiorite at a point T 5 g- mile 
 north-east of Ardchyline. Mr Teall thus describes this rock (slide 5056), 
 " hornblende (irregular), quartz, epidote, felspar (scarce), white sphene 
 with kernels of iron ore. Epidote-amphibolite or epidiorite. Almost 
 certainly an altered dolerite." The sphene is in pieces quite large enough 
 to be distinctly seen with the naked eye. In the exposure ^ mile 
 south-east of Ard na Gailich the sphene streaks are sometimes \ inch 
 long. Many of the epidiorite blocks, whether distinctly sheared or not, 
 in the sea-wall about 100 yards north-east of the pier, also show spots of 
 blue opalescent quartz and sphene streaks with iron-ore kernels; the 
 streaks often run parallel to one another and the other rock constituents. 
 
 Both bands of epidiorite are in places mixed with an unusually soft 
 and thinly foliated rock in which no hornblende is to be seen by the 
 
66 GEOLOGY OF COWAL. 
 
 naked eye. Such schists are seen in the burn 260 yards south of, 150 yards 
 E.S.E. of, and -J- mile south-east of the pier. We were long in doubt 
 whether these might not be chloritic green beds, rather than specially 
 sheared portions of the epidiorites. Green beds certainly do occur within 
 the Ardrishaig phyllites (see p. 37), and it was quite possible to suppose 
 they might be mixed with epidiorite sills most intimately. Similar 
 schists also occur alternating in thin bands with the phyllite and quartzite 
 schist next to the epidiorites. Sometimes the bands are only 6 to 8 inches 
 thick, but occur in a certain breadth of exposure in almost as great propor- 
 tion as the phyllite, etc. We have, however, never seen any clear pebbles 
 in the thin schists referred to, and Mr Hill finds abundant evidence, on the 
 other side of Loch Fine, of the gradual passage of such schists into other 
 rocks of the igneous origin of which there can be no doubt, and this in 
 localities where no green beds are known. Mr Hill states that the more 
 finely foliated chloritic parts often occur near the outsides of the igneous 
 masses parts which would inevitably be exposed to more intense shearing 
 than the interiors and also that there are many thin sills which are com- 
 posed throughout of soft chlorite schist. A specimen of one of these 
 schists from the burn 130 yards east of the pier, was sliced (slide 5060), 
 and examined by Mr Teall. It was found to be composed of chlorite, 
 carbonates, quartz, leucoxene, and a little white mica or talc. There was 
 nothing in the slide to indicate the original igneous character. 
 
 The two bands at Creggans Point are much like those at St Catherine's. 
 The north-west band is very schistose near the base, but its interior is 
 massive and shows abundant broad tremolite pieces. The north-east 
 continuation of this band is exposed at a place \ mile south-west of the 
 "g" of "Creagan an Eich." It is very massive, and in some parts 
 displays hardly any indications of schistosity. The tremolite pieces are 
 sometimes nearly \ inch in breadth : there is also a dark, almost black, 
 hornblende in some parts of the exposure. Still further north-east 
 the band seems to become thinner, and near the head of Eas Dubh there 
 is a series of outcrops on approximately the same horizon which are 
 generally so thin and so close together that in mapping they have to be 
 generalised. These thin bands are pale green chlorite schists, and do not 
 in themselves testify to their igneous origin. 
 
 On the shore 140 yards north of Stucreach (141) there is a very blocky 
 epidiorite in which the hornblende appears black in hand specimens. The 
 foliation is not pronounced, but the white and black constituents have their 
 greater lengths in rough parallelism. Near the base of the band on the 
 south-west side the grain of the rock is finer than in the interior, and 
 there are indications of porphyritic felspars. There are many veins of 
 chlorite and ferriferous carbonate, and thin streaks edged with yellow 
 mica, which cross the general direction of the rock constituents. Two to 
 three feet below the main outcrop, and separated from it by a quartzite 
 schist, is another thin band of epidiorite, also with indications of 
 porphyritic felspars. 
 
 The exposure on the coast J mile north-east of Leak is like that near 
 Stucreacb, and probably is a continuation of the same band. 
 
 At Creag nain Faoileann (141), and several places on the coast as far as 
 \ mile to the south-west, there is a close and evidently much folded series 
 of thin epidiorite schists. Some of them resemble the Loch Tay type 
 more than the St Catherine's. C.T.C. 
 
 The epidiorites, etc., on the north-west side of a line drawn from Newton 
 (151) to a little east of Lephinchapel arc rather allied in character to those 
 at St Catherine's, but are often more massive, and contain great eyes of 
 
EPIDIOKITES AND RELATED SCHISTS. 67 
 
 epidotised epidiorite or epidosite. We may speak of the type in this 
 district as the Stralachlan type, as it is found in greatest strength 
 between Loch Fine and the valley- of Stralachlan, in the more siliceous 
 part of the Ardrishaig phyllites. 
 
 In the area between Stralachlan and Loch Fine the epidiorites, etc. form 
 huge irregular masses behaving on a large scale like sills with irregular 
 protrusions, the longer axes of which coincide with the strike of the 
 main mass, and of the quartzites in which they are intruded. One 
 reason for the size of the masses found in the field compared to the 
 exposures of the Loch Tay limestone type may be the different inclinations 
 in the two areas. But apart from this, it is certain that the Stralachlan 
 epidiorites far exceed in dimensions those of the Loch Tay limestone type. / 
 
 The Stralachlan epidiorites differ amongst themselves in composition and 
 texture. Not only so, but in the same intrusion various types may be ' 
 observed. A few of these intrusions will now be described. 
 
 The strip of land between Newton Bay and Lachlan Bay is almost 
 entirely made up of these intrusive hornblendic rocks. The ground is 
 occupied mainly by two huge sill-like protrusions, each about 1J miles in 
 length. The most easterly sill has an average width of 300 to 400 yards. 
 This sill is separated from the sill to the west by a strip of sediment 
 30 to 100 yards in width. The westerly sill is more irregular, its eastern 
 and western boundaries are roughly parallel with each other, and with 
 the adjoining sill, but it is often sub-divided, and is nearly bisected by strips 
 of sediment. In places the sedimentary schist appears to entirely isolate 
 parts of the hornblende schist, but it will be convenient for the purposes of 
 description to regard it as one mass, of which the widest part is J mile across. 
 
 The most easterly or Barr nan Damh sill will be described first. The 
 rock consists essentially of coarse hornblende and felspar in variable 
 proportions. As a rule it is unsheared except near the outer edges, and 
 may be regarded as a modified diorite. The mass as it is traced along 
 presents every variety of structure. It is mostly a coarsely crystalline 
 rock. Some zones are made up of little else but crystals of black 
 hornblende packed together, in stumpy prisms of the size of marbles, 
 but the hornblende most commonly occurs in green fibrous lath-shaped or 
 tabular shapes. While in some places the hornblende occupies the greater 
 part of the mass, in others the felspar predominates over the hornblende, 
 and this perhaps at no great distance from the more basic zones. Again, 
 in other parts there may be an intimate admixture of hornblende and 
 felspar, the felspar usually occurring in lath-shaped forms, sometimes 
 enclosed in fibrous hornblende. In many cases it is clear that the felspars 
 crystallised out before the hornblende. The felspars are probably 
 original, and some of the hornblende may be so also. Scattered crystals 
 of green epidote and occasional grains of blue quartz are seen. 
 
 Mr Teall describes a specimen sent to him for slicing as follows : 
 
 " 4000 : Coarsely crystalline massive rock. Pale green hornblende in 
 blades often J inch long in greyish matrix." 
 
 " Microscope : Uralitic hornblende, a saussuritic aggregate of water 
 clear felspar and granular epidote, irregular patches of sphene (leucoxene), 
 and aggregates of chlorite. Epidiorite." 
 
 A common structure is the aggregation of felspar and hornblende 
 crystals in shapes corresponding roughly to those of the hornblende prisms. 
 These crystalline aggregates are very numerous in this area. Instead 
 of porphyritic crystals of hornblende, the outlines of porphyritic horn- 
 blende crystals occur, but the mineral substance itself that builds up the 
 crystal is an admixture of hornblende and felspar. 
 
 In some of the coarser epidiorites of the Stralachlan area, great lath- 
 
68 GEOLOGY OF COWAL. 
 
 shaped crystals of dark tibrous hornblende attain a length of 2 or 3 inches, 
 the crystals being free from any admixture of felspar. These rocks are, 
 strictly speaking, amphibolites, but they pass insensibly into the 
 ordinary epidiorites, and cannot be separated from them in the field, 
 
 At the south-west extremity of this Barr nan Damh mass, at Ban* an 
 Longairt, the rock assumes yet another character. It becomes so acid as 
 to present quite a granitic appearance in the field. Porphyritic crystals 
 of felspar are thickly scattered through the rock, some of them retaining 
 a perfectly crystalline outline. Crystals of orthoclase can be made out 
 with the Carslbad type of twinning by the aid of a lens. These crystals 
 of felspar are by far the most prominent of the minerals of which the 
 rock is composed. Blue quartz grains without crystalline shape are 
 scattered broadcast through the rock. Epidote is also common. Horn- 
 blende occurs in grains or as fibrous plates packed together. The 
 hornblende alone in the rock gives an appearance of schistosity, the 
 plates of hornblende usually lying along definite planes. Throughout 
 the rock there are distinct planes of movement, the felspar crystals 
 on approaching these lines of strain becoming pulled out, bent, and 
 broken. Besides the fibrous hornblende a little mica occurs along the 
 planes of schistosity. Between these undulating schistose planes the 
 crystals appear to have been unaffected by the movement, and are 
 arranged without any definite orientation ; but as these planes are 
 approached there is a tendency for the crystals to lie with their long 
 axes parallel to these planes. In this granitic type the felspar crystals 
 retain their crystalline form, and the surrounding schistose material 
 is hornblende. In the more basic varieties described before, the horn- 
 blende stands out in large well-formed crystals, and the inclosing 
 schistose material is felspar. In this latter case, however, the felspar is 
 probably all secondary, and certainly some of the hornblende is, as 
 sections under the microscope reveal uralite, and it seems likely that 
 these basic rocks have been derived from gabbros. On the other hand, 
 the granitic parts of the mass are distinctly more acid, and these have 
 suffered the least change ; the greater portion of the minerals we now 
 see being original. The more basic portions have broken down earliest, 
 and it is these masses that have been converted into hornblende schists, 
 which will be referred to later in dealing with the westerly sill. 
 
 The following is Mr Teall's description of a specimen of the more acid 
 type from this area. 
 
 " 4005 : Massive crystalline rock, epidote, felspar, and blue quartz, 
 easily recognised with a lens. 
 
 " Microscope : Felspar (sometimes striated), in large and more or less 
 idiomorphic individuals, and also as a constituent of a quartz felspar 
 mosaic. Epidote in local granular aggregates, green hornblende in 
 ragged aggregates, brown mica, iron ores, and apatite. Quartz in large 
 grains, and also as a constituent of a mosaic." 
 
 Before dealing with other varieties of epidiorite in this area it will be 
 convenient to describe a feature that is common to all of them, from the 
 most acid to the most basic type, and from those of the coarsest crystalline 
 structure to the finest-grained schistose varieties. In all these intrusive 
 masses cores or eyes of a yellowish-green material are common. These 
 eyes vary in size from a few feet to a few inches, and seldom show 
 schistosity : where the rock is schistose the foliation planes encircle 
 them : sometimes they are made up almost entirely of granular epidote. 
 Often hornblende crystals are scattered through them, especially in the 
 more crystalline masses. : They may also contain blue quartz, and in 
 some instances the cores differ little from the surrounding rock, except 
 
EPIDIORITES AND RELATED SCHISTS. 69' 
 
 in the colour which is due to the presence of granular epidote. The 
 colour of these eyes makes them very conspicuous objects in the field, and 
 from their general massive habit and the tendency of the foliation planes 
 to flow round them, it is evident that they belong to the earlier stages of 
 the history of the mass. The hornblende has been the first mineral to 
 crystallise out, occurring generally in the form of short stumpy prisms, 
 but occasionally in long blades of fibrous hornblende or actinolite. In 
 these coarser eyes a tendency to foliation can sometimes be seen in the 
 arrangement of the hornblende crystals with their long axes in one 
 direction. These eyes sometimes pass insensibly into the inclosing 
 mass, or they may be seen sharply divided from it. In the mass at 
 Creag Bhreac, just above the schoolhouse at Stralachlan, the hornblende 
 schist is coarsely crystalline. The hornblende crystals are as large 
 as peas. 
 
 In this mass one of these epidotic eyes attains a length of 5 to 6 
 feet, its texture being very fine-grained compared to the inclosing mass. 
 The line between the two is very sharp. Quite close to this eye, however, 
 a smaller eye is seen about 1 foot in length ; in this case the hornblendic 
 rock and the epidotic eye pass gradually into one another, hornblende 
 crystals similar to those occurring in the main mass being scattered 
 through the outer zones of the eyes, but in this instance the central 
 portion of the eye is free from hornblende, and is of an ordinary fine- 
 grained granitic texture. In some cases the hornblende crystals occupy 
 not only the outer zone of the eye but are scattered through the central 
 portions, and there is nothing to distinguish these portions from the main 
 mass excepting the yellowish-green colour due to the presence of epidote, 
 and the more acid character indicated by the less quantity of hornblende. 
 
 In the very fine-grained chlorite felspar schists and chloritic hornblende 
 schists the eyes are much smaller, and are homogeneous throughout, con- 
 sisting entirely of epidosite. 
 
 A specimen of one of these eyes from a fine-grained chlorite hornblende 
 schist was examined by Mr Teall his report is appended. 
 
 " 4003 : Eye in epidiorite. Kilbride Chapel, Stralachlan. 
 
 " Compact yellowish-green rock veined with quartz. 
 
 " Microscope : Granular epidote with very little quartz, containing 
 carbonates as well as quartz." 
 
 There occur in the Barr nan Damh sill two smaller sills of a different 
 type, which appear to be distinct in character and of a different age to 
 the rock in which they are found. One is seen on the western boundary 
 of the sill about J mile south-west of the summit of Barr nan Damh, 
 the other is quite inclosed by the sill, but occurs near its eastern boundary 
 about f mile south-west of the summit of Barr nan Damh. The former 
 is about 400 yards in length and 30 yards in width, and the latter about 
 80 yards in length and 20 yards in width. In the field they can be 
 readily distinguished by the rusty colour they assume on weathering. 
 At a distance they look like decomposing basalts, and in their harder 
 portions they exfoliate. The smaller sill is so decomposed that it is 
 difficult to obtain a fresh specimen, but is in reality more fissile and 
 schistose than the epidiorite surrounding it. It consists mostly of a 
 very fibrous hornblende circling round crystals of felspar, many of which 
 are somewhat large : it passes insensibly into the hornblende schist on 
 either side. 
 
 The larger rusty mass, J mile south-west of Barr nan Damh, is much 
 fresher in appearance. It weathers rusty brown, and shows a peculiar 
 coarse flaggy structure parallel to the foliation dip. It is composed 
 principally of fibrous hornblende, and it is almost impossible to obtain 
 
70 GEOLOGY OF COWAL. 
 
 a fresh specimen with the hammer, in striking contrast to the fresh 
 epidiorite surrounding it which is very compact and fresh. No clear 
 junction can be detected between this rusty hornblende schist and the 
 epidiorite. It rather seems as if the epidiorite was later than the rusty 
 sill, and had modified its outer boundary, which has been partially 
 recrystallised. It is not certain that the rusty sill is the earlier of the 
 two, but the evidence points in this direction. This type of sill is 
 exceedingly rare, and these are the only instances of their occurrence in 
 this area, but we have observed similar sills in the neighbourhood of 
 Locbgilphead. A specimen from one of these Lochgilphead sills was 
 examined by Dr Hatch. It is composed of colourless blades and prisms 
 of tremolite, embedded in a confused felted aggregate of fibres of horn- 
 blende and scales of chlorite, together with a little magnetite in dispersed 
 granules. 
 
 The big easterly or Barr nan Damh sill having now been described, the 
 great westerly mass will next be dealt with. As previously stated, this 
 mass lies close to the Barr nan Damh sill, being separated from it by a 
 strip of quartz schist. It is in the form of a compound mass giving off 
 numerous branches. Besides the coarse types of rock described in the 
 Barr nan Damh sill, its outer portions and some of its branches consist of 
 finer-grained hornblende schist just as foliated as the hornblende schists 
 of the Loch Tay limestone type. The epidotic eyes or cores are as 
 prevalent throughout this mass as in the easterly sill, and are as abundant 
 in the fine-grained schistose varieties as in those of coarser crystalline 
 texture. 
 
 The westerly boundary of the mass is very fine-grained and highly 
 sheared. The mass extends near the coast in a sill over | mile long, 
 and between 60 and 70 yards wide. This sill meets the coast nearly 
 1J miles south-west of Barr nan Damh. It is so sheared that in some 
 places hornblende crystals can 110 longer be detected, and the hornblende 
 has largely been converted into chlorite. 
 
 Mr Teall thus describes a specimen sent to him : 
 
 " 4006 : Green schist with pronounced lustre on the surface of 
 schistosity. 
 
 "Microscope: Felspar, water clear and often showing traces of lath- 
 shaped formes, chlorite, and irregular patches of leucoxene. Quartz and 
 carbonates both present, but not abundant. Felspar chlorite schist." 
 
 This fine-grained felspar chlorite schist can be followed into the main 
 mass, which is a coarsely crystalline epidiorite. Close to the locality 
 where this fine-grained portion occurs, bands and patches of the coarsely 
 crystalline rocks are found, one of which appears to be later than, and to 
 have cut through, the felspar chlorite schist. The boundaries between the 
 two rocks are obscured by basalt dykes, and their relations are not clear. 
 It is possible that the basalt dykes may have come up along lines of fault, 
 which the dykes have succeeded in hiding. Against this supposition, 
 however, must be set the fact that the felspar chlorite schist does not seem 
 to have been thrown by faulting : the sill on both sides of the coarsely 
 crystalline epidiorite taking an even course as if there had been no 
 disturbance. It seems probable, therefore, that the basalt dykes have 
 seized on the intrusive junction of the epidiorite with the felspar chlorite 
 schist, and having made their course along the margin the original 
 junctions have now been destroyed. The intruding mass is a very 
 coarsely crystalline hornblendic rock with hornblende crystals of the size 
 of peas closely packed together in a dark matrix. The igneous rock which 
 it has cut through is a felspar chlorite schist. 
 
 About f mile further south there is another instance of one hornblendic 
 
EPIDIORITES AND RELATED SCHISTS. 71 
 
 rock cutting another which has not been complicated by the presence of 
 basalt dykes. Slightly to the south-west of Barr an Longairt and J mile 
 north of Castle Lachlan a small mass of epidiorite occurs, about 130 yards 
 long by 70 yards broad. It evidently belongs to the same set of intru- 
 sions as the other igneous masses in the vicinity which have been 
 described. The rock is composed of dark green hornblende in crystals 
 i inch to J inch in size, intermixed with a good deal of felspar. In the 
 centre of the mass there is a dyke-like band 4 or 5 feet wide, far more 
 acid in composition and possessing no foliation, the structure being 
 granitic. This band is composed largely of crystals of pinkish felspar, 
 mixed with scattered grains of epidote, and a small amount of hornblende 
 in little prisms. It varies considerably in texture, in parts resembling a 
 very fine-grained diorite. It is sharply divided from the hornblende schist, 
 with which it is associated, but it appears to belong to the same general 
 set of intrusions, and probably represents one of the latest phases of 
 irruption. It is significant that the general diffusion of epidotic material 
 which is a prevailing characteristic of the epidiorites of the Stralachlan 
 district is present here also, the yellowish-green tint due to the presence 
 of epidotic materials being very marked. The fact that the acid part 
 of the irruption is the latest, follows the usual rule and is what we 
 should expect. 
 
 Mr Teall gives the following report on a specimen of this dyke-like 
 intrusion, sent to him for examination. 
 
 " (4008) : Medium-grained, massive crystalline rock. 
 
 " Microscope : Plagioclase felspar in allotriomorphic grains forms the 
 main mass of the rock. In the felspathic aggregates are seen more or less 
 idiomorphic prisms of green hornblende, grains of epidote and iron ore 
 (scarce). Diorite." 
 
 At Barnacarry, Loch Fine (151), very massive epidiorites occur along the 
 coast, and form the wooded hills between Barnacarry and Stralachlan river. 
 These massive beds are good examples of the epidiorites in which schis- 
 tosity has not been carried far. On the whole they are more acid than 
 the rocks to the north-westward already described. They are coarsely 
 crystalline, and, as a rule, appear to be made up of a nearly equal admix- 
 ture of green hornblende and plagioclase felspar. Here and there where 
 the rock gets finer-grained, a foliated structure is developed, the hornblende 
 crystals lying with their long axes in one direction. Many portions of 
 the mass, however, which are fine-grained, show no schistosity. Epidotic 
 eyes and cores like those already described are dispersed throughout the 
 mass, and rarely show foliation. The hornblende may occur in short, 
 stumpy prisms, or in long blades : the arrangement of the latter, with 
 long axes parallel, gives the rock a foliated appearance. The mass is often 
 traversed by veins 2 or 3 inches in width, different in texture from, and 
 of more acid composition than, the main mass. At the edge of the mass 
 on the north side the rock is very schistose for about 6 or 8 feet from its 
 margin ; inside this, although coarsely crystalline and full of epidotic cores, 
 the rock is markedly pulled out, but without destroying the coarse granitic 
 character ; there has been merely a tendency for the crystals along certain 
 lines to arrange themselves with their long axes in one plane. 
 
 At the point on the north side of Lachlan Bay close to the ruins of the 
 old castle, mica slates and epidiorite sills occur associated together. The 
 hill above is made up of massive quartzites, which have, to a large extent, 
 resisted the earth movements. The argillaceous beds below have, how- 
 ever, completely succumbed and suffered the most intense folding and 
 shearing, so that the original bedding planes have been destroyed, and 
 the accompanying sill or sills of epidiorite have been so folded and sheared, 
 
72 GEOLOGY OF COWAL. 
 
 that their original characters have been obliterated, and they are now re- 
 presented by highly fissile green schists, in many parts of which no horn- 
 blende is visible, and the rocks are nothing more than highly folded and 
 crumpled chlorite schists. They are so folded with the mica slates that 
 in places the divisions are too small to be drawn on the 6-inch Maps. 
 Some of the junctions, however, with the sedimentary rock show contact 
 metamorphism, and the igneous nature of the rocks is clear. Scattered 
 through some of the seams too are small eyes of epidosite so character- 
 istic of the epidiorites of this area. In a few instances a coarser crystalline 
 texture may be observed ; this is notably the case in a limb that is seen 
 twisting round from north to south, and finally assuming an easterly 
 course ; parts of this limb are moderately coarse in texture, and contain 
 eyes of epidosite. The north part of the limb after bending round is 
 highly sheared for some distance and converted into a fissile chlorite 
 slate, and at the junction, is folded and mixed up with the argillaceous 
 schists. At the southerly junction, however, the bed is more massive 
 and crystalline, and only shows extreme fissility near the junction with 
 the sedimentary schist. It is similar in composition to the felspar chlorite 
 schist (4006) already described on p. 70, which has been traced into a 
 coarsely crystalline epidiorite. In this instance, the greater shearing and 
 alteration of the hornblende schist has probably been due to its intercala- 
 tion in the phyllites, and their position relative to the quartzite overlying 
 them to the north. The latter owing to its greater power of resisting the 
 effects of dynamic movements, has tended to increase the deformation of 
 the underlying, more yielding strata. Hence we find that the phyllites 
 and the hornblende schist (now converted into felspar chlorite schist) 
 are traversed bv fissile planes having no clear relation to the bedding. 
 ' J.B.H. 
 
 CHAPTER VI. 
 
 SERPENTINE. 
 Inellan and Toward Serpentine. 
 
 Serpentine occurs in, or closely associated with, the schist boundary 
 fault near Inellan and Toward, and is generally in an extremely crushed 
 state, so that its original mode of occurrence is not in most places clear. 
 It is seen in the coast sections a little south of Inellan Pier and by the 
 east gates of Toward Castle policies (194 south-east), and in various places 
 inland between these, e.g., at the back of the raised beach | mile south- 
 east of Inellan Pier, and' 300 yards N.N.E. of Chapel Hall (194 south-east), 
 and at the junction of the burns J mile north of Toward Taynuill (194 
 south-east). 
 
 The Inellan section shows a crush breccia of green serpentinous rock 
 in which the pieces, all of them serpentine, sometimes exceed the size of 
 a man's head. The main band runs rudely parallel to the schist foliation, 
 but in one place, about 180 yards from the pier, a portion runs off for a 
 little way to the north at the back of some schist. Fresh fractured specimens 
 show a mottled dark grey or green matrix without any porphyritic con- 
 stituents. At times the pieces are so angular and so coated with fibrous 
 serpentine and slickensided films of talc or white steatite that no one could 
 doubt the crushed character of the rock. The pieces examined showed 
 
INELLAN SERPENTINE. 73 
 
 no traces of schistosity acquired before the advent of the fault movements, 
 and we were for some time iu doubt whether the rock should not be 
 regarded as a crushed dyke which had been intruded along a pre-existing 
 line of crush. The evidence at Toward to be shortly adduced makes it 
 probable, however, that this is not so. A portion of one of the pieces 
 was examined microscopically by Dr Hatch, and is described as follows : 
 " A confused interlacing mass of lamellae and blades of serpentine, the 
 arrangement of which bears some resemblance to the ' Balken ' structure 
 of serpentines derived from augite-bearing rocks. No ferro-maguesian 
 constituent could be detected." 
 
 Both at Iiiellau and Toward there is an alteration of the schists near 
 to the serpentine. They are, for instance, harder, break less readily along 
 the foliation planes, and weather whiter than usual for a few yards near 
 the junction : also, they contain many thin streaks and little spots of 
 chlorite arid brown mica, which may be as large as a small pea. These spots 
 occur both in phyllite and schistose grit. They sometimes have hexagonal 
 outlines and contain grains of garnet, so that it may be considered certain 
 that the constituents in them are pseudomorphous after that mineral. 
 Garnets or pseudomorphs after it are unknown in this part of Cowal ex- 
 cepting close to the serpentine, but here the little spots referred to are so 
 abundant that on some rock faces they compose nearly J of the area. 
 In slide 2835 the central portions of the spots are formed of chlorite or 
 a granular aggregate of felspar, and the peripheral portions are of biotite 
 arranged in short confusedly arranged lamellae. The spots are often longer 
 in one direction than another : this may be attributed to the same 
 action which has elongated the pebbles in the schistose rocks, and be thus 
 an independent indication that the serpentine belongs to the schist 
 series. 
 
 The Toward section is better than that at Inellan, and iu one place, a 
 little west of the broad north-east running basalt dyke, the serpentine is 
 distinctly schistose, independently of any effect produced by the fault 
 movements. The exposure alluded to shows on one side a greenish 
 pebbly schist, next a band, about 8 inches thick, of yellow or reddish 
 schist without pebbles, then a 6-inch band of green serpentine, and 
 lastly one of the fault breccias. The breccia runs rudely parallel to the 
 junctions between the rocks mentioned, but the foliation in the schist is 
 at a marked angle to the junctions, and continues through the serpentine. 
 Hand specimens of serpentine from here show a fine even schistosity 
 throughout. It is thus clear that at this place the edge of the serpentine 
 is a schist, though parts of it elsewhere are quite massive. The edge 
 of it must have been more affected by the movements which produced 
 the schistosity than the interior parts were a phenomenon, of course, 
 constantly met with in the igneous masses of schistose areas. Several 
 bauds of serpentine occur at Toward besides the one just alluded to, but, 
 in the main, they have been so much atfected by the fault movements 
 that they form now what we might call a new schist. A little west of the 
 basalt dyke a red exposure of such crush rock occurs close by high- 
 water mark. This rock contains large lenticles and eyes, some as large 
 as a man's head, weathering mottled red and grey. The rock surrounding 
 the eyes is very soft and unctuous, and microscopical examination 
 (slide 4839) shows it to consist of carbonates and talc, with the greater 
 lengths of the streaks and specks of the former roughly parallel. Some 
 of these streaks are evidently of new formation, along lines of discordance 
 and rupture, and sometimes cut off the edges of contorted talc Ia3 r ers. 
 The lenticles and eyes consist of crystalline ferriferous dolomite, with pale 
 grey patches of talc; In the hard red crush rock sticking up on the east 
 
74 GEOLOGY OF COWAL. 
 
 side of the basalt there seems but little serpentine incorporated. At the 
 sides of the basalt, before coming to either of the red rocks just mentioned, 
 there is a crushed and contorted band of green and dark grey serpentinous 
 rock : in places this contains small spots and streaks of carbonate of 
 lime. 
 
 Near the east boundary of the crush area, and within 10 or 12 yards 
 of high-water mark, we noticed a good many blocks, some as much as 3 
 feet in length, of a yellowish weathering ferriferous dolomite, speckled 
 with irregular spots and streaks, often about J inch long, of some serpeii- 
 tinous mineral. The dolomite in fresh fracture is deep red. These 
 blocks are probably nearly in situ, and may perhaps be regarded as belong- 
 ing to some vein which has been formed near the serpentine : they are of 
 essentially the same character as the eyes in the red crush rock west of 
 the basalt. 
 
 Both at Inellan and Toward the crushed serpentine is cut by dykes of 
 uncrushed basalt of supposed Tertiary Age. 
 
 At the junction of the burns J mile north of Toward Taynuill, a large 
 portion of the crush area consists of a soft greenish-grey aggregate of 
 minute crystalline scales, probably antigorite, mixed with redder portions 
 composed of some carbonate (slide 4837). Mr Teall states that the rock 
 is a serpentine now, but what it was originally is uncertain : it does 
 not resemble the serpentines formed from olivine rocks. This rock is 
 mnch crushed along rudely parallel lines of rupture and slickens, but 
 there are still eye-like masses, sometimes 3 feet in length, comparatively 
 unaffected. In parts of the crush there is an admixture of white steatite, 
 and it is stated that about a dozen years ago this was mined, and 
 samples taken for trial as French chalk. There is also dark grey and 
 green serpentine, resembling that at Inellan, near the north margin of 
 the crush area in both burns. In the west burn this lies on the north side 
 of the most northerly crush of any prominence, but there are several thin 
 crushes on the north side of it : the schist near it has the appearance of 
 contact alteration, with spots of biotite, etc., already remarked on. 
 
 Three hundred yards N.N.E. of Chapel Hall part of the crush breccia 
 contains fragments of steatite embedded in a soft unctuous red matrix, 
 but most of it is a green or streaky green and dark blue rock, showing 
 movement structures. 
 
 All the above occurrences of serpentine fun rudely parallel to the 
 general strike of the schists adjoining, and probably they may be regarded 
 as belonging to an old intrusion of sill-like character, along the course of 
 which the different movements of the schist boundary fault have subse- 
 quently occurred. lu the district between Loch Lomond and Aberfoil 
 there are frequent exposures of crushed serpentine and serpentinised 
 gabbro in the fault crush that separates the Middle or Lower Old lied 
 Sandstone from the older rocks. The character of the original rock 
 appears to have varied considerably in different places, in some places 
 containing no felspar, in others a considerable proportion. This varia- 
 bility seems best to accord with the supposition that the rocks in the 
 different exposures once belonged to a large mass during the consolidation 
 of which considerable differentiation in the magma took place. The 
 amount of alteration in the schists near the serpentine at Inellan and 
 Toward is great, especially when one considers that these rocks are gener- 
 ally separated by crushes, which may have brought together rocks once 
 lying at some distance from one another. The alteration can, therefore, 
 be regarded as more probably due to a large intrusion than to a thin 
 dyke. C. T. C. 
 
GLENDARUEL SERPENTINE. 75 
 
 Glendaruel Serpentine. 
 
 Three-quarters of a mile north of Achanelid, a mass of serpentine extends 
 on the western side of Glendaruel for rather over a mile along the strike. 
 Its greatest width of outcrop is 500 yards. It has been cut across promin- 
 ently in two places by north-west faults, and at these places it has narrowed 
 itself, along one fault to 150 yards, and along the other to 100 yards. 
 After the main mass ends, the serpentine is continued for another mile in 
 a series of five smaller disconnected patches, the largest of these attaining 
 a length of about 300 yards. For a large portion of its length the 
 western boundary of the big mass coincides with a fault. This is also 
 the case as regards the largest of the smaller patches to the north. The 
 Loch Tay limestone has been mapped between the serpentine and the 
 bottom of the glen, and affords a valuable guide for determining the 
 stratigraphical horizon. The eastern boundary of the big serpentine 
 mass, and of the smaller masses to the northward, keeps the same dis- 
 tance from the outcrop of the limestone ; as the outcrop of the limestone 
 varies in direction, so does the outcrop of the serpentine. It is evident, 
 therefore, that the serpentine is in the nature of a great sill or sills. The 
 smaller patches are foliated throughout ; in the larger patches the serpen- 
 tine becomes massive in the centre, and schistose on either side. In the 
 big mass there is little or no foliation at its lower or eastern portion, but 
 the foliation increases as we approach the upper portion or western 
 extremity, where the rock is not only well foliated, but much more 
 shattery than at its base. Fibrous serpentine occurs abundantly along 
 joint planes. 
 
 In the largest of the small patches occurring to the north of the main 
 mass, the interior of the rock has so much of the appearance of au 
 epidiorite that a specimen was sent to Mr Teall for microscopic examina- 
 tion, who described it as follows : 
 
 " Pale green, and colourless hornblende, and turbid decomposition pro- 
 ducts, after felspar " (4368). 
 
 Mr Teall thinks the hornblende is secondary, and the original rock was 
 a gabbro. It appears, therefore, that a gabbro has been associated with 
 peridotites, the latter of which have become serpentinised, so that there 
 is a transition in space from altered gabbro to serpentine. 
 
 Mr Teall examined a specimen from the main serpentine mass, but the 
 original minerals could not be determined. 
 
 The serpentine, as described on p. 153, has been pierced and veined by 
 basalt dykes. Contact metamorphism, produced by the intrusion of the 
 dykes, has sometimes been considerable, and its effects extend for some 
 distance from the edge of the dykes. The dykes themselves within the 
 serpentine mass seem to decompose readily, and have themselves become 
 partially serpentinised. In addition to the dykes there are two or 
 three small dyke-like veins which we cannot say for certain belong to 
 the basalts, but they probably do. They occur as dusky black veins in 
 the serpentine, are soft, and effervesce with hydrochloric acid. 
 
 A specimen is described thus by Mr Teall : " (4370). Black massive 
 compact rock. Microscope : Extremely minute felspars. Microlites and 
 much disseminated opaque matter between the felspars." 
 
 Mr Teall is doubtful as to the microlites being felspar, the rock being 
 too fine to make anything out satisfactorily. J.B.H. 
 
76 
 
 GEOLOGY OF COWAL. 
 
 CHAPTER VII. 
 
 MINERALS IN THE SCHISTS. DIRECTIONS OF 
 STRETCHING. 
 
 Among the minerals which may occur in the schists as part of them, 
 or in veins which seem of the age of some part of their manufacture, are 
 the following : quartz, albite of the albite schists, an albite of earlier age 
 than the former, biotite, chlorite, sericite and white mica, tourmaline, 
 garnet, epidote, rutile, sphene, ilmenite, magnetite, haematite, calcite and 
 a ferriferous carbonate, iron pyrites, copper pyrites, and an almost opaque 
 yellow mineral forming thin flat tables. 
 
 The mode of occurrence, etc. of the albite of the albite schists has already 
 been described. Though clearly of later origin than most of " the anti- 
 cline " movements, it is not quite certain that it is always later than all 
 of them : in some microscope sections there is a suggestion that it may 
 have been slightly moved (see p. 43). 
 
 A felspar of earlier age than the albite of the albite schist often occurs 
 with the quartz veins. Sometimes, as in the veins in the Dunoon phyllites, 
 the colour is pink, but more commonly opaque white. The veins at Dunoon 
 are described on p. 18. The felspar in these veins has been determined 
 as albite. The growth in rods and streaks parallel to the direction of 
 stretching, the bending and occasional cracking across their length, and 
 the subsequent infilling of the cracks with new quartz, are features which 
 readily distinguish them from the albite pegmatites of the albite schists, 
 and indicate their earlier age, provided it is satisfactorily established, as we 
 suppose, that the movements in the areas with rodded pegmatites are not 
 later than the movements in the areas with pegmatites without rodding. 
 
 FIG. 27. x 1. From a loose block mile E.KE. of Cruach na Cioba (141). 
 Pegmatite with interrupted streaks of opaque white felspar. 
 
 The folia of biotite, chlorite, and white mica, which occur so abundantly 
 along the planes of "the anticline" rocks, have often been waved and 
 crumpled. But in Inverchapel Burn, in the bend near the u n" of 
 |* Bum" (164 south-east), there are flakes of green mica, sometimes ^ 
 inch in length, which cross the foliation planes of the rock, and contain 
 inclusions which show that the rock was a schist, already somewhat 
 crumpled, before the formation of this mica : the inclusions consist partly 
 
MINERALS IN THE SCHISTS. 
 
 77 
 
 of small granules of quartz or felspar, and partly of opaque yellow prisms 
 of the doubtful mineral mentioned on p. 35. A white mica presum- 
 ably of the same age shows v a similar arrangement not uufrequently. 
 
 FIG. 28. x T^. From a thin slice of mica schist in Inverchapel Burn, cut at right 
 angles to foliation. Seen with natural light. Thin ocrhreotrs veins near top 
 and bottom of sketch. The black prisms are the doubtful opaque yellow 
 mineral. The dark circular spots are surrounded by pleochroic halos. 
 
 The most striking instance of this is shown by some thin bands in the 
 albite schists : these are nearly entirely made up of white micas lying 
 across the foliation planes (see p. 43). Some of the flakes of white mica 
 in the albite schist, from J mile E.N.E. of Ard a' Chapuill (182 north- 
 east), have at times their flat surfaces lying nearly at right angles to the 
 planes of schistosity (see Mr Teall's description in Appendix). Brown 
 or black mica, too, has at times the same arrangement, e.g., in the burns 
 \ mile north-east of Sitb an t-Sluain (182 north-east), and south-east of 
 the hamlet of Glensluain, and in the albite schist f mile slightly east 
 of north of Binnein an Fhidleir (134). The chlorite pseudomorphs, after 
 garnet and actinolite, are mentioned on p. 50. 
 
 C.TC. 
 
 FIG. 29. x 4. Bent and cracked Tourmaline needles from the albite schist of 
 A' Chruach (182). 
 
 The occurrence of tourmaline in the albite schists and green beds, and 
 in veins in these schists, has already been mentioned, pp. 35, 40. It also 
 occurs not uufrequently in the more micaceous varieties of schist which 
 do not seem referable to either of these types of rock, e.g., in Tamhnicb 
 Burn, near the " m " of "Tamhuich " (172 north-east), and on the hill- 
 side a little more than J mile slightly east of north of Cruach nan Cuilean 
 (172 north-east). In the last locality the needles are sometimes over 1 
 inch in length. Near the sharp bend of the stream |- mile north-west of 
 Ardacheranbeg (172 north), they occur in hard vvliite thin slightly cal- 
 careous laminae, which are lying in more micaceous schist. Far the best 
 locality, huwever, that is known for tourmaline, in the south part of 
 
78 GEOLOGY OF COWAL. 
 
 Cowal, is A' Chruach (182 north-east). Here it occurs in the more 
 micaceous schists whether these contain albite or not. Some of the 
 needles are 1 inch in length and ^V inch in breadth. They lie especially 
 along the foliation planes, and in some cases have also a general direction 
 along these planes, but in others there is no clear parallelism. These 
 needles are often much bent, and even broken, by the numerous small 
 " anticline " movements. This is seen particularly well at a point about 
 80 yards south of the top of the hill. Tourmaline has not been noticed 
 more than about 2 miles south-east of the centre of " the anticline," and 
 it may probably be regarded as one among the other signs of the greater 
 metamorphism of " the anticline " rocks. 
 
 In the north part of Cowal small tourmaline needles are common 
 in the albite schists and the more phyllitic mica schists, and also, in 
 longer needles and sheaths, in the quartz veins in these schists. The iso- 
 lated needles in the schist in the Garbh Allt Mor (126), near the " r " of 
 " Mor," are some of them -^ inch thick. On the south slopes of Binneiu 
 an Fhidleir (134) the quartz-tourmaline veins seem particularly abundant, 
 and rich in tourmaline. The shores near Ardkinglas are thickly strewn 
 with boulders of such vein stuff', which have probably in great part come 
 down the Kinglas Water from this and neighbouring localities. In the 
 burn | mile north-west of the "B" of " Beinn an t-Seilich (134), the 
 tourmaline needles in the quartz veins are sometimes 2 inches long, and 
 coalesce into sheaves 2 or 3 inches wide. In some parts isolated needles 
 are seen spearing through the white quartz of the vein, but there are also 
 
 smaller quartz strings which cross the 
 tourmaline areas, almost at right angles to 
 the lengths of the needles. The tourma- 
 lines are frequently waved : as far as 
 noticed the waves are roughly parallel to 
 __ those which affect the foliation of the 
 
 ^ ^jffiT schist. The quartz strings which cross the 
 
 HjSjtef tourmalines have probably been formed 
 
 ^(p subsequently having filled cracks formed 
 
 jflL ff, during the bending. In these later quartz 
 
 ^S //J/ strings, ferriferous carbonates are also 
 
 'JJ&dtjt common. Again, in a loose bit of a quartz- 
 
 * ^^ tourmaline vein found \ mile above the 
 
 foot of the Cab (141), isolated tourmaline 
 C.r.c . needles seem to penetrate into presumably 
 
 later quartz. 
 
 FIG. 30. x 1. From a loose block I n the quartzose schists tourmaline is 
 
 mile above foot of the Cab rarer, but in a quartzite schist in the burn 
 (141). Sheafs of Tourmaline in 1 m il e N.N.W. of Ben Douich, it occurs 
 
 ^Toftartr T r h T s taYs in *> f /^ congregated small 
 are shown in their natural posi- needles : the direction of each needle is the 
 tionto one another. Near "a" same as that of the lines of occurrence. 
 Tourmaline needles seem to Tourmaline and the albite of the albite 
 penetrate the cross strings of sc h ist s are in this district close companions. 
 
 The areas with prominent albites are also 
 
 those in which tourmaline is most conspicuous. Tourmaline is often seen 
 lying across the foliation of the schist (slide 3418, described in Appendix), 
 but has frequently been subjected to bending and fracturing, as just 
 described. It is occasionally included within albite (slide 5215, from a 
 specimen at the head of Stuck Burn), and so must be of earlier date 
 than it. 
 
 In the area east of Loch Riddon and Glendaruel garnets have only been 
 
MINERALS IN THE SCHISTS. 79 
 
 observed near the Toward and Inellan serpentine. Here, as already 
 mentioned, p. 73, they seem to be due to the contact inetamorphisni 
 induced by the serpentine. On the north-west side of the Glendaruel 
 limestone there is a zone in which garnets are common. For full descrip- 
 tion, see p. 48. The garnets along this zone are often deformed and 
 stretched in one direction, and intersected by thin cracks filled with 
 secondary quartz ; or, still more frequently, they are represented by 
 chlorite pseudomorphs elongated in two opposite directions. The 
 direction of elongation is usually N.W. or N.N.W. 
 
 Epidote occurs in abundance in grains in the green beds, and the veins 
 traversing these beds : also in small granules in the epidiorites and horn- 
 blende schists (slides 4740, 5056, 5061), and in long prisms in the veins 
 in and at the sides of these beds (see p. 65). An occurrence in albite. 
 schist close to its junction with a lamprophyre is mentioned on p. 114. 
 In an albite schist ^ mile slightly east of north of the Ordnance Station 
 2658 on Binnein an Fhidleir, there is a thin quartz vein which contains 
 needles, about 1 inch long, which probably belong to epidote. 
 
 Sphene occurs in slide 3795, obtained from a green bed at Tighnuilt, 
 Inverchaolain (183 south-west). Mr Teall's description of this rock is 
 given on p. 34. A quartzite schist (slide 3434), from J mile S.S.E. of 
 Aird Cottage (141), also contains it in small grains. In the epidiorites 
 and hornblende schists it is common as a decomposition product (leu- 
 coxene) of ilmenite : see, for instance, p. 67. 
 
 Ilmenite occurs in thin plates, which are sometimes 1 inch in length, 
 in the quartz veins of Glen Massan and other areas near " the anticline." 
 The small opaque grains which occur along the foliation planes are, in 
 some of the schists, ilmenite and not magnetite. In a garnetiferous mica 
 schist near the top of Cruach na Capull (133 south-east), small black 
 shining plates of ilmenite, about ^ inch in length, are abundant through- 
 out, and seem quite a part of the schist. In an albite schist ^ mile east 
 
 of the Ordnance Station 2658 on Bin- 
 nein an Fhidleir, ilmenite plates were 
 also discerned by the naked eye. In 
 the albite schists north-east of Lochan 
 Mill Bhig, ilmenite plates, partly de- 
 composed to leucoxene, are very abun- 
 dant : they are generally parallel to one 
 another and to the schist foliation, and 
 are often in close company, forming a 
 considerable proportion of some hand 
 specimens : they are sometimes an inch 
 long, and show slight bends. Kernels 
 of ilmenite, surrounded by spheiie, are 
 common in the epidiorites and horn- 
 FIG. 31. xH. i mile S.W. of blende schists. 
 
 Strachur House. Trains of mag- That the small black opaque grains 
 3tite grains on a foliation plane referred to in the above paragraph 
 
 1 ^Vi !!; <-*. w^^n.rt v.c^-i- T>U^ * o t 
 
 'a 
 
 uc 
 
 the longer axes of the micaceous b 7 M . r lea11 in . tn course of his ex- 
 minerals. haustive examination of the albite 
 
 schist from J mile E.N.E. of Ard a' 
 
 Chapuill (see description in Appendix of slide 3418). These small 
 grains sometimes give the impression that they have been formed by the 
 shearing, or dragging to pieces, of larger lumps. That this is so is 
 rendered probable, too, by the fact that in various places such a shearing 
 clown of magnetite occurs on a scale large enough to be made out 
 
80 GEOLOGY OF COWAL. 
 
 maeroscopically, e.g., on the shore of Loch Fine, 200 yards north-east 
 of Tigh na Criche (see p. 57). Magnetite crystals, about the size 
 of a small pea, are common throughout " the anticline " area, and also 
 in the green beds on the south-east side of this area. They are perhaps 
 most common in the albite and more micaceous schists, but also 
 occur frequently in massive greywackes. They are so abundant in some 
 scars, e.g., in those about J mile north of A'Chruach (182 north-east), 
 that a handful of loose crystals could readily be gathered from the rock 
 ledges, on which they have tumbled and gradually accumulated during 
 the process of rock weathering. The magnetite in the sands * of the 
 -Kyles of Bute has no doubt been derived, in part at all events, from 
 the magnetite bearing schists of the neighbourhood. 
 
 In the green beds on the east side of Lephinkill (172), and in the 
 albite schist, \ mile E.N.E. of Lochgoilhead Established Church, it is not 
 uncommon to find magnetite crystals with quartz streaks extending for a 
 little space on two opposite sides. The length of each streak is often 
 about -J inch. This is probably a parallel case to those in the phyllade aim- 
 antifere of Montherme, described by Prof. Renard (Bull. Mus. Roy. Hist. 
 Belg., vol. ii. p. 134, and pi. vi., 1883), and mentioned more recently 
 by Mr Harker in a paper " On ' Eyes ' of Pyrites and other Minerals in 
 Slate " (Geol Mag., vol. vi.. No. ix. p. 396).. To quote Mr Harker : " By 
 its strong cleavage this rock gives evidence of considerable lateral com- 
 pression. Prof. Renard has shown that prior to this compression, the 
 magnetite crystals already existed in the rock,, arid were surrounded by 
 a coating of chlorite. The crystals yielded to the pressure much less 
 readily than their matrix ; and the latter, having already a firm consis- 
 tence, became separated from the crystals, carrying the chlorite with it, 
 and was displaced along the planes which are now cleavage planes, that 
 is, in a direction at right angles to that of the pressure." And again : 
 " in yielding, it was al)le to leave vacant spaces, which were filled at a 
 later date by crystalline quartz." Mr Harker also points out that 
 similar phenomena often occur around crystals of pyrites in slate, e.g., in 
 North Wales and Ballachulish. As stated, pp. 50, 57, we have in Cowal 
 also found the same phenomena around pyrites and garnet crystals. 
 
 Hematite, in the form of iron glance, occurs in a pegmatite which 
 also contains felspar and chlorite, on the hillside f mile N.N.E. of Ard- 
 tarag (173 west). 
 
 The occurrence of iron pyrites in the Dunoon phyllites, in crystals and 
 nodules, and thin films running along the foliation, has already, p. 9, 
 been referred to. In the green and purple phyllites, on the shore between 
 Dunoon and Kirn, cubical crystal shapes, reaching J inch in length, are not 
 uncommon. The main portion of these now usually consists of limonite, 
 but there are " hearts " of iron pyrites. The phyllite, for about J inch 
 from, these shapes, is bleached to a cream colour. 
 
 A black phyllite a little above the upper end of the Dunoon reservoir 
 (not shown in 1-inch Map, but lying about 1 mile west of the pier) has 
 quite a rough surface from the abundance of hard projections, covered 
 by black phyllite adhering firmly to them. These projections are longer 
 in one direction than another, often from J to ^g- inch long and less than 
 Jg- inch broad. They are now hollow in the middle, but have quartz at 
 the sides. We suppose that the central hollow was once occupied by 
 some mineral, perhaps marcasite, of which all trace has now disappeared, 
 
 * See "On a Magnetic Sand from East Bny, Rothesay," by D. C. Glen, Trans. 
 Geol. Soc. Glasgow, vol. v. p. 158. Mr Glen states that only 9 or 10 per cent, of 
 the heavy black grains is attracted by the magnet. He takes the rest to be ilmenite, 
 and looks on the neighbouring trap dykes as their source of origin. 
 
DIRECTIONS OF STRETCHING. 81 
 
 and that the quartz at the sides is analogous to that at the sides of the 
 magnetite of Lephinkill. In several places in the Ardrishaig phyllites, 
 and especially 200 yards north-east of Tigh na Criche (Strachur), iron 
 pyrites is seen in a partially deformed state, with streaks of quartz at the 
 sides (see p. 57). The occurrence of quartzose schist, unusually rich in 
 pyrites, and with small proportions of galena, blende, silver and gold, is 
 described on p. 58. 
 
 Marcasite occurs in the tourmaline bearing schists of A' Chruach (182) 
 and in the epidiorite of Mid Hill (173 south-west). 
 
 Decomposed crystals of copper pyrites, or of an intergrowth of copper 
 and iron pyrites, have been noticed in the schists, and as quite a part 
 of them, without any apparent connection with any fault or vein, on 
 the east side of the road, \ mile north of the Clachan of Glendaruel. 
 A little carbonate of copper has been formed from the crystals by 
 weathering. They have only been seen in a band an inch or two thick, 
 and this band was only traced some 3 or 4 feet. The containing rock is 
 a somewhat pebbly schist. Crystals of some copper mineral also occur 
 in the schists of the headland lying north of the Burnt Islands, Kyles 
 of Bute, in a little cove about 60 yards N.N.W. of the Ordnance 
 Station. These also are now largely converted into the green carbonate, 
 but within this there is usually seen the red and black oxides. The band 
 in which these occur runs roughly with the foliation : it is somewhat 
 thicker than that in Glendaruel, but can only be traced a few yards. 
 
 The ferriferous carbonate of the veins seems in many cases to be an 
 almost pure carbonate of iron, and has perhaps been used in old times for 
 smelting purposes, in hillside bloomeries. See further, on p. 289. 
 
 The opaque yellow mineral mentioned at the end of the list given in 
 the beginning of this chapter is that referred to by Mr Teall in his 
 description of slide 3831, from a green bed about f mile slightly north 
 of east of Lephinkill. For this ^description, refer to p. 35. The same 
 mineral is of common occurrence in the more micaceous schists of "the 
 anticline " area. It is particularly prominent in some of the bands in 
 the crags about 1 mile south-west of Ardentinny. 
 
 Directions of Stretching. 
 
 The phenomena of stretching, or elongation of constituent parts, have 
 
 been already described as they are seen in the coast section south of 
 
 ^ Duuoon (p. 17). They are also alluded to in the green beds (p. 35), 
 
 the garnetiferous mica schists (p. 49), the Ardrishaig phyllites (pp. 56, 
 
 57), and some few other places (pp. 46, 100, 185, 196). 
 
 In the published maps the direction of stretching is indicated by a 
 special sign placed on the locality of observation. In the section south 
 of Dunoon the direction is liable to vary somewhat even in the same 
 planes (see p. 11). Similar small variations are to be noticed commonly, 
 but they do not prevent us seeing that in each locality there is usually 
 one general direction. In the Dunoon section referred to, the general 
 direction is 10 to 11 nearer east to west than the direction of the foliation 
 dip. 
 
 On the south-east side of "the anticline," the general direction is much 
 the same as at Dunoon, or else more nearly parallel to the foliation dip. 
 Instances of such parallelism are seen, e.g., 200 yards east of Corran 
 Lochan (153), in Blairmore burn near the "a" of "Blairmore," at 
 iStrone Point (174), in the burn f mile north-west of the "1" of " Kil- 
 mun," \ mile X.X.E. of Corlarach (194), the coast \ mile north of Strone 
 Point (194), and \ mile north-east of Altgaltraig Point (182). 150 yards 
 
 F 
 
82 GEOLOGY OF COWAL. 
 
 north-west of Carrick Castle, on gently dipping planes, the direction is 
 either with the dip or 12 or so nearer east to west, much as at Dunoon. 
 In Inverneil burn (183), on planes dipping about 40, on the other hand, 
 the direction is about 30 nearer north to south than the dip. 
 
 On the north-west side of " the anticline " the usual direction is either 
 with the dip or else nearer north to south than it. It is more north to 
 south than it in the following, among other places, J mile south-east of 
 Cairndow ; J mile S.S.W. of Ardkinglas House (134), nearly north to 
 south; north-west side of Stob an Eas, sometimes nearly north to south; 
 |- mile E.N.E. of Cruach nan Capull (133) ; |- mile north of Beinn Lochain 
 (141) ; f mile west of the " C " of " Carnach Mor " ; mile W.S.W. and 
 & mile N.N.E. of the "B" of "Cam Ban" (163) ; by the first "r" of 
 "Cruach Mhor " (162), nearly north to south; J mile S.S.W. of the 
 " A " of " An t-Suil " ; and mile north-east of the " k " of " Dalleik " 
 (172). 
 
 We have not noticed any clear case of alteration in direction in conse- 
 quence of the reversal of the plane on which the indications occur. The 
 foliation planes have not usually been reversed in this district by the 
 action of "the anticline," but only made to incline in different directions. 
 Consequently we cannot explain the fact that on the north-west side of 
 this anticline the direction is often more north to south than the dip 
 while on the south-east side it is more east to west, by supposing the 
 stretching lines to be roughly continuous lines which have been given 
 different directions by "the anticline" folding. But we suppose the 
 planes on which these lines occur have been reversed before the anti- 
 cline was produced through the agency of important syuclines near the 
 present centre of " the anticline " (see p. 86), and it is therefore allow- 
 able to consider that the stretching directions were once more uniform 
 than they are now, the differences now distinctive of each side of " the 
 anticline " being due to pre-auticline reversal of the planes on which they 
 occur. C.T.C. ' 
 
 CHAPTER VIII. 
 
 GENERAL PHYSICAL STRUCTURE OF THE SCHISTS.* 
 REMARKS ON THE METAMORPHISM. 
 
 The most conspicuous feature in the physical structure of the schist 
 area is the great anticline of foliation which has already often been 
 referred to as "the anticline" running in a direction about 35 west of 
 south, through the heads of Loch Goil, Loch Striven, and Loch Riddon, 
 and the hills 1 mile or so north-west of Tighnabruaich. In most parts of 
 Cowal there is no particular line we can point to as the exact centre of the 
 fold, for the schists on either side are excessively crumpled and with 
 alternating dips for some distance. Illustrations of this point, and 
 descriptions of various minute structures accompanying the anticline in 
 the area north-east of Loch Riddon are given on pp. 
 
 About the heads of Loch Striven and Loch Riddon it is observable 
 that the foliation dip on the south-east side of the anticline is generally 
 steeper than that on the north-west side : averaging, perhaps, 40 or more 
 instead of 20 to 30. The steepness of dip on the south-east side increases 
 
 * Near the end of the volume a sketch map of the solid geology is inserted. 
 
PHYSICAL STRUCTURE OF THE SCHISTS. 83 
 
 as we go north-east, and near the north margin of 1-inch Map 29, is at 
 times vertical, or even, as on the hill If mile north of Ardentiuny, slightly 
 reversed. Further north-east still, out of Cowal, the prevailing dip is 
 north-west, e.g., at Aberfoil and Callander. South-west from Loch 
 Riddon, however, the dip on the south-east lessens in amount, while that 
 on the north-west generally increases, so that we reach an area in which 
 they are about equal on either side. 
 
 There is no doubt that this anticline is a true arch of an early folia- 
 tion. Later foliations and other structures have been developed 
 together with it, as already described ; but the most prominent foliation 
 of the district, and an enormous amount of folding of the same age as 
 this foliation, \vere already in existence before it, and were folded by it. 
 
 It is clear, then, that " the anticline " cannot be a simple or exact anticline 
 of bedding. It shoum rather be looked on as an anticline of the limbs 
 and axes of the early folds which affect the bedding. To what extent 
 it departs from being an anticline of bedding must depend on the amount 
 of this early folding. There is hardly a coast section which does not 
 show how great this amount is, and we have shown, p. 24, that, even 
 where it may not at first be noticed, this is not because it did not exist, 
 but because it has been obscured by later movements. 
 
 We have not felt able to make any estimate of the amount of this pre- 
 anticline folding, so as to say how much less than the breadth of present out- 
 crop the original thickness of any bed is likely to have been, or how many 
 times it may have been repeated by folding. In the areas near the anti- 
 cline centre, rock exposures are more continuous than on the flanks, but 
 in these there has been so much later movement that we do not regard 
 them as promising localities for making such an estimate. Nor are the 
 hillsides away from " the anticline " more favourable, for they are often 
 extremely smooth and covered with drift or grass. The coast sections are 
 more promising, but as they rarely attain a height of more than 20 or 30 
 feet, it is not possible to trace individual beds in them with con- 
 fidence for any distance across the folding. We had at one time hoped 
 to make an estimate by the help of a careful comparison of the best coast 
 sections of a particular band or group of rocks to compare, e.g., the section 
 of the Dunoon phyllites near Cove and Barons Point with that at Dunoou, 
 ami these again with those at the foot of Loch Striven and in Bute. The 
 least number of exposures of a bed of particular character in any of the 
 sections would show that the number in excess of it in the other sections 
 was due to repetition by folding. This least number might, of course, 
 still be in excess of the original one, but it would be nearer to it than the 
 others. To make such a comparison with the care and detail necessary 
 would require the preliminary mapping to be done on a very large scale, but 
 we believe that the labour involved in this task might be well repaid. 
 
 After the remarks we have made on the great amount of folding in the 
 coast sections, it may surprise those who examine the Maps to see 
 such comparatively small evidence of this structure in the run of the 
 beds mapped out. This we suppose is largely due to the want of sections 
 along the margins, and to the general equality of the amount of folding in 
 different areas. Each line drawn to run evenly, no doubt, represents one 
 which is repeatedly plicated by small folds, but these are of much the same 
 frequency and importance at different parts of the line, and so the general 
 direction remains uniform so long as the foliation dip and the slope of the 
 ground do so. For the same reason the breadth of many of the bands 
 mapped continues much the same, the original thickness being increased 
 about equally in different areas. Our want of knowledge of the original 
 succession of the rocks is, too, so great that we do not feel it safe to 
 
84 GEOLOGY OF COWAL. 
 
 assume, in the case of thin outcrops lying a little off' a thicker baud of the 
 same character, that these are either folded outliers of the thicker one 
 among apparently lower beds, or inliers of it among higher beds. Doubt- 
 less they are so over and over again, but when we come to consider each 
 particular instance we are not usually, for want of clear exposures, able 
 to say whether they are or not. 
 
 The folding in the section south of Dunoon (already described, pp. 9-18), 
 is so great that we should not, before mapping the adjacent hillside, 
 have been surprised to find the beds practically flat. But they evi- 
 dently cannot be so, from the way the north-west margin of the Bull 
 Rock greywacke runs up this steep hill : for about 400 feet of vertical 
 height this margin makes quite a good line, and must, on the 1-inch scale, 
 be mapped as a simple unfolded one. So again the thin greywacke on the 
 east side of Glendaruel, by Dalleik, can be traced *fco a height of about 
 600 feet above exposures near the glen bottom, arid must be mapped as 
 an even running band. These and the other straight running schist 
 boundaries, where represented by uninterrupted lines, seem to show that, 
 great as the amount of folding is, it is still possible to exaggerate it. 
 The beds in the area generally cannot be considered as essentially flat, 
 though they are so in particular parts, e.g., along the strike line between 
 Loch Loskin (184 north-east) and Blar Buidhe, and again near Blairmore, 
 where we regard the hornblende schist running almost at right angles to 
 the foliation as an old igneous rock intrusive along the bedding, and on 
 Loch Fine side near Leak and Ardchyline. 
 
 As a preliminary to the discussion of how far " the anticline " departs 
 from being an anticline of bedding, it is necessary to compare the succession 
 of rocks found on either side of it. On the south-east side the chief groups 
 are, taking them in order as we advance north-west from the boundary 
 fault : 
 
 1. Phyllite and schistose pebbly grits, with pebbles chiefly of opaque 
 
 white quartz, often getting up to the size of small beans. Thin 
 limestones in places, but much rarer than in the Dunoon phyllite 
 series. The proportion of phyllite also less. 
 
 2. Bull Rock greywacke schist. Average breadth of outcrop about 
 
 J mile. A large proportion of pink felspar pebbles. Almost 
 unmixed with phyllite, but some thin bands with a breadth of 
 4 or 5 feet. 
 
 3. Dunoon phyllite series. Phyllite, with many thin limestone and 
 
 schistose grit bands. The grits near the south-east end are often 
 coarsely pebbly with opaque white quartz. 
 
 4. Band of "green beds." Thickness on Blar Buidhe immensely 
 
 exaggerated by folding. North-east of here it is probable that 
 the original thickness gradually decreases, and it is doubtful 
 whether there is any representative of it on the coast near Hunter's 
 Quay. 
 
 Alternation of schistose grits and greywackes and phyllites. Gener- 
 ally larger proportion of two former than in the Dunoon phyllites, 
 and no limestones. 
 
 Band of " green beds." Thickness south of Sandbank greatly due 
 to folding. This again is not seen on the coast between Hunter's 
 Quay and Sandbank, but it is possible that it may occur in an 
 obscure area. 
 
 5. Alternations of schistose greywackes, phyllites, and albite schists, 
 
 etc. Calcareous lenticles and stripes, rarely exceeding a few 
 inches thick, common in the quartzose pebbly beds. Distinct 
 albites do not generally occur until we get some 3 miles north-west 
 
PHYSICAL STRUCTURE OF THE SCHISTS. 85 
 
 of group 4, but these are due to secondary change, and may have 
 no stratigraphical value. Group keeps on to the centre of " the 
 anticline," a distance across the foliation strike in the south part 
 of Cowal of about 5 miles. 
 
 In the broad group 5 we have only been able to map out one band for 
 any distance. This is the grey wacke horizon, which is seen so well on the 
 headland north-west of Fearna Bagh. It does not consist throughout of 
 greywacke, and its margins are not always well-defined, but still it was 
 worth while to follow it in default of anything better, and it has been a 
 means of recognising various faults. So our ignorance of the physical 
 structure of this broad area is greater than of that occupied by the groups 
 
 I to 4, which altogether take up no more area than 5 alone. 
 
 In concluding that there is a succession much as indicated above we 
 think we stand on fairly solid ground. Group 1 could not be group 3 
 repeated by folding : the characters of the groups are too different. The 
 
 II green beds " are of such a peculiar character that they could not be 
 confused with the Bull Rock greywacke. Between the north-west side of 
 4 and the centre of " the anticline " there is certainly nothing to match 
 the limestones of the Dunoon phyllite series. 
 
 "Whether group 1 or group 5 is the oldest there is in this area nothing 
 that we know of to tell. That 1 now lies over the others is, of course, no 
 indication of their original relative positions. A very little greater strength 
 of push from the north-west during the time of the production of " the 
 anticline " would have made 5 the apparent top of the succession instead 
 of the bottom. As already stated, p. 83, the dip of these beds near 
 Aberfoil and Callander is north-west instead of south-east, as in Cowal, 
 and group 5 is apparently the top of the series. This alteration in dip on ; 
 the south-east side of " the anticline " was long ago called attention to by 
 Professor Nicol (" On the Geological Structure of the Southern Grampians," 
 Q.J.G.S., vol. xix., 1863, p. 180). 
 
 Let us now turn to the beds on the north-west of " the anticline." 
 Beginning at the north-west side of the district we have : 
 
 1. Ardrishaig phyllites. Soft calcareous sericite schists, with many 
 
 outcrops of quartzite schist and some limestones. 
 
 2. Graphite schists, dark graphitic limestones, and quartzose schists 
 
 intermixed with phyllitic garuetiferous schist. 
 
 3. Alternations of thin banded mica schists, commonly garnetiferous, 
 
 with some limestones and "green beds." 
 
 4. The Glendaruel or Loch Tay limestone. Coarsely crystalline marble, 
 
 with some parts mottled black and white, and others of calcareous 
 quartzite. Thickness in all perhaps 40 to 50 feet, but the lower 
 part is often more calcareous quartzite than limestone. 
 
 5. " Green beds " group. " Green beds," mixed with perhaps an equal 
 
 proportion of schistose greywacke and other mica schist. 
 
 6. Albite schists, schistose grey wackes, and other mica schists. Extends 
 
 in the south part of Cowal for a breadth of about 2J miles across 
 the foliation strike up to centre of "anticline," and in the 
 north part for a greater distance. Essentially of the same 
 character as group 5 on the south-east side of " anticline," and 
 with no satisfactory dividing line from it. In this group there 
 is an horizon which consists mainly of massive greywacke, and 
 the north-west margin of it has been mapped in some places : the 
 south-east margin is much less readily traced. 
 
 We will, for distinction between the groups, add the letter " a " to the 
 numbers of those on the south-east side of " the anticline," and the letter 
 

 86 GEOLOGY OF COWAL. 
 
 "b" to those on the north-west side : thus la, 2a, 3a, 4a, 5a, and Ib, 2b, 
 3b, 4b, 5b, 6b, There is little doubt that the " green beds " of groups 
 5b*and' 4a were of essentially the same character origiually. The differ- 
 ences between them, the greater development of chlorite, black mica, and 
 albite, in the former, compared to the latter, are only what we should 
 expect from a study of the other schists associated with these green beds 
 in the different areas. But the arrangement of the beds strictly entitled 
 to the name of " green beds " in these groups is not very similar : there 
 are many alternations of schistose greywackes and other mica schists in 
 5b, while in 4a there are two main bands, each comparatively unmixed. 
 
 Is it possible, for all this, that groups 5b and 4a are the same, folded 
 over by " the anticline " ? If it were possible^ to answer affirmatively, we 
 should be afforded a most interesting indication of the amount of "pre- 
 anticline " folding in the area between the two groups, for, in the south part 
 of Cowal, 4a is about 5 miles distant from what we may roughly call the 
 centre of " the anticline," while 5b is only 2 J miles distant, in spite of the 
 average foliation dip in the former case being not less than 40 and in 
 the latter only 25. If the groups had been the same, and if bedding and 
 foliation had coincided, the thickness of the beds on the south-east side of 
 "the anticline" between its centre and 4a would have been over 17,000 
 feet ; and we could not have got this group on the north-west side at a 
 less distance than 7 \ miles. Or, to look at the matter from another point 
 of view, the apparent breadth of beds on the north-west side is about 6000 
 feet, while on the south-east side it is about "17, 000. The beds on the 
 south-east side would then have to be considered repeated by folding to 
 nearly three times the extent they are on the north-west. 
 
 We are obliged, however, to regard these considerations as futile. In 
 all probability the green beds on either side of " the anticline " are not 
 the same folded over. If they were, the Glendaruel limestone, and 
 the beds on the north-west of this, would have also to be the same 
 as the Dunoon limestones and phyllites. The character of the 
 former limestone, both in thickness and other respects, is, however, so 
 different from any of those at Dunoon, and it keeps this different character 
 for such a distance along the strike, far away north-east out of this Map, 
 just as the Dunoon limestones also keep theirs along their strike, that we 
 consider that they cannot represent one another. However greatly the 
 original distance between the localities of occurrence of these beds may 
 have been reduced by folding, it is not likely to have rivalled that for 
 which the Glendaruel limestone is known to retain its usual character, 
 and we have no reason for -supposing the original character to have 
 changed more rapidly in a direction across the present strike than along it. 
 
 So we regard the groups Ib, 2b, 3b, 4b, 5b as unrepresented on the 
 south-east side of " the anticline." Groups 6b and 5a naturally go 
 together to form one group, which we will call 6b 5a. It is possible, then, 
 to divide the whole of the schist area into 10 zones, which are as follows, 
 beginning at the north-west corner of the Map : Ib, 2b, 3b, 4b, 5b, 6bi 
 5a, 4a, 3a, 2a, la ; and we may hold, with a fair amount of confidence; 
 that this represents an original succession, though which group is top and 
 which bottom we have so far seen nothing to determine. In the first five 
 and part of the sixth of these the present superposition would indicate 
 that Ib was the newest and la the oldest : in part of the sixth and the 
 last four it would indicate that la was the newest and Ib the oldest. 
 
 We suppose that somewhere in group 6b 5a there is a great folding of 
 " pre-anticline " age, which, roughly speaking, counterbalances the effect 
 of " the anticline " : that there has been here an important early syncline. 
 The north-west margin of the greywacke horizon, a little on the north-west 
 
PHYSICAL STRUCTURE OF THE SCHISTS. 8? 
 
 side of "the anticline," can hardly be the same line as the south-east 
 margin of the greywacke mapped on the south-east side. We may 
 temporarily look on the whole area between these lines as belonging to 
 one greywacke group of which the south-east margin of the south-east 
 greywacke is one margin, and the north-west line of the north-west grey- 
 wacke another margin : the former line we suppose never appears on the 
 north-west side of " the anticline," owing to the lowness of the present 
 ground surface : the latter line may either be folded back before it reaches 
 the present ground surface, or, if it does reach it, it is soon folded back 
 and comes out again.* 
 
 A large part of the area close to the centre of " the anticline " in the 
 south part of Cowal is low and drift-covered, e.g., the area between 
 Auchenbreck and the head of Loch Striven, and Glen Tarsan, and so the 
 opportunities of examining structure are not good. We cannot point to 
 any section in this area which confirms the supposition of the existence of 
 an important syncline of " pre-anticline " age near " the anticline " centre. 
 In the north part of Cowal, however, the hills west and south-west of 
 Carrick Castle do afford some evidence in favour of it. The tops of Cnoc 
 na Tricrich, Sgor Coinnich, and part of Cruach a' Bhuic, are formed of an 
 apparently thick albite schist. This can be traced down from the hill top 
 a little south of Cruach a' Bhuic both in a north-east and south-west 
 direction, and in both of these it rapidly decreases in apparent thickness, 
 the schistose greywackes on either side getting gradually nearer. We 
 suppose these greywackos are in fact the same, the albite schist lying in a 
 syncline between them. Further details of the structure in this locality 
 are given on pp. 201-205. 
 
 We do not wish to speak with much confidence. There may be some 
 other better explanation of the general structure of the district, but we do 
 not think it possible that the general order of succession can be invalidated. 
 
 The average strike of the schist bands on the north-west side of the 
 anticline is slightly more north of east than it is on the south-east. For 
 instance, the lowest green beds on the north-west side, near Socach, are, 
 in a direction measured at right angles to the strike, about 7 miles distant 
 from the top of the schistose greywacke horizon at the junction of Loch 
 Long and Loch Goil. But in the area between Glendaruel and Loch 
 Riddon the corresponding horizons are within 4 miles of one another, i.e., 
 they are above 3 miles nearer one another than they were. It is not 
 possible to fix on the actual centre of the anticline, but it is clear that in 
 the Loch Riddon district the horizons mentioned are both nearer the 
 approximate centre than they are in the Loch Goil district. 
 
 It is impossible to follow any particular foliation plane any distance, 
 but it seems as if the foliation planes also, as well as the bedding, have, on 
 the north-west side of the anticline, a somewhat more northerly direction 
 than on the south-east side. Xear Lochgoilhead there is a greater width 
 of ground, measured across the average strike of the foliation, where the 
 foliation seems to be essentially flat, with alternating dips now north-west 
 and now south-east, than there is at Loch Riddon. It is possible that in 
 the former locality, too, the lowest foliation planes disclosed may be some- 
 what below the lowest at Loch Riddon. If this be so it follows that the 
 crest or axis (using this word now in its strict sense see footnote on p. 
 10) of the anticline must have a slight inclination to the south-west, f 
 and it is probable that the numberless folds which together make up this 
 anticline have usually an inclination of crest in the same direction. As a 
 
 * See Plate X. 
 
 t Or, to use the expression common among American geologists, has a slight 
 " pitch" to the south-west, 
 
88 
 
 GEOLOGY OF COWAL. 
 
 mutter of fact any inclination there may be is too slight to have been 
 noticed in field sections. 
 
 Lines of actual rupture contemporaneous with the schist-making, com- 
 parable to the " thrusts " of the north-west of Scotland, probably do not 
 occur anywhere in Cowal, except on the smallest scale, represented by the 
 first foliation-throws seen in the Dunoon section, and the different strain 
 slips already so often mentioned, and some few doubtful cases, which we 
 will describe. I do not think I have ever observed the throw of a strain 
 slip to exceed a few inches, and, more commonly, it is only half an inch or 
 so. In some cases, e.g. on the coast mile north-west of Ardbeg (183 
 north-west) bands, reaching to 4 or 5 inches in breadth, have in certain 
 parts of limbs of very sharp folds, an appearance as if, for a few inches, 
 they had been drawn out to nothing ; but we do not feel sure this is 
 always the true explanation of the appearance. It may be that the band 
 was originally unequal in thickness, or even non-existent for a little dis- 
 tance. In other places there are discordances in the folding of two beds, 
 and it is suggested that this may be due to the presence of a thrust line 
 between them. In a scar on the hillside, J mile north-east of Glenmassan 
 (163 south-west), there is a section showing, in its upper part, a massive 
 pebbly schist lying almost flat, and, below this, are much folded white 
 quartzite schist bands, which lie in phyllitic mica schist. Along the line 
 of apparent discordance there are a number of quartz veins, mixed with 
 broad streaks and knots of black mica. It seems at least necessary to 
 suppose a certain amount of differential movement between the over and 
 the underlying beds in cases like this, unless it is possible that they were 
 originally of an extremely false-bedded or occasionally curve-bedded* 
 character, such as we see not uncommonly in the unaltered Torridoniaa 
 rocks. On the south side of Kinglas Water, | mile above Ardkinglas 
 House, is an interesting section in an alternating series of quartzose schists 
 and phyllitic mica schists, the latter containing occasional small albites. 
 The upper part of the section is mainly phyllitic, the lower, quartzose ; 
 for a length of 2 or 3 feet the line between the two parts seems a dis- 
 cordance, the foliation and bedding planes of the upper part striking 
 markedly against those of the under. The apparent discordance line is 
 in one place much crumpled ; it is in places accompanied by short quartz 
 veins ; in other places there is nothing to mark it except the want of 
 agreement in the beds on either side. A little above it, and running 
 parallel, are short chlorite lenticles ; these cross the foliation of the rock 
 in which they occur, and may be supposed to mark the course of a 
 subordinate discordance. In the same locality there are various other less 
 marked discordance lines. 
 
 FIG. 32. x |. Vertical section S. side of Kinglas "Water, f mile above Ardkinglas 
 Ho., in alternating albite and quartzose schists. The unshaded parts denote 
 the latter. Direction of shading indicates direction of foliation. Black areas 
 are chlorite. Cross-hatched areas are vein-quartz. The axis of fold in upper 
 part of sketch hades N.W. 
 
 We apply this term to beds of which the component laminse are partly arranged 
 in curves though the top and bottom surfaces are quite even. 
 
PHYSICAL STRUCTURE OF THE SCHISTS. 89 
 
 The numerous faults which have been mapped and have effective throws 
 are all later than the schist-making, and break up the minerals and planes 
 of schistosity, instead of helping to form them. Not unfrequently we can 
 see very thin, and perhaps almost horizontal, lines which make a prominent 
 show in scars ; but these are all of comparatively late date, and occasion- 
 ally can be proved to be later than the tertiary basalt dykes. 
 
 Attention may be called to the wide range of the green beds. They 
 occur every here and there all the way from the north-west side of the 
 Dimoon phyllites up into the Ardrishaig phyllites on Loch Fine side. 
 The character of these beds is so peculiar that it may with great 
 probability be assumed that they all belong to one great formation. It 
 does not seem likely that the different outcrops can be portion of one 
 formation folded in unconformably with another, for transitions from the 
 green beds proper into the common schistose greywackes can be observed 
 over and over again. The green beds therefore help to connect together 
 the schists of the different areas, and their distribution renders it probable 
 that the great mass of these schists belong to one great formation, 
 
 No cherts have been observed like those iu which radiolarian structures 
 hare lately been discovered near Aberfoil, Callander, etc. Nor are there 
 any beds at the south-east frontier of the Highlands in this district which 
 are so little altered as the black shales and greywackes associated with 
 the cherts.* 
 
 The curious conglomerate on the east side of Loch Fad in Bute, by 
 the "h" of "Loch" and the "F" of "Fad," contains, however, large 
 pebbles and boulders of extremely little altered grit and grey-green 
 felstone-like rock, with others of reddish limestone, which,, in state of 
 alteration, remind one very much of the beds accompanying the cherts. 
 The fragments iu this conglomerate seem entirely composed of such little 
 altered beds : we could find no pieces that could be confidently matched 
 with the schistose rocks at the opposite side of the loch. It may, there- 
 fore, well be that in old times before the formation of this conglomerate 
 there was an adjacent area of rock, belonging to the same series as those 
 near Aberfoil. 
 
 The fragments in the Upper Old Red conglomerates near the boundary 
 of the schists are almost entirely of adjacent Highland schists, or of vein 
 quartz, or of igneous rocks, probably in the main of Lower Old Red Age. 
 It is not certain that they ever include fragments like those in the Loch 
 Fad conglomerate : at all events, such fragments must be rare. We may, 
 therefore, probably conclude that the exposures, from which the fragments 
 in the Loch Fad conglomerate were derived, did not make at all so large a 
 show during Upper Old Red times as they had done previously. This, per- 
 haps, indicates that the boundary fault along the Highland frontier represents 
 a line of very old and repeated movement, and thus confirms what is 
 said, p. 95, as to the probability of a large part of the crushing at present 
 seen along it being older than the Upper Old Red Sandstone. In 
 the country between Aberfoil and Loch Lomond there is a thick crush 
 zone running X.N.E. near the Highland frontier which is certainly of 
 earlier date than the Upper Old Red Sandstone, and very probably there 
 is another still earlier line of discordance of a thrust-like character. 
 
 The direction of the boundary fault is nearly parallel to that of the 
 centre of " the anticline." There are some thin crush lines, seemingly 
 continuations or connections of the Tyiidrum set of north-east or N.N.E. 
 faults, which are also approximately parallel to these : e.g., the one cross- 
 ing Glendaruel near Lephinkill, one near Balliemore at the head of Loch 
 
 * These and the associated beds match very well with some of the Arenig and 
 Llandeilo rocks of the South of Scotland. 
 
90 OKOLOOY OF HOWAT, 
 
 Striven, one crossing the east shoulder of Ben Donich (134 and 142), 
 and others a mile or two off this last on the north- west side. These may 
 give rise to prominent features in the landscape, but they do not seem to 
 have large throws. Some of the same class, that run with the graphite 
 schists near Strachur and St Catherine's, seem to be more lateral thrusts 
 than vertical movements, and are also of special interest as being of 
 earlier date than some of the lamprophyres : most of these lamprophyres 
 are, as stated on p. 108, clearly later than most of the faults of the district, 
 and are affected by their throws. The early faults referred to cannot be 
 V classed with the thrusts of the north-west of Scotland, for they tend to 
 destroy the schistose character of the rocks, not to develop it. 
 
 In the area east of Loch Kiddon there are many important faults which 
 run nearly north and south, or between this direction and that of the 
 schist boundary fault, so that they gradually approach the latter as one 
 proceeds in a south-west direction. These have nearly always downthrows 
 to the east, the beds on the east of them having their outcrops advanced 
 somewhat to the north. They can often be made out to be in part of 
 earlier date than the basalt dykes, but to have had the movement along 
 them renewed again after the intrusion of these : for illustrations of this, 
 refer to pp. 143, 186. 
 
 On the south-east side of Glen Fine the strike of the foliation is de- 
 flected into parallelism with the adjacent granite boundary. For a distance 
 of \ mile or more from the boundary the dip is inward towards the 
 granite. Further away the dip is, in some places, away from the granite 
 towards the south-west : at other times it is west, without any clear re- 
 lation to the visible granite margin. 
 
 Some of the evidence for different faults and folds, together with an 
 account of some of the more interesting sections which have not yet been 
 described, is given in separate descriptions of the different areas. 
 
 Let us return for a little to a consideration of the coast sections which 
 have been described in chapter II. Anyone who examined cursorily the 
 section at Dunoon and that in the Kyles of Bute, could not help being 
 struck with the greater mineral change in the latter locality. He might 
 very likely put this down as an indication of the greater age of the 
 schists in it, and suppose that, somewhere or other in the intervening 
 area, an unconformity would be found, the less altered Dunoon rocks 
 lying unconformably on those of the Kyles of Bute. The rocks are now 
 so crumpled, and original structures so distorted and obscured, that 
 perhaps it would be quite possible for such an unconformable junction to 
 be overlooked. 
 
 If now the same person were also to examine the Ardentinny section he 
 would find a stage of metamorphism which seems in many respects inter- 
 mediate between the two previously alluded to, and doubts might enter 
 his mind as to whether his former theory were correct. Still more would 
 he doubt, if he had the opportunity of also examining the different 
 sections that come between the Dunoon and Ardentinny horizons and the 
 Ardentinny and Kyles of Bute horizons respectively. He would then find 
 that there is an insensible gradation between the stages of metamorphism 
 found at Dunoon and the Kyles of Bute, and that it is at all events 
 necessary to conclude that the metamorphism increases quite gradually 
 as we proceed north-west from Dunoon toward " the anticline," whether 
 the rocks are the same or of different ages. 
 
 A more complete knowledge of the Kyles of Bute section would also 
 show him, as we hope we have made clear, that those structures, strain 
 slips, etc., which occur in it and not in the Dunoon section, affect earlier 
 structures which correspond to those at Dunoon. Hence, whatever may 
 
METAMORPHISM OF THE SCHISTS. 91 
 
 be the relative geological age of the original rocks in the two localities, 
 the age of those secondary structures in the Kyles which do not agree 
 with those at Dunoon are not earlier than these last, but later. 
 
 We have shown, too, that the mineral changes, both in the Kyles 
 section and elsewhere, are intimately connected with the mechanical 
 secondary structures just referred to. They may not be the direct result 
 of the heat, etc., liberated during the formation of these structures, but 
 they have undeniably taken effect either during or after their production. 
 Therefore we are forced to conclude that the mineral changes in the Kyles, 
 in so far as they affect structures of later date than those at Dunoon, are 
 also of later date. 
 
 To what agent or agents may we attribute the general regional ineta- 
 morphism of the district ? It is perhaps premature to say much in reply 
 to this question. The whole of the metamorphism seen in any particular 
 rock can hardly be considered the result of the mechanical strains occur- 
 ring in that rock itself, for we have seen that there is a distinct increase 
 of metamorphism in the section south of Ardentinny, as compared with 
 that at Dunoon, though the mechanical movements are approximately the 
 same at both places. The Ardentinny section is, however, much nearer 
 the centre of the greatly crumpled " anticline " area, and we may perhaps 
 suppose that the heat engendered by the physical movements there would 
 travel outwards for some distance into rocks which are not themselves so 
 crumpled. 
 
 There is also another important point to be considered. "The anti- 
 cline " is certainly an anticline of foliation, whether it is of bedding or 
 not, and the rocks at present exposed in the centre of it must, before the 
 ridging up, and subsequent denudation, have been lying under a much 
 greater thickness of rock, and therefore presumably exposed to higher 
 temperatures, derived from the earth's internal heat, than those now 
 occurring far away on the flanks. The distance of the schists at the 
 boundary fault at Inellan from the centre of " the anticline " may be 
 taken as about 9J miles, and the foliation dip in the intervening area 
 may be averaged as 40. These data give 32,000 feet as the approximate 
 thickness of the beds measured across the early foliation planes, and the 
 covering over " the anticline " rocks was once, perhaps, as much as this 
 thickness greater than the covering over the rocks near the boundary 
 fault. 
 
 There are no exposures uf igneous rock in the Map to which it is 
 possible to refer the metamorphism in question. The alteration effected 
 by the Glen Fine granite does not extend much more than 1-mile from 
 the granite, and gives rise to various minerals, andalusite, sillimanite, 
 cordierite, etc., which are quite unknown elsewhere in Cowal. On the 
 other hand, the albites of the albite schists are practically no more 
 prominent near the granite than they are 20 miles away. The character 
 of the alteration around the granite, and its relation to that of the albite 
 schists, is described more fully on pp. 98-101. 
 
 The metamorphism shown by the garnetiferous mica schist gradually 
 increases along the strike in a north-east direction, but we are ignorant of 
 the cause of it. This zone lies some distance north-west of "the anti- 
 cline," and the metamorphism special to it seems of earlier date than that 
 which produced the albites (see p. 52). North-west of the garnetiferous 
 schist the metamorphism decreases, and continues to do so on the north- 
 west side of Upper Loch Fine. C.T.C. 
 
92 GEOLOGY OF COWAL. 
 
 CHAPTER IX. 
 
 UPPER OLD RED SANDSTONE. 
 
 The Upper Old Red Sandstone rocks of Inellan and Toward closely re- 
 semble those which occur in Bute below the andesitic lava flows, and are 
 probably continuous with them under the sea. They are exposed along 
 the shore most of the way between Inellan pier and the east gates of 
 Toward Castle policies, and also in most of the old cliff of the raised beach 
 between these places. Between Inellan and Chapelton they form such a 
 narrow fringe to the land that its width does not usually exceed that of 
 the raised beach, and consequently we get the schists on the west side of 
 them exposed on the old cliff for a considerable distance. South-east of 
 Chapelton they extend further inland, but with one small exception, about 
 ^ mile north of Toward Cottages, there are no inland sections save in the 
 burns, all the rest of the area being covered with drift or raised beach 
 material. 
 
 They consist in the main of red breccias and sandstones, mixed with 
 occasional blood-red shales and variegated purple and green-grey clayey 
 shales. Calcareous sandstones or cornstones and magnesian limestones 
 are also numerous on a certain horizon. No organic remains have been 
 found in any of these beds. 
 
 The sandstones are false-bedded and rapidly changeable in character ; 
 in one place they may be half-full of schist fragments ; in another, a few 
 yards away, they may be quite free from these. The inclosed schist 
 pieces are generally angular, and may reach a length of 2 or 3 feet, but 
 the bands which contain the larger pieces seem very local, and a length 
 of from 1 to 4 inches is more frequent : among the common pieces are 
 purple and black phyllite, sheared grits with large quartz pebbles, and 
 some tough green grits. The phyllites may well have come from the 
 Dunoon series or from bands on the south-east side of it : the quartzose 
 grits are like those common in the schist area immediately adjoining : the 
 green grits are of the gritty " green beds " type found on the north-east 
 side of the Dunoon phyllites. There is a general absence of the more 
 highly altered and crumpled mica schists of " the anticline " area (see p. 
 23). We may conclude from these facts, and from the angularity of 
 the pieces, that the coast line which furnished the pieces was near at hand 
 and was composed of different schists in much the same proportion as the 
 present schist margin. Some of the pieces are reddened, while others close 
 at hand are not. 
 
 Of the pieces other than schist, those of vein quartz are the commonest, 
 and after these hard reddish-yellow or purple quartzites ; of more rare 
 occurrence are magnesian limestone, soft red and yellow sandstones, red 
 and pale yellow jasper-like bits, and porphyritic igneous rocks with 
 prominent black mica. 
 
 The sandstone and limestone pieces perhaps point to contemporaneous 
 denudation, and some of the jasper-like pieces may also have come from 
 chert bands in limestones of approximately the same age. The sandstone 
 pieces are generally angular, but the vein quartz, quartzite, and igneous 
 rocks are remarkably well rounded. One of the porphyrite-like pebbles 
 was examined by Dr Hatch (slide 2836), and proved to be a nepheline 
 bearing rock. It is described by him as follows : " In a dirty brown 
 cryptocrystalline ground-mass, consisting of an admixture of turbid with 
 clear crystalline matter, are embedded a number of rectangular and hex- 
 
UPPER OLD RED SANDSTONE. 93 
 
 agonal sections, the greater part of which remains dark during a rotation 
 under crossed Nicols, only a number of irregularly distributed specks 
 transmitting light. These are probably pseudomorphs after nepheline. 
 The rock strongly resembles the so-called Liebenerite porphyry, except 
 that the secondary mineral, which has replaced the nepheline is isotropic, 
 (analcime perhaps), instead of giving, under crossed Nicols, the brilliant 
 mosaic characteristic of the Predazzo rock (Zirkel, Neues Jahrb, 1868, 
 7 and 9)." 
 
 Throughout the sandstones may be found dirty grey balls, averaging 
 about 1 inch in diameter, which contain hard dark centres, apparently due 
 to segregation of the iron oxides from the surrounding paler area. 
 
 In some of the beds the contained fragments consist entirely of schist ; 
 in others of schist and vein quartz mixed in not very unequal proportion ; 
 in others again schist is somewhat rarer. The last type occurs especially 
 in association with the limestones, and, as is seen more clearly in Bute, 
 we suppose that it and the limestones mark a definite horizon, and 
 overlie a lower coarser set of rocks in which schist pieces are very 
 numerous. This calcareous horizon, as far as known in this district, 
 does not exceed 100 or 150 feet in thickness. Of the breccias and sand- 
 stones no base is seen. 
 
 The limestones are seen best at Toward Point, on the shore west and 
 north of the Perch, and in the burn above Toward Taynuill. They are 
 nmst usually white or cream colour, compact or finely crystalline in 
 texture, and vary in thickness from the thinnest courses up to 20 feet at 
 least. The limestone on the west side of Toward Point attains the thick- 
 ness mentioned, and may be thicker, as no top is seen. Thin bands of 
 limestone or calcareous sandstone are frequently seen to occur in a len- 
 ticular manner, their outcrops rapidly varying in thickness or dying out. 
 Reddish nodules of chert occur in the Toward west limestone, and nodules 
 or thin bands of it also occur in the Toward east limestone, in the lime- 
 stone mapped by the lower part of the "C" of "Chapel," and in the most 
 northerly exposures on the shore. In the last locality the chert streaks 
 are repeatedly broken and slightly shifted by minute faults, which are 
 confined to the bed in which they occur ; below the main mass of lime- 
 stone white calcareous bands, several inches thick, descend vertically or 
 approximately so ; at other times lumps of purer white limestone occur 
 irregularly embedded in a less calcareous purple or reddish rock. Spots 
 about the size and shape of peas, and whiter than the containing rock, 
 are in places common, and project slightly on the weathered face. In 
 the burn above Toward Taynuill the irregular manner of occurrence of 
 the limestone is also marked the separating lines between the other beds 
 and it not kseping at all strictly to the bedding. Both the bed and sides 
 of this burn, from the small north-east fault, which crosses the burn at a 
 point about 80 yards south of the schist boundary, to a point 90 yards 
 south of this fault, consist of limestone, mixed irregularly with more sandy 
 portions. Other exposures are seen both above and below here, brought 
 up partly by faults and partly by change of dip. In 1886 Messrs 
 Merry & Cunningham made a trial of this limestone for lining their 
 basic Bessemer steel converters, but the sample tried, amounting to 20 tons, 
 showed 10 '8 per cent, of siliceous matter, and so could not be used alone. 
 The limestone quarried was white and crystalline, with irregular purplish 
 and reddish parts, which were softer to the knife ; it was taken out of the 
 east bank of the burn at points 50 and 100 yards south of the fault 
 mentioned. The following analyses of Toward dolomite are kindly 
 furnished by Mr R. Main of Messrs Merry & Cunningham. 
 
94 GEOLOGY OF COWAL. 
 
 No. 1. No. 2.* No. 3. No. 4. 
 
 CaOCO 2 , 53-87 54-83 54-03 57'98 
 
 M g OC0 2 , 41-52 36-87 35*73 38-37 
 
 A1 2 3 , ' 1-20 1-50 1-20 -90 
 
 SiO 2 , 3-30 4-60 8-70 2-80 
 
 99-89 99-80 99-66 100-05 
 
 On either side of the basalt dyke, 300 yards west of Toward Cottages, 
 are exposures of thin hard white limestone bands, mixed with green a ad red 
 marls and red sandstone posts. Softer red freestones of apparently some 
 thickness come on above these to the south. These limestones are evenly 
 bedded, and contrast strongly with the lenticular habit of most of the 
 thinner limestones of the series. 
 
 In the fields at points 100 yards east and 240 yards W.N.W. of 
 Toward Cottages, trials for coal are said to have been made. This cannot 
 have been since 1816, and uo information can now be obtained of them. 
 There is still the appearance of an old hole in the former locality. We 
 suppose they were in search, more especially, for the seam which occurs 
 immediately below the andesites at Loch Ascog in Bute. 
 
 As the limestones are supposed to mark a stratigraphical horizon, it is 
 clear, as we examine the ground, that it is necessary to call in the aid of 
 certain faults to explain their present different positions. 
 
 South from Inellan pier, for the first 500 yards we seem to keep on 
 much the same horizon, the beds consisting of greyish-red sandstones 
 with pebbles, chiefly of vein quartz and qnartzite, but subsequently we 
 pass into lower rocks, blood-red clays, and sandstones with thin corn- 
 stones, until we reach thicker limestones. These are seen every here 
 and there, with gently varying dips, for about J mile ; then we come to 
 red sandstones and breccias, with an apparent dip to the north of sometimes 
 as much as 20 or 25. If this can be taken as true dip, we should, on 
 getting to the shore east of the Perch, be some distance below the lime- 
 stones. That this is the case seems likely from the abundance of schist 
 pieces in the breccias. Concluding this to be the fact, then, we continue 
 south, crossing three basalt dykes running W.N.W. ; shortly after passing 
 the last of these we come again to limestones still dipping north, at much 
 the same angle as the breccias. The limestones would seem at first to 
 underlie the breccias. We suppose them to be thrown down into this 
 position by a fault, with downthrow to south, running alongside the last 
 basalt dyke referred to. This dyke hades south, and the beds for a few 
 yards on the south of it also dip south. It does not show any signs of 
 crushing, but this is no objection to the existence of the supposed fault, 
 as in this district" we repeatedly find faults of early date along which the 
 basalts have subsequently proceeded. 
 
 South from here the limestone series still continues dipping north, 
 so that we gradually pass into lower beds. On the shore near Chapelhall 
 a crash is also seen, running W.N.W. with hade to north, and this helps to 
 the same result. Thus we soon lose the calcareous bands and reach a set 
 of red sandstones and breccias, which keeps on all the way to Toward 
 lighthouse, a distance of 1 mile. For the north half of this distance the 
 dip is still to north at perhaps 10-12, but in the south half the beds 
 seem nearly flat. These sandstones may be taken to be the same as those 
 at and to the north of the Perch ; and like them, as we have seen, they dip 
 below a limestone series to the north. At Toward pier and lighthouse, we 
 are doubtless some distance below the limestones, but on a point on the 
 * Analysis is given as received, but it does not add up correctly. 
 
UPPER OLD RED SANDSTONE. 
 
 95 
 
 I? 
 
 ti 
 
 
 
 / 
 
 -; 
 
 ; 
 
 L 2 
 
 shore about 50 yards south of the lighthouse, where the coast changes 
 direction from north and south to east and west, we suddenly find a dip to 
 S.S.W. of 15 to 25, and see several outcrops of limestone striking against 
 the sandstones. This is no doubt due to a fault with downthrow to the 
 south, running in a west or W.N.W. direc- 
 tion. The west limestone was sought by 
 Messrs Merry & Cunningham in a series of 
 shallow bores, immediately behind the wall 
 of the field west of the last villa west of 
 Toward lighthouse, but as these are on the 
 upthrow side of the fault, they of course 
 failed to find it. At a point 100 yards south- 
 west of the lighthouse, a basalt dyke seems 
 slightly shifted by the fault, the south side 
 to the west, or else it had originally a slightly 
 different position on either side of this line 
 of weakness. The dyke on the north side 
 contains a thin band of pebbly sandstone 
 and also a calcareous band, with geodes of 
 quartz crystals. We may perhaps estimate 
 the throw of the fault as 200 to 250 feet. 
 It probably runs under the raised beach at a 
 point about 140 yards east of Toward 
 Cottages ; on the west of this limestones 
 and calcareous bands again appear, with a 
 general absence of the coarse schist breccias. 
 
 Some 200 yards before reaching the schist 
 boundary disturbances we again lose the cal- 
 careous beds, and meet with sandstones with 
 some bands very full of schist pieces. We 
 suggest another fault here running in a 
 N.N.E. direction, and with downthrow to 
 the east. 
 
 The sections that best illustrate the rela- 
 tions between the red rocks and the rueta- 
 morphic schists occur on the shore close by 
 the east gates of Toward policies, and at or 
 just to the south of Inellan pier. Less satis- 
 factory ones occur in the burn above Toward 
 Taynuill, and in the burn and cliff near 
 Chapeltou. It is clear that the boundary of 
 the schists is a line of strong crush, but it is 
 not so clear that this crush is of later date 
 than the red rocks. These rocks are no- 
 where seen distinctly crushed or disturbed 
 near the boundary, and in the section at 
 Toward they are lying nearly flat against the 
 crush area, along a line which in one place 
 changes sharply almost at right angles to its 
 general direction, and still show no crushing. 
 Neither could we satisfy ourselves that any 
 
 fragments of them exist in the crush ribs that bound them. In the 
 Inellan section, also, at a point about due east of the Parish Church, the 
 boundary makes a sharp bend to the west, for a few yards. In all pro- 
 bability the boundary is an old line of weakness, along which movements 
 have taken place at more than one geological epoch. It seems impossible 
 
 iiV* 
 
 1 
 
 1 
 
 *. 
 
 
 
96 GEOLOGY OF COWAL. 
 
 to imagine that all the crushes in the Toward section crushes in all 60 
 to 80 yards wide -could have been formed subsequently to the Upper 
 Old Red Sandstone, and yet have left these rocks so little disturbed. 
 
 The absence of red staining in the schists seems at first a strong argu- 
 ment in favour of considering some of the movements of later date, but 
 it is doubtful if this has the weight it at first seems to possess. The 
 line of junction was probably steep, and there may not have been much 
 tendency for the staining agents to percolate sideways through the earlier 
 crush ribs. There is a wide basalt dyke in the Toward section, running in 
 and parallel with the crush ribs, and this is quite unaffected by the crush- 
 ing, so that we may be certain that no movement has taken place since its 
 intrusion. Two similar uncrushed dykes occur in the Inellan section, run- 
 ning nearly at right angles to the direction of crush. The schists that 
 bounded the red rocks at the time of consolidation of the dykes were then 
 the same as those now doing so, and we know that no staining has taken 
 place in the interval. 
 
 Still, it does seem necessary to suppose that some movements have taken 
 place along this line subsequent to the time of the Upper Old Red Sand- 
 stone, and, though they may have done so without much crushing or con- 
 tortion, the displacement effected may yet have been considerable. In the 
 first place, we know that in the red rock area generally later displacements 
 are common, and that rocks occupying different positions in the series now 
 abut against the schists at the same level at different places thus, in the 
 cliff south of Inellan Free Church a magnesian limestone lies close by the 
 schists, while at a point T 5 ^ mile north-west of the Perch, red breccias do 
 so* In the second place, the rocks now lying close to the schists are often 
 much less full of schist fragments than we should expect if they had 
 been formed at the immediate base of schist cliffs. 
 
 C.T.C. 
 
 CHAPTER X. 
 
 THE IGNEOUS ROCKS. MARGIN OF THE GRANITE NEAR 
 CRUACH TUIRC. HORNBLENDE - PORPHYRITE AND 
 FELSITE. HYPERITE. 
 
 Margin of the Granite near Cruach Tuirc. 
 
 A small part of the igneous complex of Garabal Hill and Meall Breac, 
 described by Messrs Dakyns and Teall (Quart. Journ. Geol. Sac., vol. 
 xlviii. p. 104), comes into the north-east comer of 1-inch Map 37. We 
 make no attempt to describe the whole of this part, but give an account 
 of the edge of it near Cruach Tuirc, and the metamorphisrn near this edge, 
 chiefly with a view to contrast the rnetaniorphisin special to its neighbour- 
 hood with that found further away, near the anticline of Cowal, etc. 
 
 The edge of the complex between the River Fine and the east margin 
 of 1-inch Map 37 consists, as far as the drift allows one to see, almust 
 entirely of coarse granitic rocks, frequently hornblendic, and in some 
 places so much so as to be worthy for small areas of the name of diorite. 
 There seem all gradations from granite, or rather granitite (using this last 
 term to imply a granite which contains much plagioclase and a black mica, 
 but no original white mica) through hornblendic granitite, into a rock of 
 much the same coarseness of grain in which the hornblende is in excess 
 
MAKGIN OF THE GRANITE. 97 
 
 of the biotite. It would create a false impression if a sharp line were 
 drawn to separate the different varieties, and we have in the Map massed 
 them together as granite. There ^are, however, besides the coarse dioritic 
 granitites which pass gradually into the normal granitites, one or two 
 small exposures of a much darker fine-grained diorite which occurs close 
 to the margins of the complex, and is probably sharply separated from 
 the adjoining granitite. Unfortunately none of these exposures is clear, 
 and they are of very limited extent, too small to be satisfactorily shown 
 on the 1-inch Map. But we shall shortly describe them in detail, as it is 
 possible that they indicate the earlier existence of an extensive mass of 
 diorite near the present edge of the complex, which mass has now in most 
 places been intruded through by later granitic rock. 
 
 The granitic rocks are generally characterised by abundant porphyritic 
 crystals of orthoclase felspar (op. dt. t pp. 105, 108), sometimes as much 
 as 2 to 3 inches in length. These vary in prominence a good deal in 
 different parts : in some they are quite rare : in others they form nearly 
 half the area of certain rock exposures. They are usually, as shown most 
 clearly in some of the clean-washed boulders on the shore of Loch Fine, 
 distinctly zoned, the outer zones being of paler felspar substance than the 
 inner parts, approximating in fact to the colour of the small felspars of 
 the ground mass. Small inclusions of biotite frequently lie along the 
 sides of the zones, and have their greater lengths parallel to the sides along 
 which they lie. The biotite is, as already mentioned, usually accompanied 
 with hornblende in varying quantity. Under the microscope it is seen 
 to contain many inclusions of apatite, sometimes arranged in stellar groups. 
 The interstitial quartz is not always conspicuous in hand specimens, and 
 probably varies in quantity a good deal. It is sometimes of a slightly 
 milky opalescent colour. Sphene is an abundant accessory mineral, occur- 
 ring sometimes in large brown crystals. It is quite distinct to the naked 
 eye in the granitite in the River Fine by the " F " of " Fine," and in some 
 fine-grained dark patches included in the granitite. In these dark patches 
 (slide 6115) biotite and sphene are more abundant than in the enclosing 
 rock, but hornblende is absent. Slide 6113, from the rock in the River 
 Fine, T 5 g- mile slightly south of east of Newton Hill, shows plagioclase in 
 large porphyritic crystals. Mr Teall says of this : " A coarse-grained 
 grey horublendic granite. Very large idiomorphic crystals of zoned plagio- 
 clase, idiomorphic green hornblende, biotite and sphene with interstitial 
 
 orthoclase and quartz. The sphene occurs in very large crystals 
 
 Iron ores and apatite occur as accessories." 
 
 Dark basic inclusions, most of them probably referable to diorite, 
 are common, and are sometimes 1 to 2 feet in diameter. They are 
 rounded in outline, weather in depression, and are not conspicuously 
 longer in one direction than another. Granitic strings are sometimes 
 seen cutting through these inclusions : in some of the strings the full 
 width may be taken up by a porphyritic felspar. No marked signs of 
 fluxion structure have been observed in this area, but here and there a 
 sub-parallel arrangement of the porphyritic felspars may be seen. 
 
 The granitic rock is as coarse in grain at its junction with the schists 
 as in the interior. There is no definite line for the edge of it, but for a 
 little space there are alternations of schist and granite, the latter gradually 
 increasing north-east until it forms the whole of the rock. On the east 
 side of Craach Tuirc the area of veined schist extends perhaps 120 yards, 
 or rather mure, from the granite boundaiy drawn in the Map. In this 
 area not only are there many thin approximately vertical granitic strings, 
 sometimes several feet in width, but also, particularly near the main 
 granite mass, numberless granitic strings which run with the foliation of the 
 
 G 
 
98 GEOLOGY OF COWAL. 
 
 schist. The thickest of these last are often about 1 foot thick, but there 
 are others much thinner and very short, which sometimes give rise to an 
 appearance of almost isolated crystals of felspar along the foliation planes 
 of the schist. Neither the vertical strings nor those running with the 
 foliation are finer at their edges : the felspar crystals within the thinnest 
 of them are often about the size of peas, and occasionally take up the full 
 breadth of a string. In this locality we did not observe the large por- 
 phyritic felspars, until the main granite area was reached, and they are not 
 always apparent there. For 30 yards or so west of the line taken as the 
 generalised granite boundary, the alternations of schist and granite are 
 almost equally divided, in bands 10 to 30 feet thick, which run roughly 
 parallel with the schist foliation. The granite bands here have often thin 
 pegmatites, 2 to 3 inches thick in them : in these pegmatites the patches 
 of quartz are occasionally 1 to 2 inches thick, and are somewhat opalescent: 
 the biotite folia sometimes attain a length of f inch. 
 
 The schists into which the above strings intrude are an alternating series 
 of micaceous albite schisti and more quartzose schists. The general dip 
 of the foliation is inwards towards the granite mass. Andalusites in 
 brown prisms, sometimes J inch long, are extremely abundant in the more 
 micaceous and albite bearing schists. They form a close network which 
 projects slightly on the weathered face, and so are readily discerned. In 
 fresh fractures it is much more difficult to detect them. The prisms cut 
 across the foliation in any direction, and show no bends or fractures. 
 The albites in the albite schists are not uncommonly changed 
 into a pink tint. This change seems due to the oxidation of the magne- 
 tite specks inclosed within them (see p. 101), and is of the same nature 
 as that seen in the neighbourhood of other intrusions in Cowal. Streaks 
 of iron pyrites and nests of black mica are common in the more micaceous 
 schists. In the quartzose schists the alteration near the granite is not 
 so evident ; nests of black mica occur here and there, but not commonly : 
 the black mica along the foliation planes seems also to be in unusually 
 large flakes lengths of -J- inch being common. In addition to the 
 andalusite, two other well-known contact minerals have been detected in 
 the microscopic examination of slides from the altered andalusite rock or 
 " hornfels." These are sillimanite and cordierite. The former occurs in 
 slide 6098, in bundles of very thin colourless fibres, with transverse jointing. 
 It has also been noticed preserved in quartz in a slide of a boulder found 
 |- mile north-east of Achadunan. This boulder, of andalusite hornfels, is 
 traversed by thin strings which are composed at their sides of a coarse- 
 grained pale acid rock with abundant quartz, and no mica or hornblende : 
 in the central parts of the strings there is no macroscopic quartz, but horn- 
 blende is abundant. In slide 6099 (andalusite-hornfels) cordierite is 
 recognised by the occurrence of yellow pleochroic halos in a mineral other- 
 wise resembling untwinned felspar. 
 
 In the river mile W.S.W. of the " F " of " Fine," the schists also 
 consist of an alternating series of micaceous albite schists and more 
 quartzose schists. The general foliation dip is east. The albites are 
 reddened : the matrix of the containing schist weathers smooth and 
 black, and the red albites scattered through are prominent. Many fine 
 granitic strings intersect the schists and run with a general E.N.E. 
 direction. There are also coarser bands of hornblendic granitite which 
 occur partly as dykes and partly as irregular sheets along the foliation : 
 these are as coarse at the edges as in the middle : when they occur as 
 dykes they have the same direction as the finer dykes. Near the south- 
 west and west sides of the south-west island, there are good sections 
 showing the permeation of the schists by thin streaks and irregular 
 
MARGIN OF THE GRANITE. 99 
 
 patches of the granitite. If it were not for occasional clear intrusive 
 sections some parts of the granitite might be mistaken for an altered albite 
 schist of coarser character than usual. Sixteen yards north of the north 
 end of the south-west island, a vein of dark diorite, 3 inches thick, is seen 
 intruding in the schist. Sixty yards N.N.E. of the north end of the same 
 island another exposure of fine-grained black diorite occurs. On ex- 
 amining vertical sections, the constituents of the rock seem to run parallel 
 in a nearly vertical direction. The diorite contains scattered grains of 
 white felspar attaining the size of a pea. Some parts of the exposure are 
 composed of a coarse paler diorite, which occasionally runs in straight 
 strings through the finer rock and appear to be intrusive in it. East 
 from this place we come on an area of schist 4 to 5 yards broad, and then 
 the fine black diorite is seen a third time, and again with a parallelism in 
 the constituents. In the north-east channel of the river, 16 yards north- 
 east of the south-west end of the big island, the fine black diorite and a 
 fine-grained granite or porphyrite are in contact. The diorite has a 
 foliated appearance in vertical sections. It seems underlain by the granitic 
 rock, and to have the course of its constituents cut across by it. On the 
 east side of the exposure there is more schist before we reach the main 
 granite area. The granitic rock does not get finer at its junction with the 
 diorite : it looks very like the porphyrite which occurs in sheets within 
 the schists, etc. 
 
 In the burn J mile E.N.E. of the first "a" of " Meall Beag," there is 
 a dark fine-grained diorite, with porphyritic felspars sometimes J- inch long, 
 close to a porphyrite, but the actual contact of the two is not seen. 
 In the part of the same burn extending for J mile below this, and on the 
 E.N.E. side of Lochan Mill Bhig, there are good exposures of the altered 
 albite and quartzose schists. The rocks are all harder than usual, and 
 weather with a brown crust. Thin pyrites strings often occur along the 
 foliation. The matrix of the albite schists is darker than usual and has 
 a rather conchoidal fracture : the albites themselves often appear red, but 
 not always : the same bands in which they occur also contain andalusites, 
 and small nests of black mica : we are inclined to say, too, that both in the 
 albite schists and in the quartzose schists there is a greater abundance of 
 black or purplish-brown mica on the foliation planes than usual. Epidote, 
 generally in short irregular strings and sometimes mixed with quartz in 
 veins, is in some places common. These strings are not absolutely 
 confined to the schists : they occur also in granitic veins. Garnets and 
 ilmenite also occur abundantly in the albite schists N.N.E. of Lochan 
 Mill Bhig, but it is not probable that these have any genetic connection 
 with the andalusites. The garnets are like those in the garnetiferous 
 mica schists described on pp. 49-52. In the burn J mile N.N.E. of the 
 " M " of " Meall," strings of fine granite or porphyrite are common, 
 and sometimes about 1 foot wide. These have a general direction almost 
 at right angles to the foliation strike and the adjacent edge of the granite 
 mass. In one place an 8-inch string is edged on either side by 1 inch 
 of opaque white quartz, and thin streaks of the same mineral occur here 
 and there in the middle also. Some of the strings are accompanied by 
 throws at least a few inches in amount. In this locality none of them 
 seems to contain porphyritic felspars, but J mile further up the burn there 
 is a 3J to 5 foot vein in which the porphyritic felspars are sometimes 1 J 
 inches long : 10 yards north of the burn these crystals are so abundant 
 and large that occasionally in an exposure of several square feet they 
 compose about half the area. 
 
 In the River Fine, 70 yards above the bridge by the " G " of " Glen," 
 there is, on the south side of the fault in the river course, a band of schist 
 
100 GEOLOGY OF COWAL. 
 
 about 1 or 2 feet thick, which contains dark green hornblendes. It is 
 pale in tint and evidently too quartzose to be classed as a hornblende 
 schist derived from an epidiorite. The band also contains much black or 
 brown mica, and breaks with a marked conchoidal fracture. The lengths of 
 the hornblendes are in a common direction 14 west of north. Two 
 or three feet below the band, on the east of it, the albites of the albite schist 
 have often a red altered look, and there are some layers almost entirely 
 composed of andalusite mixed with purplish-brown mica. In other bands 
 andalusites are scattered sparingly through a rock mainly composed of 
 white mica. The andalusites interlace together to form a network, yet, 
 when looked at collectively, they seem to have one direction more fre- 
 quently than any other, and the more frequent direction is much the same 
 as that of the adjacent hornblendes. Fourteen yards further east, the upper- 
 most part of a massive quartzose band also contains dark hornblendes for a 
 thickness of about a foot. The distance of this exposure from the nearest 
 part of the main granite edge is rather more than J mile The dip of the 
 schists is nearly due east. We suppose the hornblende to be probably due 
 to contact metamorphism, and the state of the rock in other respects speaks 
 in favour of this. But only one other instance is known where horn- 
 blende appears to have been specially formed near the edge of the granite. 
 This other case occurs in the foliated lamprophyre sheet at the first " u " 
 of "Cruach Tuirc" (see p. 125). The common orientation of the horn- 
 blendes, and the tendency, though but slight, towards a parallelism in 
 some of the andalusites, are matters of importance. They seem to suggest 
 that these minerals may possibly be due to the influence of some intrusion 
 earlier than the granite. Some of the nests of black mica found near 
 the granite edge suggest the same idea. In the burn J mile E.N.E. of 
 the outlet of Lochan Mill Bhig, J mile south-east of Cruach Tuirc, and 
 just above the Eagles Fall, these nests are longer in the direction of folia- 
 tion than across it. The strike of the foliation of the schists is deflected 
 into parallelism with the adjacent granite boundary. For a distance of 
 J mile or more from this boundary, the dip is inwards towards the granite. 
 Further away the dip is in some places away from the granite, towards 
 the south-west : at other times it is west, as in the exposure of hornblendic 
 schist just described, without any clear relation to the visible granite 
 margin. This alteration of strike and dip show that there has been a 
 certain amount of local movement near the granite during or since its 
 intrusion, or since the intrusion of some other igneous rock which had 
 approximately similar boundaries. Perhaps this movement may have 
 been strong enough to bring about the orientation of the hornblendes, and 
 the other phenomena mentioned in connection with it. Or perhaps it is 
 not necessary to have recourse to such an explanation. Earlier structures 
 in the schists may have had influence enough to guide later formed 
 minerals along their own direction to some extent.* The indications of 
 fluxion structure in the granite itself, in this locality, are so slight that it 
 does not seem likely that this rock was subjected to severe stresses during or 
 after consolidation. The obscure exposures of dark diorite near the edge 
 of the granite show more parallelism of structure. If it is safe to suppose 
 that these exposures are remains of a once much larger mass which 
 existed before the granite came up, and which possessed an outer edge not 
 
 * Since the above was written, we have noticed in the altered Cambrian limestones 
 of Ben Suardal (Skye) that the contact minerals, tremolite, etc., developed near the 
 tertiary granophyres, have in some cases a distinct tendency to occur with their 
 greater lengths along the lines of "stretching" developed in the rock during the 
 great c ' thrust " movements. These thrusts are certainly of earlier date than the 
 Old Red Sandstone. 
 
MARGIN OF THE 'G'RANITE. 101 
 
 far removed from that of the granite, we might attribute the metamorphism 
 partly to the pre-existing diorite. Most of the dark inclusions within the 
 granite could be referred to the^same mass. The parallelism of structure 
 in the diorite might be taken as an indication that earth movements were 
 going on during its consolidation on a greater scale than during the con- 
 solidation of the granite. We may mention in this connection that in a 
 boulder, no doubt derived from the Garabal Hill and Meall Breac complex, 
 on the shore of Loch Fine, mile south-west of Rudha Bathaich Bhain, 
 a thick streak of some black mineral, apparently magnetite, continued for 
 some distance. In some boulders in Glencroe (134 south-east) there are 
 streaks of opalescent quartz which run parallel to one another for about a 
 foot. These boulders have probably come from the diorite mass between 
 Ben Arthur and Ben Ime (1-inch Map 38), a mass which we regard as 
 probably of the same age as the Garabal Hill and Meall Breac complex. 
 
 It seems certain that the metamorphism which produced the andalusites, 
 the alteration of the appearance of the albites, the epidote veins, the black 
 mica nests, etc., is due either to the granite or to some earlier intrusion 
 belonging to the same great phase of igneous activity, the margin of which 
 was not far off that of the granite. For all these phenomena are con- 
 fined to the near neighbourhood of the granite. We have noticed no 
 andalusites more than 1 mile from the granite edge. The reddening of the 
 albites extends a little, but only a little, further than this : in the River 
 Fine it is first met with ^ mile below the bridge near the " G " of " Glen." 
 The universally unbent character of the andalusites shows that there 
 can have been no close folding or shearing since their production. The 
 reddening of the albites is like that caused by the broader basalt dykes 
 (see p. 149), and these dykes are certainly of later age than the albites. 
 But this alteration of colour depends on an alteration produced in the 
 inclusions in the albites more than in the albite substance itself, and 
 possibly it is not quite safe to assume that the alteration is of later date 
 than the formation of the albites. It might be argued that the oxidation 
 of the enclosed magnetite grains had taken place before they were sur- 
 rounded by the albite substance. But apart from this, the continuous 
 extension of the albite schists for many miles away from the granite at 
 least more than 20 miles while the andalusites, etc., are confined to the 
 close neighbourhood of the granite, is itself enough to indicate that these 
 minerals are due to different causes and are probably of different ages. 
 The albites are of regional occurrence, are found independently of any 
 visible igneous rock, and may be regarded as one of the last minerals formed 
 in connection with, but slightly subsequent to, the completion of the mass 
 of the movements going on during the schist manufacture. The anda- 
 lusites are due to the influence of a local intrusion of later date than the 
 schist manufacture, and are in all probability of later date too than the 
 albites. 
 
 The relations of the porphyrite sheets and the foliated lamprophyre 
 intrusions to the granitic rocks are referred to on pp. 102, 125 re- 
 spectively. The sheared character of the camptonites near the granite, 
 which character is not, however, universal, is itself a sign of their greater 
 age. It may perhaps be connected with the foliated aspect of the dark 
 diorite exposures near the edge of the granite. In the area near the 
 granite there seem to have been earth movements of importance at a later 
 date than elsewhere in the district, and after the mass of the schists were 
 essentially as they are now. 
 
 We know of no mica trap within or near the edge of the granite. 
 
102 GEOLOGY OF COWAL. 
 
 Hornblende-porphyrite and Felsite. 
 
 The felsite and hornblende-porphyrite are classed together, because it is 
 not always possible, in the field, to decide to which of these groups 
 a particular band should be referred. The same porphyritic constituents, 
 felspar, black mica, or chlorite, sometimes hornblende, and scattered 
 quartz blebs, occur in both, and the general colour of the ground mass 
 is also the same pink or orange. The state of crystallisation of the 
 ground mass it is often impossible to decide with the aid of the hand 
 lens alone. There is also a probability that the same band may be felsite 
 in one area and porphyrite in another. 
 
 These rocks behave in the field in the same way as the lamprophyres, 
 generally forming sheets which run roughly with the foliation of the 
 schists, and more rarely dykes. As stated elsewhere, p. 125, there is some 
 evidence for regarding the felsites as later than the basic micaceous 
 lamprophyres. On the other hand, the hornblende-porphyrites are later 
 than the foliated lamprophyres, and later also than the granite. In the 
 district of Cowal the range of the felsites is of much less extent than that 
 of the lamprophyres. It is almost confined to the part of the water-shed 
 of Loch Fine above Strachur, and to the neighbourhood of Acharosson 
 (181 and 182). The hornblende-porphyrites are of still more limited 
 range : none are certainly known south-west of a line between Achadunan 
 and Butterbridge, but felsites are abundant south-west of this line : on 
 the other hand, no certain felsites have been observed within a mile of the 
 edge of the granite of Glen Fine. Putting these facts together it almost 
 seems as if the hornblende-porphyrites took the place of the felsites in 
 areas near the granite. 
 
 In a little burn J mile south-east of the first " e " of " Glen Fine " a 
 thin band of hornblende-porphyrite occurs in the coarse granite, and presents 
 chilled margins to it : the hornblende-porphyrite weathers in more sharply 
 jointed blocks than the granite, and is not so decomposed. On the hill- 
 side, f mile south-east of Cruach Tuirc, an exposure of hornblende-porphy- 
 rite within the granite has been traced for a little more than 200 yards in a 
 N.N.E. direction. The breadth occasionally exceeds 50 yards. At the 
 sides the ground-mass is in some places distinctly more fine-grained than 
 in the interior, but we could not make out that this was always so. A 
 thin band on the west side of the broad band shows a chilled margin 
 against the granite, and the colour of the base is changed from pink to 
 dark grey. We could see no difference between the hornblende-porphyrite 
 intrusive in the granite, and that intrusive in the schists. We have not 
 traced any band from the one area into the other, but the length of 
 granite boundary examined by us does not much exceed 1^ mile, and 
 half of this is hidden under drift. 
 
 The hornblende-porphyrites within the schist area occur in several more 
 or less irregular sheets, as much as 20 feet thick, on the south and east 
 slopes of Cruach Tuirc. The general colour of the matrix is pink or 
 buff, but for an inch or two near the margins it may become dark grey or 
 chocolate-brown. The red porphyritic felspars and black micas continue 
 to the very edge of the intrusions, and form a striking contrast in colour 
 with the matrix. This change of colour is seen at points | mile W.N.W., 
 and -| mile slightly north of west of Cruach Tuirc, and mile slightly north 
 of west of the " E " of " Eagles Fall." Together with the change of colour 
 the grain grows finer. The quartz that is seen with the hand lens is always 
 in the form of subrounded pyramids and blebs : it is not abundant and 
 cannot be noticed at all in some hand specimens. 
 
 Slides 6109 and 6110 are respectively from the middle, and 2 inches from 
 
HORNBLENDE-PORPHYRITE. 103 
 
 the side of the sheet, mile slightly north of west of Cniach Tuirc. Of 
 6109 Mr Teall says: " Phenocrysts of felspar, biotite, and hornblende 
 in a light grey compact matrix.. The large crystals of plagioclase are 
 idiomorphic and zonal allied to oligoclase. The hornblende occurs in 
 long prisms, and the biotite in hexagonal tablets partly changed to 
 chlorite. The ground-mass is mainly composed of small idiomorphic 
 felspars which often give rectangular sections and interstitial quartz, 
 together with some fine microcrystalline material. Magnetite occurs as 
 an accessory in small idiomorphic crystals. This rock represents the 
 porphyritic phase of a hornblende-granitite or quartz-miea-diorite. The 
 ferro-raagnesian constituents are by no means abundant. 
 
 The hornblende-porphy rites near the fault in the burn south and south- 
 west of Cruach Tuirc are decomposed, and the forms of the porphyritic 
 felspars are filled by a soft yellowish-green substance, which reminds us 
 of the agalmatolite formed from the felspars of the pegmatites of the 
 Lewisian gneiss in Sutherland, etc. Slide 6117 was prepared for the 
 further examination of this substance, but threw no light on its nature. 
 Mr Teall noticed, however, one interesting point in the slide. It contains 
 two subangular grains of quartz, each of which is surrounded for a con- 
 siderable distance by a zone of irregular breadth which attains its maximum 
 darkness when the grain itself is extinguished. Mr Teall supposes there 
 must have been a period of quartz building followed by one of corrosion, 
 and again one of quartz building. 
 
 In the River Fine, f mile south-west of the " G " of " Glen Fine," there 
 is a dyke of felsite or hornblende-porphyrite which runs slightly north 
 of east. It is about 10 yards wide, and crossed by flaggy joints. The 
 porphyritic felspars are sometimes J inch in length, are in stout shapes, and 
 zoned. A similar dyke, or perhaps the continuation of the same, comes 
 into the river again f mile below this place. 
 
 A sheet running by the foot of Lochan Mill Bhig expands in places 
 into an outcrop 100 yards wide. This has not been sliced, but probably 
 it should be classed with the hornblende-porphyrites. It is seen in Eas 
 Riachain by the last "a " of "Riachain." One hundred and sixty yards 
 further up the burn a similar band is thrown into the stream by a fault 
 hading east. This may be the same band repeated by the fault. On the 
 north-east side of the burn, between the two exposures in the stream, 
 there are two other small outcrops surrounded by drift. 
 
 The sheet in the burn near the second "I " of "KILMORICH" does 
 not seem connected at the surface with the one near Lochan Mill Bhig, 
 but when the one dies out the other appears and runs on in much the 
 same direction. The sheet by this "I" is traceable for about 1J miles, 
 and passes over the hilltop a little east of Binnein Fhidleir into the water- 
 shed of the Kinglas. About 200 yards south of the Ordnance Station 
 2658 it is 30 feet thick. Then it gradually thins. In the burn mile 
 south-west of the above station it is 12 feet thick, and soon after that it 
 ceases to be traceable. Another outcrop of similar rock appears, however, 
 on a lower horizon, and can be traced \ mile south-west : in this course it 
 is thrown by at least three faults, each of them running in burns. 
 
 On a lower horizon than either of these is another sheet which has 
 been traced 1J miles. This crosses the hill- top f mile east of the last 
 " e " of " Binuein an Fhidleir." In the burn a little more than \ mile 
 south-east of Binnein an Fhidleir it is 30 feet thick, and has a lamprophyre 
 sheet close above. This lamprophyre is seen in close company every here 
 and there for nearly a mile north-east, sometimes without any separation of 
 schist and sometimes with only a very thin one, but their relations in age 
 are not clear. In the Kinglas, just below the " g " of " Glen Kinglas," the 
 
104 GEOLOGY OF COWAL. 
 
 two rocks are again seen in close contact. The evidence favours the 
 later age of the lamprophyre, but it is not decisive. 
 
 There is a big sheet of felsite not far off the Loch Tay limestone, in the 
 area between Ardno and Ardkinglas. At Ardkinglas it is above the 
 limestone, but near Ardno below it. The main change of horizon is at 
 the north-west fault, f mile E.N.E. of Ardno, and is not visible at the 
 surface. The chief joints are parallel to the surfaces of the sheet : this is 
 noticeable at a point J mile E.N.E. of Ardno. Near the same place there 
 is a quarry in the felsite, and it has been extensively worked for road metal. 
 In Coire No, there are bands which probably represent the south-east 
 continuation of this sheet : one band occurs some distance above the 
 limestone, and is seen in the stream J mile south-west of the "N" of 
 " No " ; the other occurs below the limestone, and is seen at the burnside 
 by the " o " of the same word. A band of felsite, probably representing 
 one of the last mentioned, is seen in all the burns between the Coire 
 No watershed and the "E" of "ARGYLLSHIRE," in the Cur by the 
 " E," and J mile above the junction of the Cur and the Cab. Further 
 S.S.W., felsite is seen in places near the course of the disturbances that 
 run from N.N.E. to S.S.W. towards Bridgend. These disturbances 
 traverse an area in which there are no other exposures of similar 
 rock. The crush lines have afforded ready openings for the intrusion of 
 the rock, and it has come up along them for some distance outside its 
 usual area of occurrence. In Leamhanin, not quite J mile slightly east 
 of south of Socach, a crush is seen at the side of the felsite, but 
 the latter rock itself is not appreciably crushed. Between the " C " and 
 " H " of " STRACHUR " an east to west fault shifts the crush with 
 which the felsite runs. The felsite runs along the fault for 20 yards, and 
 it is not clear that it is crushed at all in this distance : it would seem that 
 the east to west fault, as well as the N.N.E. crush, is of earlier date than 
 the intrusion. The most S.S.W. point at which we have noticed felsite 
 along this line is about f mile N.N.E. of Bridgend. Here there are two 
 bands, the east band being accompanied by a crush 6 feet wide. 
 
 There is sometimes more than one sheet of felsite on the south-east 
 side of Beinn an t-Seilich (134). As stated elsewhere, p. 125, one of 
 these is clearly cut by a later lamprophyre sheet which contains stellar 
 groups of hornblende needles. In the burn f mile S.S.W. of Stob an Eas 
 there is a good section of one of these sheets about 30 feet thick. The 
 felsitic matrix is of a deep cream colour. The chief joints are parallel to the 
 surfaces of the sheet, and split it up into coarse fLags. Porphyritic fel- 
 spars are as large and abundant at the sides as in the middle of the sheet. 
 Slide 4741 was prepared at the surfaces from a specimen near the side of 
 the sheet. Mr Teall describes it as follows : " Pale coloured massive rock 
 composed of phenocrysts of soda- felspar and pseudomorphs after hornblende 
 (1) and biotite in a felsitic matrix. Under the microscope one or two 
 small more or less rounded grains of quartz may be recognised, but these 
 are scarcely present in sufficient abundance to make the rock a quartz 
 porphyry. The groundmass shows a tendency to a microlitic structure in 
 the development of the felspars." Further south-west the same sheet is 
 cut by a dark micaceous lamprophyre (see p. 125). 
 
 In the three burns, J mile slightly east of south, ^ mile south, and f mile 
 slightly west^of south, of the "n " of " St Catherine's," there is a 3 to 6 
 foot sheet with a dark grey matrix, which contains distinct quartz blebs 
 and biotite flakes. C.T.C. 
 
 Some fine-grained red felsitic intrusions, behaving as very irregular 
 sills, occur J mile south-east of Kilfinan (181), The largest of these is 
 
HYPERITE. 105 
 
 well exposed in the Acharosson Burn. It varies considerably in width 
 of outcrop : in one part it attains a breadth of 100 yards and then 
 suddenly narrows down to about 12 yards. On the south of the burn it 
 is 200 yards wide. A specimen was sent to Mr Teall and described by 
 him as follows: "4013. Eed felsitic sill. Pink rock consisting of 
 numerous small porphyritic crystals of felspar (orthoclase and plagioclase) 
 in a felsitic matrix." Several other masses that occur to the south of 
 Acharosson Burn, as far south as Loch na Melldalloch, probably belong 
 to the same set of intrusions. W.G., J.B.H. 
 
 There are two sheets of hornblende porphyrite near St Catherine's. One 
 of them occurs on the shore 100 yards east of Ard na Slaite, and can be 
 traced in a south-west direction for nearly 2 miles : it is distinctly shifted 
 here and there by faults. The other occurs within a band of epidiorite 
 230 yards south-west of Ard na Gailich : there is also a good section of it 
 in the burn J mile south-east of St Catherine's pier. The first mentioned 
 band is the soundest, and has been quarried a little below the road near 
 the top of the first "h " of " Tighe Claddich," and on the hillside J mile 
 south-east of the small " s " of " St Catherine's." The matrix is pale 
 greenish-grey : in this are small grey porphyritic crystals of felspar, and 
 larger dark green chlorite pseudomorphs after hornblende. Some of the 
 pseudomorphs are J inch long and Q- inch broad : they are sometimes 
 collected into stellar shapes. A specimen from the first mentioned quarry 
 is thus described by Mr Teall (slide 5063) : " Greenish-grey porphyritic 
 rock. Matrix compact. Pseudomorphs in chlorite, and a carbonate after 
 idiomorphic hornblende. Also more or less altered plagioclase. Both 
 occurring as porphyritic constituents. Matrix of felspar microlites and 
 chlorite. . ." The rock shows beautiful fluxion structure of the felspar 
 microlites round the larger porphyritic crystals of felspar and the pseudo- 
 morphs after hornblende. 
 
 The sheet on the shore 230 yards south-west of Ard na Gailich is of a 
 cream or orange-brown colour. It breaks up into flags roughly parallel 
 to the original surfaces, and shows many small rusty-weathering, lath- 
 shaped, decomposed hornblende crystals. Near the surfaces these small 
 hornblendes are parallel to one another, and to the surface adjoining, but 
 they change direction near the porphyritic felspars and the larger horn- 
 blendes, so as to bend round their edges. In certain places amygdules 
 are abundant and very large, sometimes more than 2 inches long and nearly 
 1 inch broad. The outer parts of the amygdules are composed of a ferri- 
 ferous carbonate and barytes : the insides are sometimes hollow. In the 
 shore section the flat sides of the amygdules are parallel to one another 
 and the flaggy joints of the rock. 
 
 Hyperite. 
 
 A specimen from a rock exposure in the burn 1 J mile E.N.E. of Donich 
 Lodge is described by Mr Teall as follows (slide 4743): " Medium to 
 coarse-grained massive rock. Hypersthene, augite (diallagic in part), 
 biotite, plagioclase (more or less lath-shaped), iron ores and interstitial 
 quartz. Quartz-biotite-hyperite." The augite and hypersthene are some- 
 times surrounded, or partially edged, by hornblende : it is more probable 
 that this is due to variations during the original growth of the rock 
 than to subsequent dynamic changes. The felspar has sometimes a 
 pinkish tint as in the mica dolerites. The biotite is hardly recognisable 
 in the hand specimen. The exposure to which this specimen belongs 
 is largely drift covered, and its margins are obscure. Enough is seen, 
 
106 GEOLOGY OF COWAL. 
 
 however, partly in the main burn and partly in the streams on the north- 
 west side of the burn, to show that it is of large extent in the map we 
 have represented it as J mile in length and -| mile in breadth and 
 thicker than any lamprophyre in the district. It seems probable that it 
 belongs to an intrusive boss, the alteration in the adjoining schists being 
 greater than any elsewhere observed in the district excepting near the 
 granite of Glen Fine, and, perhaps, near Sith an t-Sluain (152). The 
 albites of the albite schists become pink (see p. 149 for the explanation of 
 the similar change caused by basalt dykes), and the matrix in which they 
 are imbedded is considerably darkened, and speckled with strings and 
 spots of iron pyrites. In two of the side streams, the west one of those 
 shown in the Map, and another one, not shown in the Map, near the 
 south-west end of the outcrop, we see a peculiar rock, apparently a 
 hardened and altered breccia made of the different schists next to the 
 intrusion. It seems a case of brecciation in situ. We can see the darker 
 more micaceous bands of altered schist becoming more and more broken 
 by small, and often coalescing, fault lines, until at last the connection 
 between their different patches is lost, and they appear as fragments 
 isolated in a grey rather quartzose matrix. There are no pieces of the 
 igneous rock to be observed in the breccia. No other breccia like this 
 is known in the neighbourhood, and we suppose it may have been formed 
 either at the same time with, or but little later than, the intrusive rock, and 
 as an accompaniment of it. The intrusion itself is also much slickened 
 and veined with calcite, or broken up into thin breccia courses, but we 
 cannot say that these have any connection with the breccia outside it. 
 Their direction is very various, and often they are nearly horizontal. 
 
 About j- mile north of the top of Ben Donich (134 south-east) there is 
 a small irregular intrusion, sometimes sheet-like and sometimes with 
 vertical walls, which closely resembles the one in Donich Burn. Under 
 the microscope (slide 4744) hypersthene is seen to be less conspicuous 
 than in 4743, and there are also one or two (?) pseudomorphs after olivine. 
 Some of the felspar is clearly idiomorphic with respect to some of the 
 augite, but at other times the converse relation prevails. 
 
 A small exposure in a burn f mile S.S.W. of the head of Loch Restil 
 is perhaps also referable to hyperite. C.T.C. 
 
 CHAPTER XL 
 
 THE IGNEOUS ROCKS (continued). LAMPROPHYRES 
 AND MICA TRAPS. 
 
 So many different varieties of rock are included under the terms 
 lamprophyre and mica trap that it is hardly possible to describe them 
 in general terms. They are generally much decomposed, and their 
 minerals are largely replaced by carbonates. Some bands are subject to 
 rapid variations in character, or they enclose fragments and strips of 
 different colour and grain : in one part they may contain little or no 
 microscopic mica, in another part, only a few yards off, this may be exceed- 
 ingly abundant. Instances of this occur in the small burn J mile south- 
 west of Ballochyle (173 south-east), and on the west shore of Loch 
 Striven, f mile E.N.E. of Dun Mor. In the last locality the middle of 
 the band is quite breccia-like, the general mass of smooth weathering rock 
 
LAMPROPHYRES AND MlCA TRAPS. 107 
 
 enclosing numerous rough pieces which weather in depression. These 
 pieces contain more prominent mica than the rest of the rock, and are 
 coarser in grain. The lower portion of the band consists almost entirely 
 of the more micaceous rock, and so also does part of the upper portion. 
 
 Where amygdules are present, these are in the great majority of cases 
 prominently drawn out, in planes parallel to the surfaces of the sheets, 
 and they may thus be a help in distinguishing these sheets from basalt, 
 in cases where unsatisfactory exposures might otherwise leave one in doubt. 
 In the basalts, as stated, p. 129, the amygdules are almost without excep- 
 tion roughly spherical, and the flow motion must either have ceased before 
 their production, or have carried them along with it without any distor- 
 tion of shape : in the lamprophyres they were generally produced before 
 the cessation of the motion, and have been somewhat dragged out by it. 
 In some few cases, however, they have not been deformed, or only very 
 slightly, e.g., in one of the zones of the band mile E.N.E. of Springfield 
 House (182 north-east). 
 
 The amygdules are generally composed of calcite, and weather hollow 
 on hill exposures. The rock rim immediately enclosing them often pro- 
 jects slightly beyond the rest of the band, as if less readily weathered 
 than it, and it has also a more pronounced red tint. In decomposed rocks 
 the last character has often been found a help in distinguishing them from 
 the basalts. The prevailing red tint of so many of the rocks in this group 
 depends on a reddish cloudiness in the felspars. 
 
 It is only when the mica is macroscopically prominent, that the term 
 mica trap seems applicable, and in many of the outcrops it is so incon- 
 spicuous that it was necessary to adopt some other term to include the 
 different rocks of the series, whether rich in mica or not, which had the 
 same habit of occurrence in the field, and which were, as far as could be 
 judged, of approximately the same age. The term lamprophyre, intro- 
 duced by Giimbel, has been adopted in this sense. We use it to include 
 all the rocks which fulfil the conditions mentioned, except some of the 
 more evidently acid rocks, and some few hornblende-porphyrites. The 
 fact relating to the comparative age of these excepted rocks are mentioned 
 on p. 125. The chief varieties of rock included in this unsatisfactorily 
 defined lamprophyre group are noticed as we proceed. But we shall, in 
 the first place, describe the general mode of occurrence, and the characters 
 which are common to different varieties. 
 
 In the north and east parts of Cowal the lamprophyres and mica traps 
 are exceedingly numerous, being in some of the schist areas quite as pro- 
 minent a feature as the basalts, but they are not known within a distance 
 of 4 or 5 miles of the Upper Old Red Sandstone boundary. They are 
 represented on the Maps by a dark shade of Rubens' madder : in the 
 broader bands this is sufficiently distinct from the basalt colour, but in 
 thin lines they may be sometimes confounded. In such cases it will be a 
 help to notice the mode of occurrence of the bands where the colour 
 seems doubtful, for the general habit of the lamprophyres is different from 
 that of the basalts. In most of the district they rarely form vertical dykes, 
 and when they do so these dykes, more often than not, run in a different 
 direction to the basalts, e.g., a vertical band on the hillside i mile east 
 of the foot of Loch Eck runs north-east, and is crossed by four or five basalts 
 almost at right angles to it. A north-east direction is the commonest for 
 the lamprophyre dykes in the south part of Cowal, but in the north part 
 there are many east to west dykes of a camptonite variety. Sometimes 
 an intrusion which is generally sheet-like, its surface making only gentle 
 angles with the horizon, changes and acts as a vertical dyke for a short 
 distance. This irregular mode of occurrence seems more frequent with 
 
108 GEOLOGY OF COWAL. 
 
 the lamprophyres than the basalts : a good example of it may be seen 
 in the burn J mile south-west of Mid Hill (173 south-west). But most 
 frequently they occur as sheets with varying and not very steep hades to 
 the horizon. They do not keep to the bedding or foliation of the schists, 
 but may be constantly seen cutting straight across all their crumplings : 
 it is clear that all the movements which were taking place at the times of 
 the production of the different foliations of the schist had ceased before 
 their intrusion. 
 
 It is rare for these bands to exceed 20 or 25 feet in thickness. The 
 dark bands on the Toman Dubh (182), on the hillside 1 mile to the west, 
 and crossing the lower part of the Tamhnich Burn (172), must be thicker 
 than this in most of their course, but appear in places to dwindle almost 
 to nothing, e.g., the Allt Glac na'maill (182) is crossed in three places 
 by one of the above bands, and in the middle place it is only 3 feet thick. 
 A thickness of from 3 to 10 feet is perhaps most commonly met with, 
 and from this down to the thinnest strings which cannot be mapped. 
 
 The paths of the sheets have in some cases, perhaps in many, been 
 determined by the pre-existing joints, and we can see them changing 
 horizon from one joint plane to another at a slightly different level, the 
 change being made sharply along an almost vertical line, but the new 
 horizon, once acquired, is kept to for some distance. 
 
 A section on the hillside J mile south-east of Uig (above the Holy 
 Loch) well illustrates their inconstancy. Here are two sheets, the upper 
 one 10 feet thick, and the lower from 3 to 6. The lower is itself in one 
 place split up into two by a band of schist, from 1 to 6 inches thick, which 
 runs on for a distance of several yards, rudely parallel to the surfaces of 
 the sheet. In one place the sheets come within 3 feet of one another, or 
 rather less, for the upper one sends out a short arm, as if to try to reach 
 the other : in another place it sends down a 2-inch string in the same 
 direction. On the west side of the section the sheets are seen to unite, 
 and on the east also they are inferred to do so. 
 
 In another section in a scar \ mile slightly west of south of Cnoc 
 Madaidh (west side of Loch Striven) a reddish fine-grained sheet, reaching 
 1 2 feet thick, is seen to die out for a distance of 3 feet, and then it makes 
 its appearance again. 
 
 In spite, however, of their thinness and inconstancy, they are of con- 
 siderable interest in working out the geological structure of the district, 
 and a greater help than the basalts. This is because the majority of the 
 faults are later than them, and throw them, so that they afford a means 
 of finding out the different faults, and of estimating their throws indepen- 
 dently of the schists. The hillsides between Glenmassan and Sgarach 
 Mor, and 1 \ miles W.N.W. of Ardentinny, Clach Beinn (163 south-east), 
 the west slopes of Beinn Mhor, the south-east side of Stob Liath (142 
 north-east), all afford excellent examples of this faulting. But, as might 
 be gathered from what has been already said of the inconstancy of the 
 bands, it is not safe to assume that all the interruptions in them are due 
 to faulting : in most cases we can with certainty infer that this is so from 
 the evidences of crushing to be seen, but occasionally there are bands, 
 e.g., on Toinan Dubh (182 south-east) at a point about 100 yards S.S.W. 
 of Ordnance Station 963, and again about J mile south-west of the same 
 station, in which it is probable the intrusion came up originally along lines 
 which were not connected at the present surface, or only by such thin 
 strings that they escape observation in ordinary field sections. 
 
 It is certain that some of the faulting in the district was anterior to 
 some of them. In the north part of the area some of the reddish-yellow 
 fine grained bands with occasional mica must be later than some of the 
 
LAMPROPHYRES AND MICA TRAPS. 109 
 
 north- west running crushes, as they cut through the contorted and crushed 
 rocks without being crushed themselves. And in other cases where north- 
 east running dyke-like bands occur, even though these bands may now be 
 crushed, it is not unlikely that there were previous movements along the 
 same line of which they took advantage at the time of their intrusion. 
 
 On the north-west side of Eas Dubh (141), at a point about J- mile 
 north-east of the "h" of "Dubh," there is a section of contorted graphite 
 schist underlying a crush line which hades north-west. The beds above 
 the crush are quartzose schists. These are not contorted as the graphite 
 schist is, but their foliation is roughly parallel to the crush plane. The 
 contortion in the graphite schist is connected with the crush movement : 
 it seems due to a motion of the rock mass overlying the crush plane in a 
 north-east direction relatively to the lower rock mass. There are two 
 decomposed ochreous-weathering lamprophyre sheets running with the 
 crush, each of them from 1 to 2 feet thick. The lower one, quite close 
 to the crush rock, has an even surface which is not affected by the 
 contortion shown in the graphite schist. In other sections near, the 
 lamprophyre is crossed with slickens to some extent, but is never so 
 contorted as the graphite schist. It seems clear, therefore, that most of 
 these crush and contortion movements must be of earlier date than the 
 lamprophyres in the section. 
 
 Two lamprophyre dykes occur running with the strong N.N.E. crushes 
 in the burn 1 mile N.N.W. of the "S" of "Strachur" (141), but 
 we cannot say that the dykes themselves are crushed : one of the dykes 
 is of a dark basic character. At a point about J mile south-east of the 
 "n" of "St Catherine's" (133) a lamprophyre dyke, running north-west 
 for a little way, is seen to turn north-east and run as a sheet along a 
 crush line : the sheet is quite uncrushed. 
 
 We are inclined to suppose that the common north-east and south- 
 west direction of lamprophyre dykes (not the sheets) is generally due to 
 the existence of pre-lamprophyre faults running in this direction, along 
 which the lamprophyres have subsequently been intruded, and that an 
 east to west direction is in other circumstances their most general direction. 
 In the Sleat district of Skye the east to west direction is certainly the 
 prevalent one for these dykes, and in the north part of Cowal this is 
 also so, though there are many instances in the latter locality where a 
 north-east direction also occurs. In the south part of Cowal a north- 
 east direction is the most prevalent. When the dykes run east and 
 west, there may or may not be indications of crushes running in the same 
 line with them, but when they run north-east there are almost invariably 
 indications of crushing at some point or other along their course. The 
 crushing in some places has affected the dyke so strongly that we cannot 
 now determine whether there were also crushes of earlier date than the 
 dyke ; but in other places, as in those just cited, it is clear that there 
 must have been. As instances of the former class, we may mention the 
 dykes J mile south-east and f mile east of Socach (141 south-east). The 
 crush stuff in the last locality is several yards wide, and consists in part 
 of a stiff clay, from which the burn is locally called the Clay Burn. 
 Formerly, the clay had a great local reputation for pottery purposes : we 
 suppose it to be formed from the decomposed crushed lamprophyre. 
 
 If the Maps be examined, it will be evident how many of the north- 
 east or N.N.E. dykes occur with, or along continuations of, lines marked 
 as fault or crush lines. Even in the instances where little or no crushing 
 has been observed there may still have been at the time of intrusion 
 some thin break running in these directions. There are but few of the 
 longer N.N.E. faults which are not accompanied, in some part of their 
 
110 GEOLOGY OF COWAL. 
 
 course, with lamprophyre dykes; but individual dykes rarely continue 
 far in this direction. More commonly we can trace one for only a little 
 distance, and then see no sign of any for some way as we walk along 
 the fault : then another dyke-like exposure occurs, and so on. In some 
 cases, as in Gleann Dubh (152 north-west) there are several inconstant 
 dykes, all running in the general direction of the fault, and partly over- 
 lapping one another. 
 
 As the basalt dykes decrease in thickness (p. 143) when they run out 
 of their normal directions to take advantage of some pre-existing fault 
 line, so apparently do the lamprophyre dykes when they change from an 
 east to west into a N.N.E. direction. In the Kinglas Water (134) a 
 yellow-weathering fine-grained dyke can be traced westwards in and near 
 the sides of the burn for about J mile from the " G " of " Glen," the 
 general direction being slightly north of west. One-eighth of a mile south- 
 west of the " G," the dyke leaves its normal direction, and runs N.N.E. 
 along a thin crush line, and diminishes at the same time in thickness, 
 from 1J to | feet, or possibly to nothing in certain places. The dyke is 
 not crushed when running N.N.E. It takes its old direction after 
 following the changed path for the width of the burn, about 12 yards. 
 One-eighth of a mile slightly west of south, and J mile slightly south of 
 west, of the "G," similar deviations of the dyke into a N.N.E. direction 
 appear to occur again. In the last locality the thickness when running 
 east and west is about 1J feet; when running N.N.E. the dyke either 
 ceases to exist at the surface, or is represented by a sheet varying from 6 
 to 10 inches in thickness. 
 
 A few instances of apparently north-west running lamprophyre dykes 
 occur on the west side of Beinn an Lochain (134 south-east), but this face 
 of the hill is very steep, and, the hade of the dykes being to south, we may 
 get north-west running outcrops even when the direction on a flattish 
 surface would be approximately east to west. 
 
 It has already been stated that the lamprophyre bands may change 
 locally in their mode of occurrence, and after acting as sheets for a long 
 distance may for a short space run as dykes. Conversely when dykes 
 meet with low-angled strike faults, as in the locality J mile south-east of 
 the " n " of " St Catherine's," they may run along these faults and act as 
 sills. 
 
 Not unfrequently dykes and sheets of much the same characters occur 
 in the same localities, and the relation between them may not be easy to 
 determine. About |- mile south-east of the "r" of " Ardkinglas House" 
 (134 north-west) a 4 or 5 feet fine-grained yellow- weathering sheet with 
 long needles of decomposing hornblende is intersected by a gulley or 
 deep part in the burn. This gulley probably represents a dyke of some- 
 what similar rock, as such a one is seen in the line of the gulley at a little 
 distance off. In this case the sheet seems earlier than the dyke. The 
 general direction of the dyke is east to west : in the burn f mile further 
 west it is accompanied with crushes. On the hill f mile E.N.E. of the 
 "C" of "Cairndow" (134) a sheet with decomposing hornblende 
 arranged in prominent stellar groups, is shifted and crushed along an 
 east to west fault, and in the course of the fault a fine-grained yellow- 
 weathering dyke, without prominent hornblende, occurs. 
 
 One quarter of a mile slightly south of west of the " G " of " Glen 
 Kinglas " the east to west dyke already referred to is seen close to a fine- 
 grained yellow- weathering sheet. This sheet is compounded of two 
 parallel bands, there being a chilled surface near its centre. In litho- 
 logical character the two sheets seem much alike, but the lower half is 
 well cross-jointed while the upper is not. The middle portion of the lower 
 
LAMPROPHYRES AND MICA TRAPS. Ill 
 
 band shows many small brownish mica flakes. A yard or two from the 
 water, on the north bank of the river, the upper band separates from the 
 lower, which continues to run evenly while the upper ends suddenly at 
 a steeply inclined line, and then appears again at the other side of the 
 line at a slightly higher horizon. The east to west dyke is seen within 6 
 inches of the base of the lower band, and it certainly does not cross the band 
 in the continuation of its old line. So either the sheet must be the later 
 of the two, or the dyke must shift its position a little to the south-west 
 when it comes to the base of the sheet. 
 
 The great amount of faulting to which the bands have been subjected 
 is evidence that they are of greater age than the basalts. But we are 
 by no means left to depend on this evidence alone. In many places 
 north-west running basalts can be seen cutting through them in clear 
 section, e.g. t on the shore 100 yards W.S.W. of Mid Letter (141 south- 
 west), on the south-west side of the River Massan at a point J mile south- 
 west of Glenmassan, J mile N.N.E. of Glenmassan, in the burn 1 mile 
 slightly south-west of Glenmassan, in the burn f mile north of Balliemore 
 (173), on the west shore of Loch Striven, | mile E.KE. of.Dun Mor, and 
 again in two sections f mile north-east of Dun Mor, in the lower part of 
 Tamhnich burn (172 south-east), on the east side of Loch Riddon J- mile 
 north-east of Eilean Dearg, and in the bum 140 yards west of Brain- 
 gortan (west side of Loch Striven). In the second locality mentioned 
 a close jointing is set up in the lamprophyre parallel to the sides of 
 the basalt, for a distance of several yards from it. 
 
 The earlier east to west basalts are also later than the lamprophyres. In 
 a little burn J mile S.S.E. of the top of Larach Hill (164 north-east), a 
 red fine-grained amygdaloidal band, 2 or 3 feet thick, occurs close on the 
 south side of the broad east to west basalt dyke. As far as seen, which, 
 however, is only for a few yards, the lamprophyre runs parallel to the 
 basalt, but the latter is chilled at the junction line, while the former is 
 not. In the River Cur, J mile east of Strachurmore, a broad east to 
 west basalt cuts a lamprophyre sheet with prominent black mica; the 
 lamprophyre is seen on both sides of the basalt. One-third of a mile 
 W.N.W. of the "B" of "Beinn ant-Seilich" (134) the east to west 
 basalt is exposed in, and on the west side of, the middle burn shown in 
 the Map ; two lamprophyres, one a coarse rock with much black mica, are 
 seen on either side of it at only a little distance off; they do not cross 
 the basalt, and are therefore inferred to be crossed by it. Half a mile 
 west of Loch Restil outlet (134 north-east) a lamprophyre dyke is seen a 
 little from the sides of the east to west basalt ; the latter is certainly not 
 intersected by the former. The east to west broad basalt dyke on the 
 east side of Loch Riddon makes a prominent slack near the ruined chapel, 
 where it approaches the broad lamprophyre, but no basalt is actually 
 seen between the lamprophyre outcrops on either side of the slack, and 
 the presence of the slack is not by itself decisive of its presence, as the 
 lamprophyre also sometimes forms slacks. 
 
 On the south-east side of Glen Kinglas, J mile south-west of Butter- 
 bridge, there is a dolerite-like sheet with porphyritic augite, which includes 
 some parts much finer in grain and smoother weathering than the rest. 
 The fine parts seem sometimes to be running in veins through the coarser. 
 In an exposure nearly J mile north-west of this locality a sheet that 
 is probably a continuation of the last mentioned occurs again, but now 
 no fine-grained parts are observable. An exposure in Kinglas Water, 
 nearly f mile below Butterbridge, probably belongs to the same sheet, 
 but it does not show such prominent augites. The coarse dark grey 
 parts are frequently intersected by thin strings of a fine-grained reddish- 
 
112 GEOLOGY OF COWAL. 
 
 yellow rock, and also often enclosed as fragments in it ; the fragments 
 have sharp margins, and are sometimes several inches long. 
 
 There are difficulties in ascertaining to what extent variations in 
 character along the course of one continuous band may occur, because 
 bands of different characters frequently run in close contact, having 
 each taken advantage of the same line of weakness. There are two ways 
 in which it is possible that variations along the outcrop may have arisen. 
 They may be due to differences originated before or at the time of cooling 
 of any particular band, or they may be characteristic of bands which 
 are different in their age and origin, though occurring along the same 
 line of outcrop. It is rare to find exposures, between the points where 
 the variations are observed, which are so continuously bare that we cannot 
 be sure that the rock at one point may not at some place have suddenly 
 ceased to come up to the surface, and been replaced by another of different 
 character running in the same direction. 
 
 On the south side of the east to west fault f mile S.S.E. of Sgor Coinnich 
 (153) there is a band composed in its upper part of 12 feet of dark grey 
 rock, weathering in big blocks, with stout porphyritic crystals of somewhat 
 decomposed augite and small thin black needles of sounder hornblende. 
 This overlies a 5-foot sheet of sharply-jointed reddish rock with stellar 
 clusters of needle-shaped decomposing hornblende. The lower portion 
 seems the later of the two, for it becomes finer grained near the junction. 
 On the hill 100 yards south-east of the above section, the band seems to 
 consist of the upper dark part alone, nothing being seen of the redder 
 portion, either in contact with or near the other. To the north-west the 
 redder portion appears to separate from the blacker, for in the burn a 
 little over J mile south-east of Sgor Coinnich we find an upper sheet of 
 the same character as the upper one near the fault, except that it is mixed 
 near the top with some redder coarse bands. This is underlain by a 
 strip of schist about 1 foot thick, and then we see a 5-foot reddish 
 sheet with decomposing hornblende crystals in radiate clusters. Below 
 this is a strip of schist 5 feet thick, and then a second band of reddish 
 lamprophyre about 5 feet thick. One hundred and fifty yards E.N.E. 
 of the burn section, the lower part of the upper sheet weathers in a 
 breccia-like manner, owing to the inclusion of many bits of coarser grain 
 within the finer rock. The band which runs round the south side of 
 Cruach a' Bhuic (153 south-west) is entirely of a reddish fine-grained 
 type, but it must be on the same line of intrusion as the upper dark grey 
 sheet just described. 
 
 About 100 yards north of the "r " of "Meall Breac" (152) the upper 
 lamprophyre band is compounded of two sheets in close contact. The 
 upper one is a 4 or 5 foot reddish flaggy-weathering fine-grained rock, 
 and the lower a 10 foot black blocky exfoliating band with porphyritic 
 augite. Both rocks become finer near the line of contact with one another, 
 and so we must suppose that one was first intruded and chilled against 
 schists, and then the other came up along the same line and was chilled 
 against the earlier one. There is nothing to show which portion is 
 the earlier. To the west they are in contact for 10 yards, and then 
 there is an obscure interval of 100 yards, after which the augite rock 
 is seen again, but now it is unaccompanied with the red rock. A 
 few yards to the east, a red flaggy sheet appears below the augite rock, 
 though it does not appear as if such can have existed further west, and 
 at the same time we lose the overlying red sheet, so that the presumption 
 is that the augite sheet is the later of the two, and has altered its horizon 
 with respect to the red sheet. 
 
 The sheet at the base of the crag, J mile N.K W. of the " P " of 
 
LAMPROPHYRES AND MICA TRAPS. 113 
 
 " Dornoch Point " (152), is a reddish fine-grained flaggy rock : the flaggy 
 planes are generally parallel to the surfaces of the sheet but not always. 
 The microscopic characters of the rock are described elsewhere, p. 118. It 
 contains radiate clusters of sound black hornblende needles. The sheet 
 just above this in the same scar is a black rock with porphyritic augite, 
 and it weathers in very massive exfoliating blocks. The black sheet 
 is hading more steeply north-west than the red sheet, and gradually 
 approaches it iu this direction until it is within 12 or 15 feet. Then 
 it ends bluntly, but, without any surface connection, it somehow finds its 
 way into the lower sheet and cuts through it. Then for 50 or 60 yards 
 further west the two rocks keep together, the red above and the black 
 below. After this, for 100 yards or more northwest, the black band 
 alone appears, but it is possible that the red one also exists underneath 
 it. Further north-west still there is an obscure area for 200 yards, 
 and after this down to the alluvium on Loch Eck side only the red rock 
 is seen. 
 
 Spheroidal weathering is common. It occurs in bands which are quite 
 red in tint, as well as those which are dark grey or black. Where the 
 rock is not spheroidal the prominent joints are generally parallel to the 
 surfaces of the intrusions, and may be so close that the rock splits into 
 rough flags. This is noticeable in the two little outliers on the hill ^ 
 mile south of Glenmassan, on the hill J mile slightly north of east of 
 the foot of Loch Eck, and at the north-west end of Creag Capull 
 (173 north-east). Occasionally there are also indications of joints at 
 right angles to the surfaces, but we have never seen them nearly as 
 marked as in the basalts. Outcrops in scars are generally recognisable 
 at a considerable distance, as they form more or less straight, and usually 
 gently sloping bands, which weather in retreat from the harder schists 
 above and below. 
 
 Intrusions always grow finer in grain as their surfaces are approached 
 in the micaceous varieties the mica flakes become gradually smaller until 
 they cease to be visible macroscopically. Some of the exposures which 
 are dull red in the interior change colour near the margins, passing 
 through reddish-brown into dark grey. Both these changes are to be 
 noticed in the burn 1 mile slightly west of south of Glenmassan. In 
 some of the basic rocks, with porphyritic augites, the augites continue 
 right up to the original surfaces of the intrusion, as large in size as they 
 are in the interior. 
 
 Inclusions of schist, etc., are not uncommon. The band near the old 
 chapel east of Fearna Bagh is nearly half full of hardened schist and vein- 
 quartz pieces, which reach a length of 4 inches. Similar inclusions are 
 seen again in the north-east continuation of this band where it crosses 
 Allt Glac na maill. In the south exposure f mile north-east of Dun Mor, 
 an inclusion of vein quartz at least 1J foot long is seen, and this has 
 the cracked and splintery look so often found in the near neighbourhood 
 of intrusions. 
 
 The sheet going round the north and west sides of Beinn Reithe (142 
 and 153), at a point 60 yards E.N.E. of the top of the hill, is quite 
 full of schist and vein-quartz pieces ; the thickness of the sheet is 4 
 feet, arid the pieces are sometimes 6 inches long. Nearly J mile 
 S.S.W. of the hill-top the sheet is 5 feet thick, and the middle for a 
 thickness of 2 feet is full of such pieces, while the rest is almost free from 
 them. One-seventh of a mile east of the hill-top the sheet is 6 feet thick, 
 and the middle is again full of included pieces. 
 
 A dark blocky augitic sheet near the burn f mile south of the " e " of 
 " Coire Ealt" (152 north-east) contains many pieces of vein quartz and 
 
 H 
 
114 GEOLOGY OF COWAL. 
 
 some of schist. The greater lengths of the pieces are parallel to the 
 surfaces of the sheet In some bands, for a breadth of a foot or more, 
 the inclusions make up J of the rock mass. The vein quartz has the 
 cracked and splintered look already referred to ; the main cracks in it run 
 almost at right angles to its surfaces. A quarter of a mile N.N.W. of Cruach 
 a' Bhuic, a dolerite-like sheet contains near its centre pieces of much altered 
 quartzose schist, as much as 6 inches long, and vein quartz, sometimes 9 
 inches long and 2 inches broad. These pieces also have their longer axes 
 parallel to the surfaces of the sheet. 
 
 No great amount of contact alteration is usually caused by the lampro- 
 phyres, but in some cases the alteration is much more pronounced. On 
 the west side of Loch Striven, close to the mouth of the little burn 100 
 yards east of Braingortan, a great hardening of the schists is effected by 
 three thin sheets with dark matrix and large black mica flakes. The 
 albite schists near the dark sheet in Kinglas Water, not quite f mile 
 below Butterbridge, are distinctly hardened and speckled with iron 
 pyrites ; the albites, too, acquire a reddish tint. One-quarter of a mile 
 north-west of Beinn Reithe, epidote occurs in an albite schist within a few 
 inches from the side of a lamprophyre. No epidote was observed any- 
 where else in the neighbourhood, and perhaps it is due to the proximity 
 of the lamprophyre. The epidotes are much the same in size and shape 
 as the albites of the albite schist further off the intrusion. 
 
 As examples of rocks rich in mica we may mention the exposures 
 on the south-west side of the River Massan J mile south-west of Glen- 
 massan, the repeatedly faulted band between Glenmassan and Sgarach 
 Mor, the middle band on the west side of Glen Tarsan, the rock in the 
 burn 140 yards west of Braingortan, the bands on the Toman Dubh, the 
 bands on the east side of Cruach nam Mult (134 south-west), and the 
 lower band f mile N.N.E. of Stob an Eas (134). 
 
 The bands on the Toman Dubh are of the same type as those at the old 
 chapel east of Fearna Bagh, in the lower part of Tamhnich Burn, on the 
 hillsides f mile west of Glenmassan and east of Cruach nam Mult, the 
 lower band J mile N.N.E. of Stob an Eas, and the east to west dyke just 
 north of Laglingarten (133 south-east). These may all be classed as 
 mica-dolerites. The amount of mica varies considerably in different ex- 
 posures ; the Toman Dubh bands are generally rich in mica ; the band f 
 mile south-west of Glenmassan poor. The mica-dolerites have generally 
 a blackish aspect macroscopically, owing to the great abundance of stout 
 augite prisms. At times they weather in unusually massive blocks, 
 which exfoliate into a loose sparkling sand, giving rise to green grassy 
 banks or slacks. Between the augite prisms can sometimes be seen 
 macroscopically small pinkish specks, the felspar having very much the 
 same tint as in the redder lamprophyres. The red tint is sometimes, 
 as in the lamprophyres generally, especially pronounced just at the edges 
 of the amygdules, e.g., in the band f mile south-west of Cnoc Breamanach 
 (182 north-east). At the old chapel east of Fearna Bagh, and in the 
 band f mile E.N.E. of Cruach nam Mult (134), the dark rock -is crossed 
 by redder finer grained strings, about J inch thick, which project slightly 
 on the weathered surfaces. 
 
 An average specimen of the chapel rock was examined microscopically 
 (slide 3417) by Mr Teall, and is thus described by him: "Large and 
 more or less idiomorphic crystals of augite in a ground-mass of lath-shaped 
 plagioclase, brown mica (allied to that of the mica traps) iron ores and 
 ophitic calcite. The rock may be termed a mica-dolerite. It appears 
 to have affinities with certain rocks which have been called kersan- 
 tites." C.T.C. 
 
LAMPROPHYRES : CAMPTONTTES. 11.5 
 
 Along the east side of Stralachlan Glen various exposures of micaceous 
 lamprophyre occur, not as sills, but as oval patches this form being 
 due to their occurrence on a dip slope. A specimen from one of these 
 was examined by Mr Teall, and is described by him as follows: " 4012. 
 Barnacarry, Loch Fine. Massive dark grey medium-grained rock, con- 
 taining pink patches. Felspar often striated and more or less lath- 
 shaped. External zones extinguish at low angles, internal zones at high 
 angles gradually changing through a range of 20. Brown mica, magnetite, 
 carbonates, and green or grey pseudomorphs after indeterminable minerals. 
 Pink patches are mainly composed of felspar giving rectangular sections, 
 probably orthoclase. Kersantite." J.B.H. 
 
 In slide 4755, obtained from the lower band f mile N.N.E. of Stob an 
 Eas (134), irregular grains and crystals of olivine occur, but they are 
 much smaller than the porphyritic augites. They are sometimes quite 
 surrounded by biotite. The porphyritic augites appear almost colourless 
 in the slide : they are far larger than any other constituent of the rock, 
 but there is also a set of smaller colourless augites without any approach 
 in size to the large augites. The small augites are clearly idiomorphic 
 with respect to the felspar. In the west of the two dykes J mile E.N.E. of 
 Cruach nam Mult (134) the biotite is very conspicuous, occurring in large 
 ragged plates, which show under the microscope (slide 4752) inclusions 
 of the later developed rock constituents. The augites are also large and 
 abundant, but have so generally decomposed into a dull greenish tint that 
 they do not strike the eye readily. 
 
 By a gradual decrease in the amount of mica, the mica-dolerites may 
 pass into rocks of more normal dolerite aspect. In all these early 
 dolerites which have been examined, the augite differs from that of the 
 tertiary basalts in belonging to the pale form, malacolite, and in generally 
 occurring in the porphyritic form. It is usually idiomorphic with respect 
 to the felspar, but in some cases, e.g., in slide 4744, from an intrusion 
 f mile north of Ben Donich (134), some of the felspar is idiomorphic 
 with respect to some of the augite, while other portions are not. Well 
 characterised ophitic augite has never been observed. The augites are 
 generally sufficiently large to be readily seen by the naked eye : they 
 frequently attain the size of a large pea. In some bands they are 
 remarkably abundant. In some thin sheets in the coast section north of 
 the " L " of " Leak " (151) they seem to compose about \ the bulk of the 
 rock. In the sheet | mile N.N.W. of the "P" of " Dornoch Point " 
 (152 south-east), the porphyritic augites continue right up to the original 
 surface, and are as big there as they are further within the sheet. 
 
 When these rocks are examined under the microscope it is often 
 found that the augite is associated with hornblende. As the latter 
 gradually increases in amount the rock passes into a dioritic type, 
 that of the so-called camptonites. Even with the naked eye we can see in 
 certain bands that both augite and hornblende are associated together, 
 e.g., in the upper sheet f and mile south-east of Sgor Coinnich (153). 
 The augite is generally in a decomposed state, while the hornblende 
 remains fresh and with a brilliant black lustre in hand specimens. 
 When the augites decompose so as to form pale greenish-grey almost 
 opaque shapes, distinct indications of zonal growth may often be observed 
 in them with a hand lens, the different concentric bands differing slightly 
 in the depth of their tints. In cases of more thorough decomposition 
 these pale-green shapes become rusty-yellow and cavernous, or are 
 represented merely by hollows with a rusty lining. These different ways 
 of decomposition are observed in the exposures of the sheet in Garrachra 
 
116 GEOLOGY OF COWAL. 
 
 burn (163 north-west) near the "rr" of " Garrachra," and by the side 
 of the little burn J- mile north-east of this place. 
 
 The east to west dyke in the burn a little over J mile south of Bathaich 
 ban Cottage (134 north-west) contains conspicuous crystals of augite 
 embedded in a medium-grained dark-greenish matrix. "Under the micro- 
 scope (slide 4746) brown hornblende is seen also to occur, so that the rock 
 may be called hornblende dolerite, and it is to be considered one of the 
 passage forms between dolerite and diorite. The porphyritic augites are 
 pale in colour, and more or less idiomorphic. The groundmass contains 
 smaller augites of the same characters, brown hornblende (sometimes 
 surrounding the augite), plagtoclase (lath-shaped in section), and iron 
 ores. 
 
 In another dark-green east to west dyke, seen in the wood 100 yards 
 south-east of Bathaich ban Cottage, the hornblende is more abundant 
 than the augite, so that the rock may be called an augite-bearing diorite. 
 Mr Teall describes the microscopic character (slide 4747) as follows : 
 " Medium-grained, dark-greenish massive crystalline rock. Idiomorphic 
 brownish-green hornblende (Forms: {110}, {010}, {100}, {111}?, 
 and {001} ), colourless augite (malacolite), and iron ores changed to 
 leucoxene. The above minerals are embedded in a much altered 
 felspathic ground-mass containing felspar, quartz, and carbonates. As 
 the hornblende is considerably more abundant than the augite, this 
 rock may be termed an augite-bearing diorite." The hornblende never 
 becames porphyritic, or so conspicuous as the augite in 4746, but still 
 it is distinct to the naked eye, and is often about the size of a large 
 mustard seed. The malacolite is of about the same size as the hornblende. 
 
 Another dyke, of much the same macroscopic aspect as the last, occurs 
 J mile W.N.W. of the outlet of Loch Restil (134). This is described 
 by Mr Teall (slide 4748) as follows : " Similar to 4747, but somewhat 
 finer in grain. Hornblende, similar to that occurring in 4747, one or 
 two pseudomorphs after a mineral which was probably olivine. Malaco- 
 lite is not now recognisable, but is probably represented by certain 
 chloritic pseudomorphs. The felspars of the ground-mass show in 
 places a strong tendency to a feathery mode of aggregation. Both 
 this rock and 4747 are very similar to the basic rocks found as sills 
 in the limestone of Assynt near Inchnadampf (see Geol. Mag., 1886, 
 p. 346)." 
 
 The two dark-grey or black sheets occurring from to J-'mile south- 
 east of Loch Restil Head (134) weather in parts in very massive blocks 
 with rough faces and show in places lustre-mottled cleavages of some 
 porphyritic mineral. In other parts they are much finer in grain. The 
 microscopic character of a specimen from the upper sheet (slide 4753) 
 is thus described by Mr Teall: "The original rock appears to have 
 consisted essentially of malacolite , hornblende and felspar. Carbonates 
 and chlorite now abundant. The hornblende is sometimes ophitic with 
 respect to felspar. This rock must evidently be classed with the 
 diorites of camptonite type." The lustre-mottling is due to the 
 inclusion of bright shining black hornblende portions within the more 
 decomposed dull-looking augite. Similar hornblende can also be seen 
 edging the augite. The augite occurs in crystals reaching inch in length, 
 and is much the most prominent constituent to the naked eye. The 
 hornblende crystals bear evidence to a zonal growth, giving lighter tints, 
 on rotating with crossed Nicols, near their margins than at their centres. 
 As the hornblende may occur both as inclusions in the augite and 
 also surrounding it, without there being any sign of a passage from the 
 one into the other, it would seem that the growth of these two minerals 
 
LAMPROPHYRES : CAMPTONITES. 117 
 
 was proceeding pan passu. The hornblende crystals within the augite 
 may be zoned by less pleochroic margins just as the larger horn- 
 blendes are. The felspar is pink : it is only small in amount and is 
 hardly noticed on the rough weathered face. 
 
 The dykes in the burns, J mile east of Monovechadan (124 north-west, 
 slide 4749), nearly J mile S.S.E. of Bathaich ban Cottage (slide 4750), 
 and on the hill J mile west of Loch Restil outlet (slide 4751), may be 
 taken as examples of the camptonite dykes in which the hornblende is 
 generally distinctly in excess of the augite. In these slides the horn- 
 blende is in more elongated needly shapes than it is in 4747, 4748, and 
 4753, and is either quite sound with black horny lustre, or decomposed 
 into opaque grey or greenish-grey shapes. The shapes are not usually 
 more than J inch in length, and can frequently be made out, with the aid 
 of a hand lens, to be idiomorphic with respect to the felspar. In 4750, 
 the felspathic matrix is moderately fresh and pink in colour, but the horn- 
 blende is decomposed into a white substance which is almost totally opaque. 
 Sometimes a margin of such opaque matter may be seen surrounding the 
 porphyritic crystals of nialacolite. 
 
 The dark-grey diorites or camptonites are specially abundant in the 
 area between Lochgoilhead and the head of Loch Fine, and occur 
 generally in the form of east to west dykes. 
 
 More common than the grey or black lamprophyres are those of red, 
 reddish-brown, or yellow colour. The colour of the felspar in all the 
 lamprophyres has a tendency to be red or reddish-brown, and the 
 difference in colour between the redder and the blacker bands is 
 supposed to be due, either to a greater proportion of felspar in the 
 former, or to a deeper tint of red in this felspar. Judging from the 
 rocks that have been sliced, the redder lamprophyres do not differ 
 in any conspicuous way from those of darker aspect. A specimen 
 of a reddish lamprophyre in Invervegain Burn (183 north-west), was 
 taken from a place near the "r" of "Invervegain," and was chemically 
 examined in the late Prof. Dittmar's laboratory at Anderson's College, 
 Glasgow. A sample, after being dried at 100 C., gave a mean silica 
 percentage of 47'98. 
 
 As examples of the red lamprophyres without prominent mica, speci- 
 mens from the bands J mile south-west of Cnoc Madaidh (east side of 
 Glen Striven), and 300 yards north of the Craig (183 north-west), were 
 sliced and examined microscopically. The former (slide 2838) is thus 
 described by Dr Hatch. 
 
 " Diorite. Medium-grained rock with red felspar. Striped felspar 
 in lath-shaped crystals of a reddish-brown colour due to kaolinisation. 
 Hornblende in isolated brownish-green crystalline grains, sometimes 
 bounded by oc P. Pleochroisin as follows : 
 
 ( a pale yellow, 
 < fi brown, 
 I y greenish-brown, 
 
 Maximum extinction angle measured to cleavage in vertical sections 
 = 17. Scattered grains of opaque iron ore (ilmenite). Secondary 
 minerals are chlorite, and patches of flakey, colourless mineral with 
 high double refraction and iridescence (moire*) under crossed Nicols 
 (talc?). Both these minerals are alteration products of some vanished 
 ferromagnesian constituent, not of the hornblende, for that is quite 
 fresh, perhaps malacolite, if the rock bears any genetic relations to 
 2839." 
 
118 GEOLOGY OF COWAL. 
 
 The Craig rock (slide 2839) is described as follows : 
 " Diorite (Augite Diorite). Mineral constituents (1) Dark mica in 
 long, laminated, and slightly contorted lathes, showing undulatory 
 coloured polarisation under crossed Nicols. Strong pleochroism : 
 
 a pale yellow, 
 /?, y dark brown, 
 
 (2) Hornblende in isolated crystals, giving long, lath-shaped, vertical 
 sections and lozenge-shaped cross-sections ( a P, oc-Poc, a ^ x> ). Pleo- 
 chroism 
 
 {a pale yellow, 
 y 
 
 dark brown, 
 
 (3) Numerous short prisms and irregular grains of a colourless mineral 
 with moderately high index of refraction and high double refraction. 
 Maximum extinction, measured to vertical axis = 40. Optic axes 
 situated as in augite. These are the properties of a colourless augite 
 malacolite (salite). Forming a kind of ground-mass in which the ferro- 
 magnesian minerals are embedded, is a reddish felspar, the crystallo- 
 graphic nature of which could not be determined, owing partly to a 
 turbidity resulting from kaolinisation, partly to the indistinct and 
 undulatory manner of extinction under crossed Nicols. Iron ore in 
 largish opaque grains." 
 
 In some of the reddish lamprophyres, chiefly, we think, where mica 
 is not prominent, stellate groups of acicular crystal forms, attaining a 
 length of \ inch, are conspicuous, e.g., in the burn 1 mile north-west of 
 Glenlean, and at the top of a band in the burn | mile south-west of 
 Glenmassan. These forms are nearly always much decomposed, and 
 are so largely replaced by calcite that it is not always certain what mineral 
 they represent. We presume it is hornblende rather than felspar, partly 
 because of the deep rusty colour they assume near weathered surfaces, 
 and partly because in a sheet J mile N.N.W. of the "P" of "Dornoch 
 Point" (152 south-east) crystals of black hornblende are seen arranged 
 in similar clusters. 
 
 This last rock is described by Mr Teall as follows (slide 3453):" This 
 rock is composed of long hornblende prisms in a pinkish matrix. The 
 porphyritic hornblende is idiomorphic and shows the forms (110), (100) 
 and (010). Colours : a very pale brown or yellowish brown, /? and y 
 brown. The matrix is composed of felspar stained with ferrite, small 
 prisms of hornblende and iron ores. A little calcite is also present. . 
 The felspar is too much altered to admit of determination." The black 
 hornblende needles continue to the original surface of the rock. They 
 are not always in clusters, and then they run parallel to the surface. 
 
 The rock with the stellate shapes in the burn J mile south-west of 
 Glenmassan is thus described (slide 2958) by Dr Hatch: " Under a low 
 power and in ordinary light, this rock appears to consist of a brown 
 glassy base, containing granules of felspar, clusters of magnetite granules 
 and scales of some greenish minerals. Embedded in this ground-enass 
 are large porphyritic crystals, apparently of felspar." 
 
 "But under a higher power and between crossed Nicols the brown 
 ' base ' is resolved into a mass of lath-shaped crystals of felspar the 
 brown pigment (particles of oxide of iron) being accumulated along the 
 peripheral portions of the lathes. The green patches which are largely 
 distributed through the section consist of some chloritic mineral, which 
 does not, however, show any pleochroism and appears almost completely 
 isotropic. This chloritic substance is perhaps pseudomorphous after 
 augite, no trace of which can however be discovered. The rock is con- 
 
LAMPROPHYRES: SPHERULITIC STRUCTURES. 119 
 
 siderably altered, patches of secondary calcite occurring in every part of 
 the slide. 
 
 " The colourless portions with more or less crystalline contours, which 
 appear in ordinary light to be crystals of felspar, are seen under crossed 
 Nicols to consist of calcite evidently an alteration product." 
 
 A reddish-brown north-east dyke occurs in the point between Loch 
 Goil and Loch Long, and comes down to the raised beach on the south 
 side of Mark. It has been traced for about f mile, and is in places 10 
 yards wide. There is no mica discernible with a hand lens, but many 
 prominent porphyritic crystals of hornblende occur, often quite fresh, which 
 are at times as much as 1 inch long, and inch broad ; usually, however, 
 their breadth is less in proportion to their length than this. They may 
 have their long axes distinctly parallel to one another and to the sides of 
 the dyke : no radiate clusters were observed. Occasional porphyritic 
 crystals of felspar of a reddish colour were observed in the same 
 rock. 
 
 A striking feature in some of the lamprophyres, particularly the redder 
 ones, is the frequency of spherulitic shapes near their surfaces. These 
 are seen iii several sections on the west shore of Loch Striven, e.g., 
 f mile E.N.E. of Dun Mor, in the 2 exposures f mile north-east of this 
 hill, J mile N.N.W. of Braingortan : on the east shore of Loch Eiddon J 
 mile north-east of Eilem Dearg : at the sides of a reddish brown mica 
 trap on the coast j mile south-west of St Catherine's pier (133), and at 
 the surface of a dark micaceous sheet J mile south-west of the same pier : 
 in a vertical dyke 1^ mile south-west of the last " n " of " Coilessan Glen " 
 (142 south-east) : in a band a little less than J mile slightly south of east 
 of Monovechadan (144 south-west) : in an east to west dyke 1 mile south- 
 west of the top of Ben Donich : and in other places we need not specify. 
 It should be observed that some of these localities have been already 
 mentioned as showing intersections by basalts, &c. 
 
 In the north of the two localities f mile north-east of Dun Mor there 
 is a dyke like band, with a width of 4 or 5 feet. The colour is reddish, 
 and there are many small flakes of black mica, especially in the interior. 
 In many places near the sides^ for a breadth of about 2 inches, there are 
 aggregations of small spherical shapes, sometimes as large as a pea. The 
 shapes are themselves red like the mass of the rock, but the interspaces, 
 which weather in depression, and thus give prominent relief to the 
 spherical shapes, are of a grey or greenish-grey colour. Occasionally two 
 or more of the spheres are seen united. The most distinct forms are 
 often arranged in rows which run rudely parallel to the sides of 4 the dyke, 
 at a distance from one another of ^ to ^ inch. The size of the spheres 
 becomes less and less as the side is approached, until in the last J inch 
 the eye cannot distinguish them. 
 
 A lamprophyre 100 yards south of this section, in the form of a 
 sheet about 1 foot wide, is in parts quite full of similar forms. The 
 spheres are most noticeable on the weathered surfaces. A specimen 
 close to the surface of the sheet was sliced (slide 2959) and is described 
 by Dr Hatch as follows: 
 
 "Dark-coloured glassy rock, through which minute needle-shaped 
 doubly refractive microlites are seen under crossed Nicols to be plenti- 
 fully distributed. 
 
 " The colouring matter consists probably of minute particles of oxide of 
 iron finely disseminated through the base. Darker patches are due to 
 aggregates of irregular masses or patches of oxide of iron with a few 
 granules of magnetite." 
 
 " Crystals of one of the bisilicates or of olivine appear to have floated 
 
120 GEOLOGY OF COWAL. 
 
 in, and been carroded by the molten magma ; for crystalline forms with 
 opaque borders of Fe 2 3 are most frequently met with. The interior 
 portions of such crystals have been dissolved out during the weathering 
 of the rock and replaced partly by calcite, partly by other alteration 
 products. Granules of calcite are abundantly distributed through the 
 whole rock." 
 
 In the section nearly mile N.N.W. of Troustan (183), a sheet from 
 4 to 8 inches thick is crowded with pea-like forms throughout. 
 
 On the hillside f mile E.N.E. of Glenmassan similar forms are extremely 
 abundant in the upper 4 inches of the sheet; just below this comes a band, 
 about 4 inches thick, which is very amygdaloidal, the amygdules being 
 prominently drawn out in a plane parallel to the surfaces. The amyg- 
 dules weather hollow, and their insides are occasionally coated with small 
 pea-like forms. Similar forms are not observed on the weathered surface 
 of other portions of this zone. 
 
 In the band nearly J mile slightly south of east of Monovecliadan 
 (134) the shapes, about the size of small shot, are red in colour and lie 
 in a fine-grained almost black matrix. They often coalesce and form 
 bands, sometimes as much as J inch in thickness, parallel to one another. 
 On examining shapes with a lens a distinct radiate arrangement can bo 
 recognised, so that they may be called spherulites. 
 
 The dyke 1 mile south-west of Ben Donich (142) is exposed in a 
 section in the burn, just above some steep scars. It is only 1 foot 
 thick, but there is another parallel dyke close to the north side. The 
 shapes reach ^ inch in diameter, and are as usual, of a redder tint 
 than the matrix in which they lie. A hand lens suffices to show that 
 they are built up of concentric layers which differ somewhat in colour. 
 Three zones of colour can be made out in most of them, the central 
 area being generally the deepest red. When two shapes join one another 
 their outer zones coalesce without any visible line of separation, while the 
 central areas remain isolated. The matrix in which the shapes are em- 
 bedded is a dark greenish-grey rock, in which is seen a network of very 
 thin hair-like needles of pale greenish-grey colour. The same needles 
 penetrate the pellet shapes : it is not clear that their directions within 
 these have any reference to the margins of the shapes. 
 
 Radiate spherulitic structures have been observed microscopically in 
 slide 4197, obtained from a sheet ^ mile north-west of Beinn Reithe (142), 
 where it is in close contact with epidote schists (see p. 114). Mr Teall 
 describes this slide as follows : " Junction of epidote schists with lampro- 
 phyre. The lamprophyre is composed of ill-defined felspar microlites, 
 small scales of chlorite, grains and specks of iron ore. There are a few 
 pseudomorphs (carbonates) after porphyritic constituents. Near the 
 junction the felspathic matter is beautifully spherulitic : further off the 
 microlites show a tendency to assume feathery forms. Brownish granu- 
 lar matter tends to obscure the characters of the rocks." 
 
 In the locality f mile E.N.E. of Dun Mor (172) a greyish-red fine- 
 grained sheet 4 to 8 feet thick occurs, with a low hade to the north. This 
 occasionally shows the spherulitic forms on either side : in one place the 
 surface bulges outward and the breadth of the distinctly spherulitic area 
 widens correspondingly, its outer boundary bulging out with the surface 
 while its inner one keeps straight a thickness of 1 inch is thus attained. 
 Inward from the spherulitic zone we come to a band, about 2 inches 
 thick, which shows beautiful fluxion structure parallel to the surface, the 
 different flow bands being indicated on the weathered face by slight 
 differences both of colour and hardness ; then comes an amygdaloidal zone, 
 about 2 inches thick, in which the amygdules are not prominently 
 
FOLIATED LAMPROPHYRES. 121 
 
 elongated, and, after this, an area with rarer amygdules which show 
 elongation parallel to the side. 
 
 An indication of flow, shown by a fine streakiness parallel to the 
 surface, is seen in the weathered face of a 3-foot felstone-like sheet on 
 the hillside J mile north-west of A' Chruach (182 north-east). 
 
 One-quarter of a mile north-west of the top of Beinn Reithe (142 and 153) 
 a 2j-foot sheet shows, for a breadth of 8 inches from either surface, close 
 parallel lines on the weathered face, at intervals of about inch. These 
 lines run parallel to the adjacent surfaces of the sheet. 
 
 The upper dark sheet nearly mile E.S.E. of Sgor Coinnich (153) 
 is in its upper part divided into bands of coarse and fine grain, which are 
 parallel to its surfaces. 
 
 In the fine-grained band J mile slightly west of south of Beinn Bhreac 
 (152 south-west) there are various bands, about \ inch thick, which are 
 rudely parallel to its sides, and display on their weathered faces a 
 delicate lineation in the direction of the containing bands. These 
 bands are finer in grain than the rest of the rock, and darker in colour. 
 Iii places they have an appearance of slight contortion, due probably to 
 folding while they were still in the liquid condition. Sometimes, too, 
 there is a breccia-like appearance within the sheet, owing to irregular 
 mixing of different varieties of rock one variety is dark grey in colour 
 and fine in grain, like the thin bands just mentioned, while the other is 
 redder and coarser. In some places there are sharp lines between these 
 different rocks, at others there seems quite a gradual change. 
 
 Foliated Lamprophyres. 
 
 In the extreme north part of the area being described, between the 
 head of Loch Fine and the adjacent margins of the Glen Fine granite, we 
 meet with a set of intrusive rocks which resemble the camptonites, or 
 other lamprophyres, in general aspect, excepting that they have in places 
 a cleaved or even slightly foliated structure. They generally occur as 
 dykes, and run east to west, like the unfoliated camptonites. If they 
 are rightly included with the lamprophyres, they must certainly be re- 
 garded as the oldest member of this group, for in this district none of the 
 other members show any sign of cleavage or foliation. These foliated 
 camptonite-like rocks are sometimes cut by the hornblende-porphyrite 
 intrusions, and these intrusions are themselves probably earlier than 
 some of the varieties of lamprophyre (see pp. 124, 125). Their foliation is 
 extremely slight when compared to that of the schists into which they 
 intrude, and no cleavage or foliation in the schists has ever been observed 
 to correspond to that in the dykes.* The cleavage and foliation in the 
 dykes seem quite confined to themselves, and do not exist in the schists 
 at their sides : they are not, however, strictly parallel to the side of the 
 dyke, but often diagonal to it. The foliation in the schist is always 
 sharply cut by the sides of the dykes, and it is clear that at the time 
 of the intrusion of the dykes these rocks were schists, and essentially 
 in their present condition, with the exception of the change exerted on 
 them by the metamorphic influences near the Glen Fine granite. So that 
 we need not modify the statement made (p. 108) in speaking of the 
 lamprophyres generally, that all the foliation of the schists had been pro- 
 duced before their intrusion. 
 
 * In this respect the phenomena observed differ distinctly from those usually seen 
 at the sides of the Pre-Torridon basic dykes in the North- West Highlands (see 
 " Recent Work of the Geological Survey in the North- West Highlands of Scotland," 
 Quart. Joum. Geol. Soc., vol. xliv. p. 378). 
 
122 GEOLOGY OF COWAL. 
 
 The relationship of the unfoliated camptonites of Cowal to the camp- 
 tonites of the Assynt district of Sutherland has already been incidentally 
 indicated by Mr Teall (p. 116). It is known that the Assynt camp- 
 tonites have suffered from the thrusting and metamorphic changes which 
 accompanied the great Post-Cambrian movements of their district, while 
 the mica traps have not, so that it is clear they are of earlier age than 
 the latter rocks. The finding in Cowal a set of foliated camptonites 
 which are also earlier than other lamprophyres and mica traps, enables 
 us to draw a parallel between the two districts, and renders it probable 
 that the two classes of rock in the one area roughly correspond in age 
 with those in the other. But if this be so, if the camptonites of Cowal 
 are the same age as those of Assynt, at what time was the foliation of the 
 Cowal schists produced ? In Assynt it is not as yet certainly recognised 
 that there were any great thrust movements of pre-camptonite age. In 
 Cowal it is certain that the process of schist manufacture was practi- 
 cally completed before the intrusion of the camptonites. Can it be 
 that the schist manufacture began in Cowal before it did in Assynt 1 Did 
 the great movements begin at first far to the east of the zone of distinctly 
 recognisable, thrust Durness and Torridon rocks, and then travel outwards 
 from the mountain area from the south-east towards the north-west in 
 
 sui 
 
 Owing to the similarity in character and identity of direction 
 between the camptonites that may be foliated and the unfoliated camp- 
 tonites, and the fact that where the former occur they are common, while 
 those of the other class are unknown or rare, we are inclined to suppose 
 that the two represent one another in different districts, and are approxi- 
 mately of the same age. We cannot indeed say that all the camptonite 
 dykes north of the most southerly foliated camptonite show foliation in 
 one part or other of their course, but the greater number of them do so, 
 and it is probable that if they could be traced more continuously we 
 should find that all of them do. As the foliated camptonites are in some 
 places foliated, and in others not, we need not be surprised that in some of 
 the dykes, particularly in those that can only be traced short distances, no 
 foliation can be seen. Supposing the two sets of rocks are really the same, 
 there must have been some special causes in the district of the foliated 
 set for the production of foliation in them, which did not occur in the 
 region of the unfoliated set. What these causes were is not clear. The 
 absence of foliation in the Glen Fine granite shows that the causes, 
 whatever they were, had ceased before the solidification of the granite. 
 
 The most southerly of these foliated dykes occurs in the burn J mile 
 north of the " d " of " Achadunan" (126). It is a greenish rock, markedly 
 cleaved, and with a slight lustre on the cleavage planes, but there is no 
 distinct mica visible to the naked eye. It is so much less foliated than 
 the schists at the sides, which consist of alternations of albite and more 
 quartzose schists full of large flakes of mica or chlorite, that the observer 
 concludes at once that it must belong to a rock later than they, though 
 the sides of the exposure are not seen in this burn. A total thickness of 
 6 or 8 feet is seen. The direction of foliation is much the same as the 
 apparent direction of the band, and the hade is to north at about 70. 
 There are closely aggregated white specks, about the size of grains of rice, 
 which effervesce briskly with dilute hydrochloric acid. These shapes 
 rather remind us of amygdules : in most places they have their greater 
 lengths parallel to the foliation of the band, but in one place, near the 
 south side of the band, they are much less elongated, and at the same 
 time the foliation is less marked, but there is still a cleavage. Hand 
 specimens from this place show a distinct plexus of minute thin needles, 
 
FOLIATED LAMPROPHYRES. 123 
 
 apparently of hornblende: there is no orientation of them in one direction. 
 The same band appears again, in a direction slightly north of east from 
 this section, in the south branclr of Eas Riachain. Here it is divided 
 into 2 or 3 bands, a yard or less from one another, and the intrusive 
 character is perfectly clear. They are often about a yard thick, and are 
 generally dyke-like, but sometimes they act as sills for a short distance. 
 The most southerly part of the rock in this branch of the burn is nearly 
 vertical, and is cleaved roughly parallel to its sides : amygdule-like spots 
 elongate themselves parallel to this cleavage. In some places the cleavage 
 is very poorly developed, and the rock weathers in a massive way with 
 slightly projecting knobs, and is at the same time essentially free from the 
 supposed amygdules, which in this locality characterise the more cleaved 
 varieties. The cleavage, or weak foliation, is usually roughly parallel 
 to the sides of the intrusion, but not always strictly so : it often varies 
 10 to 20 from it, sometimes in a more north-east and sometimes in a more 
 north-west direction ; in one place it was noticed to cross the band at about 
 45 in this case the direction was more north-west. We could see no 
 planes in the schists corresponding to those in the dykes : the planes in 
 the schists are generally at a marked angle to those in the dykes, and 
 we saw no tendency to approximation near the dyke sides. The dyke 
 seems thrown along a feature running N.N.E. and hading east. On the 
 east side of this it seems at first all together in one band perhaps 6 or 8 
 feet thick, and is generally massive and weathering with knobs. But 
 soon it splits into two parts, each 2 or 3 feet thick, and often dis- 
 tinctly cleaved. After this, another feature also running N.N.E. and 
 hading east, is met with, and we lose the dykes for some distance. A 
 dyke of similar character and in the line of these is seen at the head of a 
 landslip J- mile E.N.E. of the " E " of "Eas Riachain " ; it is 18 inches 
 thick. Further east still, at the east side of a north to south slack, which 
 marks the line of a fault, two bands of greyish-green cleaved dyke rock 
 are seen : they are each from 2 to 3 feet thick, and must be shifted by 
 the fault in the slack. 
 
 The next exposure of this kind of rock to the north occurs in the burn 
 mile north-west of the " n " of " Lochan Mill Bhig " (126). It runs east 
 and west, and is from 1 to 2 feet wide ; the cleavage in it runs nearly 
 parallel with the side. This dyke could not be traced more than about 
 100 yards. Nearly J mile due west of it, a 3 feet greyish-green lampro- 
 phyre dyke is seen, but this shows no sign of cleavage. C.T.C. 
 
 An instance of a well foliated dyke occurs in the burn ^ mile W.S.W. 
 of the "G" of Glen Fine" (126), about 300 yards before its junction 
 with the River Fine. Just below the sheep fold, a dark green fine- 
 grained dyke about 3 feet wide is bounded by a fault trending north- 
 west. The dyke is schistose throughout, the planes of foliation striking 
 obliquely at the fault which bounds the dyke. The neighbouring rock is 
 a gnarled and contorted mica schist containing albites. The foliation 
 planes of the dyke are nearly at right angles to the foliation planes of 
 the adjoining rock, and show no tendency to penetrate the latter, the 
 junction between them being quite sharp. The dyke contains inclusions 
 of the albite schists, the inclusions being similar to the schist at the side. 
 The foliation of the dyke passes round the inclusions which retain their 
 older foliation, lying oblique to the foliation of the dyke. The included 
 fragments are entirely unaffected by the foliation of the dyke. Close to the 
 dyke two smaller dykes occur, one on each side of the central dyke and 
 running parallel with it. They are only about one foot in breadth. The 
 nearest of them is within a yard of the sheared dyke, but they possess no 
 
124 GEOLOGY OF COWAL. 
 
 foliation whatever. The sheared dyke was examined by Mr Teall, and found 
 to consist in the main of pale brown mica and carbonates, some colourless 
 quartz or felspar, chlorite, and iron ores. The interior is somewhat coarser 
 than the exterior portion of the dyke. According to Mr Teall the un- 
 sheared dykes consist of fibrous hornblende, biotite, iron ores, carbonates, 
 and colourless felspars. The felspar forms a kind of matrix, and shows 
 under crossed Nicols a tendency to a feathery mode of aggregation. It is 
 evident, therefore, that the essential difference between the foliated and 
 non-foliated dykes is the presence of hornblende in the latter, and chlorite 
 in the former. As the breaking down and shearing of a rock containing 
 hornblende frequently results in the replacement of hornblende by chlorite 
 it is probable that the composition of the dykes before foliation was the 
 same. The unsheared dykes are not seen bounded by any crush move- 
 ment. The sheared dyke is at one side bounded by such a movement. 
 It is suggested that some early movements along the side of the sheared 
 dyke may have induced the foliation in it, though the crushing now seen 
 at its side may be due to later renewed movement. J.B.H. 
 
 The two east to west bands in the burn f mile west of the " E " of 
 "Eagles Fall" (126) seem both to be earlier than the porphyrite sheet 
 on the west side of the burn, for there is no sign of their passing through 
 it : the evidence is not, however, decisive, for they are not seen on the 
 west side of the sheet. They are both greenish-grey in colour. The 
 south band is cleaved at one side for a breadth of several inches. A 
 powerful north to south fault occurs a little on the east side of them, and 
 they are probably shifted considerably by it ; on the east side of this 
 fault we suppose them to be represented by the two W.N.W. dykes 
 seen on either side of another north and south fault, about J mile 
 west of the "E"of "Eagles." The dykes show no distinct cleavage. 
 One of them is intersected by a porphyrite sheet in the west bank of the 
 burn. One-eighth of a mile south-west of the " E " of " Eagles " a 4-foot 
 slightly foliated basic dyke makes a gulley in the schist scars. It is 
 in the exact line of the dyke which is intersected by the porphyrite sheet, 
 and we suppose represents either it or the companion dyke. 
 
 In the burn J mile south-west of the " C" of " Cruach Tuirc " (126) 
 a basic dyke with stout crystals, apparently of hornblende, can be traced 
 in or close to the burn for a distance of 200 yards. The breadth is 7 feet, 
 and the direction slightly north of west. No cleavage was discerned in it. 
 One quarter of a mile S.S.W. of the same letter, a little on the north side of 
 the burn, a basic dyke again appears, in the same line as that in the lower 
 part of the burn, and this is distinctly cleaved. Further up the burn, 
 either in or close to it, a similar cleaved basic dyke is seen in several 
 places. On the west side of the north-west fault that crosses the burn, 
 such a dyke is seen just above the porphyrite sheet on the north side of 
 the burn. On the east side of the same fault a somewhat similar exposure 
 occurs ; the thickness is 2 feet, and the splitting planes of the dyke show 
 small but distinct flakes of mica. The exposure lies immediately over 
 the top of the porphyrite sheet, only a few feet above the water level of the 
 burn ; the porphyrite is, in one place, distinctly chilled against it, and 
 acquires a felsitic matrix for a breadth of about an inch from it. A little 
 further west a similar dyke is seen below the porphyrite sheet. It is pos- 
 sible that the two dyke-like exposures belong to one band now separated by 
 the later porphyrite intrusion. The lower exposure is cut across distinctly 
 by the porphyrite. The upper exposure shows a foliation which makes 
 a marked angle to the direction of the band; the dip of it is about 
 E.N.E. at about 50. The dyke can be traced up the burn distinctly for 
 
FOLIATED LAMPROPHYKES. 125 
 
 about 60 yards after the porplfyrite sheet is lost against the fault running 
 up the burn. It is accompanied with parallel crushes and strings of carbon- 
 ate of iron mixed with rarer strings of barytes, and does not, in this course, 
 always show distinct cleavage. A little over J mile south-west of the 
 " C," a camptonite-like dyke, sometimes massive, and sometimes cleaved, 
 particularly near the side, is seen again. In one place it is in contact 
 with a porphyrite sheet, but the section is too much affected by faulting 
 to be readily interpreted. On the same line of intrusion two exposures of 
 cleaved dyke are seen |- mile east of the " E " of " Eagles Fall." In the 
 bed of the Fine, near the north side of it, about 180 yards above the cart- 
 bridge, there is a 5-foot dyke which may be the W.N.W. continuation of 
 the same line of intrusion. It contains distinct hornblende, and some 
 basic inclusions of coarse grain. No cleavage was noticed in it except for 
 a breadth of 1 inch at the south side. 
 
 One quarter of a mile west of the " C " of " Cruach," another line of 
 intrusions of the same class is seen. There are at least three different dykes 
 running roughly parallel, and close to one another, in a direction slightly 
 north of west, but they are inconstant in occurrence, when one dies out 
 another coming on at a little lateral distance, and they are only 2 or 3 feet 
 thick. Further E.S.E., along the continuation of their direction, a 
 similar dyke is seen crossing the crags <5n the south side of Cruach Tuirc. 
 In some places it is almost fiee from cleavage. 
 
 By the " u " of " Cruach " a foliated basic sheet, 4 or 5 feet thick, makes 
 a conspicuous ledge among the schist crags. This differs from the sheared 
 dykes described in showing micaceous spangles much more distinctly, and 
 also large radiate shapes composed of black mica. The arms of these 
 shapes are in places nearly 1 inch long. The black mica composing them 
 may be pseudomorphous after actinolite. The exposure is less than 
 mile south-west of the great granite mass which has effected such a 
 striking contact alteration in the schists of the neighbourhood, and we 
 suppose that the exceptional character of the sheet may also be 
 attributed to its action. 
 
 Summary of the Relations of the Older Igneous Rocks in 
 Regard to Age. 
 
 Of the different varieties of rock now described, not much can be said 
 of their relative ages. As already pointed out on p. 124, the foliated 
 camptonites are certainly earlier than the hornblende-porphyrite sheets 
 with which they come in contact. We suppose it probable that the 
 camptonites not seen to be foliated are of the same age as the foliated 
 ones, and that the hornblende-porphyrite sheets, etc., alluded to, are of 
 the same age as the felsites. 
 
 A section on the north-east side of Hell's Glen (134 south-west) between 
 the " a " and " g " of " Beag " shows a dark micaceous dyke cutting 
 through a pale felsite sheet. This shows that the basic dykes are not 
 all of the same age as the foliated camptouites some are later than 
 the felsites, and, therefore, still later than the foliated camptonites. 
 
 Three-eighths of a mile slightly east of south of Beinn an t-Seilich 
 (134), a sheet with stellar groups of decomposing hornblende needles cuts 
 through a felsite sheet. Just south of the "G" of "Glen Kinglas " 
 (134) similar intrusions are also in contact. The evidence is not 
 decisive, but is in favour of the felsite being the earlier of the two. 
 
 In the section (p. 113) J mile N.N.W. of the "P" of " Dornoch 
 Point" (152), a red band with radiate hornblende seems earlier than an 
 augitic dark grey band. The dark rock, however, does not seem quite so 
 
126 GEOLOGY OF COWAL. 
 
 fine-grained at its junction with the red* as it is at its junction with 
 the schists, and it is not certain that the flag-forming joints of the latter 
 rock are cut through. When the dark rock is in contact with the schist 
 it is usually, but not always, marked by a set of joints at right angles to 
 the junction, at intervals of 6 or 8 inches, which gradually die out in a 
 distance of about a foot. Where it is in contact with the red rock we 
 could see no such joints. Perhaps the cooling of the red rock was not 
 thoroughly completed at the time the dark rock came up. C.T.C. 
 
 CHAPTER XII. 
 
 THE IGNEOUS ROCKS (continued). BASALTIC DYKES. 
 GENERAL DESCRIPTION. 
 
 In this chapter the examples given of particular structures, modes 
 of occurrence, etc., have been chiefly collected from that part of Cowal 
 which lies within 1-inch Map 29 n the east side of Glendaruel and Loch 
 Riddon. The details observed along the course of the basaltic dykes in 
 other parts of the area are mentioned subsequently. 
 
 The same colour, deep carmine, is used to express basalt, dolerite, 
 augite andesite, and tachylite : and the same letter B is applied to all 
 these, with the addition of a small T (thus B T ) in the case of tachylite, 
 where this may occur in sufficient thickness to form a special feature in the 
 exposure. 
 
 Basalts, dolerites, and tachylites, are so closely connected, forming 
 often different parts of the same dyke, that it is impossible to 
 separate them with satisfaction. Augite andesites have also much the 
 same macroscopic appearance, and such a similar behaviour in the 
 field, that they seem to form in this area a natural group with the 
 others. All these rocks are distinguished by their dark grey or black 
 colour in fresh hand specimens, their rusty and exfoliating weathering, 
 and their habit in this area of forming approximately vertical dykes, 
 which, with the exception of the tachylite, have prominent cross or 
 longitudinal joints, or frequently both of these. 
 
 A glance at the Maps will show what a very important feature in 
 the geology of the district these dykes form. Even the number shown 
 is far from complete, for in areas covered by peat or drift, their out- 
 crops have not been continued far, except in the case of some of the 
 thicker dykes, the probable courses of which we desired to indicate, 
 in order to show the connection of their different outcrops. 
 
 In rocky areas the dykes are generally easy to trace, this tracing being 
 only a question of time and labour. They make features rock-scars, 
 green grassy hummocks, slacks, or flat terraces which clearly cut across 
 the strike of the bedding or foliation planes adjacent, and which attract 
 attention even at some distance. When forming rock exposures their 
 intrusive nature is at once apparent from the difference between the 
 joints in them, and the rock at their sides ; when they form slacks or 
 terraces we are not always able to tell whether these are due to a crush 
 breccia or a dyke, but if we follow such a line for a little distance 
 we are sure before long to meet with some evidence that settles the 
 question, either some exposure of dyke-rock in the slack, or indications 
 of contact alteration in the rock at the sides. 
 
- BASALTIC DYKES. 127 
 
 It is not certain why some dykes form rock-scars, resisting weathering 
 more than the adjacent rocks, and others slacks and terraces, resisting 
 weathering less than these rocks-; but probably the reason is connected 
 with the grain of the dyke-rocks, the coarser grained being most readily 
 penetrated by water, and the other decomposing agents introduced by 
 water. It is, at all events, a fact that the coarser grained rocks generally 
 form either hollows, or smooth green hummocks and ridges, with but few 
 rock exposures. This is very well illustrated along the course of the 
 broad Dunoon Castle dyke, which, when free from drift, universally forms 
 either well-marked hollows, or dry smooth banks and mounds clothed 
 with short sweet grass, which contrast strongly with the dark peaty or 
 <f benty " ground on the sides. From the high beach near Glen Morag 
 (184 south-west) for a distance of rather more than 1J miles west, it 
 forms such banks and mounds, not continuously but so near together 
 that when you are standing on one you can usually pick out the next 
 on either side. Similar green ground is formed by it in the areas mile 
 south-west of Bodach Bochd (183 east), and on the south and south-west 
 sides of Coraddie (182 east). On the side of the hill west of Troustan 
 (183 south-west), and between Allt Glac na maill and the high beach at 
 Fearn'ach (182 south-east) it forms a conspicuous trench or slack. 
 
 Other dykes which we have especially noticed to form smooth green 
 banks occur 1 mile south-west of Craigendaive (172), f mile E.S E. of 
 Balliemore, from J to \ mile south-west of Bishop's Seat (183), and \ 
 mile E.S.E. of Tom Odhar (184). 
 
 Where the more readily decomposed dykes are running not across but 
 along the level contour lines of the hill they form flat terrace features 
 rather than slacks, as any hollow they might otherwise form has a 
 tendency to be filled up by movements of soil from the higher side. Such 
 terraces are excellently shown in the rocky area just east of the foot oi 
 Loch Eck, on the east side of Stronchullin Hill (164 south-east), and 
 on the hillface 1 mile south of Glen Lean (173 east). When they run 
 steeply across contours they form slacks or lines of ready weathering, 
 which we repeatedly find to have been taken advantage of by the 
 streams. In some districts, e.g., on the sides of Glendaruel and Glen 
 Tarsan, we can hardly find a burn which is not running along either a 
 dyke or a crush breccia, or both of these combined, and some of the 
 streams have worn such deep channels that it is extremely difficult to 
 walk continuously along them, their sides being for considerable distances 
 quite vertical, perhaps sixty or seventy feet high, and separated here and 
 there by deep pools. The burn on the hillside 1 mile S.S.W. of Glen- 
 massan is such an one, and it ha& consequently received the name of 
 ' Garbh Allt " (the rough burn). 
 
 Among the more prominent crags formed by dykes we may mention the 
 following: one mile KN.E. of Dun Mor (172 south-east) made by a 
 somewhat fine-grained basalt ; one in the Creag Mh6r 2J mile north-west 
 of Blairmore, which is a massive black scar continuing with but little 
 interruption for a distance of nearly a mile ; one J mile north of Garrow- 
 choran Hill (184 south-west), and continuing thence for \ mile north- 
 west; and one at Cluniter (195 north-west), which is very prominent from 
 the Clyde tourist steamers. 
 
 The joints in the dykes have always an evident relation to their 
 sides or surfaces of cooling. It is perhaps rare to find one that does 
 not show some joints both at right angles and parallel to the sides ; in 
 some these different sets are nearly equally prominent, but in others 
 they are so unequally developed that, in brief descriptions, we may 
 call them simply either longitudinally-jointed or cross-jointed. Good 
 
128 GEOLOGY OF COWAL. 
 
 examples of the longitudinal planes occur in the north to south dyke in 
 the burn f mile south-east of Corlarach Hill (183 south-east), and on 
 the shore of the Clyde at places | mile south-east of Glen Morag (183 
 south-west), J mile S.S.E. of Glen Morag, and J mile N.N.E. of the Bull 
 Kock (184 south-west). 
 
 Prominently cross-jointed dykes are perhaps as abundant as the above, 
 but are themselves divisible into two classes, which, in their extreme 
 forms, are markedly different in appearance. In one class the joints divide 
 the dyke into rude five or six-sided columns, the cross diameters of 
 which in one direction are not widely different from those in another. In 
 the other class the dyke is divided into slabs or flags which, though only 
 one or two inches broad, may cross most of the breadth of the dyke, and 
 extend also for several feet vertically or diagonally. The columnar cross 
 joints are well seen in the following dykes, the Dunoon Castle dyke on the 
 shore at Dunoon and on the east side of Loch liiddon ; in the dyke nearly 
 J mile slightly north of east of Cruach nan Capull (183 north-west), com- 
 bined with longitudinal joints; in the dyke just below the bridge over 
 the burn that flows into the West Bay of Dunoon; in the dyke 150 yards 
 above this bridge; in the Toward Church dyke, both at the church itself 
 and on the shore (combined with longitudinal joints near its south side). 
 The flaggy cross joints occur, in the dykes f mile N.N.W. of Ciiocan 
 Sgeir (172); | mile S.S.W. of Glen Lean (173 south-west), with dip 
 of joints varying rapidly; near the top of Leacann nan Gall (183 north- 
 east), with flags dipping either north-west or south-east, or forming curves ; 
 the top of Bishop's Seat (183 north-east), with planes vertical or between 
 this and a dip of 50 north-west ; J mile south of the top of Blar Buidhe 
 (183 south-east), with dip to south-east ; in an exposure 90 yards north- 
 west of this last locality with a steep dip to north-west ; J mile north of 
 Garrowehoran Hill (184 south-west); and from this locality for a distance 
 of J mile north-west. In the dyke near the top of Leacann nan Gall we 
 see both the flaggy joints and cross prisms of short diameter, which in 
 places cut the dyke into columns about 3 feet long and 3 inches broad. 
 It is clear from the particulars in the above list that there is no general 
 direction of dip for the joint flags. This fact is particularly well seen in 
 the dyke with central tachylite (to be subsequently mentioned) rather 
 more than J mile slightly north of east of the Clachan of Glendaruel 
 (172 north-west), where it is seen that the flags are not at all perfect 
 or parallel, if closely examined : they may perhaps be regarded as 
 prismatic columns which have had their cross diameter in one direction 
 much increased at the expense of those in others ; the general direction 
 of the flags may curve not only in tfie direction of their dip but also in 
 that of their strike, as they are traced across the breadth of the dyke, 
 though the dyke side continues straight. 
 
 The dyke by the north side of the "n" of "Glen Tarsan " shows 
 good cross prisms in the south-east half of its course, but in the north- 
 west half it is flaggy across the length : an obscure area separates the 
 differently-jointing portions. 
 
 A north-west dyke in the burn } mile south-west of Cruach na Caorach 
 (173 south-west) has cross flags for a distance of one foot from its edge, 
 and also in a part near the middle, but not so elsewhere. 
 
 The interiors of dykes are least affected by cross joints, and contain 
 also the most abundant, and the largest vesicles. The margins of the 
 most vesicular areas are rudely parallel to the dyke sides, and in those 
 dykes which contain alternating layers of more or less vesicular portions 
 the alternations are parallel with the sides. Dykes on the shore J mile 
 
BASALTIC DYKES. 129 
 
 N.N.E. of the Bull Rock (184 south-west), and 200 yards south-west 
 of this rock, show the special occurrence of vesicles in the interior portions; 
 in the last-mentioned dyke, which is the most northerly but one of a set 
 of four, the amygdules are more common in certain bands than in others, 
 and are sometimes of irregular shape ; some thin strings of basalt lie on 
 the north of it, from one of which, only 4 inches wide, hand specimens 
 can be obtained showing its full thickness, and many of the common 
 characters of dykes, including the vesicular nature of their centres. 
 
 An 8-foot dyke on the shore J mile S.S.E. of Chapel Hall (194 south- 
 east) also shows vesicular bands in rows parallel to the side : the vesicles 
 are filled with a soft green earth, or with this and calcite mixed. In 
 the burn 100 yards east of Glenlean (173 east) the vesicular portions, 
 whether near the centres or not, are clearly disposed parallel to the side. 
 The most easterly of the north and south dykes near the head of the burn 
 f mile south-east of Corlarach Hill (183 south-east) has, a little within it, 
 several bands, a few inches thick, of slaggy basalt^ mixed with other bands 
 of fine grain which are quite free from vesicles. 
 
 It has just been stated that the vesicles in the dyke 200 yards south- 
 west of the Bull Rock are sometimes of irregular shape. In all the other 
 cases alluded to they are roughly spherical, and are often about the size 
 of a small pea. The spherical shape is in the basalt dykes of such 
 constant occurrence, that we have not noticed more than 4 or 5 exceptions 
 in addition to that just mentioned. In the dyke J mile south of the top 
 of Blar Buidhe (183 south-east) the amygdules are at times distinctly 
 pulled out with their long axes parallel to the dyke side. In the north-west 
 dyke in the burn bed $ mile north-east of the " K " of " KILMODAN " 
 (162 south-west) the central portion is unusually vesicular, and the vesicles, 
 which are usually filled with calcite, are sometimes as much as ^ or J inch 
 long : they are often distinctly longer than broad, and have their greatest 
 lengths, as seen in a flat surface, parallel to the dyke side. On the shore 
 of Loch Fine, J mile south-east of the " C " of " M c Phun's Cairn," (141 
 north-west) a dyke shows calcite amygdules, especially near the centre, 
 and these are partly elongated parallel to the dyke's direction. In the 
 burn f mile north-west of Sgarach Mor (173 north-west) the vesicles in 
 a north-west dyke are abundant and most irregular in shape, joining 
 together by numerous processes so that they may, for a small area, equal 
 in bulk the rock in which they occur. 
 
 In the middle of a 5-foot dyke 130 yards south-east of the East Gates 
 of Toward Policies there are in places short bands of quartz and calcite 
 which attain a width of 4 inches, and sometimes end bluntly : they 
 run parallel with the dyke side, and continue for some distance verti- 
 cally ; there is no appearance of crushing in the dyke near them. The 
 dyke on the north side of the fault 100 yards south-west of Toward 
 Lighthouse has also a calcareous band in it with geodes of quartz crystals : 
 these also seem independent of any crushing. 
 
 The special occurrence of amygdules in the centres of dykes is an 
 indication that these were the last portions to consolidate, and that the 
 previous partial cooling of the outer parts was accompanied by a contrac- 
 tion in bulk, which led to a diminution of pressure in the interior. From 
 the spherical shape of the vesicles we conclude that the motion in the fluid 
 rock must usually have ceased after the vesicles were formed, or else that 
 they were carried on without any distortion. The setting free of the gas 
 and steam, or their sudden expansion so as to form visible cavities, would 
 lead to an absorption of heat from the surrounding mass, and this would 
 tend to cool and solidify it and stop the motion. 
 
 Calcite is much the most common mineral found in the vesicles, and, 
 
 I 
 
130 GEOLOGY OF COWAL. : 
 
 as this is readily removed by weathering, they generally appear empty 
 in natural exposures. A white radiating mineral which projects on 
 weathered surfaces, and is probably some zeolite, is not uncommon : 
 examples occur in the bend of the broad dyke \ mile north-east of Cruach 
 na Caorach, in the dyke by the big bend in Inverchapel Burn, in a thin 
 dyke on the west shore of Loch Striven 200 yards north-west of the Craig, 
 and in the most easterly dyke of the close set which occurs j- mile slightly 
 south of east of Uig (173 and 174) : the amygdules in the last mentioned 
 attain a length of J inch : those by the big bend in Inverchapel Burn 
 are supposed by Dr Hatch to be natrolite (slide 2842). A dyke, 
 about 4 feet thick, 1 mile N.KE. of the Badd (183 north-east) contains 
 some amygdules of white agate, mixed with others of calcite. In the 
 dyke already mentioned J mile slightly east of south of Chapel Hall 
 " green earth" occurs, sometimes filling the entire vesicle. On the shore 
 of Loch Fine 100 yards W.S.W. of Mid Letter (141 south-west), the soft 
 earthy substance in the amygdules in a freshly broken face is pale green 
 in colour, but after exposure to light it changes to dark green in less than 
 twelve hours, and ultimately becomes quite black. This substance seems 
 to be the Chlorophseite of Macculloch (Western Isles, i. p. 504). See 
 also Heddle, Trans. Roy. Soc. Edin., vol. xxix. p. 84. 
 
 On examining with a hand lens specimens of the coarser dyke rocks, 
 the lath-shaped forms of the felspars of the ground-mass are often quite 
 evident, and the darker augite patches may appear to be intersected by 
 them : but the last character can, of course, be made out much more 
 satisfactorily when the rocks are examined in thin slices under the micro- 
 scope. The distinctly crystalline rocks seem always to show this " ophitic " 
 character, i.e., the augite areas are penetrated and cut up into small 
 portions by lath-shaped crystals of felspar, the felspar having been the 
 first of the two to crystallize out on the solidification of the rock. 
 
 The felspars and other minerals of the ground-mass become less and less 
 as the edges of the dyke are approached, so that the general grain of the 
 rock grows finer and finer. Usually they attain the greatest dimensions 
 only in the interiors of the broader dykes. 
 
 But besides the felspars of the ground-mass, larger and more stoutly- 
 formed felspar crystals are in some dykes very prominent as porphyritic 
 constituents, and these may occur as abundantly and in as large forms 
 close to the edges of the dykes as elsewhere. They would seem conse- 
 quently to have been in existence in the fluid dyke rock at the time of 
 its intrusion. 
 
 On the south-west side of a little burn about J mile N.N.W. of the 
 shepherd's house in Glen Tarsan (173 north-west), for an inch or so from 
 a dyke side, porphyritic felspars, giving nearly square sections, sometimes 
 about ^ inch in length are common, so that they nearly equal in area the 
 ground-mass; for the next 1J inch they are decidedly rarer, occupying 
 hardly of the area exposed ; then for a breadth of 3 inches they come 
 in again nearly as abundantly as at the side ; and after that, for 6 inches 
 or more, they become rarer again, occupying perhaps from J- to ^ of 
 the whole mass. Again, in a north and south dyke, several yards wide, 
 in Gleann Laoigh burn, nearly due east of An Socach (163 south-west) por- 
 phyritic felspars sometimes 1 inch in length are common about 2 feet from 
 the side, but are practically absent in the rest of the dyke. A porphyritic 
 dyke on the shore 300 yards west of Toward Cottages also shows marked 
 variations in the abundance of the large felspars in different parts ; spaces 
 of a square foot or so can be selected which show hardly any of them, 
 while in other parts not far away they are common ; in this dyke it is 
 also evident that often the porphyritic crystals do not consist of isolated 
 
BASALTIC DYKES. 131 
 
 individuals, but of groups of crystals connected together, so that the 
 rock may be called " glomero-porphyritic." Probably this structure is 
 common in the porphyritic dykes. A 2-foot dyke, on the shore mile 
 N.N.E. of Inellan Pier, has on its south side a thin string which is, 
 in certain parts, very rich in porphyritic felspar, but these parts are only 
 small and scattered. 
 
 In a dyke in the burn J- mile south-west of the <C G" of " Gleann 
 Laoigh," we have noticed the porphyritic felspars to attain an unusual size. 
 In one small exposure a crystal with a length of 3f inch was seen, 
 another was 3 inches by 2 inches, and others 2 inches long ; the edges 
 of the crystals are, for i inch or so, of a yellower tint than the insides, 
 as if owing to the action of the magma on them. 
 
 Among other porphyritic dykes are, the two on the west shore of Loch 
 Striven about 1 mile N.N.E. of Dun Mor (172 south-east), the two on 
 the shore a little over \ mile south of Oaigendaive, the continuation of 
 of one of these in the hill exposures north-east of A' Chruach, and \ mile, 
 and f- mile north-west of A' Chruach, the dyke \ mile N.N.W. of Cnocan 
 Sgeir (172 north-east), the north-south dyke \ mile S.S.E. of Cruach na 
 Caorach (173 south-west), the dyke in the burn mile W.KW. of 
 Sgarach Mor (173 north-west), a thin dyke on the shore a little over 1 
 mile south of Fearn'ach (182 south-east), the north-east portion of a 
 compound basalt band which runs \ mile south-west of Cruach nan Capull 
 (183 north-west), the dyke in the burn f mile south-west of Kilbride 
 Hill (183 and 184), some of the north and south bands in the burn \ mile 
 south-east of Corlarach (194 north-west) and a thin dyke \ mile east of 
 Cluniter, just at the edge of the high beach. 
 
 It is suggested in several places that the occurrence of porphyritic 
 felspars is liable to vary not only in isolated dyke exposures, but also, 
 and to a larger extent, in the direction of their lengths. We cannot, how- 
 ever, mention any case that is quite clear ; intrusions in this area are so 
 abundant and so variable in occurrence that we cannot safely conclude 
 that one dyke that appears in the same line as another at a little distance 
 is really the same, unless there is a continuous exposure between the two. 
 An apparent replacement of a porphyritic dyke by one that is not porphy- 
 ritic occurs in the east and west bum f mile KN.W. of Bodach Bochd (183 
 north-east). The most easterly north and south dyke in the burn f mile 
 south-east of Corlarach Hill (183 south-east) is in one place very por- 
 phyritic, but is not at all clearly so elsewhere. 
 
 Olivine in small greenish grains, and pseudomorphs after it, have 
 been observed by the naked eye in, a porphyritic basalt, which occurs in 
 the shore 200 yards E.S.E. of Brackleymore School (194, slide 2845, 
 described on p. 142), the parallel dykes 150 and 250 yards N.N.E. of 
 M 'Plain's Cairn (141), the dykes \ mile N.N.E. and \ mile east of this 
 cairn, a thin dyke crossing the burn ^ mile east of the "u " of " Gleann 
 Dubh" (152 north-west), the dyke ^ mile E.N.E. of the "M "of 
 " Meall Reamhar" (152 north-west), and some few other places. But 
 macroscopic observations have not generally enabled us to detect it, and 
 we think there are comparatively few of the dykes in this district in which 
 it is prominent : it does not seem as abundant as it is in the Sleat district 
 of Skye. 
 
 In slide 2844, the north-west dyke which intersects the east and west one 
 on the south side of Larach Hill (164 north-west), there are beautiful 
 pseudomorphs of serpentine after large well-formed crystals of olivine of 
 pyramidal habit : other little patches of serpentine with calcite probably 
 represent altered augite. In slide 2849, from the dyke with prominent 
 porphyritic felspar exposed on the raised beach 300 yards west of Toward 
 
132 GEOLOGY OF COWAL. 
 
 Cottages (194), pseudomorphs after olivine also occur: for description of 
 slide see p. 136. In slide 2842, from the dyke by the big bend in 
 Inverchapel Burn (164 south-west), there are abundant iron-yellow 
 patches, which may be pseudomorphs after olivine. 
 
 In the dykes on the shore 250 yards south-east, and J mile S.S.E. of 
 Glen Morag (184 south-west), the weathered surfaces of the interior 
 portions have a peculiar spotted appearance. The spots are often about 
 J inch in diameter and project slightly from the intervening areas. They 
 may either closely adjoin one another, or be separated by a distance equal 
 to, or greater than, their diameters. When the rock is not too much 
 weathered it can be seen that the spots have no sharp boundaries, and 
 that the minerals in them sometimes extend into the adjoining areas. Their 
 felspar seems in a much fresher condition than it is outside, where it has 
 usually acquired a dirty yellowish-green tint. The condition of the 
 augite is not recognisably different as far as can be made out with a hand 
 lens, nor is the proportion different. 
 
 Thin margins or selvages of distinctly glassy rock, " tachylite," are com- 
 mon over the whole district, but are generally very thin, and consequently 
 not to be found without close search. They may be seen in the follow- 
 ing places, the burn J mile south-east of Dun Mor (172 south-east); 
 one of the north-west dykes in the section mile south-west of Bodach 
 Bochd (183 south-east); the north-west dykes in the section J mile south- 
 east of Bodach Bochd ; a thin dyke in the burn about J mile S.S.E. of the 
 Horse Seat (183 south-east) ; on the east side of Loch Striven, mile 
 N.N.W. of Inverchaolain Church, and 300 yards south of Ardbeg (183 
 north-west); on the west shore of Loch Striven, J mile N.N.E. of 
 Troustan; on the hillside 1 mile S.S.E. of Sgian Dubh (183 south-west), 
 at the head of a big landslip ; one of the dykes in a set of three closely 
 parallel ones on the east shore of Loch Striven, 200 yards south of 
 Brackleymore School (183 south-west); the dyke in the bum J mile 
 E.N.E. of Garrowchoran Hill (184 south-west); the burn J mile south- 
 west of Cluniter (195 north-west); the coast immediately north of Inellan 
 Pier, and again J mile north and f mile south of the pier. Even this 
 is far from an exhaustive list. 
 
 These selvages rarely exceed J inch in thickness, and range perhaps 
 from J- inch down to the thinnest possible film. They seem almost 
 universally to show on their outer surfaces somewhat round-edged rhom- 
 boidal or polygonal shapes, often from J to T \- inch in length, which seem 
 to be of a perlitic character. On breaking across one of the thicker selvages 
 these shapes may be seen to be really only the surfaces, apparently more 
 or less flattened against the rock intruded into, of solid forms which usually 
 take up the whole of the distinctly tachylitic portion. When the selvages 
 are very thin, the forms, being necessarily restricted to the thickness of 
 the glassy area, are much thinner across the selvage than in other 
 directions : but in other places there is no constant distinction between 
 their breadths in different directions, and we may find more than one 
 perlitic form as we cross the selvage from side to side. 
 
 In the most northerly of the north-west dykes in the section f mile south- 
 west of Bodach Bochd, the shapes are seen to be separated from one 
 another by extremely thin lines, which project slightly on the weathered 
 surface, and are marked by a central line of depression. We think that 
 similar lines are not uncommon elsewhere. 
 
 A slide (2852) from the glassy margin of the dyke J mile E.N.E. of 
 Garrowchoran Hill is thus described by Dr Hatch : " Opaque tachylite. 
 With minute colourless microlites (felspar)." 
 
 Besides selvages of tachylite we occasionally meet with broader masses 
 
BASALTIC DYKES : TACHYLITE. 133 
 
 of the same substance within and generally near the centres of dykes. 
 The best examples occur on the east side of Glendaruel, and are not very 
 far from one another : we do not know whether this may not depend on 
 the relation of the sources of the dyke material to this locality or on 
 some other condition. 
 
 A KN.W. dyke \ mile east of the Clachan of Glendaruel contains, 
 besides the tachylite, two other types of rock. The inner part has a 
 distinctly finer matrix than the outer, and shows small porphyritic felspars 
 distinctly : it has no joints peculiar to itself, but is crossed by those 
 which affect the rest of the dyke, and seems in places to pass into the 
 coarser rock gradually and in others abruptly. The tachylite is only found 
 within the porphyritic or inner portion, and itself shows more or less 
 conspicuous porphyritic felspars : it can be seen within this inner portion, 
 every here and there, along the length of the dyke for a distance of over 
 J mile. The tachylite may form several thin bands in the breadth of the 
 dyke, and these may vary considerably in hade and direction, and be 
 connected with one another. But where it is most developed it occurs 
 in a central band, which sometimes attains a thickness of 5 or 6 feet. 
 Where it is thick it is usually easy to distinguish at some distance', as 
 it is not affected by the same joints as the rest of the dyke, and projects 
 with a black glossy surface as if more able to resist weathering. Satis- 
 factory hand specimens are hard to obtain for the rock is either excessively 
 hard, or else breaks under the hammer into numberless small cuboidal 
 pieces along joint lines. What we may call the tachylite area is not 
 all glossy to the eye, but is divided up into more or less round-edged 
 rhomboidal or oblong forms of glossy rock, separated from one another by 
 bands, sometimes 3 inches thick, which are not so glossy and weather 
 with a somewhat rusty colour, or else a paler grey than the rest of the 
 rock. These bands are prominently jointed across their lengths. 
 
 The above bands no doubt correspond to the " sheaths " of the pitch- 
 stone of Eskdale, figured and described by Sir A. Geikie and Mr B. N. 
 Peach (" The Pitchstone of Eskdale," Proc. Roy. Phy. Soc. Edin., vol. v., 
 1880), and the interior parts to the "cores." The figures and description 
 in this paper correspond in most respects with what we observe in the 
 Clachan dyke, but Fig. 1, showing prominent prisms across the breadth 
 of the pitchstone from side to side, and the description on p. 242, 
 where the sheaths are mentioned as occurring along the sides of these 
 prominent cross prisms, do not apply to this case. On the contrary, a 
 peculiarity of the tachylite centre is, that there is no regular set of joints 
 which have a clear relation to the sides. The rhomboidal forms are seen 
 whether we look at vertical or horizontal surfaces of the rocks, and we do 
 not think that they have generally a greater length in one direction than 
 another, though they may have locally for a little distance. Instead of 
 comparing them with the cross prisms of ordinary dykes we would liken 
 them to the perlitic shapes which, as already stated, are of almost universal 
 occurrence in the tachylite selvages, though not unnaturally in the broader 
 tachylite bands the shapes may attain a much larger size, a length of 9 inches 
 being not uncommon. The sheaths have often, perhaps usually, a median 
 suture as described in the Eskdale rock, but sometimes there is no suture 
 and at other times three or more sutures in one sheath. The sheaths 
 generally project slightly on the weathered face, and show small porphy- 
 ritic felspars just as the cores do. We have never seen the glossy rock in 
 contact with the outer coarse-grained dyke rock : it is always the sheath 
 rock that is next to it. 
 
 Specimens of a glossy core and of a sheath from this locality were 
 examined by Dr Hatch, and are described by him as follows. The core 
 
134 
 
 GEOLOGY OF COWAL. 
 
 (slide 3268): " Andesitic glass. Consists of isolated porphyritic crystals 
 of fresh felspar imbedded in a chocolate-coloured glass, containing 
 microlites, often forked, of felspar, long slender needles or microlites of 
 a pale yellowish augite (large extinction angle), characterised by a fibrous 
 appearance and cross-jointing and studded with minute granules of 
 magnetite. The glass is clear in the neighbourhood of the augite and 
 magnetite, elsewhere it is cloudy from the presence of minute belonites, 
 the aggregation of which has, thus, evidently formed the augitic micro- 
 lites and iron-ore. The porphyritic felspar is in part striated. The 
 crystals are much corroded and contain inclusions and inlets of the glassy 
 base." The felspar microlites are often as long as any of the porphyritic 
 crystals, and the augite microlites longer. Each of the larger augite 
 microlites has sometimes shorter augite microlites arranged rudely at right 
 angles to its sides. 
 
 The sheath (slide 3269) : " Andesitic glass, of same general character 
 as 3268, but more devitrified, being crowded with skeleton crystals of 
 felspar and trichites of iron-ore. The rock is somewhat decomposed as 
 there is a quantity of brown granular matter (limonite 1) present in the 
 slide." 
 
 FIG 34. x^V. Half a mile slightly W. of S. of Cruach Mhor (162 and 172). 
 Ground plan of a portion of the centre of the dyke. The darker parts are the 
 more glassy, black, and sounder. The paler parts are the more grey or yellow- 
 weathering. 
 
 In another N.N.W. dyke, about \ mile south-west of Cruach Mhor 
 (162 south-east), a glossy portion can be seen near the centre for a distance 
 of nearly a mile, and its breadth in places is as much as 6 or 7 yards. 
 The dyke occasionally makes sharp twists, but the glossy portion still 
 keeps near the centre. The tachylite differs somewhat from that in the 
 Clachan dyke in that it displays less commonly porphyritic felspars ; 
 in some places it is as porphyritic, but more usually the felspars are evenly 
 dispersed and closer together, except in certain small well-defined and 
 usually spherical areas with diameters of J inch or less, which to the eye 
 show none at all. The outer sides of this dyke consist usually of a uniform 
 medium-grained basalt, but occasionally it varies slightly, even in parts 
 near to one another, arid acquires a much finer matrix speckled with small 
 porphyritic felspars. The glossy portions are divided into sheaths and 
 cores, and the remarks made on the irregularity of these forms in the 
 Clachan dyke apply equally to this dyke. It has also been noticed 
 additionally that the sheaths in this appear to the eye sometimes as glossy 
 as the cores, e.g., on the south-west side of the dyke at a point about 
 J mile south-west of the Ordnance Station on Cruach Mhor ; but they 
 more commonly present rusty surfaces to the spectator owing to their 
 
feASALTTC DYKES: TACHTLITE. 135 
 
 numerous cross joints allowing readier access to water, etc. The sutures 
 in some places are filled with thin milky-blue opalescent quartz strings. 
 In some places, portions of the dyke that are not glossy, are themselves 
 cut into corelike shapes by thin bands, which weather lighter grey, and 
 have opalescent quartz strings down their centres. About 30 yards south- 
 east of the places where the sheaths are at times seen to be glossy, more 
 or less incomplete spherical forms, with no apparent radial structure, are 
 observed within the glossy area. They may be compounded together, 
 or lie one within another, and have no sheath-like bands at their 
 margins. They occur in the cores and sometimes attain a diameter of 
 3 inches. 
 
 A slide (3270) obtained from near the centre of the Cruach Mhor dyke 
 is described by Dr Hatch as follows: "Andesite (Tholeite type). 
 Perfectly fresh rock, consisting of short lath-shaped crystals of colourless 
 striped felspar and granular aggregates of pale yellowish-brown augite, 
 imbedded in a base of clear chocolate -brown glass. Porphyritic felspar 
 in isolated crystals." There seem indications of irregular perlitic cracks 
 in the thinnest portion of the slide when examined by J inch objective. 
 
 A slide (3271) obtained from the centre of the same dyke in a part of 
 its course further north-west, about mile south-east of Lower Duillater, 
 
 is thus described : " Andesite (Tho- 
 leite type). Same as 3271, but with 
 larger felspars and augites, and glass 
 more devitrified, being full of cloudy 
 matter and numerous barbed arid 
 forked trichites of iron-ore." 
 
 A fine-grained north and south 
 dyke, 5 or 6 yards wide, close to the 
 east side of the north to south burn, 
 1J mile south of Craigendaive (172 
 east), shows, here and there, near the 
 FIG. 35. x J. One and a half mile S. side, and crossing diagonally in an 
 of Craigeudaive (172). Ground plan irregular way so as occasionally to 
 
 S4^inC3j &$ Jf < ^> "lack *"** f a 
 
 left white in the sketch weather in glossy or resinous appearance. In 
 
 relief and with a yellowish tint : the breadth they are somtimes as much 
 
 longer straighter ones are approxi- a s 14 inches. Their weathered sur- 
 
 face f S Sh w ' ***** Pf" em f da * 
 portions inclosed by other yellowish 
 
 bands, which are often about J inch wide, weather in relief, and are 
 divided by a median suture. The other parts with no resinous appear- 
 ance show on close examination somewhat similar yellow bands, but at 
 wider intervals; and also occasional short strings of opalescent quartz, 
 which sometimes attain a breadth of J inch, running rudely parallel 
 with the dyke side. 
 
 The most north-easterly of the north-west running dykes in the section 
 mile south-west of Bodach Bochd is only 4 or 5 feet wide, and it has, 
 besides the tachylite margins already described, an inter-mixture of a 
 glassy with a duller fine-grained rock for most of its breadth. A speci- 
 men of this type was examined microscopically (slide 2850) by Dr Hatch 
 and is thus described : " Tachylite (Basalt Glass). The lighter coloured 
 portions (in thin sections) are of a pale yellowish-brown colour, and 
 contain isolated granules and microlites of felspar. Penetrating these 
 are streaks of a blackish-brown glass, in some cases quite opaque. The 
 line of division between the 2 glasses is marked by a layer of doubly 
 refractive substance. In other parts of the lighter-coloured glass are 
 
136 GEOLOGY OF COWAL. 
 
 local accumulations of blebs of a dark brown pigment, uniting here and 
 there to opaque patches." 
 
 Some intrusive strings on the south side of the thick basalt f mile 
 E.N.E. of Inverchaolain Church (183 south-east) show a somewhat 
 similar admixture (slide 2851), and distinct perlitic structure. 
 
 In a quarry (now disused, 1893) in the porphyritic dyke east of Toward 
 Cottages there is a band, about 4 or 5 feet from the east side of the dyke, 
 which is said by the quarrymen to take three times as long to bore as the 
 rest of the dyke. The band is 2 or 3 feet wide and runs with the length 
 of the dyke. To the eye it has a more glossy look than the rest. A 
 specimen was examined microscopically by Dr Hatch, and is thus 
 described (slide 2849) : " Porphyritic basalt. Abundant large grains of 
 plagioclase felspar visible to the naked eye. Under the Microscope : 
 large porphyritic crystals of plagioclase and isolated serpentine-pseudo- 
 morphs after olivine, embedded in a ground mass made up of felspar- 
 microlites, grains of augite and abundant glassy base, the latter powdered 
 over with magnetite-dust which here and there accumulates to extremely 
 dark patches." 
 
 It has been pointed out (J. J. H. Teall, Brit. Petrog., p. 402) that we 
 may plausibly explain the occurrence of glassy bands near the centres of 
 dykes like those described, by an application of " Soret's " principle. 
 " Suppose a mass of molten matter be injected into a fissure and to remain 
 stagnant for a considerable length of time, the mass will be cooled at 
 the margins, and the compounds with which the solution is most nearly 
 saturated will accumulate in the marginal portions, leaving the centre 
 richer in those which play the role of solvent medium." 
 
 Other dykes divided in a way which reminds us of the sheaths and 
 cores of the Glendaruel dykes are not uncommon, though there is no 
 glossy or resinous appearance to be noticed in them. A clear exposure 
 of such a dyke occurs on the west shore of Loch Long, J mile slightly 
 east of south of Stronchullin (174 north-west). The dyke runs slightly 
 west of north, and is about 7 or 8 feet wide ; in the more central decom- 
 posing part frequent hard thin bands occur of a breadth varying from 3 
 inches to \ inch. They are all more or less cross-jointed ; sometimes 
 the joints go right across their breadth, at other times there is a median 
 suture from which joints proceed on either side. The joints that go all 
 the way across are, however, in this exposure the commonest. These bands 
 are disposed in a most irregular pattern, without any reference that could 
 be discovered to the side of the dyke. Sometimes they go right up to 
 the sides of the dykes. Sometimes they form circular or oval shapes 
 which are quite isolated as seen in plane section. Such shapes may 
 be seen inclosed in one another, or a band at one side of a shape may 
 divide into two portions, or twist into sharp complicated curves. The dyke 
 in the burn \ mile north-west of the " D " of " Dunoon " (184 north-west) 
 shows a somewhat similar pattern. 
 
 FIG. 36. Half a mile slightly E. of S. of Stronchullin (174). Some shapes of the 
 cross-jointed strings within the dyke on the shore. On a reduced but not 
 uniform scale. 
 
 Excepting as regards the glassy central portions and the porphyritic 
 felspars, very few variations in the character of individual dykes have 
 
BASALTIC DYKES: FLUXION STBUCTURE. 137 
 
 been noticed, which do not evidently depend on the distance of the 
 surfaces of cooling, the coarseness of grain varying as the distance, as 
 already described. But occasionaily we do meet with thin alternating 
 wavy stripes near their sides, which are not of quite the same character ; 
 e.g., in a dyke running nearly north to south in the burn 1 mile S.S.W. 
 of Glenmassan (163 south-west). In the most north-easterly dyke of the 
 closely parallel set mile north of Glenstriven (183 north-west), there 
 is throughout its whole breadth, about 3 feet, a banding parallel to the side, 
 and this is particularly distinct for a few inches next the side. Some of 
 the bands are more amygdaloidal than others, aud these, as seen at a little 
 distance from the weathered surfaces, appear darker than the others. The 
 bands near the side are often about ^ inch thick. In one place the dyke 
 changes direction sharply, and the bands partly change also, but some of 
 them become gradually cut through by the side of the dyke. The bands 
 remind us of those mixtures of slightly different types which so often 
 indicate fluxion structure in surface lavas. 
 
 Other cases on a larger scale may be supposed due to intrusions 
 of oiie rock into another before the older rock had got thoroughly cooled 
 and consolidated. In these cases we cease to find the difference in the joints 
 of the two rocks, and the ready parting along the side of one of them, 
 which are such helps to the first recognition of intrusions. We need not 
 be surprised, then, at having observed only a few such cases. They are 
 probably only a small part of those which actually exist. The difference 
 in texture does of itself lead to a difference in smoothness of the weathered 
 rock surfaces, but unless it be unusually great it is not likely to be 
 observed at any considerable distance. 
 
 An instance of this kind occurs on the hilltop f mile E.X.E. of Bailie- 
 more (173 north-west), where, within a north-west dyke of medium and 
 uniform grain, marked with conspicuous, flaggy cross-joints, there are 
 much finer-grained strings, sometimes as much as 4 inches thick. They 
 run irregularly, hading at various angles and are sometimes almost horizon- 
 tally, but in the main they may be said to be rudely parallel to the dyke 
 side. They have no joints peculiar to themselves, but are crossed by 
 those which affect the rest of the dyke. 
 
 A still better instance occurs in the dyke with tachylite centre on the 
 east side of Glendaruel near the Clachan. Rather more than J mile 
 slightly north of east of the Clachan, and about 100 yards from the small 
 burn that runs through the Clachan, there is a good exposure of the dyke. 
 For a space of from 2 to 4 yards from the sides there is a closely-flaggy 
 cross-jointing basalt of uniform and somewhat fine grain : then comes on, 
 quite gradually, an interior portion, in which these joints are replaced 
 by others which cut the rock into cross prisms. On hammering the 
 prismatic rock it is seen that the out-sides are of the same rock as the 
 flaggy sides, but there are bands within this which show a much finer 
 matrix speckled with porphyritic felspars. These bands do not stand out 
 from the rest in a dyke-like way, do not separate readily on hammer- 
 ing along their junctions, and they are crossed by the same joints 
 as the rest of the rock. The junctions are by no means so straight as 
 those usually seen in basalt intrusions with joint differences, and some 
 bands, as seen in plane section, are of extremely local occurrence. Yet, 
 at this particular locality, the outer rock must have been partly cooled 
 before the porphyritic rock came up, for, immediately at the junctions, 
 the matrix of the latter is finer than it is further away. A little distance 
 away in a north-west direction the same two varieties of rock occur 
 again, and again share the same joints, but there does not seem to be now 
 any sharp line between them. This is also the case in the two quarries 
 
138 GEOLOGY OF COWAL. 
 
 in this dyke by the roadside 300 or 400 yards south of Auchateggan ; in 
 both, the interior rock, for a breadth of 8 or 9 yards, is composed of a 
 very fine-grained matrix speckled with a varying abundance of porphy- 
 ritic felspar, and the outer 2 or 3 yards on either side is of a more 
 uniform, coarser rock. Though the two types occupy fairly definite 
 areas, and are in the extreme forms quite distinct, we could not, in either 
 quarry, see any sharp line between them, but for a foot or two on either 
 side, there seems a gradual change, the interior rock acquiring a coarser 
 matrix, and the porphyritic felspars continuing for a little distance in the 
 coarser rock. In the lower quarry the entire dyke is crossed by stout 
 rudely horizontal prisms ; in the upper quarry this is also the case except- 
 ing where the central band of tachylite occurs. 
 
 Apart from the indications of fluxion structure already alluded to, e.g., 
 the rare elongation of amygdules, stripy structure near the side, and the 
 occurrence of porphyritic felspars in bands parallel with the side, there 
 are one or two other modes in which it sometimes shows itself. The 
 most common of these is in the arrangement of the felspars ; when we 
 approach the edge of a dyke we can often see that the felspars, con- 
 sisting of extremely thin plates, are arranged with their greater lengths 
 parallel to one another, so that, in sections cut parallel to the edge, 
 a number of brightly shining flakes of felspar are observed, while, 
 in sections cut at right angles to the side, only thin needle-like 
 shapes can be seen. This is shown clearly on the shore nearly | mile 
 north of Blairmore Farm, and in the north-west dyke which inter- 
 sects the broad east to west one in the burn on the south side of Larach 
 Hill (164 north-west). The microscopical structure of the last dyke, 
 slide 2844, is described on p. 156. 
 
 Again, when the dykes contain inclusions of foreign rocks, these are 
 often arranged with their longer axes parallel to the side of the dyke. 
 The banded dyke alluded to on p. 137, f mile north of Glenstriven, shows 
 this excellently : the inclusions consist of schist and vein-quartz, the latter 
 in greater proportion to the former than we should expect ; where the direc- 
 tion of the dyke changes, the direction of the lengths of the inclusions also 
 changes. The dykes just on the south-west of this show similar inclusions 
 to a less marked extent, and a similar large proportion of vein-quartz 
 pieces. The most north-easterly dyke but one of the set of dykes in the 
 burn 150 yards south-west of Blairmore Farm contains pieces of altered 
 and cracked vein-quartz which are often several inches wide, and longer 
 than this in the direction parallel to the side of the dyke. 
 
 There are three other places in which inclusions, on a large scale, have 
 been observed, but in which no parallel arrangement was noticed. The inner 
 coarsely vesicular portion of the dyke f mile north-west of Sgarach Mor 
 (173 north-west) contains angular pieces of hardened schist and vein- 
 quartz (we think also of basalt of a less porphyritic type than the inclosing 
 rock), sometimes 6 or 7 inches in length ; in places near the side of the 
 dyke there are calcite strings running parallel with the dyke, but we do 
 not think the inclusions can be regarded as parts of a crush breccia of later 
 date than the dyke. The dyke in the burn a little more than J mile south- 
 east of Bishop's Seat (183 north-east) includes, for a breadth of 4 yards 
 in the middle, blocks of schist up to 3 feet in length embedded in un- 
 crushed dyke rock. The most south-westerly dyke in the burn nearly 
 1 mile slightly east of north of Bishop's Seat includes many pieces of 
 schist and vein-quartz. A dyke on the east side of Loch Striven, f mile 
 E.S.E. of Meallan Glaic (194 north-west), contains pieces of hardened 
 and darkened phyllite ; strings of porphyritic basalt, an inch or two thick, 
 occur within the same dyke. 
 
BASALTIC DYKES: TWO CHIEF DIRECTIONS. 139 
 
 A brief examination of the Maps shows that the majority of the dykes 
 have a north-west or N.N.W. direction ; that they are by no means 
 straight lines, but show many rather sharp changes of direction, which 
 sometimes continue for a considerable distance ; that the abundance of these 
 dykes varies greatly in different parts of the area as we traverse it from 
 north-east to south-west, across their general direction, but much less so 
 as we cross it from north-west to south-east, the dykes occurring in groups 
 which continue for long distances in the direction of their length. The 
 part of Cowal north-east of St Catherine's and Carrick Castle (1-inch 
 Map 37) is almost free from north-west dykes, but it contains east to 
 west dykes in moderate abundance. The peninsula, west of the Kyles of 
 Bute, is also comparatively free from north-west dykes. 
 
 The difference in the general directions of the dykes corresponds to 
 a difference in age. The broad east to west dykes are the earliest, and 
 there was at the time of their intrusion a tendency for the earth's crust 
 to split in this area along east to west lines ; the other dykes were 
 intruded at a later time when this splitting tendency had changed into a 
 north-west direction. 
 
 The broad east to west dyke which forms the green hillock on which 
 the ruins of Dunoon Castle stand, and which is exposed in a clear section 
 on the shore immediately east of the castle, is older than any of the other 
 dykes with a north-west direction with which it has been seen in contact. 
 This is observable in sections, and, in other places where there are no 
 sections, it can be inferred from the relations of the features made by Ihe 
 respective dykes. 
 
 Hand specimens of central portions of this dyke appear decidedly coarser 
 than most of the later dykes, and the rock in hillside exposures weathers in 
 unusually massive exfoliating blocks which disintegrate into a rich soil. 
 Besides the coarseness of grain, field sections occasionally show other 
 characters which are helps in identifying the dyke where it is not con- 
 tinuously traceable. Firstly, it is often crossed by thin red jasper-like 
 strings, and secondly, thin hard bands of rather less coarse, and usually 
 reddish, rock may occur in some abundance within the dyke, and confined 
 to it. Such bands are exposed in the shore section at Dunoon; they 
 lie at various angles, sometimes nearly horizontally, sometimes nearly 
 vertically, and at all intermediate angles ; they do not usually occur 
 within seven or eight feet of the dyke side, but one was noticed to go 
 quite to the side ; they are cut by various thin calcite and quartz strings, 
 which also traverse the rest of the dyke ; their average breadth is perhaps 
 from J to 3 inches, and there is no difference in grain between the outer 
 and the inner parts. 
 
 A specimen of one of these strings was examined chemically in the 
 laboratory of the late Professor Dittmar of Anderson's College, Glasgow, 
 and was compared with the normal dyke rock. The sample of the normal 
 'rock was obtained by mixing together two portions of the coarse dyke 
 interior with one portion of the finer rock near the sides. The results 
 obtained were as follows : percentage of silica in the red bands, after 
 drying the powdered rock at 100 C., 68'62 ; percentage of silica in the 
 normal rock, after drying the powdered rock at 100 C., 48*05. 
 
 In reference to similar strings in intrusive basic sills, Sir A. Geikie says 
 (" Presidential Address," Geol. Soc. Land., 1893, p. 179): " There ran 
 hardly be any doubt that they represent the still fluid, and somewhat 
 acid, parts of the mass which, owing to internal movements, were injected 
 into portions that had already consolidated." 
 
 Similar reddish strings are seen in the section of the dyke mile 
 south-west of Bodach Bochd (183 south-east), and attain a breadth 
 
140 GEOLOGY OF COWAL. 
 
 of 9 inches. In the section on the east side of Loch Eiddon there are 
 several fine-grained strings near the interior of the dyke, which are pro- 
 bably of the same character essentially, though the colour is grey in place 
 of red. 
 
 Microscopic slides were prepared from a junction specimen of the red 
 bands (slide 2841 b) with the darker rock (slide 2841a) in the locality 
 mile south-west of Bodach Bochd, and are thus described by Dr Hatch, 
 28416 : " Lath-shaped crystals of plagioclase felspar, more or less turbid 
 by the separation of reddish-brown powdery material ; this substance also 
 occurs accumulated sometimes in, but more often around, the crystal, form- 
 ing, in several instances, an almost opaque border. Penetrating the fel- 
 spar are abundant microlites of green hornblende. This felspar must 
 have a different composition to that in the greener rock, or else, why 
 fresh in the one ,and weathered in the other ? Patches of serpentine and 
 calcite." 2841a : " Diorite or perhaps epidiorite. Striped felspar 
 (plagioclase) in fresh lath-shaped crystals. Bluish-green pleochroic horn- 
 blende (uralite) in fibrous masses, often with a fringe of fine needles of 
 the same mineral, probably paramorphic after augite, of which, however, 
 no trace is to be discerned. Scattered irregular grains of iron ore 
 (ilmenite) and a small quantity of serpentinous matter." In the last 
 slide there is a parallel arrangement of the constituents for a little 
 breadth near the junction of the rocks, and this is perhaps due to slight 
 mechanical movement that has taken place along the junction. The fact 
 that there is no unaltered augite in the slide may be due to the same 
 cause ; a slide of the dyke at Dunoon showed augite in some quantity. 
 
 In similar red strings in an east to west dyke which occurs near Loch- 
 goilhead (142) Mr Teall considers that a large part of the felspar is 
 probably orthoclase (slide 4200) : the felspar forms a much larger per- 
 centage of the entire rock than in the normal dolerites : there is some 
 quartz also. 
 
 Among the localities which show clear intersections of this Dunoon 
 east to west dyke by later ones we may mention, the south end of the crags 
 J mile south-east of Bodach Bochd, the section f mile south-west of Bodach 
 ' Bochd, and the burn \ mile west of Troustan (west side of Loch Striven). 
 In all these localities the intersection is evident even at a little dis- 
 tance, for the older dyke weathers in its usual massive exfoliating and 
 somewhat readily disintegrating blocks, while the later ones stick out 
 through it as hard ribs, or are possessed of joints peculiar to themselves 
 and with a definite relation to their margins. The later dykes in these 
 sections consist either of porphyritic basalts with a very fine matrix, or 
 of uniform-grained rock. In the former, the chief joints usually cross the 
 dyke at right angles ; in the latter, the cross joints may be subordinate to 
 others which run longitudinally. In all the sections mentioned, there are 
 several of the later dykes to be seen, and in each, at least one of them 
 shows tachylite selvages. 
 
 Besides this dyke, there are occasional short and thinner parallel dykes 
 at no great distance from its side which we think are of the same age. 
 The continuation of this dyke west of Loch Biddon can be followed at 
 intervals nearly to Loch Fine (see p. 151). 
 
 Other dykes of the same kind also occur in the north part of the area : 
 one passes 1 mile or so south of Carrick Castle, and runs W.S.W. through 
 the head of Ardentinny glen and the south slopes of Beinn Mhor : a second 
 generally represented by 2 or more branches, runs between Lochgoil- 
 head and Strachur : a third passes by the outlet of Loch Restil (134), 
 and comes to the shore of Loch Fine 1 mile E.N.E. of Ard na Slaite : two 
 more run by Achadunan (126), one on the south and the other on the 
 
BASALTIC COMPANION DYKES. 141 
 
 north side of it. Details observed along the courses of these dykes are 
 given elsewhere, pp. 155-160. 
 
 The later dykes with a general north-west or N.N.W. direction are 
 certainly not all of exactly the same age : a good number of them are 
 intersected by others, which by their joints or fineness of grain at the 
 junction show that the earlier ones were thoroughly consolidated before 
 the intrusion of the later. We cannot say that, among these later dykes, 
 rocks of a certain character are older or younger than others of another 
 character. This apparent want of distinctness of age, combined with their 
 common direction, may indicate that the differences of age among them 
 are not great. 
 
 One-quarter of a mile west of Troustan a porphyritic basalt running 
 locally nearly east to west is cut by a more uniform-grained rock which 
 runs north to south. On the other hand, 300 yards north-east of Tom 
 Conchra (162 south-east), a porphyritic basalt intrudes into a uniform- 
 grained dyke. In the burn 1 mile S.S.W. of Glenmassan (163 south-west), 
 a thin fine-grained sharply-jointed dyke, running slightly south of west, 
 cuts across a coarser dolerite running north-west. In the north to south 
 burn east of An Leacann, about 1 mile south of Craigendaive (172 east), 
 a dolerite of much the same character cuts through a fine compact aphanite- 
 like rock. In a burn nearly f mile north-east of Dun Mor (172 south- 
 east), there are two dykes running locally east to west (the south one 
 presenting a glassy margin to the other), and two north to south dykes : 
 the west north to south dyke cuts the north-east to west dyke, and is 
 distinctly cross-jointed while doing so, but it is not clear that it is later 
 than the south east to west dyke. We do not regard the east to west 
 dykes in this burn as being of the same age as those early east to west 
 dykes we have just been speaking of : the east to west direction is only 
 local, such as we often find in certain parts of the courses of many of the 
 north-west dykes. 
 
 Each of the two neighbouring dykes J mile W.S.W. of Cruach nan 
 Capull (183) consists of two parallel bands : in the east dyke the west 
 portion sends an irregular thin intrusion into the other portion, which is 
 coarsely porphyritic. 
 
 Even without intersections it is often possible to prove that dykes are 
 of different ages by finding their chilled margins in contact. Closely 
 parallel dykes are common, particularly when they are running along some 
 previously existing line of weakness, such as a fault line, the dykes having 
 come up, first one and then another, along this line of weakness. The 
 dykes first intruded have chilled against schist, or the crush breccia of the 
 fault : the later ones partly against these rocks and partly against the 
 earlier basalt. Good instances of such companion dykes occur in the 
 following places, the north to south burn -f- mile south-east of Bodach 
 Bochd, the depression in the hills J mile west of Craigendaive, the thick 
 band in the burn f mile W.S.W. of Troustan (183), the thicker band in 
 the burn | mile S.S.W. of the top of Leacann nan Gall (183), the 
 craggy band |- mile slightly east of north of Inverchaolain Church (184), 
 and on the east shore of Loch Striven 200 yards south of Brackleymore 
 School (194 north-west). The four first-named sets are certainly running 
 with faults. 
 
 In the section south of Brackleymore School there are five parallel north- 
 west dykes without any separations of other rock. The most westerly 
 dyke is much decomposed, longitudinally banded, and about 7 feet thick. 
 Next comes an even-surfaced harder basalt with sharply defined margins on 
 either side, the west margin being glassy and the east margin approaching 
 this character. The third band, about 9 feet thick, is like the one first 
 
142 GEOLOGY OF COWAL. 
 
 described. The fourth, about 12 feet thick, is prominently porphyritic, 
 and has sharp junctions on both sides. The fifth is like the first and 
 third: it is 6 feet thick in one place, but is cut out by the porphyritic band 
 as it goes south-east. The most south-westerly band (slide 2846), the 
 harder band (slide 2847) next to this, and the porphyritic band (slide 2845) 
 have been sliced, and are described by Dr Hatch as follows. 2846 : 
 "Basalt (would be called a dolerite by the Germans, i.e., a coarse-grained 
 basalt), composed of plagioclase felspar in small crystals, giving lath- 
 shaped sections, and grains of augite, allotriomorphic with regard to the 
 felspar, but without a well-characterised ophitic structure. Separating 
 these constituents by thin films or occurring in small wedge shaped masses 
 is a dark-coloured glass. Olivine does not appear to be present." 2847 : 
 " Glassy Basalt. Consisting of plagioclase felspar and small grains of 
 augite, irregularly distributed in an abundant glassy base. The glassy 
 base is of a dark-brown colour and perfectly isotropic. It contains 
 abundant spicules and trichites of magnetite which have united to pro- 
 duce the most fantastic skeleton forms, or have attached themselves by 
 one end to the four sides of a microlite of felspar. Isolated microscopic 
 fragments of limestone (effervescing with acid) appear to have been 
 caught up by this rock while in the molten state. By the corrosive action 
 of the magna they have been rounded to almost perfectly spherical forms. 
 The disposition of the felspar microlites around the periphery of one of 
 the bodies in question excludes the idea of their being secondary 
 amygdules." 2845 : " Porphyritic Olivine Dolerite. With the naked 
 eye crystals of striped felspar and grains of green olivine can be made 
 out. Under the microscope are to be seen : 1. Large porphyritic crystals 
 of felspar (labradorite) of ideal freshness, showing polysynthetic twinning 
 on the albite and pericline types : 2. Isolated grains of unaltered olivine. 
 These porphyritic constituents are embedded in a microcrystalline ground- 
 mass, made up of microlites of felspar, grains of olivine and augite, and 
 granules of magnetite confusedly aggregated. The porphyritic felspars 
 contain numerous inclusions apparently of a dark-coloured glassy material, 
 arranged either centrally or in rows, marking zones of growth. The 
 crystals are also somewhat corroded at the periphery, by the action of 
 the magma when molten." 
 
 The influence of previously existing lines of weakness, faults, prominent 
 joints, etc., in modifying the direction of both the early east to west dykes 
 and the later north-west ones is extremely marked, arid owing to this we 
 find individuals of each of these classes assuming, for some distances, 
 directions almost the same as those which normally belong to the other 
 class. There may hence appear to be some confusion between the two 
 classes, and it is not always possible to say to which class a particular 
 dyke belongs. But where dykes can be traced for a distance, through 
 several changes of direction, there should be no doubt as to which set they 
 belong to : for in each set the thickness of the dykes is found to be 
 appreciably less when they are proceeding along an abnormal path. 
 
 The course of the Dunoon Castle dyke between Loch Striven and Loch 
 Riddon shows this fact well. No less than three times in this distance 
 of about 4 miles it is distinctly seen to make sharp changes in direction, 
 nearly at right angles to its ordinary course, and in all cases there is 
 good evidence that there are north to south faults where the change 
 occurs. Wo cannot say that the dyke is always continuous in the 
 changed direction ; indeed, we think that in two of the cases it is not, but 
 in all cases it is clear that the dyke exists, and in a state not markedly 
 crushed, in a portion of the changed course, so that it is impossible to 
 suppose that the change is due to a throw by a later fault. In all cases, 
 
BASALTIC DYKES: APPARENT SHIFTS. 
 
 143 
 
 too, the dyke is distinctly thinner in its changed course than in its normal 
 east to west path : instead of 30 yards or more, breadths of 8 or 12 are 
 now to be seen. In one case the dyke continues in its changed course 
 for as much as J mile. In each case the west portion of the normal path 
 lies to the south of the east portion. 
 
 FIG. 37. Diagram to illustrate the behaviour of dykes when coming to pre-existing 
 fault lines which run almost at right angles to their usual direction. In this 
 district it applies to east and west dykes meeting with north and south faults, 
 and to north-west dykes meeting with north-east faults. Cross hatched bands 
 are dykes. Single lines are faults. 
 
 The faults do not appear to be large ones, as far as we can judge from 
 the few bands in the schists that are of value as horizons, but they make 
 crush breccias of some thickness hading generally to the east. In the 
 most westerly instance, where the change continues for J mile, the fault 
 probably shifts the outcrops of the schists about 60 yards. This is at 
 all events the displacement seen along the same line of disturbance 
 about 1 mile further north : the beds on the east side of the fault lie 
 to the north of those on the west, which is as we should expect when 
 beds dipping steeply south-east, as these, are cut by a fault hading east. 
 We have never noticed the Dunoon Castle dyke to have any marked 
 hade, and in the best sections it is practically vertical : and on the 
 supposition of a later fault of vertical movement there should, of course, 
 be no lateral shift of a vertical dyke. A later fault of lateral movement 
 would, on the other hand, effect a lateral shift in a vertical dyke corres- 
 ponding to its own movement. But the finding of the dyke in its normal 
 condition along a portion of the changed path does, in itself, refute any 
 explanation depending on the possible action of a later fault. 
 
 Cases like these naturally remind us of others where, in areas with 
 less clear sections, dykes appear to be suddenly shifted for considerable 
 distances, and it would seem likely that, as a general rule, if there is a 
 fault at all along the apparent line of shift, that this is in part of earlier 
 date than the dyke. 
 
 In places, e.g., in the north to south burn near Ardbeg (183 north-west), 
 in the north to south burn south-east of Bodach Bochd, and in the bum 
 east of Toward Hill (194 north-east) there are unusually broad bands of 
 basalt running north to south, with directions different from the general 
 direction of the dykes in the district. These broad bands are really 
 compounded of dykes of different character and age, which oppose 
 chilled margins to one another, arid they are running along lines of fault, 
 or of sets of faults. Sometimes we can see distinctly that some of the 
 intrusions are later than some of the crushes, for unbrokeu tachylite 
 margins occur close against crush breccias, but it is also common to find 
 crushes breaking up the dykes to some extent, or slicken-lines within them, 
 so that we must suppose there have been repeated movements along the same 
 
144 
 
 GEOLOGY OF COWAL. 
 
 S 
 
 line of fracture, the first movements, before any intrusion, and these acted 
 as lines of weakness for the dykes to come up along ; and other movements 
 again after the intrusions. 
 
 In the higher part of the burn near Ardbeg some of the basalt bands 
 seem much more crushed than others, and are probably of a different age. 
 When N.N.W. or north-west dykes change into a north to south direc- 
 tion there can only be a difference in direction of from 22J to 45, 
 
 and in these cases we have not noticed any 
 marked alteration in breadth when diverted 
 from their normal paths. There is, in all 
 probability, some alteration, but it did not 
 attract oiir attention when first surveying 
 the area, and we have not had an opportunity 
 of further examining this point. When the 
 north-west dykes meet previously existing 
 fault lines at an angle more nearly approach- 
 ing a right angle, they act in just the same 
 way as we have already seen the Dunoon 
 Castle dyke to do : they are distinctly 
 thinner than usual as long as they keep the 
 abnormal path, or even cease to come up to 
 the surface at all along it. A good instance 
 of this on a small scale occurs on the east 
 shore of Loch Eiddon, about f mile south 
 of Springfield House : a locally running 
 north to south dyke seems to stop at an east 
 to west crush, and the first impression is 
 that it has perhaps been thrown by the 
 crush, but a little search reveals the dyke 
 in a much thinner, but still perfectly sound 
 condition, running east to west along the 
 crush : so that it is clear that the crush is 
 not later than the dyke, but earlier. 
 
 In the burn a little more than J mile 
 N.N.E. of Knockdow (194 north-west) a 
 north-west basalt about 4 feet thick comes 
 from the south-east against an east to 
 west fault or joint line, and then runs 
 west along it : when going west it is only a few inches thick. 
 
 A burn section about f mile south-west of Caol-ghleaim (162 north- 
 east) shows still more clearly the thinning of several N.N.W. dykes as 
 they twist out of their usual course along a thin crush or carbonate 
 of iron vein, which runs N.N.E. to S.S.W. In the most northerly of 
 these the thickness when running N.N.W. varies from IJ'to 2 feet: 
 the abnormal direction assumed is N.N.E., and it extends in this 
 direction 3 yards : it either ceases to come to the surface at all for this 
 distance, or is thinner. Another dyke, about 20 yards further up stream 
 than this, has a thickness, when running normally on the south-east side 
 of the stream, of about 4 feet, but when running along the crush, which 
 it does for a distance of 20 yards in a N.N.E. direction, it is only 1J or 
 2 feet thick : it is clear that the dyke is not crushed along its altered 
 course. On the north-east side of the burn this dyke goes off in two 
 parts : the first part that goes is, on resuming its normal direction, about 
 2 feet thick : a 6 inch part still keeps on in a N.N.E. direction, but after 
 a little way suddenly turns at right angles, and assumes its normal 
 direction again, attaining there a breadth of about 15 inches. 
 
 Fro. 38. Diagram to illustrate 
 the behaviour of the north- 
 west dykes when meeting pre- 
 existing north and south 
 faults ; and the consequent 
 common occurrence of com- 
 pound dykes along such 
 faults. Cross hatched bands 
 are dykes. Single lines are 
 faults. 
 
BASALTIC DYKES: RELATION TO FAULTS. 145 
 
 The broad north to south bands running with faults are not usually 
 traceable for more than about a mile, for the dykes will not be diverted 
 from their regular paths for mor than a certain distance, and so the 
 different dykes of which the band was compounded leave it one by one, 
 on either side, to resume their normal directions. The occasional 
 great thickness of these compounded bands depends on the size of the 
 north-west dykes which the fault line has diverted into itself, and also 
 on the closeness of the crowd of them : when the fault is traversing an 
 area with less numerous north-west dykes, the band becomes thinner, or 
 even ceases altogether. 
 
 The abnormal north to south directions of the east to west dykes have 
 not been noticed to extend for more than mile. This is less than the 
 north to south paths of the north-west dykes are often observed to be, and 
 we may suppose that the greater the angle between the normal and 
 abnormal paths the shorter are the abnormal paths likely to be. 
 
 In the Maps the dykes which are accompanied with crushes are marked 
 with fault lines along their sides. But we are not able by this means to 
 indicate whether the crushes are earlier or later than them, and so add 
 here the particulars which have been observed about their relations in 
 age. In the burn nearly 1 mile west of Glenmassau (163 south-west) a 
 nearly horizontal crush crosses a north-west dyke, and perhaps throws it 
 slightly : the crush is extremely thin and is not shown in the Map, but 
 it is interesting as an example of horizontal crushes which are not un- 
 common in the district, and as an indication of the probable age of, at 
 all events, some of them. The dyke that crosses the road slightly west 
 of north of Ardtarag (173 south-west) has a 1 foot breccia on its side which 
 contains basalt pieces, and it must therefore be earlier than part of the 
 crush. Three-quarters of amile E.IST.E. of Ardtarag various north-east running 
 crushes, hading south-east, go through a north-west basalt : one of them 
 shifts its north-west side toward the north-east for 3 feet. A dyke, J- mile 
 W.S.W. of Glenlean (173 south-west), has a hardened breccia rib within 
 it, and there are parallel crushes on the outside also. There are thin 
 uncrushed basalt strings within the north-east running crush i mile east of 
 Balliemore (173 south-west): frequently they run in the same direction as 
 the crush. One-half mile slightly west of north of Ardbeg (174 north- 
 west) there is a 3-foot basalt with reddened vein-stuff on either side which 
 seems hardened by the dyke. Some of the breccias running with the 
 basalts | mile E.N.E. of Ardbeg (174 north-west) are altered by them. 
 The two thin north to south dykes in the burn, nearly J mile north-east of 
 Cnoc a Mhadaidh (174 north-west) are in places quite full of slickensides, 
 running parallel with them and the breccias on the sides : calcite strings 
 also occasionally occur within the dykes. The most westerly of the two 
 dykes ~ mile east of Stronchullin (174 north-west) is quite crushed to 
 pieces : the width is about 7 feet. The breccias close at the side of the 
 basalt at the head of the burn nearly J mile south of Blairmore Hill (174 
 north-west) contain pieces of decomposing basalt, and are therefore in part, 
 at all events, later than the dyke. One-third mile N.N.W. of Blairmore 
 Farm, there are two basalts, each from 2 to 4 feet thick, the east one of 
 which is crossed by an east to west crush. On the west side of the north 
 to south basalts 1 mile east of Feorlean (182 north-east) there is a hardened 
 crush breccia on the west side of the most easterly basalt band ; the basalt 
 itself is not crushed. The dykes of basalt in the broad band in the burn 
 f mile S.S.W. of the top of Leacann nan Gall (183 north-east) are not 
 crushed, but various breccias run between them and are presumably 
 earlier than them. The compound basalt band ||mile "VY.S.W. of Troustan 
 is crushed parallel to its length. The basalts in the burn \ mile north of 
 
 K 
 
146 GEOLOGY OF COWAL. 
 
 Glenstriven (183 north-west) are broken by crushes alongside of or within 
 them. A crush in the burn J mile north-east of Bishop's Seat (183 
 north-east) contains distinct basalt fragments. The north to south dyke 
 in the burn f mile south of Corlarach Hill (183 south-east) has altered 
 vein-stuff at its side. In a burn f mile south of Corlarach Hill, a W.N.W. 
 basalt changes into a direction slightly north of east along crush lines : 
 there are breccias on the sides, and also another, 1 J foot thick, within the 
 basalt : the sides of the basalt are chilled against the latter breccia, and, 
 apparently, against the former also. In one of the north-west dykes in the 
 burn nearly 1 mile south-west of Glen Morag (184 south-west) there is a 
 breccia, several yards thick, of altered phyllite pieces, which sometimes 
 attain a length of several inches : there is also basalt within the breccia, 
 but this is often in large and irregular shapes, and may be parts of intru- 
 sive veins. The N.N.E. basalt in the burn \ mile east of Loch Loskin 
 (184 north-west) is slightly thrown by a fault hading south. On the 
 shore 240 yards N.KW. of Dunoori Pier, a N.N.E. dyke, about 20 feet 
 thick, has a rim, 2 to 3 feet thick, of hardened crush breccia sticking close 
 to its north side, and there is another breccia at a distance of 2 feet. 
 One hundred and fifty arid two hundred and twenty yards north-west of 
 Cluniter (195 north-east) several crushes cross a thick north-west dyke 
 almost at right angles : the crushes hade south-east. The schist-boundary 
 disturbances are not known to affect any basalt : near the east gates of 
 Toward Policies two dykes occur which are clearly not crushed : 200 and 
 270 yards south of Inellan Pier others occur which are equally unaffected. 
 
 We have not noticed many instances of basalts running in a sill-like way, 
 i.e., running roughly along bedding or foliation planes. Those that do 
 occur have, we think, taken advantage, not so much of these planes directly, 
 as of the thin crush lines which so often occur running nearly between 
 these planes. 
 
 Near the west end of the east-west dyke mile south-west of Meall 
 Buidhe (Arg. 173 south-east), a 2-foot sill-like band branches off in a 
 south-west direction. One-half mile north-west of Clachaig (173 
 south-east) there is a basalt connection between two N.N.W. dykes : the 
 connection is almost horizontal, and as the dip of the foliation is steeply 
 south-east, the band cannot be along the foliation : haematite-stained 
 strings run parallel to the lower edge of the sheet, and some thin basalt 
 strings also, which have suffered from crushing. The most westerly dyke 
 in the burn f mile slightly west of north of Blairmore piar is crossed by 
 a thin crush on the south side of the burn : the crush runs nearly with the 
 foliation ; on the south side of the burn there is a basalt band 3 to 6 feet 
 thick, which runs also east and west, and is traced from the east edge of 
 the dyke to about 10 yards west of the west end. One-third mile south- 
 west of Braingortan (183 south-west), a 1-foot basalt runs with an east 
 to west crush which hades south : this band is only seen near a north-west 
 dyke, so that we may conclude it is connected with it. The most westerly 
 dyke in the burn a little more than one mile south-west of Glen Morag 
 (184 south-west), has a thin band running from its east side for a little way 
 along the foliation ; it is crossed by a thin crush line. One-third mile 
 N.N.E. of Corlarach (194 north-east) a north-west basalt, about 12 foot 
 thick, and porphyritic with felspar, gives off a thin sheet on the south side. 
 
 The hades often vary in different dykes close to one another or even in 
 the same dyke. We have not noticed one direction of hade to be more 
 common than another. In the broad dyke f mile north-west of 
 A' Chruach (172 south-east) the hade is sometimes not more than 45 
 west. 
 
 Occasionally, impressions of the schist layers which have been intruded 
 
BASALTIC DYKES: THEIR DIFFERENT AGES. 147 
 
 into are shown by the sides of the dykes, the sides showing prominent 
 parallel lines dipping the same as the schists, e.g., in the most southerly 
 of the two burns mile east of the^Badd (184 north-west). 
 
 The indications of the age of the dykes which are furnished by this 
 area, apart from the particulars of their relations already given, may be 
 summarised in the following statements. 
 
 Throughout the schist area intersections of lamprophyres by north-west 
 basalts are numerous (see p. Ill), and it is also certain that the east 
 to west basalts are later than the lamprophyres. 
 
 All the trachyte dykes that are known are later than the north-west 
 basalts with which they have been seen in contact. 
 
 In the adjoining portion of Bute both north-west and east to west dykes 
 cut through the rocks of Upper Old Red Sandstone Age : these dykes 
 are of the same kind as those in Cowal, and in some cases clearly con- 
 tinuations of them. 
 
 The district was much broken by faults before the time of their intru- 
 sion, much more so than it was before the time of the lamprophyre in- 
 trusions. This remark applies to all the basalts, but in the most marked 
 degree to the north-west ones; Notwithstanding this, faults and crush 
 movements of later date than the later basalts are not uncommon. 
 
 The presence of more acid cotemporaneous crystalline strings has not 
 been noticed except in the early east to west dykes. In them it is common : 
 they occur, e.g., not only in many exposures of the Dunoon Castle dyke, 
 but also in the two parallel dykes to the north of this in sheet 37. These 
 strings seem closely akin to those found in many intrusive sheets of trap 
 in the midland valley of Scotland, and it is suggested that the rocks in 
 which they occur may be of the same age. The segregation veins in 
 the Tertiary sheets do not seem to be of quite the same character : these 
 (Sir A. Geikie " History of Volcanic Action, " Trans. Roy. Soc. Edin>, vol. 
 xxv., part 2, pp. 113-115) appear to differ from the rest of the rocks 
 iu which they occur, mainly, in the larger size and more definitely 
 crystalline form of the constituents in them, which are the same as those 
 in the inclosing rock. According to Sir A. Geikie ("Presidential Address," 
 Geol. Soc. Land., 1892, pp. 140-143), the sheets in the midland valley of 
 Scotland are probably of late Carboniferous Age.* If we suppose the 
 early east and west dykes to be also of late Carboniferous Age, the interval 
 of time between them and the north-west dykes must be immense ; for 
 there can be no doubt that many of the latter belong to the same set as 
 those which, still with a north-west direction, are seen in the island of 
 Mull to intersect the bedded basalts of Tertiary Age. It is supposed by 
 Sir A. Geikie (" History of Volcanic Action," Trans. Roy. Soc. Edin., vol. 
 xxv., part 2, p. 182) that some of the north-west basalts are of the same 
 age as the bedded basalts, and the source of them; but these also are 
 tertiary. 
 
 The amount of denudation that has taken place even since the north- 
 west dykes must be enormous. f If any of them flowed out at the surface, 
 these outflows have now been entirely destroyed. If none did outflow, 
 the existing glens must have been formed since their intrusion, for the 
 dykes, which now mount up to the highest hilltops, would otherwise have 
 overflowed into one part or another of these glens. In some places we 
 can see the upward course of dykes stopping very near the present ground 
 surface, e.g., in the burn f mile S.S.W. of the top of Leacann nan Gall, 
 where a dvke, some 20 yards lower down stream than the broad basalt 
 
 * It is probable that a sheet in the south part of the Isle of Bute, near Garroch 
 Head, is also of this age. W. G. 
 t See Sir A. Geikie, " Scenery of Scotland, 2nd edition (1887), p. 149. 
 
148 GEOLOGY OF COWAL. 
 
 band, is overlain by schist on the south side of the burn. No doubt many 
 other instances of this kind occur, but it is unlikely that the dykes which 
 cross over the high hills would all have stopped at low levels in the glens, 
 just before reaching the then existing surface. 
 
 A basalt on the hill 1 mile W.N.W. of Glen Morag shows a very fine- 
 grained surface sloping south-east, i.e., nearly at right angles to the general 
 direction of the dykes, and this surface may represent approximately an 
 original surface of contact with the schists. A dyke in the burn mile 
 W.N.W. of Glen Morag is in the same line as the above exposure, but it 
 has a flat top at its north-west end, and so is probably not connected 
 with it at the surface. C. T. C. 
 
 In some areas it appears as if the dykes considerably diminish in 
 number as the elevation of the ground surface increases, and if the hilltops 
 were clear of superficial deposits perhaps they would be found to con- 
 tain fewer dykes than are revealed at the coast line. There is a coast 
 section between Newton Bay and Lachlan Bay (151), about 1J mile in 
 length, which contains no less than twenty-three dykes, some of them occurr- 
 ing along fault crushes. Most of these dykes pierce the outside edge of a 
 great epidiorite mass. About | mile from the coast the epidiorite forms a 
 big ridge, the highest part of which is 570 feet. This ridge is for the most 
 part quite bare, still retaining the smooth outlines that were left on it by 
 the ice sheet. Along this ridge only three dykes have been observed. 
 While this area illustrates an extreme case of the diminution of dykes as 
 elevation increases, the adjoining tract from Lachlan Bay to Otter Ferry 
 shows similar phenomena, but in a less marked degree. It is perhaps 
 possible that the very compact nature of the epidiorite would itself lead to 
 a diminution in the number of dykes which succeeded in piercing into 
 its interior. J. B. H. 
 
 The schists in the neighbourhood of the dykes are, for a distance of 
 several feet, generally distinctly hardened, break less readily than usual 
 along the foliation planes, and have not such a marked micaceous lustre. 
 Many small specks of sulphide of iron are developed in them, and their 
 lenticles of vein-quartz acquire many additional short lines of joint or 
 crack, which form a distinct feature macroscopically. The greater hard- 
 ness of the altered schists frequently causes them to project beyond the 
 general level of the other schists, and form more or less prominent ridges 
 at the sides of the dykes : this is seen on the south side of the Castle 
 Dyke in the Dunoon shore section. 
 
 The green or grey-green phyllites on the coast a little south of 
 Dunoon are frequently changed to a dark grey or purple tint for a dis- 
 tance of several feet from the sides of the dykes. A good example occurs 
 mile south-east of Glen Morag. 
 
 In some places the phyllites and more micaceous schists have colour 
 differences developed in thin bands, running generally with the foliation, 
 which are not evident at a distance from the intrusion : some bands are 
 rendered much darker than the normal tint, others an opaque grey or 
 greenish-grey. This is seen in the altered schist lying between the north- 
 west basalts a little more than 1 mile south-west of the top of Beinn Mhor 
 (163), and f mile east of Socach (141 south-east) close to the N.N.E. 
 basalt, where it is running along an earlier fault. Under the microscope 
 the rock of the first mentioned locality (slide 4737) no longer shows the 
 original characters of the constituents, but appears made up of alterna- 
 tions of snow white or pale green opaque bands with other darker green 
 almost opaque bands. The dark green bands appear black in the hand 
 
BASALTIC DYKES : CONTACT METAMORPHISM. 149 
 
 specimen : they sometimes traverse the pale bands, and in this case are 
 bordered by a still darker rim, which contains a considerable amount of a 
 black opaque substance with a metallic glitter. There is generally a good 
 deal of the black opaque substance within the dark green areas, and but 
 little of it in the paler. 
 
 In the albite mica schists the micaceous matrix is darkened and speckled 
 with iron pyrites, while the albites acquire a reddish tint. This is seen 
 at the north side of the east to west dyke 1 mile slightly west of south 
 of Carrick Castle (specimen 4738), by the east to west dyke J mile 
 W.S.W. of Drimsynie (H2 south-west, slide 4734), by the east to west 
 dyke on Beiun Tharsuinn (142 south-west, slide 4733), etc. Slide 
 4733 is thus described by Mr Teall : " The felspars (albite) make up the 
 greater portion of the mass. The inclusions of magnetite have been 
 more or less stained by oxidation, so that they appear red by reflected 
 light and give a reddish tinge to the felspar as a whole. The albites 
 are usually separated by a small quantity of brownish material, which 
 evidently represents the original matrix in which the albites were formed 
 and consisted largely of white and black micas with which chlorite was 
 probably associated." Examination of the slide with a hand lens shows 
 clearly that it is only the central parts of the albites that are reddish, the 
 inclusions of magnetite having, as usual, been confined to these parts of 
 the crystals. In slide 4738 there is much black opaque matter, partly 
 with metallic glitter, lying in patches of different size between the mica 
 flakes. These end abruptly against the albites. In slide 4734 the 
 magnetite inclusions near the centres of the albites are also seen to be 
 altered into ferrite. The hand specimen shows a thin pegmatite vein 
 with felspar, and the felspar in this is the same colour as the albites of 
 the rock mass. 
 
 The "green beds" often have their green colour changed to dark 
 grey or black for a distance of a foot or more off the sides of the dykes. 
 This is seen clearly in the following places, near the east to west dyke 
 i mile west of Socach (141), mile E.S.E. of the bridge at the head 
 of Loch Fine (126), near the foot of Auchateggau burn (172 north- 
 west), in a burn J mile N.N".W. of Cnocan Sgeir (172 north-east), and 
 in the burn mile slightly east of north of Bishop's Seat (183 north- 
 east). A specimen from such a blackened "green bed" was obtained 
 from the last locality, at a distance of 1 foot from the basalt, and was 
 examined microscopically (slide 4736). Mr Teall describes it as 
 follows : " Very dark, massive compact rock showing slight traces of 
 banding. Under the microscope alternating coarse and fine bands 
 the latter containing a considerable amount of opaque material. 
 Definitely recognisable constituents quartz and felspar. Brown mica 
 appears to have been present, but the flakes have been modified so 
 that the mineral can scarcely now be recognised. Micro-flaser structure. 
 Original rock probably a very fine-grained felspathic grit or sandstone." 
 Some parts of the opaque matter have a slight metallic glitter by reflected 
 liiiht. The parts of the slide that are snow white by reflected light are 
 almost opaque to transmitted light. These differently coloured parts are 
 no doubt the same in character as those in slide 4737. 
 
 In the section |- mile west of Socach the blackened green beds contain 
 also a quartz vein with a black carbonate : the vein cannot be traced 
 far from the dyke. On the shore 216 yards east of Glen Morag (184 
 south-west) the carbonate in a quartz vein 1 foot from a basalt dyke be- 
 comes a similar black colour. A string of black carbonate also occurs 
 close to the side of a north-west basalt in Glen Finart, near the " e " of 
 " Glen" (164 north-west). The veins referred to effervesce briskly with 
 
150 GEOLOGY OF COWAL. 
 
 dilute hydrochloric acid. We do not remember any carbonate veins of 
 this colour at a distance from intrusions. 
 
 A north-west basalt in the burn a little over J mile W.S.W. of Glen 
 Morag seems to slightly bleach the schistose limestone on its east 
 side. 
 
 In a little burn J mile N.N.E. of Glenmassan (163 south-west) a close 
 iointing is set up in a lamprophyre in a direction parallel to the sides 
 of a north-west basalt which intersects it. The jointing extends for a 
 distance of several yards from the basalt. 
 
 The porphyritic basalt east of Toward Cottages alters the colour of the 
 red sandstones on its west side for a distance of about 20 yards, changing 
 it into a dirty yellow : the breadth of the dyke varies from 15 to 20 
 feet. A thinner N.N.W. dyke on the shore about J mile west of this 
 effects a similar change for a distance of about 6 feet. C. T. C. 
 
 CHAPTER XIII. 
 
 THE IGNEOUS ROCKS (continued). DESCRIPTION OF 
 BASALTIC DYKES IN PARTICULAR DISTRICTS. 
 
 District of Tighnabruaich. 
 
 This district includes the part of Cowal which lies west of the lower 
 part of Loch Riddon and the west Kyle of Bute, and south of a line that 
 runs east to west between Eilean Dearg and Drum Point. 
 
 East and West Dykes. The east and west dykes occurring in the most 
 southerly part of Cowal at Ardlamont are not seen to ba crossed by any 
 running north and south. They are, however, almost certainly the con- 
 tinuation of the two large dykes which have been traced across the Island 
 of Bute : one from Bogany Point to the south side of Ettrick Bay, and 
 the other and largest, from Ascog Point to Watch Hill. The Bogany 
 Point dyke is clearly cut by later tertiary dykes, running north and 
 south, and there is no doubt that both these dykes are of a much earlier 
 date than the Tertiary Period. 
 
 The most northerly of the Ardlamont dykes is 20 yards in width and 
 appears on the shore at An Gnob, where it projects into the sea. It is 
 generally a coarse dolerite but is finer at the edges where the schist in 
 contact with it is considerably hardened. The dyke may be traced west- 
 ward to the Fort at Camp Cottage beyond which it is hidden beneath 
 beach-gravel and till. It is visible again west of Ardlamont House, some- 
 what to the north of its line of bearing, but soon disappears again under 
 beach-gravel to come out again in the old sea cliff on the west side of 
 Ardlamont Bay, some 200 yards south of where it might be expected. 
 From this point it can be traced westward for f of a mile to Rudha na 
 Peilige where it is nearly 50 feet broad. It seems broader than this J 
 a mile to the eastward but it probably has a hade southward nearly 
 coinciding with the slope of the bank, and so has a wider outcrop. 
 
 The large dyke at Ardlamont Point is also coarsely doleritic and is on 
 the average about 50 yards wide towards its east end but widens west- 
 ward in Port a Ghobhlan to 70 yards or more, where it ends off so 
 abruptly as to suggest a fault running north and south. On the west side. 
 
BASALTIC DYKES : TIGHNABRUAICH DISTRICT. 151 
 
 of the little bay we find it again but shifted 100 yards south of its course, 
 and it is here also 70 yards wide. It takes a somewhat curved course 
 westward, gradually thinning however, till on the other side of the 
 peninsula where it meets the sea it is only 10 yards wide. About 50 
 yards to the south of this, there is another dyke running in the same 
 direction 18 yards in width, and this is probably a branch from the main 
 dyke. The schist between the two is much altered. 
 
 On the west side of Loch Eiddon is a large dyke belonging to this 
 class, being the continuation of the Dunoon dyke, which is on an average 
 about 100 feet in width here. It can be traced almost uninterruptedly 
 from the lochside westwards for nearly a mile, but is lost before reach- 
 ing the AUt Dubh burn. Other dykes in the same general direction 
 and probably of the same age can be traced for short distances on either 
 side the main dyke. This is encountered again 300 yards west of AUt 
 Dubh and J mile south of its former course. It can be followed with 
 interruptions, but somewhat diminished in width, to the head of the 
 south branch of the Acharosson Burn, where it includes fragments of 
 altered schist, and a branch may be observed going in a south-west direc- 
 tion for more than 100 yards. It now turns first north-west and then 
 W.X.W. following generally the course of the burn for about a mile and 
 being accompanied by veins of quartz and ferriferous carbonate. There 
 are gaps, however, where it is not seen, and near the sharp northerly 
 bend of the burn it is much thinner than usual, and the alteration it 
 effects in the schist is very slight. We lose it for 600 yards and find it 300 
 yards south of where it might be expected, first going north-west and then 
 westwards till it strikes the burn and disappears. Again we find it some 
 200 yards to the south, and trace it W.KW. till it crosses the burn and 
 is lost. This time we find it again 350 yards to the south and it run? 
 westward for 600 yards to the burn. In this length it is 75 to 100 feet 
 wide, a coarse dolerite much decomposed. At the burn opposite 
 Acharosson it seems nearly 50 yards wide and contains veins of calcite 
 and quartz. A little further west a dyke is seen in the burn, but it is 
 much thinner, and again 400 yards south of the sharp bend in the burn 
 there is a basalt dyke about 20 feet wide, ranging KN.E. The dyke has 
 been quarried near Drum, on the west side of the road, where it is 12 
 yards wide and amygdaloidal ; and beyond this no trace of it could be 
 found. Nearly J a mile to the northward of Drum a thin dyke ranging 
 a little north of west crosses the limestone and epidiorite bands. This 
 dyke seems to be either a branch of the Dunoon dyke or a parallel dyke 
 of the same age. 
 
 Probable Tertiary Dykes. The basalt dykes of probable Tertiary age 
 which run approximately in a north-west direction occur very sparingly 
 in the area west of the Kyles of Bute and Loch Riddon, except in the 
 neighbourhood of Tighnabruaich and Callow. One of the more noticeable 
 of these is shown on the Map on the west side of Tighnabruaich Burn or 
 Easan Doun. In the southern part of its course it follows the burn 
 and crosses it several times. It is about 20 feet wide and hades eastward 
 60. In one part of its course it is a double dyke, enclosing a strip of 
 schist, and at the top of the wood close to Dun Beag it divides into two 
 parts which cannot further be traced. There is a large blue-grey dyke 
 north of Callow which, after running north-westward, bends round in a 
 X.X.E. direction and behaves as a sill dipping in a south-east direction 
 nearly with the schist. There is a thinner and blue dyke to the west 
 of this which starts in a N.N.W. direction nearly vertical, but in 
 following it along its course we find that it eventually bends round 
 nearly parallel to the preceding and behaves like it. "W. G. 
 
152 GEOLOGY OF COWAL. 
 
 District of Kilfinan and Stralachlan. 
 
 This district is bounded on the east side by Newton Bay, Gaol Ghleann, 
 Glendaruel and the upper part of Loch Riddon. On the south side the 
 boundary is a line running east and west through Eilean Dearg and 
 Drum Point. 
 
 Basalt dykes of the north-west type are more or less abundant over the 
 whole area; but if the district be divided into three divisions with bound- 
 aries running north-west and south-east, the dykes in the central division 
 will be found to considerably outnumber those in the northern and 
 southern divisions, in fact about one half of the dykes are found in the 
 central portion. These zones of relative dyke abundance are persistent 
 on the north-west shore of Loch Fine where this central zone has been 
 traced as far as Loch Awe. There is also a diminution in the number of 
 dykes on the more elevated parts of this area in consequence apparently 
 of some of the dykes not having reached so far as the present ground 
 surface. This is described in detail on p. 148. 
 
 The basalt dykes frequently come up along lines of fracture. In some 
 cases the faulting has been continued after the irruption of the basalt. A 
 good example of this is seen in the Lephininore burn (162). A north and 
 south fault runs along the burn, and there is a dolerite d} r ke parallel 
 with the fault which has in part been brecciated along its length. The 
 dolerite has evidently come up along the fault line and later movements 
 along the same fault have crushed and brecciated the dolerite. The 
 dolerite is coarsely crystalline throughout and contains clear glassy crystals 
 of porphyritic felspar which by their rounded edges are evidently earlier 
 than the injection of the dyke. Along the line of brecciated dolerite a 
 fine-grained crypto-crystalline basalt about 4 feet wide has been intruded 
 between the brecciated and the undisturbed portion of the dolerite. The 
 later basalt does not contain the porphyritic felspars of the dolerite and its 
 junction with the brecciated dolerite is clearly seen. 
 
 Another good instance of a basalt being affected by a later fault occurs 
 at the western boundary of the serpentine of Glendaruel. At this locality 
 the boundary between the serpentine and the mica schist is a fault which 
 cuts a basalt dyke, and throws the basalt for the distance of several feet. 
 
 The courses of the burns are often determined by the presence of basalt 
 dykes, and in these cases the gorges excavated are deeper and more 
 precipitous than when the burns cut their channels out of the schists. 
 Amongst the basalts themselves the coarsely crystalline varieties have 
 yielded to erosive agencies more readily than the finer-grained varieties 
 and have given rise consequently to the deepest gorges. At the Enacher 
 (162) a tributary of the Lephinmore Burn a fine gorge has been eroded 
 along the course of a massive dolerite. At the head of the gorge merely 
 three small dykes occur, two of which can only be traced for a very short 
 distance. The larger dyke gradually widens till it attains a width of 20 
 to 30 yards. The burn before the dyke is met with is quite an 
 insignificant stream, but it deepens rapidly after meeting the dyke and 
 runs in a deep precipitous gorge. After running for half a mile along 
 the bottom of the gorge the dolerite is joined by another dyke to which 
 it has been gradually converging. They ran side by side for some 
 distance separated only by a few feet of schist till they finally coalesce 
 into a single dyke of about 40 yards in width. The dyke gradually 
 decreases again to a breadth of 20 yards and a mile from where it is 
 first seen at the head of the gorge disappears altogether, or is represented 
 by a series of smaller parallel dykes separated by schist. 
 
 Another instance of the sudden deepening of a stream bed into a 
 
BASALTIC DYKES : KILFINAN DISTRICT. 153 
 
 gorge, on the coincidence of a basalt dyke with the bed of the stream, 
 may be 'seen in the valley of Stralachlan, within easy reach of the 
 roadside, about J mile from the -junction of the Eas Dubh bum with 
 the Stralachlan river at the village of Stralachlan. 
 
 Although the coarse dolerite dykes attain great breadths the finer- 
 grained basalts may be still wider. The broadest of these latter are 
 those which traverse the serpentine area of Glendaruel. Here we have a 
 system of dykes extending over an area 1J miles in length, which instead 
 of following the usual rule of running along more or less parallel straight 
 lines and then dying out, have a habit of deflecting from their course and 
 coalescing with one another. After continuing as single dykes for some 
 distance they again split up into branches, each of which may again sub- 
 divide, and one or other of them will either again meet and coalesce with 
 another, or they may meet and coincide again with the main trunk. 
 The whole somewhat resembles the assemblage of streams in a delta. 
 While the individual dykes are irregular in their course, the system taken 
 as a whole has a general north-westerly and south-easterly trend ; corres- 
 ponding to the general direction of the basalt dykes in the area. The 
 different dykes of this system are fine-grained basalts with a strong 
 tendency to split up into plates. The small branches are often about 3 or 
 4 yards in breadth, and the main trunk sometimes reaches a width of 30 
 to 40 yards or even more. Close at hand a dyke of similar composition 
 is met with which belongs to the same phase of irruption. At its south- 
 east portion near the serpentine two dykes are seen to approach one an- 
 other and coalesce. At the watershed this dyke still remains as a single 
 dyke, but on crossing the watershed it almost immediately splits up into 
 two dykes running close alongside one another, the northerly dyke being 
 about 50 yards, and the southerly dyke about 30 yards, in width. The 
 ground here gets so covered with peat that it is difficult to say for certain 
 what takes place, but it looks as if they coalesced again about J mile 
 further north-west the entire width being then about 50 yards. For 
 the next J mile the peat is too thick to enable the dyke to be traced at 
 all, but after that distance has been traversed, what appears to be the 
 same dyke comes up again on the same course, but dwindled to a width 
 of about 12 yards. From this place it increases gradually to 20, 30, 
 and finally 40 yards, and then, just before entering Loch Fine, splits 
 into 4 or 5 smaller parallel dykes separated from one another by a few 
 yards of schist. In its habit of dying out, it corresponds to the coarse 
 dolerite previously described ; indeed, the two dykes die out in this way 
 quite close to one another, so close that if they had been prolonged a 
 little further they would have cut one another. These basalts have often 
 produced great contact metamorphism on their passage through tbe 
 serpentine, far more so than has usually been observed where they have 
 pierced the sedimentary rocks and epidiorites of the district. Moreover, 
 the serpentine in turn seems to have produced marked effects on the 
 basalts. Serpentinous products seem to have penetrated into the joints 
 of the basalts and have, as it were, partially serpentinised them. 
 
 Porphyritic dolerites and basalts are exceedingly common in the district. 
 They contain porphyritic crystals of felspar which were evidently in 
 existence at the time the dykes were injected into their present position. 
 These porphyritic felspars are found in the glassy margins as well as in 
 the more crystalline interior of the dykes. One of these porphyritic 
 dolerites occurring on the hillside above Glendaruel House, was submitted 
 to Mr Teall for microscopic examination. It was a dolerite with por- 
 phyritic crystals of a glassy felspar in a dark fine-grained matrix. Mr 
 Teall describes it as follows: "(4014) Microscope: Porphyritic felspars 
 
154 GEOLOGY OF COWAL. 
 
 allied to bytownite in a ground-mass composed of lath-shaped felspar, 
 brown ophitic augite, small grains of olivine more or less serpentinised 
 and magnetite." 
 
 Some of these porphyritic felspars exceed a square inch in size. 
 
 The finer-grained basalts show a great tendency, to split up into fine 
 plates. In the bluish finely crystalline dykes, this platy structure is 
 more often set up across the dyke than along it, though sometimes both 
 types are met with in the same dyke. The tendency is to split parallel 
 to one of the faces of the prismatic blocks that cross the dyke. The 
 plates sometimes dip in opposite directions, owing to the tendency to 
 split parallel to two faces of the prism. The structure is obviously due 
 to an excessive development of prism faces in one or more directions. The 
 fissile character prevails to its greatest extent at the edges of the dyke. 
 If the dyke happens to be of larger size, such as 20 feet or 30 feet across, 
 the inside plates are more in the nature of slabs. A good example of this 
 structure may be seen in the Allt Buidhe, Lephimnore, Loch Fine. 
 
 In this district the spheroidal type of weathering has been met with in 
 the coarser dolerites more than in the finer-grained basalts. The coarser 
 dolerites often show massive prismatic jointing. 
 
 There is another type of dyke, with a glassy resinous lustre. This 
 glassy type is the least common of the types described. In size these 
 dykes approach the biggest dolerite dykes of the district, and can be 
 traced continuously for as great a distance, and have, like them, a north- 
 west direction. 
 
 The following are the localities of the principal dykes of this class. 
 
 1 mile south of Glendaruel House (172), and the course of the stream 
 to north-west for J mile. When the dyke leaves the burn it continues 
 in a north-westerly direction slightly south of Cruach Chuilceachan and is 
 met with along the same course for a mile from that hill. The place 
 where it is finally lost sight of is 2 J miles from where it emerges from the 
 alluvium of the Glendaruel Valley to the south-east. 
 
 One-third of a mile north of Lephinchapel (162). The dyke occurs on 
 the coast and can be traced up the hillside in a south-easterly direction 
 for about J mile. 
 
 Half a mile north-west of Lower Duillater, Glendaruel (162). This 
 dyke can only be followed for a short distance on the hillside. 
 
 1 mile south-west of Tom Soilleir (162). A dyke about 20 yards in 
 breadth cuts the Lephinmore burn; after following a south-easterly 
 course for about a mile it is lost. 
 
 These glassy dykes have already been treated of in the general 
 description. Next to their glassy or resinous lustre, their most 
 striking characteristic is their tendency to split up into more or less 
 rounded or rhomboidal segments separated by divisions of lighter- 
 coloured material. The divisional planes between the segments vary 
 from -J inch to | inch across. A series of divisional planes transverse to 
 the dyke appears to be accompanied by another set parallel to the dyke 
 which gives a reticulated appearance to the mass. When one set 
 predominates over the other set a kind of banded structure is set up, 
 consequent on the difference in character of the main mass from the paler 
 divisional planes. Sometimes the reticulated and banded conditions are 
 seen in the same dyke. Near Cruach Chuilceachan (172), the dyke is 
 found in a more or less de vitrified condition, with tiny crystals of por- 
 phyritic felspar. It assumes the curious reticulated appearance already 
 described, its surface being divided into innumerable segments separated 
 by partings of paler material. The segments are sometimes perfectly 
 rectilineal, the larger exhibit a tendency to subdivide into smaller segments. 
 
BASALTIC DYKES : STRACHUR DISTRICT. 155 
 
 Besides this structure, the dyke appears to be divided into longitudinal 
 bands about 1 foot in thickness of dark-black and yellowish- white colours, 
 which alternate with one another. " Some of these inside stripes are quite 
 glassy. The dyke assumes in weathering both a reticulated, and a 
 longitudinal banded appearance. Sometimes these glassy portions of the 
 dykes occupy one-half the width of the dyke, the outer parts being quite 
 crystalline, and sharply divided from the glassy variety, so that first sight 
 suggests an intrusion of one dyke within another. 
 
 A typical specimen of the glassy dyke was examined microscopically 
 by Mr Teall, who describes it as follows : " 4016. Black rock with pro- 
 nounced resinous lustre, similar in macroscopic appearance to some of 
 the Cheviot hypersthene-andesites. Microscope The porphyritic con- 
 stituents include plagioclase (probably labradorite) and a pyroxene. 
 The plagioclase is much honeycombed with inclusions of the ground- 
 mass. The pyroxene possesses the pleochroism of hypersthene, but as 
 there are only two or three sections, and these are not cut in favourable 
 directions, it is impossible to determine the nature of the mineral with 
 certainty. The ground-mass consists of long microlites of augite, micro- 
 lites of felspar and much pale-brown glass containing minute opaque (?) 
 hair-like bodies and grains. Pyroxene-andesite." 
 
 The dykes do not always preserve a uniform increase of coarseness in 
 passing from the outer edges to the interior portions. Occasionally, coarser 
 and finer material may be seen alternating in the same dyke. A good 
 instance of this is seen in a burn section J mile south-west of Balloch- 
 andrain, Glendaruel, within 200 yards of the roadside. This dyke shows 
 good longitudinal jointing. 
 
 Original upward terminations of dykes are but rarely met with. A 
 good instance, however, of the roof of the dyke passing under the neigh- 
 bouring rock, occurs in the Lephinchapel Burn, rather more than J mile 
 S.S.E. of Lephinchapel, Loch Fine. Here, in the deep gorge, a dolerite 
 dyke can be clearly seen passing underneath a quartz schist. 
 
 The upward passage of a dyke through the schist is often irregular, 
 and frequently accompanied by small side-veins of basalt which pierce the 
 adjoining rock. A good example of the uneven passage of a dyke may 
 be seen in the Barnacarry Burn, Stralachlan. A dyke 2 or 3 feet in 
 width passes through a mass of hard quartzites alternating with micaceous 
 beds. The junction of the harder quartzites and softer micaceous beds 
 has served for planes along which faulting has been produced, and the 
 dyke on meeting one of these planes has been deflected, and runs on for 
 some little distance as a sill before continuing its upward course. 
 
 The general trend of the dykes is north-west and south-east. When 
 they take other directions they do not as a rule continue for any great 
 distance, except perhaps between Ormidale and Upper Callow (Loch 
 Riddon) where a north and south direction is most prevalent. 
 
 The older type of east and west dykes does not occur in this area. 
 
 J. B. H. 
 
 District of Strachur and Lochgoilhead. 
 
 This district includes all that part of Cowal which is contained in 1 
 inch Map 37, with the exception of the area which lies west of Newton 
 Bay, Caol Ghleann and Glendaruel. 
 
 The Car rick Duke. The AV.S.W. dyke that passes a mile south of 
 Carrick Castle is of the same character, and no doubt also approximately 
 of the same age as the Dunoon Castle dyke (p. 139). Just west of the 
 peat moss 1 J mile slightly west of south of Carrick Castle, it contains 
 some thin reddish strings of apparently the same character as those 
 
156 GEOLOGY OF COWAL. 
 
 described in the Dunoou dyke. The main dyke probably lies a little 
 seawards of the point between Loch Goil and Loch Long, but there is a 
 thin dyke, from 2 to 6 feet thick only, which runs through the point 
 with the same direction as the main dyke. The locality west of the peat 
 moss just mentioned is also of interest from showing the contact alteration 
 induced in the albite schists on the north side of the dyke : the albites 
 are reddened, and the rock loses its micaceous lustre to a large extent, 
 and the fissile tendency along the foliation planes. 
 
 One-sixth of a mile east of the " n " of " Cruach an Draghair," the south 
 side of the dyke runs north and south for 10 yards along a thin crush line : 
 the dyke itself does not seem crushed : we suppose it to be running out of it's 
 normal course, to take advantage of an earlier line of weakness, p. 142. 
 A similar change of path is inferred just on the west side of the Cruach : 
 the dyke feature is quite distinct as it crosses the top of the Cruach, and 
 for some distance down it's west side, until it comes to a north to west 
 fault feature : the dyke certainly does not continue on the west side of 
 this feature in the straight continuation of it's old path, and it must either 
 cease to exist at the surface for a little distance, or run along the feature 
 in a thinner form. 
 
 In the burn 200 yards slightly west of south of the top of Larach Hill 
 (164 north-west) the dyke is cut by a N.N.W. dyke from 1 to 3 yards 
 wide. The section can only be examined when the burn is low. The 
 N.N.W. dyke occupies the stream bed. There are thin strings of vein 
 stuff and haematite running parallel with the N.N.W. dyke, and crossing 
 the W.S.W. dyke, but they do not affect the N.N.W. dyke. The later 
 dyke is interesting from the clear way in which the felspars are arranged 
 with their thin plate-like forms parallel to the sides of the dyke. Slide 
 2844 from this later dyke is thus described by Dr Hatch. " Porphyritic 
 olivine dolerite. Felspars of two generations. The large porphyritic 
 felspar gives striped lath-shaped sections, extinguishing with a large 
 angle, and is therefore a lime-soda felspar near the anorthite end of the 
 series, probably labradorite. Beautiful pseudomorphs of serpentine 
 after large well-formed crystals of olivine (of pyramidal habit). Other 
 little patches of serpentine with calcite probably represent altered augite. 
 The porphyritic constituents are embedded in a plexus of minute 
 microlites of felspar, interspersed with granules of magnetite and perhaps 
 augite, separated by thin films of dark-coloured glass." A slide of the 
 earlier dyke (2843) from the same locality, is described as follows. 
 " Dolerite. Plagioclase in fresh crystals giving lath shaped sections. 
 Augite in irregular grains, allotriomorphic with regard to the felspar. 
 The crystals sometimes show twin lamellation. Magnetite in large 
 skeleton patches and grains. Apatite in slender needles. Secondary 
 minerals are calcite and patches of serpentinous material containing 
 blades of brown mica. The presence of brown mica suggests contact 
 metarnorphism (see " Allport's researches on the Metamorphosed Dolerites 
 in Cornwall and Devon)." Wedged in between the crystalline con- 
 stituents is a little brown interstitial matter (glass) with dendritic 
 devitrification products." The mica might have been attributed to 
 contact alteration induced by the N.N.W. dyke, but for the fact that 
 such flakes are not uncommon in the dyke in other places also, some 
 distance off later dykes, e.g., ^ mile south-east of the first " r " of 
 "Garrachra Glen" (163 west). In slide 4200 (see p. 157) from the 
 Lochgoilhead east to west dyke, biotite also occurs in small quantity. 
 
 Half a mile south-east of the top of Beinn Mhor (163 north-east) a 
 north-west dyke cuts the W.S.W. one : the actual junction of the two is 
 not visible, but the difference between them is shown distinctly by the 
 
BASALTIC DYKES: STRACHUR DISTRICT. 157 
 
 main joints, which in each dyke are approximately at right angles to 
 the sides. 
 
 Only the north end of the change of path into a north to south direction 
 on the east side of Garrachra Glen is seen. The section here is complicated 
 by the presence of 2 or 3 fine-grained yellow weathering north to south 
 lam prophy re bands, and a thin-crushed N.N.W. basalt: an east to west 
 fault seems to throw the lamprophyres : it seems possible to infer that 
 the broad basalt cuts the lamprophyres. 
 
 The most westerly place at which this dyke is distinctly seen is the 
 burn section about J mile south-west of the " D " of " Meall Dubh " 
 (163 south-west) : it is in two parts, the north, and wider one of the two, 
 crosses the burn 60 yards north of the other. 
 
 The Locligoilhead Dyke. The Lochgoilhead east to west dyke is seen 
 well in and near the burn above Donich Lodge, from the "h" of 
 " Donich " for a distance of rather more than J mile west. One-twelfth of 
 a mile west of the "h" the dyke hades north, and there are thin crushes 
 with barytes strings running parallel at the side. In the little burn 
 nearly J- mile E.N.E. of the same letter a strong crush, also hading north, 
 runs parallel to the dyke at a distance of 20 yards on the north side. 
 The dyke itself has calcite strings within it, and a branch going off in a 
 south-west direction has a crush in the middle : this crush hades south- 
 east. The albite schists near the dyke are much hardened and altered : 
 the albites themselves are reddened (see p. 149), while the rest of the rock 
 is darkened and pyritised. Three-eighths of a mile east of the " h " in a 
 little stream on the north side of the burn, the dyke is represented by two 
 parts on the east side of a north to south fault line. The south branch is 
 not quite in the straight continuation of the dyke on the west side of the 
 fault, but some few yards south of it. There are several thin inconstant 
 strings of basalt running with the fault, and these connect the north and 
 south bands. These strings vary from a few inches to a few feet in 
 thickness : the total thickness of them all does not exceed 4 or 5 feet. 
 They are not crushed more than the dyke generally is in other places, 
 and in one place one of them is seen to be distinctly chilled against the 
 altered schists at its side. After going along this fault for about 30 
 yards, these north to south strings change their direction and widen out 
 to form the north branch of the dyke. 
 
 ]S"ear the middle of the dyke on the west side of the fault, there is an 
 8-foot band of reddish colour : it is somewhat sharply denned from the 
 blacker rock at the sides, but has no chilled margin and no joints separate 
 from those of the rest of the dyke. The south branch on the east side 
 of the fault shows the same reddish band for a certain distance east of 
 the fault, but at a place nearly ^ mile east of the fault, we could not 
 find it, though there is a good section on the north side of the burn. 
 This red baud is of the same type as the red more acid strings in the 
 Duuoon Castle dyke (see p. 139). The microscopic character of a slide 
 (4200), from f mile east of Donich Lodge, is described by Mr Teall 
 as follows : " A dark coarse-grained rock containing a considerable 
 amount of pinkish felspathic material. Rocks of this character are often 
 found associated with the coarser carboniferous dolerites. The minerals 
 are often, as in this case, in such an imperfect state of preservation as 
 not to admit of very satisfactory determination. Felspar, more or less 
 decomposed and stained with ferrite, forms a much larger percentage of 
 the entire rock than in the normal dolerites. It is probably in large part 
 orthoclase. In addition to the felspar, we find in this case augite and 
 green alteration products, magnetite (fairly abundant), and pyrite ; also 
 quartz." The normal dyke rock (slide 4199), is described by Mr Teall 
 
158 GEOLOGY OF COWAL. 
 
 as follows : " Dark massive, medium-grained rock, essentially composed 
 of plagioclase, augite, and iron ores. The plagioclase occurs in forms 
 giving lath-shaped sections. They are striated and the extinctions are 
 high, indicating labradorite or an allied species. The augite is pale 
 brown in thin sections and ophitic, though not in large masses. Dial- 
 lagic striation may sometimes be seen. The iron ore occurs in irregular 
 plates, often very ragged. They are sometimes seen to be moulded on 
 the felspar. A small quantity of very fine micropegmatite occurs in 
 places as interstitial matter. The accessory minerals include apatite, 
 pyrite, and some extremely thin hexagonal plates of a brown colour 
 (titaniferous iron mica). Dolerite." There seems also to be a little 
 biotite present. 
 
 West of Lochgoilhead there are two main dykes running roughly 
 parallel to one another at distances of from ^ to f mile, and each of these, 
 but particularly the north one, may subdivide into branches. The altered 
 albite schist near the south branch J mile west of Drimsynie is exposed in 
 a section on the hillside : slide 4734 from this locality is referred to 
 on p. 149. The supposed change of path into a S.S.W. fault 1 mile 
 slightly south of west of Drimsynie is only inferred : the dyke is seen in a 
 burn 130 yards west of the fault, and also on the hill close on the east 
 side of the fault, but the intervening ground is drift covered. 
 
 The north dyke is represented by three branches in the burn N.N.W. 
 of Drimsynie, but the most northerly of these is only thin. The north 
 and the middle branches are seen to be crushed by the fault running 
 N.N.W. in the burn : the north branch is not seen close on the west side 
 of the fault, but the middle branch is it comes on 3 little south of its 
 exposure on the east side of the fault. The south branch is crushed by 
 the same fault in an exposure a little west of the burn ; the exposure 
 west of the crush lies a little south of the exposure east of it. 
 
 The microscopic character of the altered albite schist near the dyke on 
 Beinn Tharsuinn is described on p. 149. 
 
 The southerly dyke on the south side of Beinn Tharsuinn seems to be 
 accompanied in places with a downthrow to the north of about 30 feet. 
 
 In the burn called Liogan, J mile south-east of the " n " of " Liogan," 
 a 1-foot basalt dyke lies about 20 or 30 yards north of, and parallel to, 
 the dyke : this thin band is seen to end as it goes west. 
 
 There is a good section of the north dyke in the burn i mile slightly 
 south of west of Socach. The dyke is, as usual, divided into blocky cross 
 prisms which run at right angles to its sides. Just on the south side of, 
 and sometimes touching, it, there is a thin greenish dyke, apparently a 
 camptonite. The " green beds" on the north side of the dyke are turned 
 quite black (see p. 149). There are only two exposures of the dyke west 
 of the above section on the east side of Loch Fine : one is in the burn 
 | mile E.N.E. of the " u " of " Strachur," and the other in the burn i mile 
 N.N.E. of the " S " of the same word : the hillsides near these sections 
 are thickly covered with drift, and the low ground west of Strachur is 
 composed of raised beach and alluvial material. 
 
 The south branch, as already mentioned, p. Ill, is seen to cut a mica- 
 trap sheet in the river Cur, J mile E. of Strachurmore. In the burn f- mile 
 slightly south of west of the "S " of " Strachur" it cuts another lampro- 
 phyre band running north and south. On the shore of Loch Fine it is 
 exposed about J mile slightly east of south of the "B" of "Strachur 
 Bay." 
 
 The Loch Restil Dyke. The Loch Restil east to west basalt is re- 
 presented by two parallel bands, the south one the wider, near the little 
 stream 160 yards west of the outlet of the loch : there is a crush between 
 
BASALTIC DYKES: S1RACHUR DISTRICT. 159 
 
 the bands. The dyke makes a conspicuous gulley in the steep crags on the 
 north-west side of Beinn an Lochain : at the sides of this, | mile west of 
 the loch outlet, there is evidence (see p. Ill) that the basalt is later than 
 a lamprophyre dyke at its sides. Another gulley is formed by it in the 
 crags at the south-west side of a landslip i mile north-west of the " B " 
 of " Beinn Lochain." A little west of these crags it is accompanied by a 
 basalt dyke a few feet thick, which TUDS parallel to its north side at a 
 distance of about 16 yards. 
 
 A sudden change of path for a distance of 40 or 50 yards along a north 
 to south fault, with ferriferous carbonate strings, seems to occur \ mile 
 north-west of the " B " of " Beinn an t-Seilich," but the basalt is not 
 actually seen in a north and south course, and possibly it ceases to come 
 up to the surface. One third of a mile W.N.W. of the same letter there 
 is a good section of the dyke in and on the west side of the middle burn 
 shown in the Map : two lamprophyres, one a coarse rock with much black 
 mica, are seen on either side of it only a little distance off ; they do not 
 cross the basalt, and are therefore inferred to be crossed by it. 
 
 In the burn J mile south-east of the " k " of " Ardkinglas Ho," the 
 dyke is split into blocky cross prisms : the hade of the dyke is south- 
 west, and therefore the sides of the prisms incline somewhat north-east : 
 there is a thin crush at the north-east side and a thin parallel dyke. In 
 the burn f mile south of the " k " of " Ardkinglas 5 ' the dyke is unusually 
 thin not more than 6 or 7 feet, and perhaps it does not exist at the 
 surface at all in some places. In the burn J mile south of the " A " of 
 " Ardkinglas," it is not less than 10 or 11 feet broad, and there may be 
 more than this as the south side of the dyke is not seen. On the shore, 
 1 mile E.X.E. of ArJ na Slaite (133), the dyke is not less than 14 yards 
 wide. In a slide (4756) of the rock from the burn nearly J mile south of 
 Bathaich ban Cottage, no olivine was detected. 
 
 Other East and West Dykes. A dyke, seemingly a basalt, is seen along 
 the line of an east to west fault, nearly J mile south of the " oi " of 
 " Upper Clasheoin " (126). It is only seen for a few yards, and perhaps 
 does not belong to the set of early east to west dykes. 
 
 The east to west basalt south of Achadunan is seen at the east side 
 of the raised beach J mile slightly east of south of the bridge at the head 
 of Loch Fine. One-sixth of a mile further east the dyke is much better 
 seen; it is* 16 yards wide and marked with blocky cross joints. The 
 colour of the "green beds" near it is changed from green to black (see 
 p. 149). One-eighth of a mile south of the "r " of "Garbh Allt Mor," 
 there is an 8-foot branch on the south side, which is only seen in the 
 burn sections close by. There are two branches in the course of a big 
 north to south burn, not shown in the Map, ^ mile south of the " R " of 
 " KILMORICH " (parish) : which of these it is that continues east is 
 uncertain : the south one is the widest, and is seen in another burn 100 
 yards east of the burn just mentioned, while the north branch is not 
 seen. The dyke is seen in all the burns east of this which are shown 
 in the 1-inch Map, but its path between these burns is drift covered. 
 
 The basalt dyke north of Achadunan is finer-grained and thinner than the 
 others described, and seems in places, e.g., in the burn J mile north of the 
 " d " of " Achadunan," to contain macroscopic olivine. In the other east 
 to west basalt dykes of the Dunoon Castle dyke type, no olivine has in 
 Cowal been determined. There is nothing to show the relation in age of 
 this dyke to the north-west dykes. It has a direction somewhat north 
 of west, and perhaps it should be classed with the later north-west 
 dykes. In the burn ^ north of Achadunan it is 6 feet thick. In Eas 
 Kiachain it is in two or three different bands, each cross jointed and 
 
160 GEOLOGY OF COWAL. 
 
 about 5 feet thick. It is seen on the hill on the east side of the " g " of 
 " Lochan Mill Bhig," and is drawn in the Map from there through an 
 obscure morainic area in an E.S.E. direction for \ mile, to join an exposure 
 in a little burn, not marked in the Map, J mile S.S.W. of the " M " of 
 " Meall Beag." 
 
 North-west and N.N.W. Dykes. The north-west or N.N.W. basalts 
 are extremely abundant in the south-west part of the area, but rare north- 
 east of the line joining Carrick Castle and St Catherine's. In fact only 
 one is known that runs in this direction on the north-east of this line : 
 this is the dyke that crosses Glen Kinglas near the " g " of Kinglas." It 
 is seen along the south-west margin of a landslip on the south side of 
 the water, with a thickness of 5 or 6 feet and hading south-west. The 
 section in Kinglas Water does not show it, but it appears again in the 
 different burns on the north side of the alluvium : in these a crush rock 
 runs along with and is altered by it. In the burn f mile S.S.W. of the 
 " B " of "Binnein an Fhidleir," it makes a slight change of direction along 
 an early N.N.E. fault line, and in the changed path is thinner than usual. 
 
 Along the course of the N.N.E. fault a little east of Cruach nan Capull 
 (133) there is a basalt, of perhaps the same age as the north-west dykes, 
 that is taking advantage of an earlier line of fault as a ready direction of 
 intrusion, but we cannot be certain that this may not be connected with 
 the early east to west dykes, like the north and south strings connected 
 with the east to west dyke in Douich Burn near Lochgoilhead. That 
 the crush rock and vein stuff along this line are earlier than the basalt is 
 shown conclusively in several places, e.g., ^ mile E.N.E., and a little 
 more than J mile east, of the " h " of " Socach " (241), and in the burn 
 by the last " o " of " Coire No " (133), by the great amount of alteration 
 it has undergone, while the basalt is uncrushed. The exposures of 
 basalt along the line are generally isolated by considerable stretches of 
 drift-covered country, and it is not certain that they are all connected. 
 South-west of the Coire No, all the clear sections of the fault show also 
 basalt accompanying it until we come within less than J mile of Cruach 
 Bhuidhe (152 north-east); and further south-west still, various north-west 
 basalts can be seen to shift out of their ordinary course, and run along 
 the fault for little distances. The dykes are often in several parallel 
 parts, e.g., in the section J mile east of the " h " of " Socach " there is a 
 band 13 feet thick on the west side, then another 2 feet thick, and further 
 east still a third, a few inches thick. In the burn section f mile slightly 
 east of south of the " r " of Cruach nan Capull the dyke is in 2 bands : 
 the west one is 8 feet thick. 
 
 The N.N.E. faults in the area where north-west dykes are abundant, 
 are, as we should expect, much more commonly accompanied by basalts than 
 they are in the area where these dykes are scarce. We will mention a few 
 sections which show the relation in age between the dyke and the fault 
 rock. One quarter of a mile south-west of the top of Meall an-T (163 north- 
 east), the vein stuff on the west of the N.N.E basalt is distinctly hardened 
 and altered : a band of basalt can be traced running along this fault for 
 5 miles, partly in 1-inch Map 37, and partly in 1-inch Map 29 : there 
 is a parallel fault, also accompanied with basalt, near the north end of the 
 line. 
 
 In the burn J mile N.N.W. of the " M " of " Maol Odhar " (162 north- 
 east) there are 2 basalt dykes which change t their course along a thin 
 N.N.E. crush. In both cases the south-east part of the dyke advances 
 north-east along the crush not south-west ; the dykes in their N.N.E. 
 courses are quite uncrushed and sound, and thinner, see p. 144, than 
 when running north-west. The most south one is in its normal path 7 
 
BASALTIC DYKES : STRACHUR DISTRICT. 161 
 
 or 8 feet wide ; in its changed path it is at first 3J feet, but gradually 
 diminishes to 1 J- feet, and finally ceases to appear at "all. We did not see 
 either of these dykes resuming their old direction on the north-west side of 
 the burn. 
 
 On the shore j- mile north-east of the < : L" of "Leak" (151 north- 
 east) a basalt and a fine-grained lamprophyre dyke run together in a 
 N.N.E. direction. The basalt is chilled against a vein of ferriferous 
 carbonate. 
 
 On the shore 100 yards W.S.W. of Mid Letter (141) a 6-foot basalt 
 changes into a north-east direction on coming to the side of a north- 
 east lamprophyre band. The lamprophyre is rather crushed in a 
 direction parallel to its length, while the basalt is not so. The basalt 
 dwindles to 3 feet in width while it is running north-east ; it cuts the 
 lamprophyre just before resuming the old north-west direction. The same 
 dyke contains chlorophaeite amygdules (see p. 130). 
 
 The X. X. E. dyke in Gaol Ghleann (152) is accompanied with parallel 
 crushes. 
 
 On the south side of the road nearly 200 yards above Leanach (151) 
 there are several basalts near together, running nearly north and south, 
 and with parallel crushes. The most west band, itself a compound one, 
 is crushed, but the one next to this, a hard cross-jointed dyke which 
 has been quarried, does not show distinct crushing ; yet it would seem 
 that there must be a fault with it, for the graphite schist at its side is 
 striking against beds which come below the graphite schist in the burn 
 I mile north-east of Leanach. 
 
 An altered crush rock occurs in the burn J mile S.S.E. of the 
 " S " of Strondavain " (162). It is prettily veined with red and green 
 strings, and has a pronounced splintery fracture. The north-west basalts 
 which intersect it were not noticed to be crushed themselves. Vein stuffs 
 altered by north-west basalts have also been noticed on the shore J mile 
 south-east of the "C" of " M'Phun's Cairn " (HI north-west), and by 
 the north-west basalt in Gleu Kiiiglas (see p. 160). 
 
 Sections which show north-west basalts themselves considerably affected 
 by crushing parallel to their sides, occur in the following places, J mile 
 W.S.W. of the "B" of " Ballimore " (141 south-west), 1 mile north-west 
 of the " C " of " Cruach Bhuidhe " (152), J mile north-east of the " a " of 
 "Meall Dubh" (163 north-west), and J mile N.N.E. of the "C" of 
 " Creag Tharsuinn " (163 north). 
 
 Intrusions of basalts through lamprophyres are seen on the shore J mile 
 N.N.W. of the "L" of "Leak" (151), and J mile west of the "S" of 
 "Sgor Coinnich " (153). The relations of the two sets of rocks can be 
 inferred with confidence in many other cases, from the way the hill 
 features gulleys, &c., formed by the basalts, cross the features made by 
 the lamprophyre sheets. 
 
 The " cracked " state of the quartz veins of the schists, which is due to 
 contact alteration by the basalts (p. 1 48), is particularly well seen in a 
 burn } mile W.S.W. of the "B" of " Beinn Ruadh" (164 south-east), 
 in a strip of schist 2 feet wide which occurs in the middle of one of a 
 close set of parallel or bifurcating dykes. 
 
 The basalt band in the burn J- mile N.N.E. of the " C " of " Conchra " 
 (162 south-east) is composed of three different dykes, all running in the 
 same direction, and all hading slightly west. The east part consists of 
 an uniform medium-grained rock with a 4 inch intrusion of porphyritic 
 basalt with fine-grained matrix. The medium grained rock is not chilled 
 against the porphyritic rock, and therefore the latter must have been in- 
 truded into the former. The west part is of porphyritic basalt much like 
 
 L 
 
162 GEOLOGY OF COWAL. 
 
 the porphyritic string just mentioned, but both this and the medium- 
 grained rock oppose chilled margins to one another ; hence we suppose 
 the medium-grained rock was first intruded and became chilled against 
 the schists, and then the porphyritic rock subsequently came up along the 
 chilled edge of the other, and became chilled against it in turn. 
 
 Amygdules of a white radiating zeolite occur in the dykes in the 
 following places, J mile north-east of Tigh na Criche (141 south-west, 
 slide 5435), 1 mile and a little more than J mile south-west of the same 
 place, by the "a" of "Clach Beinn" (163), in the burn J. mile below 
 the "S " of "Strath nan Lub" (163 south-west), and elsewhere. 
 
 A quarter of a mile north-east of the "D " of "Dunans" (162 north- 
 east) a flattish basalt surface crosses the burn in a north-west direction. 
 This shows many irregular dark fine-grained strings, from ~ to 1 inch in 
 breadth, which run parallel to the direction of the surface. The strings 
 project slightly on the rock face. There are some porphyritic crystals of 
 felspar in the dyke, and these are in places crossed by the fine strings. 
 The parallel strings are in some parts exceedingly numerous, and also 
 joined diagonally by other strings of the same appearance, so that the 
 fine-grained matter may almost equal the normal rock in bulk. Besides 
 the dark fine-grained lines there are other yellowish-red lines, which also 
 run in much the same direction. These last probably represent thin crush 
 lines, and perhaps the other dark strings do also. Two feet from the north- 
 east side of the surface, on the south-east side of the burn, is a bit of 
 altered schist that lies horizontally on the flat surface of the basalt. Five 
 feet further north-west of this side of the burn, and about 5 feet from the 
 south-west side of the surface, another flat strip of schist is seen adhering 
 to the top of the basalt exposure : and in various other places it can be 
 seen that the basalt, apart from the fine-grained strings just mentioned, 
 is much finer in grain at the top of the surface than it is a little below, so 
 that it would seem that all the top must be close to an original cooling 
 surface. Both banks of the burn are drift covered. 
 
 In the burn J mile N.N.E. of the "T" of "Creag Thareuinn " (163 
 north-west) a north-west basalt seems either not to exist at the surface 
 for a space of 20 yards along its general direction, or to be very much 
 thinner than at either side of this space. 
 
 Tachylite selvages have not been noticed so abundantly as in 1-inch 
 Map 29. Instances occur on the shore of Loch Fine, 250 yards N.N.E. 
 of M'Phun's Cairn (slide 5437 belongs to this dyke, but not to the 
 tachylite portion of it), and | mile south-east of the " C " of the same 
 " Cairn." These dykes are also noteworthy from containing olivine. 
 
 C.T.C. 
 
 CHAPTER XIV. 
 
 THE IGNEOUS ROCKS (continued). INTRUSIVE ANDESITE (?). 
 THE SITH AN T-SLUAIN DOLERITE. TRACHYTIC DYKES. 
 
 The rocks described in this chapter have no connection with one 
 another, but they are grouped together in one chapter, as the information 
 we possess about each of them is but scanty, and does not take up much 
 space. 
 
 Intrusive Andesite (?). 
 
 The rock to be described occurs in several small exposures on the coast 
 
INTRUSIVE ANPEMTE (?) 163 
 
 about I mile north-west of the Perch near Inellan : the exposures are 
 only seen at low tide, and are so covered by sand and seaweed that their 
 margins are often very obscure. 
 
 The most north-westerly exposure, only about 12 yards long and 6 
 broad, is surrounded by the Upper Old Red Sandstone on all sides, and it 
 seems as if the north-east exposure was also so surrounded, excepting 
 in a seawards direction. The exposures on the south of these may be 
 connected along a line running west or W.N.W. 
 
 It is most probable that these small outcrops are of an intrusive 
 character, such as are not uncommon near the base of the andesite flows of 
 the south end of Bute, but the sections do not allow us to assert this with 
 confidence, and it is possible that they belong to these flows : their place 
 of occurrence, a little below the limestone series, is considerably below the 
 geological horizon of the general base of the flows in Bute. 
 
 Close flaggy joints characterise the rock of all the exposures. The 
 directions of these joints are various : in the north-west exposure they 
 seem arranged in a syncline ; in the north-east exposure they dip south ; 
 and in the south-west exposure, at the north end, they are vertical and 
 parallel to the length of the exposure, but seem to flatten in the middle. 
 
 Macroscopically the rock is of a purple or reddish-purple colour, and 
 too fine-grained to allow us to distinguish the different constituents. A 
 specimen from the north-west exposure has been examined microscopically 
 (slide 2837), and is thus described by Dr Hatch : " A plexus of 
 interlacing needles of a colourless, straight extinguishing mineral of low 
 double refraction together with spicules and granules of iron-ore 
 (magnetite). A small quantity of interstitial matter richly sprinkled 
 over with opaque granules. The needles have an average length of *52 
 mm., and a width of '06 mm. They show no cleavage. A portion of the 
 section after being etched with HC1 gave no definite staining-reaction 
 with fuchsine (test for nepheline). The mineral is perhaps oligoclase, 
 although no twin-striation could be detected. This felspar occurs fre- 
 quently in basaltic and andesitic lavas in lath-shaped microlites, giving 
 approximately straight extinction. Resulting from the decomposition of 
 the needles are little patches of calcite, causing effervescence when a 
 drop of HC1 is placed on the section. [N.B. One would hardly expect 
 oligoclase to weather into calcite.] " 
 
 The Sith an t-Sluain Dolerite. 
 
 The Sith an t-Sluain (152 north-west) dolerite forms a prominent and 
 steep rocky hill, somewhat oval in shape, with a length of about 300 
 yards, running slightly west of north, and a breadth of about half this. 
 The north, and part of the east and west sides, are almost inaccessible. 
 
 A view of the south side from a little distance shows a prominent 
 band at the edge of the rock which is marked off with some sharpness 
 from the central portion ; we see at once that it is in a sounder condi- 
 tion and possessed of sharper joints, and that the main joints are parallel to 
 its length, hading steeply slightly south of west. Our first impression 
 at a distance was, that this might be a dyke quite unconnected with 
 the rest of the rock on the hill. But this certainly is not so, for both 
 at the north and the south ends of the hill, and some other places, a 
 similar edge rock is seen, excepting that the joints in it are not always 
 so prominently longitudinal, but sometimes are cross joints and the same 
 in direction as, but closer than, those in the coarser interior rock. The 
 prominent joints on the north side hade east at 20 to 50 ; the outside 
 margin of the rock is vertical or hades steeply north. 
 
164 GEOLOGY OF COWAL. 
 
 The junctions between the edge and the interior rock are not usually 
 clear, but it is certain that the former is not chilled against the latter. 
 The edge rock is comparatively fine in grain, but not so fine that it cannot 
 be seen macroscopically that the structure is ophitic white needles of 
 felspar clearly penetrating an abundant black mineral, augite. Small 
 yellowish grains of olivine, sometimes the size of a large shot, also occur. 
 The interior rock is in most parts very decomposed, disintegrating readily 
 into rough gravel, which rolls far down the slopes below the outcrop of the 
 dolerite, and supports a growth of short sweet grass. The same minerals 
 occur in it as in the edge rock, but the individuals are larger. It is 
 abundantly mixed -with still coarser but sounder bands, which usually 
 project slightly on the weathered face. These bands are often from 4 to 
 6 inches thick ; they may run either horizontally or vertically or obliquely 
 to the horizon : or we may, in plane sections, find rudely oval or circular 
 masses of similar rock, sometimes as large as a football. They are in 
 many parts prominently ophitic, white felspar spears penetrating the 
 black augite individuals and cutting them into strips, which are orientated 
 similarly, in some cases for a length of 3 or 4 inches. In other parts 
 the felspar and augite seem to be iutergrown in a pegmatitic manner. 
 We have noticed no olivine in these strings. Not uncommonly cavities, 
 apparently amygdaloidal, filled with circular or fan-shaped radiations of 
 some white or bluish- white zeolite, occur in these coarse veins ; they 
 sometimes attain J inch in breadth, and abut against the coarsest crystals. 
 Similar zeolite cavities also occur in places in the edge rock. The coarse 
 veins are not chilled at their margins ; they pass directly into the normal 
 rock of the interior. 
 
 On close examination it is seen that the edge rock at the south end of 
 the hill is not separable by any sharp line from the interior. There is a 
 continuous exposure from the edge rock, and probably from not far off 
 the outside of it, into the interior rock, and there seems quite a gradual 
 passage from the one into the other. At no place anywhere round the 
 edge could we find a rock much finer than the ordinary type of the edge 
 rock, though at the north side altered schist is seen only a few feet from a 
 rock feature, vertical or hading steeply north, which must be close to 
 the original cooling surface. In the edge rock generally there is consider- 
 able variability in the relative proportions of augite and olivine, and in 
 places olivine may scarcely be seen, while in others it is unusually 
 prominent. The parts specially rich in augite are generally rather coarser 
 in grain : they occur either in strings, or in small patches which are not 
 much longer than broad as seen in section : areas about the shape and 
 size of marbles are common, and these sometimes pass into short strings, 
 about 2 inches long and J inch broad. Such irregular mixtures of coarse 
 augitic parts with other finer-grained parts rich in olivine are particularly 
 well seen near the south end of the hill. The augitic parts in the edge 
 rock have not their constituents in such large size as the coarse veins in 
 the interior rock. They sometimes contain zeolites like those in the 
 interior veins. 
 
 Close to the south side of the hill, the edge rock in one place 
 shows a banded appearance, due to varying abundance of the white 
 felspathic material, and the varying size of the olivine specks. Along 
 the margin of two bauds comes in in one place a row of zeolites, averaging 
 J inch in diameter. The conspicuous banding is only seen for a length 
 of 2 or 3 yards, and a breadth of 1 yard. It seems to strike roughly 
 parallel to the edge of the intrusion, but may hade slightly into the hill 
 instead of outwards: we suspect the edge of the intrusion, judging from 
 the prominent joints in it, inclines outwards. A loose piece gathered 
 
SITH AN T-SLUAIN DOLERITE. 165 
 
 on the east side of the bill showed similar banding. Some parts are 
 rich in olivine, and, taking the whole of the edge rock together, it is 
 possible it is slightly richer in this^mmeral than the interior rock is. But 
 it is hard to come to any confident conclusion about this, owing to the great 
 variability of both rocks. Besides the well-marked coarse strings and parts 
 in the interior rock already described, there are numberless other patches, 
 from { inch to 1 inch long, of rock specially rich in augite, which are 
 mixed in irregularly through the rest of the mass. This is seen particu- 
 larly well along the west side of the hill ; in one square inch of surface 
 there may be little else than felspar and augite ; in another square inch 
 little else than felspar and olivine. The olivine is generally decomposed 
 into a rusty tint, while the augite remains bright black. The portions 
 specially rich in augite have a habit of projecting somewhat on the 
 weathered face. 
 
 In one of the well-defined coarse veins, about 3 inches wide, the outer parts 
 seemed nearly all of felspar, and the inner part was specially rich in augite. 
 
 Slides of the interior rock (5438), of the edge rock (5439), and of the 
 coar.se veins in the interior (5440), are thus described by Mr Teal), 
 5438 : " Coarse-grained greyish rock. Basic plagioclase with a tendency 
 to idiomorphism, and olivine (fresh) are the two principal constituents. 
 The olivine is often allotriomorphic with respect to the felspar. In 
 addition to the above there is a little ophitic augite wedged in between 
 the felspars and iron-ores (scarce). The rock is intermediate between 
 olivine gabbro and troctolite." As already stated, however, there are many- 
 parts of the interior rock, which are much richer in augite than the speci- 
 men sliced. The felspar is certainly of earlier consolidation than either 
 the olivine or augite. The olivine is of earlier consolidation than the 
 augite. A large part of the iron-cores is later than the felspar, and later 
 also than some of the olivine ; but in other parts crystals of magnetite 
 are inclosed within felspar. There are many bits of iron-ore inclosed in 
 augite. 5439: "Medium-grained dark coloured rock. Same minerals 
 as in 5438, but possibly containing more of the ferromagnesian constitu- 
 ents, especially augite. Olivine-dolerite." In other parts of the edge 
 rock, however, the olivine is, as already described, more prominent than 
 the augite. 5440 : " Very coarse-grained rock composed of white felspar 
 more or less idiomorphic, and black ophitic augite. Augite shows a kind 
 of radial grouping in places. Under the microscope, plagioclase and 
 ophitic augite with a few patches of iron-ore. This appears to be a kind 
 of basic pegmatite." The proportion of felspar does not seem greater 
 than in the other two slides, nor is the proportion of iron-ore less. 
 
 The variability of the rock is very interesting, but it does not seem 
 that there is any recognisable law regulating the distribution of the 
 different varieties. The whole of the rocks described belong to one period 
 of intrusion, and we cannot say that the edge rock is more basic than 
 the interior. The coarie pegmatite-like veins may be considered to 
 represent the residue of the magma left after the consolidation of the other 
 parts ; they contain no olivine, and in the other varieties of rock, olivine 
 was seen to be of earlier consolidation than the augite. 
 
 It has already been stated that the main joints on thewest side hade 
 steeply slightly south of west, i.e., outwards from the hill: on the north 
 side also, the apparent original surface is either vertical or hades steeply 
 north, i.e.) outwards from the hill; on the south-east side the prominent 
 joints hade south-east, outwards from the hill. Now we suppose these 
 main joints to be parallel to the edge of the intrusion. The evidence 
 therefore strongly favours the idea that the intrusion is part of a boss, 
 gradually diminishing in size upwards. It may be that the present top 
 
166 GEOLOGY OF COWAL. 
 
 of the hill is not far from the original surface of the intrusion, with 
 little more than the edge rock denuded off, arid that the portions of 
 the interior now exposed are none of them far from the edge rock. 
 
 No clear junction of schist with the dolerite is seen, but schist is 
 observed to be much hardened and altered at various points within a 
 few yards of the edge rock, e.g., near the " n" of " an," at the top of the 
 " S " of " Sluain," and just on the north side of the " 2 " of " 1428." The 
 altered schist no longer splits with readiness along the foliation planes, 
 and these planes, when the rock can still be split open, do not show their 
 customary micaceous lustre. A good many bands of it are dark grey, and 
 must in some way have been darkened by contact alteration (see p. 148). 
 The quartz veins of the schist are now, too, much more readily broken by 
 the hammer, breaking up into a kind of sugary mass along a set of 
 numberless little joints (see p. 148). The colour of the quartz is in 
 places rather purplish or pink, colours unknown in the veins of the 
 unaltered schist. 
 
 Near the " n " of " an " the schist is for a few yards from the edge of 
 the intrusion, tilted up in a direction almost at right angles to the usual 
 strike in the neighbourhood, so as to run parallel to the side of the 
 intrusion and dip at a steep angle into it. Near the " 2 " of " 1428 " 
 the schist is, for a distance from the dolerite of a few yards only, in 
 a vertical position with a strike parallel to the edge of it. These 
 evidences of the mechanical distortion effected by the intrusion confirm 
 the supposition that it belongs to a boss, not a sheet. 
 
 The supposed Tertiary, or north-west running set of basalt dykes are 
 not uncommon in the neighbourhood of the intrusion, but none are seen 
 cutting it or in close contact with it. The generally uncrushed state of 
 the rock rather suggests that it also may be of Tertiary age, and the 
 character of the pegmatite-like veins in it, so different from that of the 
 red acid strings of the early east to west dykes, and dolerites of the 
 midland valley of Scotland (see p. 147), agrees with this supposition. 
 
 It may be mentioned that the name Sith an t-Sluain ( The Fairy Hill 
 of Sluain) is given to the hill in consequence of the old local belief that 
 it was a favourite haunt of the fairies. The hill appears to possess some- 
 what unusual acoustic properties. We were informed by the late Mr 
 Rhynd of Strachur, that he was once on the top of it, all alone on a clear 
 calm Sunday evening, one of those evenings when everything seems 
 unusually distinct and vivid, when he heard some voices apparently 
 close to him. So close they seemed that he concluded they proceeded 
 from some people who were climbing up the steep hidden slope just below, 
 and who would soon join him at the top. But time passed on, and they 
 never came. Still the voices continued. He listened again more intently. 
 Now he could make out clearly what was said. It was a mother talking to 
 and chiding her children, and mingled with the words came the splash 
 of oars. So downwards he looked to the loch side, and there at Newton 
 Bay, about If mile away in a straight line, he saw the people and the 
 boat from which the sounds ascended. It was Mr Rhynd's opinion that 
 some such incident as this may, in time long past, have started the idea of 
 the hill being a fairy haunt : sounds and whisperings were heard about it 
 which could not be readily explained, and were therefore attributed to 
 the Spirits of the Hill. 
 
 Trachytic* Dykes. 
 
 In this area only five intrusions have been recognised as trachyte. 
 These are all dykes ; one running N.N.E. in the burn f mile east of 
 * It is doubtful whether this is the best term to apply to these rocks. 
 
TRACK YT1C DYKES. 167 
 
 Cruach Mhor (162 south-east), one also running N.N.E. in the burn 200 
 yards west of Craigendaive, a thicd running N.N.W. in the burn J mile 
 south-east of Dun Mor (172 south-east), and two more running north- 
 west in the burn |- mile east and J mile south-east of the " D " of 
 "Dunans" (164 south-east). But as they are, on hasty inspection, not 
 easy to distinguish from many of the basaltic dykes, and occur in much 
 the same way in the field, it is possible that some dykes coloured as basalt 
 may properly belong to them. 
 
 In the interiors of these dykes the colour of fresh fractures is pale 
 greyish brown, less dark than most of the basalts, and the texture a uni- 
 form medium grain. But as their margins are approached the texture 
 grows distinctly finer, and for about the last f inch the colour also changes, 
 and becomes dark grey or black. A black glassy selvage is seen in the 
 Cruach Mhor, Dun Mor, and one of the Dunans dykes, but in the first 
 and last does not always exceed -^ inch in thickness. 
 
 As already stated, two of the dykes run N.N.E., a direction which is 
 not very common in the basaltic dykes, but we cannot, on this account, 
 conclude that there is any difference in general habit of direction between 
 them and the basalts, because in each of these two localities the basalts 
 are also running ^N\N.E. The general direction of the basalt dykes is 
 N.N.W., but they often vary from this in order to take advantage of 
 some pre-existing line of weakness, such as a crush line, and the directions 
 of the Trachytes are clearly subject to the same influences. 
 
 In the burn east of Cruach Mhor there is a strong crush, stained with 
 haematite, hading slightly west, and running in the same 'direction as the 
 trachyte. The schists near are much reddened and traversed by haematite- 
 stained strings, and so also is a small exposure of lamprophyre in the bed 
 of the burn, about 200 yards north-east of the broad basalt dyke. It 
 has not been possible to show this small exposure in the 1-iuch Map. 
 The trachyte itself is not reddened in the slightest, nor are the basalts. 
 It is clear, therefore, that the red crushes must be of earlier date than 
 they, and that they both have locally taken a N.N.E. direction so as to 
 take advantage of a line of weakness. It seems probable that some 
 crushing may also have taken place at a later date after the intrusion of 
 the trachyte, for a dark grey-green crush is seen at one place close to its 
 side, but the dyke itself does not show any crushing. A little south 
 of the most northerly exposure of trachyte in the burn two exfoliating 
 basalts conie in from the north-west direction, but at the crush they change 
 direction, and run parallel with it and the trachyte, keeping on the west 
 side of the latter. Just north of the reddened lamprophyre another 
 basalt conies in from the north-west. What becomes of this is not clear ; 
 it certainly does not cross the trachyte, neither could we see any sign 
 of it twisting into parallelism with it. It is hence suggested that the 
 trachyte is of later date. 
 
 The dykes near Dunans are clearly seen cutting through north-west 
 running basalts, and the facts observed in other localities in no case dis- 
 agree with the idea that the trachytes are later than the basalts. 
 
 In the burn east of Dunans the dyke lying most to the south-east 
 is distinctly more blocky than most of the basalts of the neighbour- 
 hood. The main joints run parallel to the length of the dyke, but there 
 are also others almost at right angles to these. On the west side of it, 
 on the east side of the burn, there is a prominently cross jointed dyke 
 about 6 feet wide, of medium-grained exfoliating basalt. On the west 
 side of the burn close down to the water edge nothing is seen of this 
 basalt, but the west side of the trachyte is opposed to schist. A little 
 way up above the water, however, the basalt again appears bstweeu the 
 
168 GEOLOGY OF COWAL. 
 
 trachyte and the schist. The line between the basalt and the schist meets 
 that between the basalt and the trachyte at an angle. There is a thiii 
 crush along the former line. The latter line is not easy to examine, 
 being partly covered with dripping moss, etc., but it is clear that the 
 trachyte is chilled at it, and is not crushed. The east side of the trachyte 
 on the east side of the bum is also uncrushed, though the rock next it is, 
 in places, a much crushed and decomposed basalt. The east side of the 
 trachyte on the west side of the burn is traceable for about twenty-five 
 feet in a straight line, and is chilled at the margin ; it cuts distinctly 
 through a rather coarse-grained basalt dyke. The other trachyte dyke 
 lying on the north-east of this locality is, on the west side of the burn, in 
 close contact with a somewhat crushed basalt dyke on its north-east side. 
 The margin of the trachyte is seen to be chilled against the basalt wher- 
 ever it is distinct, and in some places at the very edge is glassy. 
 
 In the burn on the south side of Dunans one of the above trachyte 
 dykes appears again, J mile S.S.W. of the " S " of " Strondavain." 
 The best section is that on the south side of the burn. The dyke 
 is about six yards wide. It breaks into large blocks, the main joints 
 running roughly parallel to its length. Both margins are distinct, and 
 clearly chilled. On the north-east side of it is a rather coarse-grained 
 basalt ; the joints in this do not give rise to such large blocks as those of 
 the trachyte. The basalt is considerably crushed, and veined with many 
 thin calcite strings, while the trachyte is in a quite sound uncrushed 
 state throughout. The main joints in the basalt, which run parallel to 
 the dyke side, are clearly seen to strike against the side of the trachyte, 
 and to be cut across by it one after the other, while the corresponding 
 joints of the trachyte are parallel to this side. 
 
 At Craigendaive the trachyte opposes a chilled margin to a decomposed 
 somewhat coarse basalt, which runs parallel with it on its east side, but 
 the basalt has also a chilled margin against the trachyte, and so it is 
 impossible to say which is the earlier ; one of them must first have been 
 chilled against schists, and then the later of the two afterwards chilled 
 against the earlier. Another basalt dyke occurs close to the east side 
 of the trachyte, and again parallel with it, so that there is evidently a 
 tendency for all the dykes in this locality to run out of their usual 
 course. There is a flat feature on the hillside just to the north, running 
 
 N.N.K., and this is perhaps due to 
 some line of weakness. The trachyte 
 dyke is about five yards wide ; it is 
 not seen except in the burn. 
 
 The Dun Mor dyke has a coarse 
 exfoliating basalt dyke on either side 
 also, and running parallel. It shows 
 glassy selvages against these, and lines 
 FIG 39. ~ K 2. From near edge of of flow and elongated amygdules 
 dyke 200 yards W. of Craigendaive. n , . J& 
 
 Part of a natural section at right Pf allel to . xt f margins for a breadth 
 angles to dyke side : radiate spheru. of several inches. 
 
 litic structure unusually distinct. All these trachytes are distinguished 
 
 by the possession, near their margins, 
 
 of marked spherulitic structures which can be discerned by the 
 naked eye. This is one of the most readily recognised points in which 
 they differ from the basaltic dykes of the area. We will especially 
 describe those of the Craigendaive dyke. In this there are many planes 
 running parallel to one another and the sides, at intervals of about J 
 inch, for a distance of several inches from the sides. Most of these 
 planes show, on their surfaces, close parallel rods, which may run in 
 
TRACHYTIC DYKES. 169 
 
 different directions on the different planes sometimes horizontally, some- 
 times diagonally, and sometimes vertically, but always parallel to ths 
 others on the same plane. On examination these rods are seen to be 
 made up of polygonal bodies, the angles of which are quite sharp, but 
 their sides often slightly curved. We may suppose the bodies to have 
 resulted from the mutual pressure of forms which, with more room, would 
 have assumed a spherical shape. Even to the naked eye cross sections of 
 these bodies often disclose a radiate structure. At other times we can- 
 not distinguish any rods, though there may be polygonal forms. The 
 breadth between the planes and the size of the pftlygonal forms in them 
 grow gradually less and less as we approach the margins of the dyke 
 three or four inches off the forms are about the size of peas, and from this 
 become less until finally they cease to be visible to the eye. At a distance 
 of a foot from the side, in the quite coarse rock, indications of spherulitic 
 fibres can often still be seen, but the polygonal forms are not con- 
 spicuous. 
 
 40. x 1, From near the side of the dyke % mile E. of Cruach Mhor. The 
 coalesced spherulites increase in size in proportion to the distances of the planes 
 on which they lie from the dyke side. In the sketch the plane at the right 
 hand top corner is the furthest from the side, and the spherulites on this 
 plane are the largest. 
 
 Under the microscope the spherulitic portion of the rock (slides 391 
 and 2962) is seen to consist of a pale brown glass full of minute depolari- 
 zing spicules, granules of magnetite, and brown granular matter. The 
 spicules are sometimes aggregated into stellar groups. It is not clear 
 that all the spherical patches are true spherulites bodies possessed of a 
 radiate structure. Some may be accumulations of a dark coloured 
 ingredient of the rock, but certainly near the outer edge there are true 
 spherulites, both singly and in groups aggregated together with length 
 parallel to the general flow structure, and it is possible, that if the slide 
 had been thinner, the darker spherical bodies would also have shown a 
 radiate structure. The spherulites are often seen to be crossed by the 
 spicules. 
 
 Several slides of the Dun Mor rock (slides 2961, 3922a, 3922b, and 
 392 2c) were prepared, in order to show the gradual alteration in size of 
 the spherulites as the edge is approached. The still glassy selvage (3922a) 
 is thus described by Dr Hatch : " Clear yellow glass, only containing a 
 few streams of granules, some isolated long spicules, a few prisms of augites 
 and abundant most perfectly-developed little spherulites, presenting a 
 fibrous structure, and sometimes with a central nucleus. Between crossed 
 Xicols they give a black cross." A part further away (slide 3922c) con- 
 sists of " brown granular matter filled with long slender depolarising 
 spicules which often radiate from a small granule of magnetite. There 
 are also present large crystals of magnetite, also furnished with a fringe 
 of spicules. A pale coloured augite also occurs in isolated prisms." In 
 the slide 392 2b, which comes between the two already described, the 
 brown granular matter in the glass seems often to have accumulated 
 
170 GEOLOGY OF COWAL. 
 
 around the stellar aggregates of spicules, leaving small interstitial patches 
 of clear coloured glass. The aggregates become smaller and smaller as the 
 original surface is approached, and in 3922a they are so minute before 
 the distinctly spherulitic portion is reached that they appear merely as 
 dark structureless granules under the J inch object glass. These still are 
 disposed in rows roughly parallel to one another, and show beautiful 
 instances of fluidal structure : at times they show, sharp folding, ^ or 
 adjacent rows separate and bend round some early formed crystal, which 
 has been caught up in the glass. They are often seen to go straight 
 through the spherulites without any distortion, as if the latter had not, 
 in these cases, been developed until after the flow motion of the rock had 
 ceased. 
 
 The slide of the Cruach Mhor rock (2960) is also a spherulitic glass. 
 A specimen from an inch or two off the side of this dyke gave, with 
 Walker's balance, a specific gravity of 2-34. It is possible there are some 
 small hidden cavities within the specimen: small air bubbles continued 
 to escape for some time while it was being weighed in water. 
 
 The central well crystalised portion of the dykes in the burn J mile 
 south-east of the " D " of " Dunans " has been microscopically examined. 
 This (slide 3452) is composed mainly of small lath-shaped crystals of ortho- 
 clase, together with scales of brown biotite, and a few prismatic crystals 
 of pale, somewhat altered, pyroxene, and scattered granules of magnetite. 
 Interstitial glassy matter appears originally to have been present. This 
 rock was kindly analysed by Mr Player with the following results : 
 
 Silica, . . . . .56-4 
 
 Alumina, . . . . .19 
 
 Ferric oxide, . . . . . 3 '5 
 
 Ferrous oxide, . . . . . 4*8 
 
 Lime, . * . . . .2-6 
 
 Magnesia, . . . . . 1'5 
 
 Soda, ...... 4-5 
 
 Potash, . . . . 5-0 
 
 Loss x>n ignition, . . . . 2 '6 
 
 99-9 
 
 The specific gravity of a specimen from the same part of the rock was 
 determined by Walker's balance as 2 '4 8. 
 
 The shape of the amygdules forms another conspicuous point in which 
 these dykes differ from the basalts. In the latter, as stated, p. 129, the 
 amygdules are almost universally rudely spherical, whereas in the 
 trachytes they are either very irregular in shape, or prominently 
 elongated parallel to the dyke sides. At Craigendaive and Cruach Mhor 
 they consist chiefly of calcite with occasional specks of sulphide of iron 
 near the centres, and some are an inch in length. Close to the surfaces 
 of the prominent planes there is a tendency for extremely thin rust- 
 covered hollows to show themselves on weathering : the sides of these 
 hollows seem formed by the sides of the polygonal spherulites, and so 
 have a crenulate aspect. At Dun Mor the amygduies sometimes attain a 
 length of about J inch with a breadth not exceeding -^ inch, and they 
 are composed of an undetermined greyish-brown substance with gummy 
 lustre, which is quite soft to the knife. Possibly this is the chlorophseite 
 of Maculloch ("Western Isles," vol. i., p. 504 ; see also Heddle, Trans. 
 Roy. Soc. Ediri., vol. xxix. p. 84). In a section by the road J mile 
 slightly north of west of the " D " of " Dunans " the elongated vesicles, 
 weathering in hollows, are especially abundant at a distance of about 18 
 
STRUCTURE OF DUNOON DISTRICT. 171 
 
 inches from the north-east side of the trachyte: their greatest lengths 
 are parallel to the side, and usually nearly horizontal : their dimensions 
 vertically are often rather more than their breadths measured at right 
 angles to the side of the dyke. One vesicle was noticed at least H 
 inch long, though less than J inch broad, and lengths of f inch are not 
 uncommon. C.T.C. 
 
 CHAPTER XV. 
 
 GENERAL GEOLOGICAL STRUCTURE OF PARTICULAR 
 DISTRICTS. 
 
 District of Dunoon. 
 
 The district to be now described includes all the area inclosed by 
 Loch Striven, the Clyde, the Holy Loch, Glen Lean, and the lower 
 part of Glen Tarsan with the exception of the small area near Inellan and 
 Toward which is occupied by rocks of Upper Old Red Sandstone 
 Age. It extends from " the anticline " down to the south-east boundary 
 of the schists. The small area of Upper Old Red Sandstone is described 
 separately on pp. 92-96. 
 
 The schistose grey wacke horizon in the north-west of this area is the 
 same as that mapped in the areas north-east and south-west. For a 
 little space west of Ardtarag the marginal lines have not been engraved. 
 There are plenty of rock exposures in this space, and the impression con- 
 veyed by examining them was, that the bed was much folded and the 
 margins repeatedly " v " shaped. Even in the sections elsewhere the 
 margins are not sharply defined we can only say that after passing an 
 interval of about 6 or 7 yards we reach a schist in which the proportion 
 of pebbly rock is certainly greater than it was on the other side, and in 
 this area they seemed still less defined. "We think the south-east margin 
 is generally more definite than the north-west. On the south-west side 
 of Glen Lean we were in doubt whether we should not take the north- 
 west margin about 30 yards north-west of the line engraved. 
 
 On the east side of Loch Striven, ^ mile north-west of the Craig, the 
 same baud of coarse pebbly schists occurs as that described more fully on 
 the other side of the loch, pp. 186-187. It has not been traced up hill to 
 the north-west. 
 
 Crossing over Mid Hill is a band of fine-grained hornblende schist con- 
 taining many crystals of magnetite and small specks of ferriferous carbon- 
 ate. On the hilltop the outcrop is. 8 or 9 yards wide, but near the south- 
 west end of the line engraved for the band it is only between 1 and 6 feet. 
 The band is on much the same horizon as those near Ardentinny. 
 
 There are three outcrops of hornblende schist a little north-west of 
 the lowest band of green beds. The one on the west side of Inver- 
 cliaolain Burn a little south of the " G" of " Glen," is only seen obscurely : 
 it overlies a thin-foliated quartzose schist, but the line separating them 
 has rather the aspect of a thin crush : the ground around is obscured 
 by drift aud the slipped material from a large landslip, and it is uncertain 
 how far the bed extends. The band near the " G" of " Glen Kin " is 
 exposed in both the burns which unite near the " G," but cannot be 
 traced away from them owing to the thick drift covering. The outcrop 
 north-west of Strone Saul makes a prominent show on the hillside, its 
 
172 GEOLOGY OF COWAL. 
 
 edgse generally sticking up in little crags' over the surrounding smooth 
 ground. There is a good section of pebbly schist and phyllite in the little 
 burn on the east of the exposure, but no hornblende schist. 
 
 The most north-westerly broad band of green beds on the south-east side 
 of Inverchaolain Glen is not shown on the shore of Loch Striven, the ground 
 it should occupy being all covered by drift or raised beach deposits. 
 But it is seen in the little east to west burn near Tighnuilt : some bands 
 are coarsely pebbly : a little above the base some schists occur which do 
 not belong to the green bed type. Further north-east we see in several 
 places thin bands of green beds a little below the base of the lowest broad 
 band : e.g., there are two such in the bum which comes into Inverchaolain 
 Burn from the south-east by the " n " of " Inverchaolain " : one f mile 
 north of the foot of the above little burn : three on the south-east of 
 Bealach na Sreine and the head of Glen Kin Burn : and one about J mile 
 south-east of the "G" of "Glen Kin." It is not known whether these 
 bands are partial repetitions of the broad band due to folding, or bands 
 on a slightly different horizon. Much the greater portion of the broad 
 zone consists of typical green beds, but here and there, e.g., near the top 
 of the band f mile south-east of Strone Saul, schists without any green 
 tint are intermixed. A little above the top in the burn J mile west of 
 the "B" of " Bochd" two thin bands of green bed occur. In the same 
 burn the top of the broad band is drawn for a little space at a considerable 
 angle to its usual direction : the dip of the foliation here is to the north- 
 east, having probably been twisted into parallelism with some line of 
 movement : a crush breccia is seen running with the foliation strike, but 
 it is not necessary to suppose a large throw. 
 
 The north to south fault that runs with the basalt through the " n " of 
 " Knowe," causes the foliation on its east side to twist into parallelism 
 with it for a considerable distance, for a breadth of 6 or 7 yards. Such 
 twists of strike are not common in this district, even near the faults 
 which effect a great displacement. The shift at the surface in this case 
 is about 110 yards, the west side to south. A little west of this fault is 
 another parallel fault, also accompanied with one or more basalt dykes. 
 This shifts the outcrop in the same direction but to a greater extent, 
 about J mile. These faults with their accompanying dykes both make 
 prominent gulleys through the crags, and give rise to the wildest bit of 
 scenery there is within a few miles of Dunoon. One-third of a mile 
 further west are two more faults which may unite before the top of the 
 green bed is reached : the sum of their displacements is rather more than 
 J mile, the west side again to south. We suppose all the faults mentioned 
 in this paragraph to unite in a south direction, and to be together in the 
 lower part of the bum J mile south-east of the "d " of " The Red Well." 
 South of this, the fault seems to pass along the west side of Corlarach 
 Hill, and runs up the burn on the west side of Toward Hill, in company 
 with various basalt dykes, shifting the Bull Rock greywacke nearly the 
 full width of its outcrop. In a north direction from the Giant's Knowe, 
 the faults cannot be traced well owing to the wide-spread covering of 
 drift. In the burn J mile W.S.W. of the "1" of "Glenkin" there is a 
 crush face, hading east and with horizontal slickens, which we suppose 
 -belongs to one of the more easterly faults. 
 
 One-quarter of a mile west of the first " B " of " Bodach Bochd " there is 
 a north-west fault, causing a shift hi the opposite direction to the faults 
 last mentioned. The displacement at the surface is about 200 yards. 
 This too is accompanied by a basalt dyke. The evidence for the throw is 
 best seen a little more than J mile W.N.W. of the " B " mentioned, where 
 there are on the north-east side of the basalt good sections of green beds, 
 
STRUCTURE OF DUNOOX DISTRICT. 
 
 173 
 
 and on the south-west side quartzose schists. We have not been able to 
 trace this fault in either direction. 
 
 The supposed shift in the green bed along an east to west fault about 
 half way between Tighnuilt and Invercholain is not actually seen, but there 
 are two strong, nearly east to west, crushes a little east of these localities, 
 one in the burn J mile E.N.E. of the " t " of " Tighnuilt," and another in 
 a burn, not in the 1-inch Map, a little on the south side of this burn. 
 These both hade south, and shift the margin of the south-east green bed, 
 the south side to the west. The com- 
 bined displacement is about 200 yards, 
 but this is in a direction diagonal to 
 the strike. Nearly J mile north-east 
 of Blar Buidhe there is a crush in the $ 
 
 line of these, and hading in the same *|^ 
 direction, in the course of a little burn ^ 
 not marked in the 1-inch Map. The 
 throw cannot be ascertained, but we 
 suppose it to be down south, in accor- 
 dance with the hade and the appear- 
 ances described on the west side of 
 the hill. 
 
 The N.N.W. fault that throws the 
 green beds on the south of Finbracken 
 Hill (174) is sometimes made up of 
 several branches, and the amount of 
 displacement due to each is not always 8 
 
 evident. The base line is shifted by '^ 
 the most easterly fault for about 260 ^^ 
 yards : this fault makes a crush 10 
 yards wide in the burn J mile west of 
 the " A " of " Ardnadam " : near where 
 this fault, going south, is made to join s 
 
 the next fault on the west, some phyl- *:| 
 lite and quartzose schist are seen in 
 the burn a little above the base line 
 taken. The movement has to some 
 extent been horizontal, for horizontal 
 slicken lines are seen in one of the 
 fault breccias in the burn \ mile 
 W.N.W. of Ordnance Station 697. 
 Another exposure of the same breccia 
 contains small strings and specks of 
 copper pyrites which have been partly 
 converted into the green carbonate. On "* 
 the south-east side of this compound j| 
 fault the green beds make a broad 
 spread. The boundaries of it are not 
 definite. No other rocks but green 
 
 beds are, however, seen on the west side of the Ardnadam 100-foot 
 beach, and there are several small rock islands in this beach which 
 consist of green beds, generally of a pebbly character. The area east 
 of the beach is drift covered for \ mile or more, and the nearest rock 
 exposures on this side consist of phyllite with alternations of more 
 quartzose schist, which show repeated folding along north-east to south- 
 west axes. We suppose that the green bed base cannot be traced north- 
 east along the foliation strike, owing to the gr^at number of folds by 
 
1/4 GEOLOGY OF COWAL. 
 
 which it is affected. The even run of the hornblende schist by the foot 
 of Loch Loskin seems to preclude the idea of there being any large fault 
 shifting the green beds. It is clear, too, that the top line of the green beds, 
 though not visible in section, must cross the foliation strike. There is 
 no feature on the hillside which could belong to a fault bounding the 
 green beds, and we conclude the appearances are due to a repetition of 
 small folds. The individual " v's " of the boundary drawn in the Map 
 are not seen on the ground, but they are inserted to indicate the style of 
 structure we suppose to exist, 
 
 The green beds are seen in the branches of the burn that run into 
 Loch Loskin. An east to west crush occurs in the west branch, and a 
 thin crush hading east is also seen in places in the east branch, running 
 near to, and parallel with, the basalt : but it is not clear how the boundaries 
 of the green beds are affected by these. Close to the east side of the 
 burn the green beds seem lost, and there is hardly room even for a 
 thin bed to run north-east as far as the edge of the peat at the head of 
 Loch Loskin. Nor could we see any further indication of green beds on 
 this horizon further north-east. We cannot say for certain, however, that 
 such do not occur, for the ground is largely obscured by drift and raised 
 beach deposits, and the coast near Hafton is destitute of rock exposures. 
 
 It is suggested that possibly this lower baud of green beds is really an 
 infold, along a synclinal, of the overlying band. If this is so, both margins 
 of it represent the same line, the presumed base line, and the beds on either 
 side of it are the same. But why then do not the hornblende schist 
 bands, which occur near the south-east margin for so long a way, also 
 get repeated near the north-west margin ? There is a band -of this schist 
 near the latter margin on either side of the burn that runs into Inverchao- 
 lain Burn between the " h " and the " a " of ' Inverchaolain," but it has 
 not been traced for a distance of \ mile. It appears too, from facts to 
 be shortly stated in connection with the green beds that come next to the 
 Dunoon phyllites, that the green beds may vary rapidly in thickness or 
 may die out altogether. 
 
 It is not possible to suppose the north-west green bed the same as the 
 band next the Dunoon phyllites, brought on again in the north-west limb 
 of an isoclinal anticline with both limbs dipping south-east, for in this 
 case the beds west of the north-west green bed would be the Dunoon 
 phyllites, and this they cannot be. There is a much greater proportion 
 of quartzose pebbly schist west of the north-west green bed (see, e.g., the 
 section in the burn on the south-west side of Bealach na Sreine) than in 
 the phyllite series, and also an absence of limestone. 
 
 The hornblende schist near the south-east margin of the lowest broad 
 green bed is represented by two bands on the west and north of Bishop's 
 Seat, but only one band, the lowest, is known west of the fault that 
 runs north to south through the " G " of " Giant." It should be noticed 
 that this schist does not appear to keep strictly to the same geological 
 horizon, being on the south-west side of Bodach Bochd well within the 
 green bed, while to the north-east it is at the top or some little way above 
 the top. Only one band is seen in the burn J mile north-east of the 
 Bishop's Seat, and this is only thin. It could not be traced east of the 
 burn. It is probable, however, that the folded hornblende schist near 
 Loch Loskin is on much the same horizon. This band is readily traceable 
 on the hillside by a succession of rocky knolls separated by peaty hollows 
 and flats, which have a general KN.W. direction. The shape of outcrop 
 at once suggests folding, particularly when it is known that in the area 
 east of the apex of apparent fold the band has kept approximately 
 parallel to the north-west margin of the Dunoon phyllites, and has there- 
 
STRUCTURE OF DUNOON DISTRICT. 
 
 175 
 
 fore a sill-like character. The north extremity of the band, north of the 
 burn that flows into Loch Loskin is, however, of such irregular shape 
 that we can hardly suppose the sill-like character is constant. No horn- 
 blende schist is seen where it 
 would be expected to cross the 
 above burn, but there is an 
 obscure area where it may cross. 
 The band is bare on the raised 
 beach at Hunter's Quay, and 
 makes a prominent ridge for 
 about 120 yards inland. 
 
 The exposure of hornblende 
 schist J mile north-east of the 
 Badd probably represents part of 
 the apex of fold seen in the band 
 1 mile N.N.E. of the Badd, this 
 portion being cut off and shifted 
 by the same fault as that which 
 shifts the green beds on the 
 north. The vein stuff of the 
 fault is seen in the burn at the 
 north end of the exposure, and 
 again at the south end : the hade 
 in both places is east. 
 
 In the shore section 250 yards 
 south of Hunter's Quay an 
 outcrop of hornblende schist 
 about 6 yards wide occurs. This 
 is a little north of the line taken 
 as the boundary of the Dunoon 
 phyllites. East of high-water 
 mark it meets a small north to 
 south fault, which advances the 
 east side about 2 yards to the 
 north. Just south of the outcrop 
 there seems a small folded inlier 
 of it. In the old cliff of the 
 raised beach we could see noth- 
 ing of the bed. In the wood 
 J mile south of the " n " of 
 "Loskin" another exposure of 
 similar rock occurs among pebbly 
 schists : the thickness cannot ex- 
 ceed 10 feet: the horizon seems 
 much the same as that of the 
 band south of Hunter's Quay. 
 Near the top of the Horse Seat 
 (183) there is also another ex- 
 posure on the same horizon. 
 
 The green bed on the north 
 side of Brackleymore may perhaps 
 be regarded as a folded outlier of 
 the band on the south-east. It is 
 not seen on the sea-shore, but there is a section along the old cliff of the 
 20-foot beach. The band on the south-east certainly advances its margin 
 nearer to the north-west band the nearer the shore is approached, 
 
176 GEOLOGY OF COWAL. 
 
 presumably by a succession of small folds, and the interval still remaining 
 between the two bands on the shore is partly occupied by thin bands of 
 green beds, which may well represent limbs of further folds. On the 
 shore, 40 or 50 yards north of the north-west margin of the north-west 
 green bed, another thin outcrop of green beds occurs. This is not shown 
 on the map. 
 
 The area coloured as green beds between Brackleymore and the south- 
 east slope of Kilmarnock Hill is about 1 mile in breadth across the strike 
 of foliation. This great breadth is no doubt mainly due to folding along 
 axes agreeing roughly with the foliation strike. Bands of green, grey, and 
 black phyllite, like those of the Dunoon series, occur along the shore be- 
 tween outcrops of green beds, and run for some distance up the hill north- 
 east. These we suppose to represent infolds of the Dunoon series lying 
 on the green beds, and we cannot take the original thickness of the latter 
 to be even so great as that of the north band of green beds between the 
 school and Brackleymore. Though the phyllite is gradually lost as we 
 ascend the hill it is more likely they are resting on the green beds than 
 under them. The latter supposition would imply that the longer limbs 
 of the pre-anticline folds in this locality were the north-west limbs, whereas 
 in the coast sections on the south-east side of " the anticline " the south- 
 east limbs are the longest almost universally (see p. 1 3). The " v " 
 shape of the detached phyllite areas is not actually seen on the ground ; 
 we can only say that as we go up hill to the north-east their breadths 
 become gradually less, or split up by bands of other rock. These other rocks 
 are not always green beds : sometimes they are massive pebbly quartzose 
 schists, like some seen between the phyllite and the green beds on the 
 south side of Kilmarnock Hill. It is therefore probable that they 
 represent a zone between the phyllites and the green beds, and should 
 strictly have been separated from both. But the ground did not show 
 sufficient rock exposures to enable us to separate them with satisfaction. 
 To the north-east this intermediate zone seems to die out, or almost so : 
 this is seen in Ardyne Burn f mile south-west of the " C " of " Corlarach," 
 and by the " D " of " DUNOON " -(parish). 
 
 A traverse across the foliation strike, over the top of Blar Buidhe 
 shows, as far as observed, no schist other than green beds. A little 
 east of this hill a band of hornblende schist can be traced running 
 almost at right angles to the foliation. This hornblende schist seems 
 to occur approximately along the junction of the green beds with the 
 underlying rocks, at the apex of the same fold as that which affects the 
 hornblende schist of the Badd, etc. To the N.N.E. of this schist the 
 green beds seem gradually to thin away, and we suppose them to fold out 
 along the same axes as those which affect the phyllite areas west of 
 Kilmarnock Hill, and the green beds by Ardnadam. 
 
 There are good exposures of the green beds in the burns south of the 
 Badd, but the hillsides adjacent are obscure and do not allow us to fix 
 rock boundaries with confidence. We suppose there is a good deal of 
 folding, and also a fault which, east of the Horse Seat, cuts out part of 
 the folded green beds and brings beds which are below the green beds against 
 the Dunoon phyllites on the east. The little burn east of the Horse Seat 
 is mostly in drift : the only rock seen, near the head of it, is black phyllite. 
 If it had not been for this, we could have supposed a connection between 
 the green beds on either side of Horse Seat. The supposed fault is 
 nowhere seen in section, but there is a N.N.W. running feature, facing 
 east, on the east side of the Horse Seat, which may be caused by it. 
 The fault on the east side of this fault is seen distinctly in the burn ^ mile 
 south-east of the Badd, and again in the burn between the " D " and the 
 
STRUCTURE OF DUNOON DISTRICT. 177 
 
 " U " of "DUNOON " (parish) : in the first place there is a crush with 
 quartz, ferriferous carbonate and specks of copper pyrites, and a subor- 
 dinate breccia, hading east, some SO yards on the north-east, and various 
 parallel strings of ferriferous carbonate, by which the adjacent green beds 
 have been stained an ochreous colour : in the last place the fault is in 
 two parts, both of which hade east. 
 
 The green beds are seen well in the burn f mile slightly north of east 
 of the Badd, but are mixed with a quartzose pebbly schist in one part. 
 The next section to the north-east is that at the head of the burn near the 
 * " of " Tom Odhar," where the breadth of the zone is less than it is 
 south-west, and there is also a considerable admixture of phyllite. Still 
 further north-east the zone continues to decrease in breadth. In the 
 burn going through the word " Dunloskin " it occurs in many different 
 bands, belonging apparently to different limbs of folds, and the thickness 
 in the east exposures is not more than a few yards. We saw no green 
 beds on this horizon between this burn and the Clyde. There is an 
 almost continuous rock section between Hunter's Quay and Kirn, and no 
 genuine green bed is seen. In the want of one we are left in a little doubt 
 as to the best line to take for the north-west margin of the phyllites, for 
 there is no sharp change from this series to the rocks on the north-west. 
 No doubt this want of definition would have been felt in the area to the 
 south-west had it not been for the opportune occurrence of the green beds 
 on approximately the best line between the more phyllitic and the more 
 quartzose zones. It was considered allowable therefore to adopt them as 
 the boundary without further scruple. 
 
 The two hornblende schist outcrops within the green beds area on 
 Kilmarnock Hill (194) form prominent hillocks. The hornblende is rather 
 darker in macroscopic aspect than is usually the case on the south side of 
 " the anticline." About J mile south of the hilltop, close by the boundary 
 of the phyllites, a third outcrop of such schist occurs : the thickness and 
 boundaries of this could not be determined. 
 
 The section of the Dunoon phyllite series on the coast south of Dunoon 
 and the structures to be observed in it are fully described on pp. 9-18. 
 There are on either side of this phyllite series, through most of the area, 
 well characterised bands of schist, a green bed on the north-west and the 
 Bull Rock greywacke schist on the south east. The opposed margins of 
 these beds can be mapped with comparative ease, and include between 
 them the schists which we have called, as a group, the Dunoou phyllite 
 series. On the coast south of Hunter's Quay there is, as just said, no 
 green bed to define the north-west margin of the series, and we feel in 
 doubt as to where the edge of it should be taken : the Hue could not 
 well, however, be made to diverge more than 20 to 30 yards from that 
 adopted. Fortunately this is the only clear section wherein this green 
 bed fails us (see p. 31). 
 
 There are several north-east running crushes in Ardyne Burn from 150 
 to 250 yards north of the " A " of " Ardyne " : we suppose these to be the 
 same as those seen about 1 mile N.N.E. of here, one at the east side of 
 Ardyne Burn, and the other crossing the burn that flows past Corlarach. 
 There are two prominent features facing north-west on the north-west side 
 of Corlarach Hill. These probably represent the fault lines seen in the 
 burn north-east of here, between the "D" and"U" of "DUNOON" 
 (parish), and already mentioned on this page : the north-west one probably 
 runs on to one of those in Ardyne Burn ; the south-east one we have 
 drawn south to join the fault which shifts the south-east margin of the 
 phyllite series on the west of Toward Hill. 
 
 The fault that shifts the south-east margin of the phyllite series on the 
 
 M 
 
178 GEOLOGY OF COWAL. 
 
 south of Dunoon runs along a hollow in the hills west of Ardhallow. 
 The schists in the burn are mainly phyllites, often stained with haematite 
 and crushed, and intersected with many basalt dykes which seem 
 to converge as they approach the main fault. To the north the fault 
 makes a prominent feature facing west, as long as it has the Bull Rock 
 greywacke on its east side, and the exposures of greywacke near it are 
 sometimes stained with haematite. Further north still, the direction 
 becomes doubtful : close to the foot of Glen Morag Burn there are a few 
 thin crushes, and we have carried the line on doubtfully to join these. 
 
 The character of the Bull Rock greywacke is described elsewhere, p. 
 15. Its outcrops are distinct on either side of the Ardhallow fault, 
 forming more craggy ground than the phyllites. This difference prevails 
 generally, but it is not so marked as one would have expected, and 
 between Beinn Ruadh and the crags near Tor Aluinn is hardly noticed. 
 On the east side of the raised beaches near the foot of Ardyne Burn the 
 band is almost covered with boulder clay for a length of J mile along 
 the strike, but on the west of the burn it appears again in four small 
 island-like exposures within the gravel area. In three of these it has 
 been quarried. The shore at Ardyne Point, where the greywacke should 
 occur, is covered with gravel. 
 
 This bed makes one of the best building stones of the district, and 
 there is a large quarry in it, a little north of the Bull Rock, which provides 
 most of the Dunoon building material. In the quarry a good many 
 quartz veins occur, and, on looking over some of the loose blocks derived 
 from these, we noticed many small specks of copper pyrites, iron glance, 
 chalybite, and small pyramidal crystals of quartz. 
 
 The fault between Toward Hill and Beinn Ruadh seems to effect a 
 surface displacement in the base of the Bull Rock greywacke of about J 
 mile, the south side to west. The fault cannot be traced with confidence 
 in either direction. One-third of a mile slightly west of north of the " B " 
 of " Beinn Ruadh " there is a north to south bank feature facing east, 
 which we suppose due to it. The feature can be followed north for about 
 3- mile. . 
 
 The N.N.W. fault drawn a little over J mile south-west of Garrowchoran 
 Hill is not established with certainty. The only evidence for it occurs 
 near the north-west margin of the bed. Here a north-west basalt 
 dyke has some breadth of massive pebbly schist on the north-east side, 
 striking north-west of some phyllite exposures on the south-west side. 
 But these exposures are not extensive and possibly they are due to 
 phyllites folded within the greywacke area. 
 
 Between the Bull Rock greywacke and the serpentine no schists have 
 been mapped out of the general mass for more than a short distance. The 
 craggy east face of the Tom near Inellan is formed by a massive pebbly 
 schist, with pebbles chiefly of quartz and white felspar. This schist is 
 bounded on the west by black and purple phyllites, which were formerly 
 quarried for roofing slates. The line between these rocks is drawn on 
 the map for a short distance : on the north side of the Tom phyllites 
 appear to strike against the pebbly rock, but whether this is owing to 
 folding or some fault we are unable to say. 
 
 The high band of phyllite marked in the burn north of the " a " of 
 " Chapelton " was formerly extensively worked for rooting slates in a 
 quarry on the east of the burn. The colour is purple or green. The low 
 band is purple or black. 
 
 The serpentine and the schists close to it, and the schist-boundary 
 fault are described already (pp. 72-74, 95). So also (p. 30) are the peculiar 
 gritty phyllite beds which are seen in places a little north-west of this fault. 
 
STRUCTURE OF BLAIRMORE DISTRICT. 
 
 Three changes of direction of the broad east to west basalt dyke have 
 been suggested in this area, where this dyke meets with north or north- 
 west faults : viz., on the east of Ihverchaolain Burn, in the burn south- 
 west of Bodach Bochd, and on the west side of Kilbride Hill. The last 
 locality is much obscured by boulder clay, and all we can say is, that, 
 if the dyke exists at the surface, its course on the south-west side of 
 the fault must be considerably south of its course on the east side of the 
 fault. In the Bodach Bochd locality, the dyke is seen within 80 yards 
 of the burn on the west side, and 200 yards on the east side, and the 
 exposure on this east side is so much north of that on the other that the 
 dyke must either change its direction approximately along the burn and 
 fault course, or else cease to come to the surface in the intervening area. 
 The basalts actually seen in the burn are of different characters to the 
 east to west broad dyke, but it is possible that under the drift at the sides 
 of the burn the latter may also occur. On the east of Inverchaolain 
 burn the south end of the changed path is seen distinctly. 
 
 District of Blairmore. 
 
 This district is inclosed by Loch Long, the Holy Loch, the Loch Eck 
 valley, and the north margin of 1-iuch Map 29. 
 
 As far as known, all the schists, with the exception of some hornblende 
 schists, belong to the group of alternating schistose grits, phyllites, and 
 albite schists, which occurs between " the anticline " and the " green 
 beds " on the south-east side of " the anticline." The schists mapped out 
 are, the south-east portion of a massive greywacke horizon on the east of 
 Loch Eck, a band of coarse pebbly schist on Blairmore hill, the series 
 of thin hornblende schists which strike across Stronchullin hill, and a 
 broader hornblende schist near Blairmore. 
 
 The schistose greywacke near Loch Eck is part of a zone which has 
 been traced a considerable distance to the south-west. The schists on its 
 south-east side are more thinly flaggy, more micaceous and less pebbly 
 than it. The margins are not sharp lines, but a certain breadth of rock 
 has to be traversed before we can see that most of the schists on one 
 side differ from those on the other in the characters mentioned. 
 
 The greywacke is crossed, at a distance of about J mile from Loch Eck, 
 by a north to south fault. This advances the margin of the band on its 
 east side about J mile to the north : to the south the fault forms a con- 
 spicuous slack just before it reaches the superficial deposits of the valley ; 
 to the north, outside the area being described, it also forms a slack at 
 intervals for about 1J mile, and two basalts occur along with it in one 
 place. 
 
 The Blairmore Hill pebbly schist has a quartzose matrix : this eon- 
 tains pebbles both of quartz and felspar (generally white), and there are 
 also lumps, 2 or 3 inches long at times, of grey, compact, creamy- 
 weathering felstone or hornstone-like rock, which form hollows on the 
 weathered rock faces. These lumps are crossed by the foliation planes 
 of the matrix. There is an outcrop, almost entirely of pebbly rock, for 
 a breadth of at least 100 yards. The north-west margin is definite, and 
 has been mapped : the south-east side has not been examined with 
 much care. 
 
 Two north-east faults traverse the hill, and both advance the south- 
 east side towards the north-west. The crushes belonging to the west 
 fault occur in different bands, occupying in all a breadth of about 
 12 yards, and hade south-east : they effect together a shift of about 150 
 yards. The breccia of the east fault is about 6 feet wide. 
 
180 
 
 GEOLOGY OF COWAL. 
 
 The Stronchullin Hill hornblende schists are best seen in the crags on 
 the E.KE. side of the hill. None are observed on the sea-coast, the area 
 where they would be expected being all covered with superficial deposits. 
 There are at least five bands, all of much the same type : the hornblende 
 is represented by shreds of pale green fibrous actinolite, and the felspar 
 by saussurite : abundant specks of ferriferous carbonate also occur. They 
 can hardly be distinguished from the schists around except on hammering, 
 
 and it is probable that there are 
 other bands, besides those mapped, 
 which have escaped notice. Perhaps 
 the thickest outcrop is that in the 
 little burn f mile E.KE. of the hill 
 top. This is about 25 yards wide. 
 A fault vein runs along the burn 
 course across the outcrop, and shifts 
 the east side 10 yards to the north : 
 the vein is 2 feet wide and hades 
 east. 
 
 The hilltop is too obscure to allow 
 the bands to be traced continuously, 
 but on the south-west slope several 
 are seen again. The most southerly 
 band is affected by two or three 
 faults near the little bum J mile 
 south-west of the hilltop : it is very 
 full of carbonate specks, some as 
 large as a pea, and these give a 
 slaggy aspect to the weathered rock. 
 Between the basalt dykes f mile 
 south-west of Stronchullin Hill, 
 there are at least three outcrops of 
 the rock, but in the Map these have 
 been generalised as two. The most 
 southerly one is 10 feet thick. 
 
 The east margin of the Blairmore 
 hornblende schist makes some crags 
 facing east, which form a conspicuous 
 contrast with the rest of the hill-side. 
 The west margin is probably nearly 
 coterminous with the inland edge of 
 a flattish area, which is overlooked 
 by a feature with abundant exposures 
 of thin flaggy mica schist and pebbly 
 schist. Perhaps the feature is due to 
 some small crush line. The greater 
 length of the outcrop trends N.N.W., 
 at right angles to the strike of folia- 
 tion. The bed is probably of sill-like 
 character, with its greater length lying along the arch of an anticline 
 into which it has been folded. It is not seen well in the limbs of the 
 supposed fold : perhaps this is due to the pulling out and thinning which 
 these received during the folding. There is, however, an exposure, much 
 veined and decomposed, on the shore, nearly J mile north of Blairmore 
 Pier, and this continues into the cliff at the back of the raised beach. The 
 bed is not seen on the shore south of the pier, but there is room for it. 
 The rock is generally rather more massive in character than those of 
 
STRUCTURE OF GLEN MASSAN DISTRICT. 1S1 
 
 Stronchullin Hill, and the grain coarser : the hornblende shreads some- 
 times attain a breadth of -$ inch. Supposing the physical structure 
 is as we have suggested, the hornblende schist should, if it continued, 
 reappear again further north-west, in confimiity with the ordinary rule 
 of " pre-auticline " folding (see p. 13). As a fact, no such schist is known 
 to the north-west until we reach Stronchullin Hill. 
 
 The chief faults observed in the area run in a north or N.N.E. 
 direction, and are doubtless continuations of those on the south-west side 
 of the Holy Loch. Four of them have been described already, and it may 
 have been noticed that they all advance the beds on their east sides 
 towards the north : they downthrow therefore to the east. Apart from 
 the evidence afforded by the schists, we often obtain great help in esti- 
 mating the throws of faults in this district by their effect on the 
 lamprophyre sheets : there are some good instances of this close by the 
 north margin of the Map. The faults can also frequently be traced by 
 the features they make on the hill. The crush rock is generally softer 
 than the uncrushed, and yields more readily to denudation, so that it has 
 a habit of forming gulleys in streams, and slacks or terrace shapes on 
 hillsides. 
 
 The crush that trends north from near Finnartbeg is seen well in the 
 burn between Finnartbeg and Cnoc a Mhadaidh. A little before it reaches 
 the basalt dyke it is in all about 10 yards wide : the dykes coming into it 
 twist out of their ordinary course and keep along it for some distance. 
 These basalts a little on the north-east of Cnoc a Mhadaidh are themselves 
 crushed, and so the fault movement must be of two ages, one before 
 and one after the basalt intrusion. 
 
 The north and south features, facing west, which run north from the 
 Holy Loch a little on the east side of Finnartmore are no doubt due to 
 crush breccias. These uuite in the burn due east of the " n " of " Kilmun 
 Hill," and breccias, hading east, are seen in the burn below this point in 
 several places. Further north still, the continuation of the crush is cut 
 on the north side of Blairmore Burn in two places, by levels driven in 
 search of lead ore. These trials, and a third one in a different crush on 
 the north side of Cnoc a Mhadaidh, are mentioned further on (p. 287). On 
 the east side of the features, near Finnartmore, there are others at intervals 
 all the way to Loch Long, but these are not so prominent and only one 
 has been engraved in the Map. 
 
 The best coast section is that on Loch Long from about ^ mile north 
 of Gairletter Point to about J mile south of Ardentinny. This is described 
 on pp. 18-22. Other good sections occur, at Strone Point, in much 
 folded alternations of micaceous and more quartzose thinly foliated schists ; 
 in Blairmore Burn ; and in Stronchullin Burn, for nearly 1 mile above 
 Strouchullin. Both these burns run almost at right angles to the folia- 
 tion, and show repeated folds of the schists, with a steady foliation which 
 runs approximately parallel to the axes of fold. In parts nearer " the 
 anticline," many of the hillsides Creag Liath and the adjoining side 
 of Loch Eck particularly show good sections. 
 
 District of Glen Massan. 
 
 This district is enclosed by the Loch Eck valley, Glen Lean, the lower 
 part of Glen Tarsan, Glen Laoigh, and the north margin of 1-inch Map 29. 
 
 With the exception of a hornblende schist on the south side of Coire 
 Athaich, all the schists appear to belong to the group of schistose grits, 
 phyliites, and albite schists which occur at or near "the anticline." The 
 bands mapped are the hornblende schist, an horizon of greywacke which 
 
182 GEOLOGY OF COWAL. 
 
 runs across Sgarach Mor, and one or two other greywacke bands on 
 the north-west side of Glen Tarsan. 
 
 The schistose greywackes on the north-west side of Glen Tarsan are 
 on the north-west side of " the anticline," and the Sgarach Mor bed on 
 the south-east side, but, for the reasons stated elsewhere (p. 86), it is 
 not believed that they represent one another. The interval between 
 the two subdivisions of the bed on the north-west side is but little, and 
 perhaps it does not run so continuously as shown on the Map. It con- 
 sists of very thinly foliated mica schists, and is best seen on the north and 
 north-east sides of Balliemore, within j mile of this place ; an interval 
 is seen again close by the north margin of the Map. The north-west 
 margin of the north-west greywacke is the most definite of the lines bound- 
 ing these two beds. Just on the east side of Glen Laoigh this margin 
 appears thrown along the line of a basalt band which is compounded of 
 more than one intrusion. The amount of displacement cannot be estimated 
 accurately, as the ground is covered with drift for a little distance on either 
 side. The Sgarach Mor bed is not well defined near the head of Coire 
 Athaich, and lines have not been drawn for its margins here. The 
 obscurity may be partly due to folds through which the margins cannot be 
 traced, owing to lack of clear definition, and partly to the numerous 
 faults which break through the outcrops of the lamprophyre sheet on 
 the south-east side of Glen Tarsan, etc. Within the bed, and generally 
 rather nearer the south-east margin than the north-west, there is some 
 breadth of thinner more micaceous schist. This is seen on the north-east 
 side of the Eiver Massan ; it occurs in two bands, each about 50 yards 
 broad, and separated by the same width of more massive pebbly rock. 
 On the south-west side of Glenmassan, near Stonefield, a north running 
 basalt crosses the band, and, judging from the outcrops at the sides of 
 the alluvium, it must be accompanied with a considerable amount of dis- 
 placement, the west side towards the north. This fault seems to divide 
 into two parts on the north-east side of the glen, the basalt continuing 
 with the west part. The east part is quite distinct just outside the north 
 margin of the area being described, throwing a lamprophyre sheet about 
 120 feet down to the north. On the south side of the greywacke, the 
 fault shifts the Coire Athaich hornblende schist for about 100 yards 
 along the ground surface, and, after this, makes a conspicuous slack on the 
 hill. We could not see it crossing Eas Mor, but we suppose it may 
 continue across both this and the Glen Lean burn (probably near 
 Clachaig, where the course of the burn is through drift and alluvium) 
 and join the fault crossing the west side of the Bishop's Seat. 
 
 On the west side of A' Chreachau there are other north and south 
 basalts traversing the bed and accompanied with fault crushes. The crushes 
 are at least several feet wide in some places ; the east side appears to 
 be somewhat advanced to the north, as before. These crushes are not 
 seen in Coire Athaich Burn, but there is a space in which no rock is 
 seen, and we have carried the line on through this to a north to south 
 gap in the crags of Creag Capull. This gap contains a series of basalt 
 dykes; the presence of such a series all running out of their ordinary 
 course of itself affords a strong presumption that they are taking advan- 
 tage of some previously existing line of weakness ; and besides this, a 
 crush breccia, about 1 foot wide, is seen just on the east side of the gap. 
 There is room for more crushes on the west side also. On the north side 
 of Glenmassan the same crushes are seen again in the burn that goes 
 through the " 1 " of " Glen." At a distance of J mile from the burn-foot 
 a thin basalt dyke is seen running with the fault, and this is shortly 
 afterwards joined by another dyke coming in from the south-east. Forty 
 
STRUCTURE OF COLINTRAIVE DISTRICT. 183 
 
 yards above this a lamprophyre dyke comes in from the same direction ; 
 this is not seen on the other side of the burn, and is no doubt faulted. 
 The dyke mapped on the north-west side is a portion of the basalt. Another 
 portion of it contiuues up the stream a little further, but in a very crushed 
 state. 
 
 About J mile slightly north of east of Glen Lean the south-east margin 
 of the greywacke is perhaps folded. It is not actually seen to be so, but 
 the pebbly schist in a small stream not marked in the Map seems to strike 
 against the thinner foliated more micaceous rocks in the burn a little 
 to the north. 
 
 The section in the burn J mile north of Glenmassan shows one^orltwo 
 north running basalts accompanied with a crush. West of these are 
 several thin lamprophyre sheets, generalised as one in the Map, and on 
 the east a single broader sheet at a slightly lower level. These are 
 clearly shifted by the fault movement. 
 
 The hornblende schist in Coire Athaich shows an apparent thickness of 
 from 12 to 20 feet. It is so full of ferriferous carbonate that it has the 
 aspect of a limestone. The Stonefield north to south fault displaces it as 
 already described. A little on the east side of this another north to south 
 fault displaces it again in a similar way, but only for a distance of about 
 10 yards. It is probable that this fault also is a part of the Stonefield 
 fault. No trace of the bed was seen in the burn on the north-east side 
 of Clachaig hill. 
 
 Apart from the faults already mentioned, it may^be well to call attention 
 to the two or three X.N.E. faults in the area between Glen Tarsan 
 and Glen Laoigh. The throws of these do not appear to be large, but 
 they may form prominent features, and represent the south termina- 
 tions of a set of faults which have been traced a great distance to the 
 north-east. The great Tyndrum fault is one of the set. In Sheet 37 
 there are indications that part of the movement along these is of earlier 
 date than some of the lamprophyres. 
 
 The little bit of coast line in this area shows hardly any rock exposure. 
 A great part of the burn courses of the larger glens are also covered 
 with superficial deposits. The slopes of A J Chruach, A' Chreachan, and 
 Sgarach Mor show excellent rock exposures. 
 
 District of Colintraive. 
 
 This district is enclosed by Glendaruel, Loch Riddon, the east Kyle of 
 Bute, Loch Striven, Glen Laoigh, and the north margin of 1-inch Map 
 29. 
 
 The schists in this area extend from the " green beds " on the north- 
 west side of " the anticline" to the " green beds " on the south-east side, 
 and include some hornblende schists. 
 
 Two bands of the last-mentioned rock occur at the north end of the 
 area. The base of the lowest of them runs about J mile north-west of 
 the base of the green beds, and is apparently on a considerably lower 
 horizon than any other hornblende schist which occurs in 1-inch Map 29 
 on the north-west of the anticline. A W.N.W. fault, accompanied 
 with a basalt dyke, traverses these on the south-east side of Cruach 
 Conchra, and advances their outcrops on the south-west side towards the 
 north-west. The advance in the case of the lower band is about 120 
 yards. Smaller shifts also occur along the basalts dykes J mile north of 
 Cruach Conchra. On the south-west side of Cruach Mhor a wide peat 
 moss covers the hilltop, and neither band was seen on the far side of this. 
 
 In the Map it will be seen that a little north-west of the base of the 
 
184 
 
 GEOLOGY OF COWA1. 
 
 green beds various other lines, running roughly parallel to it, have been 
 engraved but not coloured. These were drawn in an attempt to separate 
 out, one by one, those beds which had the characteristic green-bed 
 character from those which had not. The attempt had to be left incom- 
 plete owing to the amount of time required. As a fact, it is probable that 
 hardly half the beds included in the green beds zone on the north-west 
 
 side of the anticline are typical 
 green beds, the rest being grey 
 quartzose pebbly beds and more 
 micaceous thinly foliated schists. 
 Below the basement green bed 
 mapped near Lephinkill there is, 
 in the feature on the north-east 
 side of the fault by the " h" of 
 " Lephinkill," another outcrop of 
 a similar character, but it is only 
 2 feet thick and is not shown in 
 the Map. Such bands may be 
 infolds of the higher lying bed, 
 but it has not been possible to 
 make this out with certainty in 
 any case. The mapped base is 
 distinct almost continuously from 
 Lephinkill to a little north-east 
 of Cnocan Sgeir, and by its help 
 many faults have been picked out 
 eight in all. Some of these 
 throw in one direction and some 
 in the other, and taken together 
 they almost compensate for one 
 another. The general direction 
 is north-west. The fault nearest 
 Lephinkill is indicated by a pro- 
 minent N.N.W. feature, facing 
 west, which passes through the 
 "h" of "Lephinkill." The 
 amount of shift at the surface is 
 about 80 yards, the west side to 
 the south. The fault next this 
 is the largest of the series men- 
 tioned. It passes | mile south- 
 west of Cruach nam Mult. The 
 basement green bed is very 
 distinct on the north-east side, 
 at a place about ^ mile slightly 
 east of south of the Ordnance 
 Station 1009. On the south- 
 west side it is not so distinct, 
 but it is probable that the amount of shift is about J mile, the south-west 
 side to the north-west. This fault is nowhere seen in section. One-half 
 mile S.S.W. of the Cruach there is an east to west feature which we sup- 
 pose to mark its course for a little way. A basalt dyke runs at the base 
 of the feature, and the schist on its south side is in one place striking 
 nearly parallel with it, with a dip to the north. On the east side of the 
 burn that passes by the last " n " of " Auchnagarran " there is another 
 feature, facing south-west, which may be due to the fault. The amount 
 
STRUCTURE OF COLINTRAIVE DISTRICT. 185 
 
 of shift in the top of the greywacke horizon cannot he made out satis- 
 factorily. The next largest of this set of faults is the fault that passes 
 mile east of Cnocan Sgeir. It is accompanied by one or two porphyritic 
 basalt dykes. The basement green bed is seen near both sides of the 
 fault. The amount of surface displacement is a little over J mile the 
 south-west side to the south-east. It is clear that there must be a shift in 
 the same direction in the top of the greywacke horizon on the east side of 
 Tamhnich Burn, for between the " n " and the last " h " of " Tauihnich " 
 there are good sections of the thinly fissile phyllitic mica schists that 
 come over the greywacke, while the schist exposures striking at them, on 
 the east side of the burn, are nearly all massive, often pebbly, schists. 
 Probably the fault runs along an obscure feature about J mile north-east 
 of the "n"of "Tamhnich." 
 
 At the sides of Tamhnich Burn the basement green bed is hidden by 
 boulder clay, but it is shown in the stream itself. About J mile south- 
 west of An Socach it is crossed by a broad zone of basalt and crush rock 
 (seen best in the two burns north-west of Balliemore), which seem to 
 cause some shift ill it, the north-east side towards the north-west, the 
 same direction as is indicated by the top of the greywacke zone to the 
 south-east. Some 300 or 400 yards on the north-east side of the slack one 
 of the best exposures of green beds in the district occurs, sticking up in a 
 prominent hillock. 
 
 Good sections of typical green beds, alternating with other schist, occur 
 in most of the burns that fall into the Ruel from the east side above 
 Lephinkill ; perhaps the one in the burn passing by the " O " of 
 " KILMODAN " may be specially mentioned. 
 
 As elsewhere stated (p. 149), the green beds have their colour changed 
 into dark grey or black near basalt dykes for a distance of a foot or more. 
 This is seen near the foot of Auchateggan Burn, and in a burn J mile 
 N.N.W. of Cnocan Sgeir. 
 
 On the south-east side of these green beds there is a breadth of about 
 | mile which consists largely of thinly foliated micaceous albite schists ; 
 but within this is a band of massive quartzose pebbly greywacke which 
 has been mapped where possible. This is seen in a crag J mile north- 
 east of the " k " of " Dalleik." In the crag it seems about 20 feet thick, 
 and a little way below is another similar outcrop which may be the upper 
 band repeated by folding. The direction of stretching in the crag is about 
 20 north of the direction of dip of the foliation. Some of the felspar 
 pebbles are pulled out in this direction for a length of If inch, and crossed 
 at right angles to the length by four or five cracks (sometimes -j inch broad) 
 which are filled with granulitic quartz. A band which is presumably the 
 same is seen again in the crags J mile N.N.W. of Cruach nan Cuilean. 
 
 A little below the above pebbly band we come to a broad zone of schistose 
 greywacke, the top of which is moderately definite, and has been mapped. 
 This zone extends south-east across the strike, at least as far as the 
 " ch " of " Auchenbreck " and the " d " of " Craigendaive," but the ground 
 is too obscure to permit of drawing a base line with any confidence. The 
 fault in Tamhnich Burn is seen distinctly in the stream bed ; the hade is 
 west ; the horizonal shift at the ground surface seems about 50 yards. 
 The two larger faults on either side of the burn are not seen in section, 
 but are continuations of breaks which are distinct in the green beds base. 
 
 The grej' wacke horizons on the north side of Fearna Bagh, and ou the south- 
 west side of Dun Mor, are no doubt the same, but they have not been joined 
 to one another, as there is an area near Cuoc Breamanach where the marginal 
 lines are unusually indefinite. Perhaps this is due to folding, but the folds 
 could not be traced out. The Fearna Bagh greywacke is on the south-east 
 
186 GEOLOGY OF COWAL. 
 
 side of the anticline of foliation, while the greywacke above Auchenbreck 
 and Craigendaive is on the north-west side. They might hence be supposed 
 to be the same, but for reasons elsewhere mentioned (p. 86), we do not 
 think they are. Even on the supposition that the foliation agreed with 
 bedding, which of course is frequently not the case, there would be a 
 difficulty in supposing these horizons the same, as a greater thickness of 
 thin micaceous schist is seen (e.g., on Dun Mor) below the south-east grey- 
 wacke, dipping south-east, than there is dipping north-west below the 
 north-west greywacke. Near the centre of the Fearna Bagh bed there is 
 some thickness of thinner more micaceous schist ; this is seen well in the 
 Fearna Bagh section. On the north side of the 100-foot beach, inland 
 from this bay, the south-east margin of the bed is unusually indefinite. 
 The appearances may well be due to folding. 
 
 The fault crossing the greywacke J mile west of Cnoc Breamanach 
 seems to shift the north-west margin of the bed about 60 yards, the east 
 side being advanced to the north. The crush is seen by the side of the 
 most westerly basalt dyke, about \ mile south of the last "11" of " Allt 
 a' Chapuill." The crush rock is hardened and altered by the basalt; 
 the basalt itself shows no sign of crushing. We have continued this 
 fault south along a feature facing west, and this leads to a place where 
 the broad east to west basalt dyke becomes much thinner, or even dies out 
 for a certain space, and changes its direction so as to run along the 
 supposed fault line. We suppose the dyke to have come up along this 
 previously existing line in much less volume than usual, owing to the 
 line being so different in direction to its normal course (see p. 144). 
 Some other basalts, probably of later date than this east to west one, have 
 also come up along the same line a little south of this locality. 
 
 The fault that crosses the greywacke at the head of Allt Glac na maill 
 makes a strong hematite-stained breccia, occasionally accompanied by 
 basalt, nearly continuously in the west branch of Milton burn between 
 the "n" of "burn" and the "h" of "Breamanach." 
 
 One-quarter of a mile south-west of the top of Coraddie the broad 
 basalt changes its direction sharply. A fa ult is supposed to accompany 
 it in the changed path. No crush is actually seen, but the changed path is 
 in the same line as a powerful crush in the burn north of Lochan na Leirg 
 which can be traced up to this place by a prominent feature. The dyke 
 is seen in the changed path, but in a thinner form ; it is not faulted nor 
 unusually crushed. 
 
 In the locality J mile north-east of Beinn Bhreac the east to west 
 dyke is only seen in the north part of the changed path. It is more 
 crushed than the later north-west dykes that intersect it, but is by no 
 means a train of crushed pieces dragged out along a fault of date sub- 
 sequent to the intrusion. The intrusion has originally had a nearly 
 north and south direction. In the burn to the north the crushing 
 affects some of the later dykes also, and throws some lamprophyre sheets 
 on the west of the burn. 
 
 On the west side of Loch Striven, about J mile north-west of Ardbeg, a 
 massive coarsely pebbly bed is seen, and is shown in the Map up 
 the hill to the north-west for a little distance. The appearances in 
 nature are much more complicated than would be judged from the 
 Map, but the small scale compels us to generalise. As a fact, there are no 
 fewer than three outcrops of this schist in the coast section. The most 
 northerly is clearly along the crest of an anticlinal, and, though it is 5 or 
 6 yards wide at the sea level, it thins out to 1 yard in a distance of 20 
 feet above this. On the south side of this north portion it is seen clearly 
 how the first foliation which elongates the pebbles, though folded, is still 
 
STRUCTURE OF COLINTRAIVE DISTRICT. 187 
 
 constantly crossing the original bedding. Just on the south-east of the 
 burn which runs from Lochan na Leirg various pebbly schists come on 
 the south-east side of the mapped baud, and these may be repetitions of 
 the same bed. In the burn itself there are various basalt dykes, and 
 crushes running with them, and these shift the pebbly bands somewhat, 
 the west side towards the north. On the north-west side of the burn two 
 pebbly bands are seen ; the south-east one is the broadest and as coarsely 
 pebbly in some portions as the north-west one. But suddenly at a point 
 170 yards west of the burn the south-east band in replaced, presumably 
 owing to folding, by thinly foliated very micaceous schists. And so it 
 seems probable that this band is only a repetition of the other one. West 
 of Lochan na Leirg some more pebbly portions occur, both south-east and 
 north-west of the main band, but how they come in is not clear. A 
 massive pebbly band on the west side of the fault which runs through 
 the " h " of " Breamanach " may be on the same horizon, but it is not 
 so coarse. 
 
 No other schists have been mapped until we come to the green beds on 
 the south-east side of the anticline, near Strone Point. There are two 
 bands, both well seen in the raised beach margin ou the north of the 
 point, which can be traced west as far as a prominent feature facing 
 west. Various exposures of basalt are seen along the continuation of this 
 feature to the north, and in all probability basalt occurs with it here also ; 
 but, besides this, it is necessary to suppose a fault of some magnitude, for 
 on the west side of the feature we see nothing of the green beds, though 
 they may occur, after a considerable shift to the south, in the drift- 
 covered area south of Glaic ; but striking against the top of the upper green 
 bed is a considerable breadth of black phyllite and thin quartzose schist. 
 On the south-east side of the upper bed come some thin alternations of 
 grey-green phyllite and quartzose schist, arid then a considerable breadth 
 of massive grey pebbly schist ; after this, for J mile or more, as far as 
 the extreme end of Strone Point, the ground is drift covered, with the 
 exception of a very small exposure at the raised beach margin. The ex- 
 posure consists of grey phyllite and massive pebbly schist ; on the whole 
 it did not suggest the presence of beds of the Dunoon series. On the 
 east side of Loch Striven there is some massive pebbly quartzose schist 
 between the most south-east green bed and the phyllites on its south-east 
 side (see p. 176). Whether the beds at Strone Point belong to the same 
 series we are unable to say. The outcrops of green beds on either side of 
 the loch do not match in number, or strike accurately for one another. 
 
 Good sections are abundant both on the coast and in the inland scars. 
 Several of these are elsewhere described (pp. 23-28). They are scarce on 
 the north-east shore of the Kyles of Bute, but nearly continuous on the 
 west side of Loch Striven. One-quarter of a mile N.JST.W/of Troustan the 
 limbs of early folds, themselves twisted by the later " anticline " folding, 
 are well shown by the thin impure calcareous bands. The coast to the 
 north-west is also interesting, because it shows clear instances of the first 
 foliation crossing the stripe or bedding of the schists. C.T.C. 
 
183 GEOLOGY OF COWAL. 
 
 CHAPTEE XVI. 
 
 GENERAL GEOLOGICAL STRUCTURE OF PARTICULAR 
 DISTRICTS (continued). 
 
 District of Tighnabruaich. 
 
 This district forms the most southerly part of Cowal, and lies south 
 of Kilfinan and the hills, Cruach Kilfinan, and Beinn Bhreac. Its northern 
 boundary is an east and west line from Eilean Dearg in Loch Riddoii to 
 Drum Point on Loch Fine, and the sea forms its other boundaries. It 
 comprises the southern part of the parish of Kilfinan, * but the only place 
 of importance in it is Tighnabruaich, which, stretching with Kanies 
 for two miles along the Kyles of Bute, is a favourite summer resort. 
 The only part of the area Avhich is more than 1000 feet in elevation 
 lies around Beinn Capuill, and this high ground slopes rapidly down 
 to the shore at Loch Riddon and Tighnabruaich. The greater part 
 of the district is extremely undulating, being much cut up by a number 
 of small streams and hollows into many isolated hills, not a few of 
 which are steep and craggy. The coast in Loch Riddon and the Kyles 
 has a comparatively smooth outline, while in the south and west, 
 bordering on Loch Fine, the outline is varied by a good many small 
 bays, the shores of which are diversified by beautiful patches of native 
 wood. The finest of these is Kilbride Bay at the mouth of Allt 
 Osda. The shores of Loch Riddon and the Kyles are also beautifully 
 wooded. There are two natural lochs of considerable size, Loch na 
 Melldalloch and Loch Asgog, besides a good number of old lochs now 
 silted up and overgrown with peat, which are coloured on the Map as 
 alluvium. 
 
 The district embraces strips of the following sets of beds ; 
 
 Garnetiferous schist horizon. 
 
 Loch Tay limestone, with its associated epidiorites and hornblende 
 schists. 
 
 Green beds. 
 
 Mica schists, with subordinate gritty and pebbly bands. Nearly whole 
 
 extent. 
 
 The country occupied by these bands is very narrow in the north-west, 
 gradually widens out to about the central part of the district where the 
 anticline is, and narrows again gradually to Ardlamont Point, the southern 
 extremity. 
 
 Garnetiferous Schist Horizon. This band occupies the coast from the 
 north side of Auchalick Bay to beyond Drum Point, and is the most north- 
 westerly of the strips to be described. It is a fine-grained and thinly foliated 
 sericite mica schist, extremely crumpled, and traversed by very numerous 
 quartz veins, many of which are parallel to the foliation planes. Gritty bands 
 are met with occasionally, but none of sufficient importance to be separately 
 noted, and towards the base on the north side of Auchalick Bay there are a 
 few thin green bands of the type hereafter to be mentioned, besides a thin 
 band of limestone ; and this, together with the limestone of Ach Chreagach, 
 will be described with the Loch Tay limestone. Good sections of the beds 
 can be seen along the rough and craggy coast and in the interior about Ach 
 Creagach and Inveryne Barr( A 268), but the interior generally is not very 
 
 * The name has nothing to do with Fionn, the mythical Gaelic hero, but is derived 
 from St Finan, who lived in the 7th Century. 
 
STRUCTURE OF TIGHNABRUAICH DISTRICT. 189 
 
 rocky, and has a somewhat tame appearance. Several small faults or marked 
 joints are seen on the coast at Drum Point and to the southward, which 
 have various directions, and at -Port Leathan are two more important 
 parallel faults, running N.N.E., about 30 yards apart. These are best seen 
 on the south side of the bay, where the rock is much stained near them, 
 but they are also seen on the north side. A very large north-west 
 fault conies into this bay, and this will be described in the sequel. The 
 dip is everywhere to the north-west, but the contortions are so violent and 
 frequent that it would be useless to give any estimate of the average 
 amount. There is a marked feature running nearly due north from the 
 north side of Auchalick Bay to the summit of Inveryne JBarr, which may 
 be a fault line. The rock has not been much worked. There is a quarry 
 in it east of the road, about \ mile north of Drum. 
 
 Loch Tay Limestone. This is a light-coloured highly crystalline limestone 
 with abundant plates of white mica on the foliation planes. It 'is generally 
 accompanied by bands of epidiorite, and often divided by them into two 
 or more separate bands. There are small old quarries in the upper part, 
 W.N.W. of Acharosson, and the lower part is thin bedded, and seems more 
 micaceous than the upper. The limestone can be traced pretty continuously 
 from the path leading between Kilfmanand Acharosson down to the north 
 shore of Auchalick Bay. As no good section shows the top or bottom of the 
 limestone it is impossible to give its exact thickness, but it seems altogether 
 as much as 30 or 40 feet. It cannot be seen for some distance on either 
 side the main road, but south of the bog which crosses its course both 
 parts can be well seen up to the fault that runs east and west to the south 
 of Cor Mheall. This shifts the outcrop altogether between 150 and 200 
 yards to the west, and would seem to have a downthrow north of 200 
 to 300 feet. At Inveryne, south of the fault, both bands are seen again 
 for a short distance, and there is a quarry in the upper one, showing that 
 it rests on the epidiorite. Both bands soon get covered up with drift, but 
 they must be shifted to the north-west, nearly 400 yards, by the Mell- 
 dalloch fault, and if the dip of the beds is 30 to 40, as it seems, the down- 
 throw on the north-east would be as much as 600 feet. On the other side 
 of this fault there are old quarries in both the bands, but they show little 
 rock, and the limestone finally disappears under the old marine alluvium 
 of the beach. About 150 yards to the north-west there is a thin band of 
 calcareous schist, probably 2 to 3 feet thick at least, which has been traced 
 for i mile to the north-east, under the hill called Inveryne Barr ( A 268 
 on the 1-inch Map). This band seems to be quite distinct from the 
 Loch Tay limestone. 
 
 To the south-west of Ach Chreagach and north-west of Drum a baud of 
 limestone occurs that is quite different from that last mentioned. There 
 are several quarries which show a good thickness of limestone and 
 calcareous schist. The most northerly quarry is in rock of the latter kind ; 
 in the next there is a good and thick limestone on the same line of strike. 
 Perhaps there is a fault to the south of this quarry, for the third quarry is 
 much further east, out of the line of strike. This last 8hows calcareous beds 
 for 20 yards wide across the strike, but it cannot be traced northward. 
 Xo trace of these beds could be met with to the north or south of these 
 quarries, and their occurrence here is certainly puzzling, but it seems 
 possible that they may be parts of the Loch Tay limestone brought up 
 again by sharp folds. 
 
 Epidiorite and Hotmblende Schist. This, which nearly everywhere 
 accompanies the Loch Tay limestone, has the general characters which 
 have been elsewhere described. In this district, however, the rock is more 
 massive than usually it is further north, and is more an epidiorite than a 
 
190 GEOLOGY OF COWAL. 
 
 hornblende schist. There are two, and in one place three, bands of the 
 rock, but near the main road not one of the bands could be found, and 
 they are not supposed to be quite continuous, but to behave as intrusive 
 sheets often do, die out for a time and set in again nearly on the same 
 horizon. 
 
 Near the Acharosson path there is one band 50 feet broad intercalated 
 with the limestone, and a much broader and very massive band above 
 the limestone. Only the upper band is seen between the main road and 
 the bog, but south of this two bands are visible in force near Cor Mheall, 
 and probably each is as much as 50 feet thick, for the upper one is quite 
 1 00 feet in width at the surface, while the lower one spreads over a pretty 
 wide area seemingly as much as 250 feet wide. There is no section, 
 however, from which the thickness of either can be exactly ascertained. 
 Both bands are shifted equally with the limestone by the Cor Mheall fault, 
 and can be traced for some distance till they disappear under the drift. 
 They seem to be thinning gradually, for when they appear again south of 
 the large Melldalloch fault they are much less thick, being only about 30 
 feet in width all the way to the bay, where another and higher band of 
 about the same width appears about 40 yards north-west. This can be traced 
 for about 300 yards inland. It is coarsely crystalline generally arid pretty 
 massive, but finer at the edges and more properly a hornblende schist. 
 The rock generally contains small garnets, and the schist into which it 
 has been intruded is decidedly hardened along the line of contact. 
 
 Green Beds. These are characterised by the abundance of black mica, of 
 chlorite and of epidote, not only in the finer portions but also in those which 
 are strong arid gritty, and are occasionally quarried. The less gritty bands 
 often decompose into a very soft greenish schist, e.g., in the burns which 
 run into the Acharosson burn from the south, between Auchariaskioch and 
 Acharosson, especially the one engraved on the 1-inch Map. The bedding 
 and foliation in these schists seem much more regular and not so 
 crumpled as in the ordinary mica schists, and the quartz veins are much 
 less numerous, except in the mica-schist bands, which occur in places 
 among the green beds. The line for the base of the green beds is a fairly 
 good one, for the lower part of the strip mapped is mainly composed 
 of beds of the genuine " green-beds " type, but the upper line coinciding 
 with the Loch Tay limestone is a purely conventional one in this district. 
 It marks nearly, though not quite accurately, the upper limit of the green 
 beds, but includes in the upper part of the strip also a good deal of mica 
 schist of the ordinary type, which could not well be separated out from it. 
 It must therefore be clearly understood that the upper half of the strip 
 coloured as " green-beds " is a mixture containing perhaps more ordinary 
 mica schist than green beds proper. 
 
 The coast between Auchalick and Ardmarnock bays gives good sections 
 in some of the upper beds, showing mainly grey mica schists much con- 
 torted, with the usual quartz veins, and with occasional bands of green 
 chloritic schist. There is a strong and marked band of the latter on the 
 south side of Auchalick bay, and another on the north side of Ardmarnock 
 Bay, close to which are three thin basalt dykes trending W.N. W. generally, 
 but somewhat meandering ; one of these is 3 feet wide, and another 2 feet 
 6 inches.* To the northward is a long curved fault, the general trend 
 being east of north, and west of this, and north of Carraig nam Ban, 
 is another small basalt dyke 2 feet wide. Strong chloritic schist occurs 
 about Cor Mheall, and a soft green bed, much decomposed and 10 feet 
 thick, may be seen on the north side of the basalt dyke quarry near Drum. 
 
 * It is probably one of these dykes that has been quarried about | mile inland 
 in a plantation. 
 
STRUCTURE OF TIGHNABRUAICH DISTRICT. 191 
 
 Alternations of green and grey schist may be seen in many places of the 
 lower part of the Acharosson burn, and in this ground, to the north-east 
 of Drum, occurs a band of hornblende schist about 20 feet broad, 
 which is probably an intrusive rock. 
 
 There are good sections of the green beds proper in Ardmarnock Bay, 
 about Black Harbour and to southward. Two small basalt dykes traverse 
 the beds in Ardmarnock Bay in a W.N.W. direction. A strong green 
 gritty band has been quarried by the roadside J mile north of Ardmarnock 
 House, and in the plantation east of the road, J mile further north, there 
 is a marked grey mica schist baud which runs north-east past the site of 
 the old fort. There are good sections in the green beds about Melldalloch 
 and in many other places, and in the Acharosson burn. Thin lampro- 
 phyre dykes occur in them at Auchanaskioch, and both north and south 
 of Melldalloch Farm. The Kilfinan fault is probably prolonged south- 
 ward across the Acharosson burn, shifting the green beds there, but the 
 evidence for it did not seem clear at the time the survey was made, 
 and the line tor the base of the green beds was left unfinished. The 
 fault passing by Melldalloch shifts the base of the green beds about 
 2000 feet, so that if the dip be taken as 30, which seems an under- 
 estimate, the throw must be as much as 1000 feet down north. 
 
 Mica Schist. This rock occupies by far the larger portion of the district, 
 which probably contains representatives of nearly all the horizons between 
 the two sets of green beds on the north-west and south-east. Two marked 
 bands of strong gritty and pebbly schist stretch across it from south-west 
 to north- east, one on either side the anticlinal line, and the whole from 
 Ardmarnock House to Ardlamont Point, in whatever way dipping, is 
 probably one set of beds. Very little of it seems to be a true phyllitic 
 mica schist, and the prevailing type of fine-grained mica schist gives one 
 the impression that the mass of it was originally a fine-grained shaly or 
 flaggy sandstone, in cases alternating with sandy shale. 
 
 The strip of mica schist which comes south-east of the green beds 
 falls to be described first. This strip contains here and there thin 
 bands of strong gritty or pebbly schist, which cannot generally be traced 
 very far, but as many as four of these were followed for some distance in 
 the southern part of the strip and coloured yellow on the Map. The 
 most important of these is the one west of Creag Mhor, which is 50 
 feet broad. These gritty bands contain less mica than the finer parts, 
 and few of the quartz veins so common in the ordinary schist, and gener- 
 ally they are not so much contorted. Several of these thin gritty bands 
 may be seen on the coast about Rudha Preasaoh, alternating with the 
 finer type of schist. One of these bands south of the point can be traced 
 inland for 300 yards. Another occurs further to the north-west, which is 
 crossed by a fault throwing down a few feet on the west side. A marked 
 feature, running in a north-east direction parallel to and east of this gritty 
 band, is probably a fault feature. Sections are numerous inland in the 
 little crags on the moors, particularly west and south- west of Creag Mhor 
 and north of Loch na Melldalloch. The best stream sections are in 
 the Acharosson burn and in Stowhall burn, which joins it, running near 
 the foot path to Acharossou. Two veins or faults are to be seen in these 
 beds in the Acharosson burn, both having a direction a few degrees north 
 of west. The lowest of these is a breccia, with much red ferriferous 
 carbonate, and occurs a little west of the point where a small burn joins 
 the main stream from the north ; the other, which is a pink ferriferous car- 
 bonate, is about 600 yards further east. If the Kilfinan fault continues 
 across this area, which is likely enough, it must pass by the west end of 
 the crag called Sron Dubh, and to the west of the big moss. There are 
 
192 GEOLOGY OF COWAL. 
 
 four detached bits of intrusive red lamprophyre, dykes and sills, along the 
 western edge, south of Acharosson, which are engraved on the 1-inch Map, 
 but perhaps not coloured, and there is a thicker mass of the same kind 
 further east, which crosses the Stowhall burn. The width of this strip 
 of mica schist is a little more than the shift of the Melldalloch fault, 
 which crosses it about its centre, so that its total thickness may be about 
 1000 feet, on the supposition that the north-west dip averages about 30. 
 It certainly seerns to average a good deal more on the east side of Bagh 
 Buic, where the north-west joints are so prominent, but the crumplings 
 are so numerous in places that not much reliance can be placed on the 
 above estimate. 
 
 Gritty Schist of Glenan. Under this head will be described a band 
 of strong schist, containing numerous gritty and pebbly bands, which 
 stretches from Glenan Bay to near the Acharosson burn. It is about 
 1000 yards in average width, but contains within it a good deal of 
 the fine-grained ordinary mica schist. Lines have been drawn for the 
 top and bottom of the mass, and coloured, and the more markedly 
 gritty or pebbly bands, inside the area, have also been indicated by 
 a yellow colour. The most traceable of these bands is the coarse and 
 pebbly one 30 to 50 yards in width, which can be clearly followed 
 for 2 miles along the west side of East Glenan burn, past Creag an 
 Fhasgaidh and Carn Bhuilg to the Melldalloch fault. It forms a good 
 feature in several places, and under Creag an Fhasgaidh is crossed by 
 several faults ; two (most southerly) throwing down to south about one 
 half the thickness of the band, while two others throw down to the north 
 nearly its whole thickness. This is almost certainly the same band which 
 is marked as trending northwards from the west side of the upper dam 
 towards the Acharosson burn. At Capull Cloch, J mile E.N.E. of Loch 
 na Melldalloch, the band is very conspicuous, about 70 yards broad, a 
 conglomerate schist with much drawn out pebbles of quartz and felspar. 
 Another marked pebbly band can be traced along the west-side of West 
 Glenan Burn and under Creag Mhor. The upper limit of the whole 
 group is not so clearly defined as the lower one, and in the northern part 
 of the area is somewhat obscure. It would seem to run from near the 
 east end of Loch na Melldalloch N.N.E. to the big peat moss, and on- 
 ward in the same direction towards the Acharosson burn. Two sheets of 
 red lamprophyre, or perhaps more properly of felsite, 30 to 40 yards in 
 width, occur here in the schists south of the Acharosson Burn, and a 
 broader band of about 50 yards on the north side of the burn, the latter 
 dying out rapidly at either end. The large felsitic mass, which is found 
 further east at the great bend in the burn, has been previously noticed, 
 p. 150. A band of the same character occurs south-west of the Acharos- 
 son footpath, and seems about 70 yards broad, and another or the same 
 is quarried for road metal on the eastern side of Loch na Melldalloch. 
 
 There seems to be a fault cutting off the coarse gritty band west of the 
 upper dam, and there are two large faults, trending about N.N.W., 
 between Ardmarnock House and Glenan, both of which throw down to 
 the west and shift the beds from 100 to 150 yards. Sections of these 
 gritty schists are also to be had in the islands off the coast, Eilean Buic, 
 Eilean na Beithe, and Eilean Buidhe. The dip generally seems as much 
 as 30 or 40. 
 
 Up the East Glenan burn there is a fairly well defined horizon of gritty 
 schist, 200 to 400 yards east of the main band which has been described. 
 
 Anticlinal Area. It will be convenient to treat under this head, 
 of the schists which are found between the two bands of gritty schist 
 coloured yellow on the map. " The anticline " iu the foliation passes 
 
STRUCTURE OF TIGHNABRUAICH DISTRICT. 193 
 
 through the middle of the band from south-west to north-east, from Port 
 a Mhadaidh on Loch Fine, over Cnoc a Chasteil, south of Binnein Ban, 
 past Craignafeich, Tighuabruaich reservoir, north of Barr Liath, along 
 a small stream and moss south of Beinn Capuill to the head of Loch 
 Blddon. It must be understood, however, that it is not a simple 
 anticline, but a compound one, with many minor folds, which aie 
 practically nearly flat for some distance on either side of the central 
 line, the position of which it is not always easy to fix. Thus, for 
 instance, north-west and west of Binnein Mor, near Loch Riddon, 
 the foliation is nearly horizontal for a considerable distance " The 
 anticline " seems, however, to be steeper, especially on its north side, and 
 more simple as we proceed from this point south-west towards Loch 
 Fine. 
 
 The rocks of this division are in general more folded than the preced- 
 ing, and the dip more variable. The ground occupied by them is also 
 rougher and more decidedly craggy. The rocks seem for the most part to 
 be of the finer-grained variety of mica schist, but a few gritty bands are 
 met with occasionally. The whole, however, have undergone a more 
 pronounced metamorphism than the beds further removed from the 
 anticlinal line. 
 
 Sections of the beds on the north side of " the anticline " may be had on 
 the shore of Loch Fine, between Port a Mhadaidh and Lub Faochaige : 
 fine grey mica schists, full of quartz veins, much crumpled, and with many 
 reversed folds. Inland these beds are well exhibited on the hill, Barr 
 nan Damh, west of Derybruich, where they have similiar characters, and 
 several marked features running north-east, perhaps caused by joints, 
 may be noted. These much crumpled rocks can also be well seen on 
 Cnoc a Chasteil, west of Asgog Loch, and on Binnein Ban, also on Creag 
 an Fhithich, A' Chruach, and other crags and hills, especially Cnoc 
 Uaine and around Beinn Capuill. To the north-east of the latter, and 
 near the head of Allt Dubh, two basalt dykes penetrate the schist, run- 
 ning pretty close together and nearly parallel to the burn ; one of these 
 is 5 to 6 feet wide. 
 
 On looking at the Map it will at once be seen that the horizon under 
 description, between " the anticline " centre and the gritty schist band to 
 the north, is the one along which lamprophyre intrusions are most numerous 
 along the strike, in fact there is an almost continuous band of these running 
 from Lub Faochaige, on Loch Fine, by Beinn Capuill, to the head of Loch 
 Riddon. Red bands of this description occur just east of the summit of 
 Beinn Capuill, and further to the north-east, from 6 to 10 feet thick. A 
 thicker and coarser band on the west side of the hill is crossed by the 
 Dunoon dyke, and seems cut ofTby a fault at its north end. It is a coarse 
 red mica trap, much decomposed in places, and is shifted more and more 
 westward by a series of faults ranging east and west. The first of these, 
 north-west of Beinn Capuill, shifts it 100 yards, and at a little south of 
 this the mass contains lumps of quartz. The next fault at Coire Ban, 
 south head of Allt Mor, shifts it westward 200 yards, and the third about 
 100 yards. South of this the sill is much wider and is soon lost sight of 
 in a doubtful way. Similar bands may be seen westward near Allt Mor 
 and the eastern branch of the Creag-an-fhithich Burn, where one band is 
 at least 15 feet thick, but there is a good deal of drift about the heads of 
 these burns, and the sections are poor. In the Creag-an-fhithich Burn, 
 about 350 yards east of the Actarosson footpath, there is a fault trending 
 AV.X.W., which seems to cut off a red lamprophyre sill on the north, and 
 a quartz vein, 2 to 3 feet wide, runs northward in the burn. A little 
 further east is a calcareous breccia, also running W.N.W., near which are 
 
 N 
 
194 GEOLOGY OF COWAL. 
 
 thin veins of ferriferous calcite. About 300 yards west of the footpath 
 there is a thin grey amygdaloidal basalt dyke running along the south 
 side of the burn. South-east from this, and east of the upper dam, 
 is a coarse red mica trap, with large red felspars and black mica, which 
 may be the continuation of the one last described in the burn east of the 
 footpath. Eastward of this, and on the other side of the footpath, a quartz 
 vein 6 inches thick is sticking to a vertical face of schist trending W.N.W. 
 
 Two parallel red intrusive lamprophyre sheets occur south of Loch na 
 Sgine, running under A' Chruach, and the most westerly one is prolonged 
 under Creag an Fhithich, where it is 5 feet or more. There are marked 
 features in these two hills which seem often to run along north-east joints 
 parallel or nearly so to the strike. Passing to the west side of the Creag- 
 an-fhithich Burn we come on the sills again, near the main road, and one 
 runs up the west side of Allt an Eas, west of which the strike joint 
 features are very prominent. Another baud is on the east side of Allt an 
 Eas and north of Binnein Ban, where its course is a zigzag. West of 
 Binuein Ban there are three of these red intrusive bands, the lower or 
 most easterly one being 7 to 8 feet thick, and traceable, with interruptions, 
 to Derybruich. South of Binnein Ban is a marked hollow along the 
 strike, probably due to a fault or joint, and to the east of this three 
 N.N.W. lines of fault. There is a fine feature running north from Alltan 
 nam Breac which flows into Asgog Loch, to the road at Allt an Eas. Two 
 red sheets are seen on the coast, one being opposite to Eilean na Beithe, 
 and the other on the south side of Lub Faochaige. This last is a reddish 
 brown band of a few feet thick, curving in direction and giving of! thin 
 strings at its eastern end. A vein of ferriferous calcite is to be seen in 
 several places in the upper part of the Acharosson burn, accompanying 
 the Dunoon east and west dyke there. 
 
 The north-westerly dip in this area is much greater than it is in the 
 adjoining district to the north-east, and as illustrating this it may be 
 mentioned that the distance of the base of the gritty group from the 
 centre of " the anticline " is half as much again near Beinn Capuill as it is 
 on Loch Fine. Good sections of these rocks on the south side of " the 
 anticline " may be seen on the coast between Kudha Stillaig and Port 
 a Mhadaidh. South of the latter they are much folded, with numerous 
 quartz veins, and a gritty band, 30 to 40 yards broad, may be seen at the 
 top of the old coast cliff. The dip is comparatively low, and south of 
 Port Ghabhar, the beds seem practically horizontal in places \ still they are 
 much of the same fine character, fine mica schists, with occasional thin gritty 
 bands. A fault here runs north-east, and can be traced to near Polphail. 
 The coast is rocky, with only traces of the old shelf cut by the sea, on 
 which are the stacks of the old coast line. Near the fort Creag a' Cbasteil 
 are four nearly parallel faults, trending 25 to 30 north of west, and the 
 rocks continue to be of the same character round the head-land of Kudha 
 Stillaig to Port Leathan, where occur two thin dykes or sills, probably of 
 the lamprophyre type, running in the direction of the strike, about 50 
 yards apart. 
 
 The fine grey micaceous schist, much crumpled and quartzy, may be 
 observed inland along the strike in many places. There is a marked 
 strike feature 500 yards south-east of Polphail, extending for nearly \ mile. 
 Some coarse bands occur about Barr lolaich, where the prominent foliation 
 dip is 30 to S.E., and another foliation dips 60 in same direction. Rocks 
 of a eimilar character are found round' Loch Asgog and Craignafeich. 
 South of the latter place, 80 yards, is a basalt dyke running east and west, 
 which has been quarried, though only '2 to 3 feet wide. Another basalt, 
 dyke trending W.N.W. crosses the small stream to the west, and is 6 feet 
 
STRUCTUEE OF TIGHNABRUAICH DISTRICT. 195 
 
 wide where quarried by the roadside ; and south-west of this in the burn 
 and running along it is another, 4 to 5 feet wide. In the field east of the 
 powder works plantation, and west of the road leading to Kames, there is 
 outcropping much strong grey mica schist, and rock of the same character 
 appears between Achanlochan and the pier, where it has been quarried. 
 There are sections along the upper road here (new road) showing : 
 North Side, 
 
 Basalt dyke, 12 to 18 inches. 
 
 Mica schist, 8 feet. 
 
 Basalt dyke, soft brown decomposed, 8 feet. 
 
 Mica schist. 
 
 On the roadside south of Craignafeich is a soft purple mica schist. A 
 bit of rock crops out in the moss west of Achanlochan, with much contorted 
 nearly flat foliation, and another foliation which is nearly vertical. To 
 the east of this, about 300 yards, the dip varies from to 20 while the 
 dip of the cleavage foliation is high. To the south and south-east of 
 Barr Liath the beds are extremely plicated, but probably nearly flat on 
 the whole. Good sections can be seen in the lower part of Allt Mor, 
 where there are two thin basalt dykes, and in the branches of the 
 Tighnabruaich Burn. At the foot of Allt Mor much quartz occurs on 
 the shore in strings, veins, and lumps. Between the two branches of the 
 Tighnabruaich burn a thin lamprophyre sill occurs in the schist, and a 
 ba>alt dyke up the burn west of Rudha Ban. There is another basalt 
 dyke in Allt Dubh, E.S.E. of Benin Capuill, which runs along one 
 of the bends of the burn, and is accompanied by a vein. Numerous 
 sections may be had in the crags about Binnein Mor, north of which are 
 several lines of fault, the most important of which is W.N.W. 
 
 The schist behind Tighnabruaich is in places of a very fine-grained 
 character, it might indeed be called a phyllitic mica schist. It may be 
 seen in the new road south of the Established Church, and schist of a 
 similar character crops out in the path west of Stillaig Farm. 
 
 The Stillaig Band of Gritty Schist. This has a width across the 
 strike of nearly 400 yards, and on the coast it forms the western part 
 of Eilean Aoidhe. It is mostly a strong, coarse and gritty schist, with 
 some pebbly bands, and some that are thin, fine, and very micaceous with 
 numerous quartz veins. Beds of the latter kind much corrugated are 
 found at the extreme western end of the island and seem separated from 
 the main gritty mass by a fault along the strike. The south-east dip 
 seems to average 30 or 40 throughout, and near the upper boundary 
 occurs a fine grey dyke or sill 5 to 6 feet thick, which runs nearly along 
 the strike, but dips in the opposite way to the schist, or north-west. It 
 is probably of the lamprophyre type. 
 
 Strong bands of gritty schist appear in the woods to the north-east ; and 
 about Stillaig and Asgog farms the breadth of the band continues much 
 the same ; but the sections inland are not good though some may be seen 
 in it, in its course past Achadalvory, Auchagoyl, and Kames farm till it- 
 strikes the shore about the pier at Kames. It seems to miss the Tighna- 
 bruaich shore but appears again in strong force at Rudha Ban, where it 
 can be clearly differentiated into three gritty bauds with partings of fine 
 mica schist. The most southerly of these has on the shore on the east 
 side of Port Driseach a width of about 100 yards. It is mostly a rather 
 fine quartzose strong and massive-looking schist very finely foliated with 
 abundant mica, and white in colour. The dip south-east seems 30 or 
 more, and there are signs of a later foliation dipping 75. To the north- 
 wards is a band of fine micaceous schist, 50 to 60 yards broad, with 
 quartz veins. The second gritty band is 80 to 100 yards broad, and there 
 
196 GEOLOGY OF COWAL. 
 
 follows a second band of mica schist, 75 to 90 yards broad, similar in char- 
 acter to the first. The third gritty band is 100 to 150 yards broad. The 
 two foliations may be seen in several places, e.g., 300 yards south of Allt- 
 Dubh and near the summit of the hill south of the footpath leading to 
 Callow. In the first of these places both dip south-east, one at 35, the 
 other at 70, and there are some reversed dips which are probably over- 
 folds. 
 
 The south part of Eilean Dubh opposite Callow for a width of 150 
 yards is mostly gritty and pebbly schist, with a few finer micaceous bands, 
 one of which seems to form the southern hollow crossing the island in a 
 north-east direction, while another forms the hollow near the northern 
 boundary of the mass. The gritty schist is white, quartzose, finely 
 foliated and crumpled. A fault on the west side of the island trending 
 north-west seems to throw down to south-west about a foot. About 
 the middle of the island on the east side is a very prominent joint 
 which dips north-west about 10, and near this the foliation is much 
 crumpled, ranging from nearly horizontal to the vertical. At the south- 
 east end in some coarse pebbly schist are traces of secondary foliation. 
 The interior of the island is rough and rocky and very difficult to 
 traverse, being covered with tall heather and brushwood. 
 
 The Ardlamont Peninsula. The remainder of the district forming a 
 triangle of which Ardlamont Point is the apex may be thus conveniently 
 designated. We will begin with the shore section at Asgog Bay. 
 Moderately fine grey micaceous schist full of quartz veins and much 
 plicated in places forms the island of Sgat Mhor, the east side of Eilean 
 Aoidhe, and the west side of Asgog Bay. A N.N.E. crush crosses Sgat 
 Mhor ; two faults run east and west along the south side of Eilean 
 Aoidhe, and one trending north-west is in the hollow which cuts off the 
 eastern end from the rest of the island. There seems also a large fault 
 going W.N.W. between the island and the mainland on the" north. 
 There are irregular cracks filled with breccia and quartz 100 yards west 
 of the point bounding Asgog Bay on the west, and near the mouth of 
 the burn is an east and west crush line. The rock east of the bay is 
 much the same in character, round by Sgat Bheag and Port na Beiste, 
 and numerous faults are seen, the major part of which run in a W.N.W. 
 direction. On the east side of Sgat Bheag is a grey intrusive sill of 
 the lamprophyre kind. It is 4 to 5 feet thick, and appears on the 
 mainland opposite, striking with the schist, arid being faulted by its 
 faults. The most northerly of these faults shifts the sill about 60 yards 
 to the west. A few gritty bands are found in places, arid there are some 
 lines of crush going N.N.E. or nearly with the strike, and others ranging 
 nearly east and west. The same kind of rock forms both sides of Kilbride 
 Bay, and is generally full of quartz veins and much crumpled, with 
 occasional crushes in various directions. A little north of Kudha na 
 Peilige, a gritty band occurs 25 yards in width, which maybe the same band 
 that has been quarried to the north-east and north-west of Corra, not far 
 from the road. To the eastward of the point on the shore, the rock is 
 mostly fine and very micaceous, but there are gritty bands occasionally ; 
 and 100 yards east of the mouth of a little burn are two thin basalt 
 dykes running northwards close together. To the N.N.E. of this and 
 beyond the large east and west dyke, is a very coarse pebbly band, a few 
 feet thick, in which are quartz pebbles drawn out to an inch in length ; 
 and there is a goud deal of coarse schist on the shore about the centre of 
 the bay, with several lines of crush . Passing to the east side of the bay 
 there are some thin coarse bands, one of which is 10 yards wide ; and 
 350 yards further south another strong coarse band is 25 yards in width. 
 
STRUCTURE OF KILFINAN DISTRICT. 197 
 
 There are several thin dykes and sills on the shore about 600 yards to 
 south of this, which may belong to the lamprophyre type, and one in the 
 same direction, E.N.E., is seen nTa quarry west of Point Farm. There is 
 also a larger dyke on the shore 15 feet wide in the same direction. We 
 pass the large east and west dole rite dykes described on p. 150, and come 
 near Ardlamont Point on a greyish-brown fine-grained sill, a few feet in 
 thickness, clearly intrusive in the fine mica schist, but running nearly along 
 the strike. It does not seem to cross the big dyke, being apparently of 
 earlier date than it, but it appears again in the bay on the north side 100 
 yards from the dyke, where it is 3 to 4 feet thick, and it can be traced 
 interruptedly to the north-east running out to sea, and either widening or 
 splitting into two near low-water mark. This is probably a somewhat 
 basic lamprophyre. There are also some thin sills which lie to the south- 
 east of it, fine and white, and only a few inches thick. Between this and 
 Point Farm a few thin sills can also be traced for a short distance. In 
 the fine grey mica schist to the northward along the shore, there is a coarse 
 band several feet thick which thins out very rapidly along the strike in 
 both directions. The usual kind of mica schist prevails along the shore 
 past An Gnob where it is altered by the big dyke, and soon after we 
 come to a smash running W.N.W. North of Blindman's Bay there are 
 strong bands occasionally ; some very coarse and pebbly are to be seen 
 south-east of Carry, nearly vertical, among alternations of various kinds 
 with an E.N.E. strike. Northward to Kames, rock of the usual fine char- 
 acter prevails with occasional alternations of a stronger kind, but the 
 sections on the coast are poor, and no detailed description is necessary. 
 
 Numerous outcrops of the fine-grained mica schists are found in the 
 interior on the moors about Cnoc Mor and west of Colachla. On the 
 east side of Allt Osda there are several strong grey gritty bands south-east 
 of Coille na Sithe alternating with the ordinary kind, and one of these 
 bands has been traced to the north-east beyond the large peat bog. There 
 is another south of this which forms a fine feature, perhaps partly due to 
 a fault. There are several N.N.W. features due to joints or faults to the 
 east of Kilbride Church, and one feature long and prominent running due 
 south from Allt a Chaoruinn. Others occur about Cruach a Kames, one 
 of which is nearly along the strike. Numerous sections may be observed 
 in addition about Sithean Mor, Cnoc na Carraigh, Cnoc na Carraige, and 
 Cnoc na Cailliche. W.G. 
 
 District of Kilfinan and Stralachlan. 
 
 This district lies west of Newton Bay, Caol Ghleann, Glendaruel, and 
 the upper part of Loch Riddon, and north of the Tighnabruaich district. 
 The schists lying within this area belong to the following groups : 
 Anticlinal grits and mica schists. 
 Green beds. 
 Loch Tay limestone. 
 
 Mica schist (with green beds and other schists not differentiated). 
 Quartzites and Phyllites of the Ardrishaig series. 
 
 The anticlinal grits and schists occupy the whole of the ground to the 
 south-east of a line a little north of Ormidale, passing through Cruach 
 Camuillt, a little to the east of Cruach na Broighleag, and 1 mile to the 
 west of Kilfinan. 
 
 This line forms the south-east boundary of the "green beds." The 
 " green bed " zone extends north-west as far as the first appearance of the 
 Loch Tay limestone, which passing just above the village of Kilfinan con- 
 tinues a north-easterly course along the western slopes of Glendaruel, and 
 
198 GEOLOGY OF COWAL. 
 
 finally crosses the boundary burn of this area J mile north-west of Sron 
 Cruaich. 
 
 The next zone of mica schists is bounded on the south-east by the main 
 mass of the Loch Tay limestone, and on the north-west by the Ardrishaig 
 series. 
 
 The south-east horizon of the Ardrishaig series follows a line from the 
 head of Stralachlan Glen to a point on Loch Fine about 2J miles north 
 of Otter Ferry. 
 
 As a glance at the published Map (sheet 29) will show, the demarcation 
 of the "green beds" from the anticlinal grits shows the existence of 
 numerous faults, giving a general irregularity to the boundary. The 
 mapping out of the base line of the " green beds " was the means of 
 detecting many of these faults, which otherwise would have escaped 
 observation. 
 
 There are occasional bands of u green beds " to the south-east of the 
 boundary drawn. They are not numerous, are generally of small extent, 
 and have not been shown on the published Map. Two such bands occur 
 about J mile south-west of Cruach Camuillt. The farthest of them from 
 the main " green bed " zone is about J mile distant from it. 
 
 The " green beds " are well seen in the burn sections of Allt Lean 
 Achaidh (a north and south tributary of the Kilfinan Burn), and the 
 main trunk of the Kilfinan Burn from the exposure of the limestone to 
 the " green bed " boundary to the east. This last section traversing the 
 entire " green bed " series is the most important section of the " green 
 beds." 
 
 There are also good sections of the " green beds " exposed in most of 
 the burns of the western slope of Glendaruel, among which may be 
 instanced the burn that joins the Ruel just to the south of Glendaruel 
 House, and the burn joining the Ruel near Moymore. 
 
 The Loch Tay limestone, as regards its main mass, follows a more 
 or less even course in a north-east and south-west direction. The 
 superficial deposits prevent its being traced continuously along the 
 line of strike, but wherever burn sections occur along its horizon the 
 limestone is invariably found. In burn sections more than one zone of 
 limestone may be seen associated with beds of hornblende schist or of 
 mica schist. It cannot be said with certainty how far this repetition of 
 the limestone may be explained by folding. But as some dip sections 
 contain only one exposure of limestone, it -is probable, when more than 
 one band is seen, that folding will best explain the appearances. For 
 a similar reason, the width of outcrop in different sections varies con- 
 siderably. 
 
 Bands of hornblende schist first make their appearance close to the out- 
 crop of the Loch Tay limestone, and they may occur in any of the sedi- 
 mentary zones that lie to the west of the Loch Tay limestone outcrop. 
 They do not, however, always accompany the limestone. There are 
 some good sections containing the Loch Tay limestone which have no 
 trace of hornblende schist. As a general rule, however, the Loch Tay 
 limestone is associated with hornblende schist. 
 
 In that part of the area that falls within sheet 29, limestone outcrops 
 sometimes occur to the west of the main limestone outcrop. Numerous 
 bands are found in the neighbourhood of Otter Ferry and Largiemore. 
 As the associated beds are similar to those found in association with 
 the main limestone mass, it is supposed that they belong to the Loch Tay 
 limestone and owe their present position to folding. 
 
 Good sections of the limestone and hornblende schist in association 
 occur in the Kilfinan burn close to the village of Kilfinan, but still better 
 
STRUCTURE OF K1LFINAN DISTRICT. 199 
 
 sections are met with in the numerous burns on the western slope of Glen- 
 daruel, notably the Kilbridemore burn, where repeated folding has given 
 rise to large continuous exposures of limestone. The burn at Largiemore 
 also affords a good section. 
 
 The sedimentary zone above the main limestone mass contains " green 
 beds," but they are not nearly so numerous as the "green beds" to 
 the south-east of the limestone, in fact they occupy a very subordinate 
 position, occurring as small bands scattered over the area. There is, 
 however, one locality \ mile south-east of Barnacarry, in which they are 
 strongly developed : this locality shows the most north-westerly " green 
 bed " exposure in this area. 
 
 In this zone various sills which occur scattered through the area are 
 similar in character to those found in association with the limestone. 
 
 A big mass of serpentine occurs within this zone, the characters of 
 which are described on p. 75. The main mass is nearly \\ miles in 
 length, and in its widest part has a breadth exceeding \ mile. The 
 northern extremity of the mass occurs \ mile south-west of Kilbridemore, 
 from which point it extends nearly 1 J miles to the south-west, occurring 
 as a big sill similar in behaviour to the epidiorites. A fault coincides 
 with the western boundary for a considerable distance, and in one place 
 a north-west fault divides the mass which has narrowed at the fault. Four 
 smaller masses of serpentine occur along the same horizon to the north- 
 east, which makes the whole line of serpentine extend over 2 miles. 
 
 The next zone to the north-west is represented by a set of siliceous and 
 micaceous beds of the Ardrishaig phyllite series, in which the siliceous 
 constituents are the stronger. These rocks are well displayed along the 
 coast section between Largiemore and Stralachlan. There are also good 
 sections in the burns which cut through this series, the courses of 
 which are usually transverse to the strike of the beds. Amongst them 
 may be specially enumerated : The burn running into Loch Fine at Leph- 
 inmore. The Barnacarry Burn at Barnacarry. The burn which joins 
 the Stralachlan river immediately to the south of Stralachlan church. 
 
 Various sills of epidiorite and hornblende schist are met with, but they 
 occur in greatest strength in that portion of the area that lies between 
 Stralachlan Valley and Loch Fine. They approach, in this locality, in 
 size and habit, the Glendaruel serpentine mass rather than the long even 
 sills of the Loch Tay limestone area. The big ridge of which Barr nan 
 Damn (571 feet) is the highest point, is made up almost entirely of one of 
 these great epidiorite masses. Although they attain great dimensions 
 their characters here are still those of sills rather than bosses. 
 
 Over the entire area the folding is intense. In the Ardrishaig series, 
 however, the liinbs of the folds point in the same direction, and are rarely 
 crumpled. Hence, in walking along a hill slope, the enormous folding of 
 the bsds would never be suspected, the beds appearing to succeed one 
 another with a steady dip. It is only when they are seen in section that 
 the repeated folds can be detected, and they are not well seen then unless 
 good alternations of quartzose with micaceous bands occur. 
 
 In the zones to the south-east of the Ardrishaig series the beds are not 
 only intensely folded, but the limbs of the folds are themselves crumpled, 
 and the highly-folded nature of the beds is obvious in examining any rock 
 exposure. 
 
 Good instances of these foldings of the Ardrishaig series can be seen 
 in the Barnacarry Burn, the Lephinmore Burn, and the burn running into 
 the south end of ^Tewton Bay. 
 
 The valley of Stralachlan occurs along the strike of the Ardrishaig 
 series, and owes its existence to the erosion of the zone of softer micaceous 
 
200 GEOLOGY OF COWAL. 
 
 beds which occur along the course of the present valley, flanked on either 
 side by highly siliceous rocks. 
 
 Of the faults which have been observed in this area, some follow 
 roughly the line of strike of the beds. One of the most persistent of 
 these is the extension of the fault from the east side of Glendaruel, which 
 after being lost sight of under the alluvial terraces emerges again close to 
 Ballochandrain on the west side of the glen, continues its south-westerly 
 course for about a mile along the bed of the big stream flowing past 
 Ballochandrain, which has excavated a deep gorge along the line of fault. 
 For the distance of f mile beyond the head of the burn, all trace of the 
 fault is lost, the ground being covered with peat and heather. It 
 can then, however, be picked up again continuing its normal direction 
 along the bed of a stream which joins the Kilfinan Burn, nearly 1 mile 
 due west of Cruach na Broighleag, where a basalt dyke has come up along 
 the vein breccia. After leaving the Kilfinan Burn no further trace of it 
 is seen in this area. Although this fault can be followed for several miles, 
 there is no evidence of a big throw. 
 
 In the parish of Stralachlan, close to Cruach Mor and Cruach Fasgach, 
 long features occur along the line of strike, which probably owe their 
 origin to strike faults. The surface of the ground is so thickly covered 
 with peat and heather that nothing definite can be made out. 
 
 A strike fault also forms part of the western boundary of the Glen- 
 daruel serpentine, already described. 
 
 Numerous faults are found transverse to the strike, the large majority 
 of such faults having a trend a little north of west. The trend of the 
 basalt dykes often coincides with the lines of fault, as for example in the 
 Barnacarry Burn, and in the Lephinmore Burn. 
 
 J.B.H. 
 
 CHAPTER XVII. 
 
 GENERAL GEOLOGICAL STRUCTURE OF PARTICULAR 
 DISTRICTS (continued). 
 
 District of Carrick Castle. 
 
 This district is inclosed by part of Loch Eck, the valley west of 
 Carnach M6r, Curra Lochain, the lower part of Lettermay Burn, Loch 
 Goil, part of Loch Long, and part of the south margin of 1-inch Map 37. 
 
 The schists in this area consist of albite or phyllitic mica schists, and 
 greywacke or quartzose schists. These rocks alternate so repeatedly 
 with one another in thin bands, that it is not usual to meet with horizons 
 of either type, which promise from their thickness to be readily trace- 
 able for some distance. Sometimes we start on a band which seems 
 definitely bounded and homogeneous in character, but after tracing it a 
 little distance, it gets mixed with schists of a different class, either near 
 the margins or in the middle, and we lose the power of identifying it 
 from the schists at the sides. Probably these difficulties are largely due 
 to mixture of different bands by acute folding with axes lying parallel to 
 the prominent foliation. 
 
 The schist lines which have been traced for the greatest distance, are 
 the tops of greywacke schist horizons, one on the north-west side of " the 
 anticline," and the other on the south-east side. Neither of these is 
 
STRUCTURE OF CARRICK DISTRICT. 201 
 
 very well defined, but in a district like this, where better lines are scarce, 
 it was advisable to make the most of them, and they have certainly 
 helped to disclose some of the larger faults and folds. 
 
 The top of the greywacke schist horizon on the north-west side of " the 
 anticline," enters the area from the north, a little above the foot of Curra 
 Lochain. There is drift for a little distance on either side of the loch, 
 and the position of the line can only be located roughly. From the foot 
 of the lochain down to the N.N.E. lamprophyre dyke, J mile south of 
 the second " a " of " Curra Lochain," the rock in the burn is nearly all 
 massive quartzose schist, often distinctly pebbly. On the east side of 
 Beinn Bheula, the quartzose schist is overlain by thin alternations of 
 phyllitic albite schist and quartzose schist. The separating line between 
 this series and the under one is not definitely marked. We see merely 
 that after passing over a certain thickness of beds, we get on to a 
 series in which the proportion of massive quartzose schist is less than 
 it was before. The difficulty of tracing the line is increased by the 
 difficulty of access to some of the crags. Near the top of the line, mile 
 E.N.E. of the last "n" of "Beinn Bheula," there are several faults 
 coming together from different directions. There are two ranging north- 
 east or N.N.E., but their effect is uncertain. Another runs E.N.E. and 
 hades north. The crush in this is sometimes 3 feet wide, but liable to 
 sudden variation. Near the hill top to the west, it throws a thin lampro- 
 phyre sheet down to the north, 40 or 50 feet. The amount of throw at the 
 greywacke top is uncertain, the other faults largely obscuring the section. 
 
 Five-eighths of a mile south-east of the " 1 " of " Beinn Bheula," the line 
 is crossed by a N.N.E. crush, and a crushed lamprophyre dyke on the east 
 side of this, but it is not clear that either of these causes appreciable altera- 
 tion in level. Three-eighths of a mile south-west of the foot of Lochan 
 nan Cnaimh, the line is crossed by another N.N.E. crush. In the burn 
 near this locality, the fault throws down a lamprophyre dyke consider- 
 ably to the west. The shift in the greywacke schist is not clear. South 
 of this place we have carried on the line doubtfully for more than 2 miles. 
 There are good exposures of albite schists above the greywacke for all 
 this distance, on Cnoc Tricriche, Sgor Coinnich, Beinn Bhreac, and 
 Cruach a' Bhuic ; but on the tops of some of the hills, thin bands of 
 quartzose schist come on again over the main mass of albite schist. The 
 line between the series which consists mainly of albite schists, and the 
 underlying greywackes is too poorly defined to enable us to find out 
 small faults and folds. "We have frequently found that a certain band 
 of greywacke or quartzose schist, that seemed in one place to act as a 
 good top to the greywacke horizon, having little else but albite schist 
 above it, would, on passing north a little distance, become overlain by 
 schist, in which the proportion of quartzose schist was, for a certain 
 thickness of section, as great as, or greater than, that of albite schist. To 
 keep the line a consistent division between the more quartzose and the 
 more phyllitic parts of the section, we have apparently to ascend every 
 here and there into higher beds as we go north. The general course 
 of the line adopted is almost level from the N.N.E. fault near Lochan 
 nan Cnaimh to Cruach a' Bhuic, yet the impression derived from 
 examining cursorily the dip of the foliation on the hill tops between 
 these places is that, the general dip, except on Cruach a' Bhuic, is dis- 
 tinctly north-east. This is probably due to the existence of many small 
 acute folds with both limbs hading north-west, which have the effect of 
 bringing up the top beds of the greywacke again and again as we go 
 north. Unfortunately, none of these folds is so distinct as to be shown 
 on the Map with confidence. The line must only be regarded as a 
 
202 
 
 GEOLOGY OF COWAL. 
 
 generalisation. The horizontal character of the line forms a conspicuous 
 contrast to that of the different lamprophyre sheets, which are mapped 
 in the neighbourhood. These have distinct hades to the north-west. 
 They may be considered to keep almost parallel to the prominent foliation 
 without regard to those north-west limbs of synclines, through the 
 influence of which the bedding of the schists is being repeatedly brought 
 back again to its old level. 
 
 FIG. 45. 1 inch = 20 feet. One-quarter of a mile E. of Lochan nan Cnaimh (153). 
 Contorted phyllitic mica schist and greywacke schist. Axes of folds and strain 
 slips hade N.W. 
 
 The remarks made about the top of the greywacke on the east side of 
 the hill-top apply also to that on the west side. In the burn \ mile 
 south of Beinn Dubhain, the top is thrown down west by a north to 
 south fault, perhaps about 40 feet. West of this place the line gets 
 quickly to a lower level. Just before it reaches the alluvium at the head 
 of Loch Eck it is poorly defined, and on the west side of Loch Eck we 
 were not able to map out any thick horizon until we advanced some 
 distance down Garrachra Glen (163). 
 
 Below the top of the greywacke there is usually a large proportion of 
 massive quartzose pebbly schist on both sides of Cnoc na Tricriche. 
 Such is seen, e.g., on the west side, in Coire Ealt and the burn drawn 
 through the "Point" of "Dornoch Point," and, on the east side, in the 
 upper half of the burn that flows south-east from Cnoc na Tricriche. 
 
 East and south of Cruach a' Bhuic the structure requires further de- 
 scription. In the burn head J mile south-east of this hill there are 
 massive quartzose schists at a higher level than those below the albite 
 schist to the south-west. We suppose this is due to a north to south 
 fault. On the east side of the supposed fault there are two outcrops of 
 albite schist. The north outcrop is about 300 yards wide. More than 
 half this width has various outcrops of quartzose pebbly schist opposed 
 to it on the west side of the supposed fault a circumstance which helps 
 to confirm the existence of the fault. The south outcrop is riot so wide 
 and is not distinct close to the fault. The dip in both these outcrops is 
 south-east, and they both, but particularly the north one, get thinner as 
 they are traced downhill towards Loch Goil. In the more southerly of 
 the two burns j mile south-west of Carrick Castle, the width of the 
 north band seems only 50 yards. North-east of this section the ground 
 is drift-covered until we come near the aids of the loch. We saw no 
 albite schist near the loch thick enough to map : a large proportion of 
 
STRUCTURE OF CARRICK DISTRICT. 
 
 203 
 
 the rock is massive quartzose pebbly schist. The south band is not so well 
 defined as the north one : north-east from the fault the north margin of 
 the south band recedes slightly from the south margin of the north band, 
 and at the same time there is apparently a slight diminution in the width 
 of outcrop of the south band. One-quarter of a mile south-west of the 
 "A" of "Ardnahien" the south band enters on a drift area, but on the 
 shore 120 yards N.N.E. of Ardnahien there is an outcrop of albite schist, 
 
 FIG. 46. x . Near Carrick Castle. Folded quartzose and more phyllitic mica 
 schists. The more shaded parts are the more micaceous, and contain more 
 magnetite crystals than the rest. The limits are but slightly thinned, yet, in 
 the same bed, considerable differences have been developed between them and 
 the crests. Axis of fold hades N. W. 
 
 about 20 yards wide, which may be a continuation of it. This is the 
 only mapable albite schist seen in or near the shore between Carrick and 
 i mile south-east of Ardnahien. The albite schists south-east of Ardna- 
 hien have been traced uphill to the W.S.W., and strike to the south-east 
 of the Cruach a' Bhuic albite schist. 
 
 South of Cruach a' Bhuic, west of the supposed fault, the albite schist 
 runs downhill with a south-east dip. Both margins are well-defined, and 
 gradually approximate towards one another the lower they descend. 
 South-east of Cnoc Fraorach the width of outcrop is 300 yards: J 
 mile S.S.E. of this Cnoc it is 80 to 90 yards. At the last place there is 
 a fault feature running W.N.W., and on the south side of the fault the 
 albite schist is shifted to the east, and is also thinner, hardly 50 yards. 
 Further south-west the outcrop continues to get narrower until in the 
 burn between the "F" and "i" of "Glen Finart " it is hardly 16 
 yards. About 50 yards east of the outcrop, on the south side of the 
 fault, there is another albite schist, of about the same thickness. 
 
 We seem thus gradually to lose the thick albite schist of the hills be- 
 tween Cnoc Tricriche and Cruach a' Bhuic, as we descend to low levels 
 a little on the south-east side of " the anticline." Anyone who examined 
 the section between Rudha nan Eoin and Carrick, and then that on 
 the hills mentioned, would certainly find a difficulty in matching the 
 two. Yet if " the anticline " had been a simple anticline of bedding the 
 beds on the hills must have been seen again on the coast line. It seems 
 necessary to suppose that the Beinn Bhreac, etc., albite schist has 
 practically all died out, or else been folded out, by the time we reach 
 the sea level. The latter alternative is much the most probable. Besides 
 the great amount of folding always seen in good schist sections, there 
 are other reasons in support of this supposition. Near Rudha nan Eoin 
 we pass gradually, in a south-east direction, from a thick massive 
 quartzose pebbly horizon on to much more thinly fissile schist, in which 
 there is a considerable proportion of phyllitic and fine-grained albite 
 
204 
 
 GEOLOGY OF COWAL. 
 
 schists. Apart from the smaller size of the albites (see p. 42) this 
 series does not much resemble the schist of Beinn Bhreac, etc. The 
 mica in the former is not so prominent. It is rare to get distinct 
 micaceous " satiny " bands more than 4 to 6 inches thick. There is 
 
 nearly always a mixture of fine-grained granulitic quartzose schist, but 
 never any considerable thickness of this schist. Often it seems as if the 
 more micaceous bands occurred along lines of special strain and were 
 secondary. The north-west boundary of this thinly-foliated series is not 
 well-defined. It is doubtful whether it is best to take it a little north- 
 
STRUCTURE OF CARRICK DISTRICT. 205 
 
 west of the Rudha, or a little south of it, the rock at the point itself 
 being an alternating series, with a larger proportion of massive rock than 
 there is to the south. The line adopted in the Map is the south line. 
 This line can be traced to the south side of Creachan Mor, and it is 
 certain that the massive rocks of this hill, and of Cruach Eighrach, 
 correspond to those on the coast between Toll nam Muc and Rudha nan 
 Eoin. If " the anticline" had been a simple anticline of bedding, this 
 massive horizon should overlie the Beiun Bhreac albite schists, and we 
 should have met with this horizon again either on the south slope or top 
 of Beinn Bheula. But we never meet it again either on Beinn Bheula, or 
 between Beinn Bheula and the base of the green beds to the north-west. 
 
 These are the facts which, taken in conjunction with the other impor- 
 tant differences in the beds on either side of " the anticline " (see p. 86), 
 have led us to suppose that very near the centre of " the anticline " there 
 are also important folds, the axes of which have been folded by " the anti- 
 cline." The top of the greywacke schist we have mapped on the north- 
 west side of " the anticline " is not the same as that on the south-east side, 
 but the one line may be considered the one margin, and the other the 
 other margin of a great greywacke series. 
 
 On the top of Cruach a' Bhuic there is a somewhat flat band of massive 
 pebbly schist, which may possibly represent part of the underlying grey- 
 wacke folded over. 
 
 On the south-west side of Creachan Mor there is a N.N.W. scar feature, 
 facing west, which develops to the south into a slack or depression. By 
 the " u " of Cruach a Chaise, a clayey crush, 2 to 3 feet wide, is seen 
 along this feature. The top of the greywacke horizon seems shifted 80 
 to 90 yards to the south on the west side. One-fifth of a mile north- 
 west of the " C " of " Coille Mheadhonach " the same margin is again 
 shifted by a fault, the west side to south, 80 or 90 yards. Half a mile 
 north of this place, various parallel crush breccias are seen along the 
 fault, hading east. The surface displacement of the line taken for the 
 base of the greywacke is 50 to 60 yards, the west side to south. For 
 a little way north-west of the greywacke horizon the beds are not so 
 massive or quartzose as they are to the south-east, but we reach massive 
 pebbly schists again before the albite schist which runs up to Cruach a' 
 Bhuic is reached. It must not be supposed that all the schists on this 
 greywacke horizon are greywacke schists : there are thin phyllitic mica 
 schists as well, but the proportion of these is less than outside the horizon. 
 Xear the middle of the horizon, between the fault last described and the 
 hilltop to the north-east, the south-east margin of a phyllitic interval has 
 been mapped : it is overlain by an unusually quartzose schist without 
 evident pebbles, which forms a strong contrast in colour with the phyllitic 
 schist, so that it is easy to map the line between them. The line is 
 much folded and often dips north-west for a little space, but the general 
 inclination is distinctly south-east. 
 
 There are good sections of the greywacke schist on Castle Crag and 
 the hillside to the south-east, from the first " C " of " Castle Crag " for 
 nearly % mile south-east. On this hill both the north-west and the south- 
 east margins of the horizon are unusually well-defined. 
 
 Between 200 and 300 yards east of Loch Eck the greywacke schist 
 horizon meets with a north to south fault ; the surface displacement is 
 rather more than ^ mile, the west side to south. There is a conspicuous 
 slack along the course of the fault which continues to J mile south of 
 the "T" of "Tom Soilleir." In the burn nearly i mile north of Coylet 
 there are two basalt dykes accompanying the fault. The crush breccia 
 near the east dyke is distinctly hardened and altered. 
 
206 GEOLOGY OF COWAL. 
 
 The albite schists south-east of Ardnahien have been already referred 
 to. Three hundred and fifty yards south-east of Ardnahien there is a 
 fairly-defined south-east margin of an alternating series of albite or 
 phyllitic mica schists with other more quartzose schists. South-east of 
 this comes a bed, 60 to 70 yards wide, of massive pebbly schist, and then 
 a bed chiefly of albite or phyllitic mica schist, about 130 yards wide. 
 This last albite schist is well-defined on both sides, but J mile south-west 
 of the shore an outcrop of quartzose schist, 20 yards wide, appears in the 
 middle of it. The quartzose schist may be a folded inlier of the under- 
 lying bed.. South-west of the quartzose schist the margins of the albite 
 schist rapidly approximate ; 1 mile north-west of the " C '.' of " Cruach 
 an Draghair " the width is hardly 30 yards. At the " C " of " Cruach " 
 it is only 16 yards, and soon after that ceases to be traceable. 
 
 Five-eighths of a mile slightly north of east of Cruach nam Miseag there 
 are two small patches of albite schist resting on more massive pebbly quart- 
 zose schist. These we regard as outliers of the lower part of the albite 
 schist of Cnoc Tricriche, Beinn Bhreac, etc. 
 
 There are two faults in this district which may represent the Ben 
 Donich N.N.E. fault. The west fault makes a feature facing north-west 
 all the way between the burn mile E.S.E. of the "r" of "Mullach a' 
 Chuirn " and J mile north of Lochan nan Cnaimh. The crush rock is seen 
 close to the burn mentioned. This is the fault which throws the lampro- 
 phyre at a place f mile south-west of the foot of Lochan nan Cnaimh, as 
 already mentioned, p. 201. The east fault is exposed in the burn ^ mile 
 south-east of the " i " of " Corriesyke." The hade is east. It keeps in 
 or near this burn as far as the sharp bend to the west. A little further 
 south-west it comes into another burn and keeps along it for J mile or 
 more. No doubt the direction of the fault has determined the directions 
 of both these burns as far as they coincide with it. The crush must 
 cross the glen south of Cruach nam Miseag near the 700-foot contour. 
 It forms a slack or depression on the hill-top south of this glen, just east 
 of the 1000-foot contour. There is a section of the crush, still hading 
 east, and associated with ferriferous carbonate strings, f mile west of the 
 "C" of " Cuilrnuich." We suppose this fault may be the one the 
 indications of which we have already described near Chruac a' Bhuic (see 
 p. 202), and in the greywacke schist \ mile north-west of the " C " of 
 " Coille Mheadhonach " (see p. 205). The surface displacement in the 
 albite schist of Chruac a' Bhuic is in the opposite direction to that near 
 Coille Mheadhonach, but it is not easy to see what can become of either 
 fault unless they are the same. On the south-west side of Glen Finart 
 the fault probably continues through the second "a" of " Barnacabber," 
 and the last "o" of "Tom nan Con." In the burn just south-west of 
 this " o " the crush is exposed : it consists of crush clay and quartz 
 veins hading east. 
 
 North to south or N.N.W. faults run from Loch Long by Toll a' Bhuic 
 and Knap Burn and make conspicuous features in the landscape. The fault 
 at Toll a' Bhuic effects a surface displacement in a lamprophyre dyke of 
 30 to 40 yards, the west side to the south, but it cannot be traced far. It is 
 not clear that there is any shift in the lamprophyre along the course of 
 the Knap Burn fault. 
 
 Three-eighths of a mile south-west of the " P " of " Port an Lochan " 
 there are indications of several N.N.W. crushes. One of these shifts a 
 lamprophyre dyke about 3 yards, the west side to south. 
 
 The fault mentioned (p. 205) on the south-east side of Creachan Mor 
 seems to divide into two parts ^ mile north of " A " of " Am Birinein." 
 The west part makes a scar feature, facing west, on the south side of Am 
 
STRUCTURE OF CARRICK DISTRICT. 
 
 207 
 
 Binnein, and enters Loch Long on the east side of Shepherds Point. 
 The crush on the shore is 9 feet wide and hades east : the slickensides 
 are horizontal. The east part also forms a scar feature facing west. It 
 runs through the " i " of " Glume Wood " down to the " oc " of " Stron- 
 vochlan," and formed the east margin of the old Finart Bay in raised 
 beach times. One-eighth of a mile north of the " i " of " Clunie " two or 
 three parallel crushes are seen along the line, all hading east. 
 
 On the shore J mile north-east of Toll a' Bhuic there is a gulley 
 about 16 yards wide, running nearly with the strike of foliation. We 
 suppose it due to a thin crush or to two thin parallel crushes : the main 
 part of the rock within the gulley is sometimes, e.g., on the west side of 
 Toll a' Bhuic N.N.W. fault, sound schist, but there is always a space 
 where no rock is seen, and there may be a crush beneath this. The 
 gulley is readily traced as far as the east side of the Shepherd's Point 
 fault, where it is accompanied with a larnprophyre dyke. 
 
 Part of the Coire No (133) N.N.E., disturbances come into or near the 
 north-west corner of the area being described, and may perhaps be con- 
 sidered the originating cause of the low valley crossing the watershed 
 between Sugach Aodainn and Leamhanin. In Sugach Aodainn, f mile 
 south-west of the "u" of "Sugach," a 6-foot basalt dyke is seen running 
 with parallel crushes in a N.N.E. direction : there is a smaller basalt 
 branch on the east side : some crushes seem to trend north, crossing over 
 to a X.N.E. feature, along the course of which, other crushes, hading west, 
 cross the stream due east of the " d " of Bridgend." 
 
 The foliation dip between Am Binnein (164) and Loch Long is often 
 vertical or sometimes even dipping north-west (see p. 83). The north- 
 west dip is particularly to be noted between ^ mile and J mile south-east 
 of this hill- top. On the north-east side of Tom Soilleir (163 north-east) 
 there is a tendency for the foliation dip to be west or south-west, instead 
 
 SE 
 
 N W 
 
 FIG. 48. 1 iuch = 8 feet. Two hundred aiid fifty yards E.S.E. of Ardnahien (153). 
 Plan of folded pebbly quartzose schist band in a steep rock face sloping N.E. 
 The first foliation near the margin is indicated in several places. It often 
 crosses the margin, and in some places is parallel to axes of early fold. Line 
 " CD " may be a discordance. 
 
208 GEOLOGY OF COWAL. 
 
 of north-west. We could not see any clear reason for this. Some of the 
 exposures showing the south-west dip are a considerable distance off the 
 north-west depression along the road between Larach Hill and Whistlefield, 
 and it hardly seems feasible to connect the dip with possible disturbances 
 along this line. 
 
 The quartzose bands mixed with the more thinly fissile schists on the 
 south-east side of the Creachan Mor greywacke contain a good many 
 impure calcareous bands, but these are rarely more than an inch or two 
 thick. 
 
 There are good sections along the side of Loch Long, particularly 
 between Carrick and Finart Bay. The " pre-anticline " folds and 
 structure lines are often folded by the later folds with axes hading north- 
 west. Good hillside sections are also abundant throughout the district. 
 Plate V., near the end of the volume, represents part of a cliff section 
 on the roadside a little south of Coylet Inn, Loch Eck. The prominent 
 folds in the section are probably of " anticline " age. 
 
 FIG. 49. x. One-third of a mile S.E. of Mullach a Chuirn (142). Quartzose 
 schist band in phyllitic mica schist. Band is repeatedly broken through by 
 foliation-faults which throw an earlier foliation and bedding constantly in the 
 same direction. There are four or five times as many breaks in the phyllitic 
 schist as in the quartzose, and the hades of these become steeper when crossing 
 the latter schist. 
 
 District of Beinn Mhor. 
 
 This district is inclosed by the Strachur and Loch Eck Valley, part of 
 the south margin of 1-inch Map 37, the River Ruel, Gaol Ghleann, the 
 upper part of Stralachlau River, and the part of Loch Fine between 
 Newton Bay and Strachur. 
 
 All the schist zones from the Ardrishaig phyllites to the alternating 
 greywacke and albite schists occur within this region. Most of it lies 
 on the north-west side of " the anticline," but a small portion near the 
 south-east corner, on and near Clach Beinn, is on the south-east side. In 
 the north-west half of the area there are many bands of epidiorite and 
 hornblende schist, but south-east of a line a little below the green beds 
 none are known. 
 
 The sections of the Ardrishaig phyllites on the shore, and the folding 
 shown in this series, are described elsewhere, p. 58. The ground near 
 the centre of "the anticline" is more elevated and more craggy than that 
 to the north-east. Sections are so abundant in this rocky area that it is 
 not necessary to mention them in detail. The crags south of Coirantee 
 show very clear instances of folding of the axes of early " pre-anticline " 
 folds, like those described on p. 24. 
 
 We think it probable that the epidiorite and hornblende schist exposures 
 on the shore near Stucreach and Leak belong to one bed repeated by fold- 
 ing and faulting. The exposure J mile south-west of Stucreach has pebbly 
 green beds a little north- west of it : a fault, to be shortly described, 
 lies a little east of it : its west end is also cut off by another north to 
 
STRUCTURE OF BEINN MHOR DISTRICT. 209 
 
 south fault. Near Leak there are four or five exposures of epidiorite 
 which are quite isolated at the surface. The two smallest near the 
 lamprophyre on the east of the hamlet, can hardly be shown on the 1-iuch 
 Map. The exposures west of the hamlet are larger and irregularly oval 
 in shape. In the rocky point J mile north-west of the "L" of " Leak" 
 there are two exposures, one lying north-east of the other. They are 
 separated by a thin band of phyllitic mica schist. 
 
 The line adopted to roughly divide the Ardrishaig phyllites from the 
 garuetiferous mica schists is the most north-westerly zone of graphite 
 schist (see p. 48). On the shore south-west of Strachur Bay garnets are 
 abundant iti the schists to within 200 yards of Creag nam Faoileann, 
 but they are probably north-west of all the graphite schists. The numerous 
 thin outcrops of epidiorite and hornblende schist on this Creag (see 
 p. 66), belong probably to the same series as those near the head of 
 Eas Dubh (142). The schists on the shore north-east of the Creag 
 probably occur between these epidiorites and the most north-westerly 
 graphite schist. 
 
 Between Creag nam Faoileann and Mid Letter there are several 
 north-west faults. The most south-westerly fault has a slight down- 
 throw south-west, as shown by a baud of pebbly green beds on the shore, 
 but the others throw down north-east, and the general effect of the group 
 is to advance the graphite schist on its south-west side towards the 
 south-east. 
 
 200 yards south-west of Mid Letter there is a north-west fault in two 
 parallel parts, which throw down to north-west. The direction of shift 
 can be made out in the band of green beds alluded to in the last paragraph. 
 The effect on the graphite schist is uncertain. 
 
 In the burn J mile S.S.W. of Mid Letter there are strong crushes 
 ranging slightly west of north, and the strike of the foliation is parallel 
 to them for a little space. These crushes probably keep a little east of 
 the burn to the south, and cause the graphite schist exposures in this 
 burn to be further to the south-east than we should otherwise have 
 expected. A little below the most south-easterly graphite schist there 
 is an obscure exposure of limestone. On the west side of the burn is 
 another crush, seen in the burns ^ mile north-east of An Carr and rather 
 more than J mile south-west of Mid Letter. In the latter locality the 
 hade is west. There are no exposures of graphite schist on the west 
 side of the fault for J mile or more. 
 
 In the burns J mile south-east of Stucreach there are good sections of 
 graphite schist : the most north-westerly outcrop is accompanied with a 
 lamprophyre sheet in part of its course, but in the branch off the west 
 burn there are prominent folds in the graphite schist, and, coincident with 
 these folds, a gradual separation from the lamprophyre. Close to the 
 section a small fault seems required with downthrow east, but the course 
 of the supposed fault is not clear: in a north-west direction there are 
 some crushes in the burn -J mile south-east of the " h " of " Stucreach," 
 but these hade west. 
 
 Between f and f mile S.S.W. of the "S" of " Stucreach " there is 
 evidence for a good many north-west faults. The effects of these are seen 
 best in a green bed north-west of the graphite schist. The most north- 
 easterly fault that has an important throw is the* fault in the burn f 
 mile south-west of the same "S." The hade is north-east and the down- 
 throw, both in the green bed and an accompanying lamprophyre, is also 
 in this direction. The displacement at the surface is about 130 yards. 
 The strike of the foliation is parallel to the crushes for a little distance. 
 The other faults, at least three, south-west of this, all throw down 
 
 
 
210 GEOLOGY OF COWAL. 
 
 south-west, and the green bed is gradually lifted to a little above its 
 old level. There is a fault on the shore f mile south-west of the " S " of 
 " Stucreach " which is accompanied by a thin basaltic dyke, and the fol- 
 iation on the south-west side is twisted into parallelism. This may be 
 compounded of several of the faults that are observed further south-east. 
 The downthrow appears to be south-west, for an epidiorite, like that at 
 Stucreach, is brought on to the shore again a little south-west of the fault. 
 The hill-side where these faults would be expected to cross the graphite 
 schists is almost entirely covered by drift or a patch of peat and alluvium, 
 which runs nearly with the strike of the beds. Graphite schist is seen 
 at a point f mile N.N.E. of the "h" of "Sith an t-Sluain." This is 
 probably just on the high side of the fault which throws down south-west. 
 There are no exposures of this schist further south-west until we come J 
 mile north of the " n " of " Leanach," where the burn displays a good 
 section of graphite schist underlying a graphitic limestone and separated 
 from it by a strong crush hading north-west, nearly with the schist. The 
 schist under the crush is muck contorted. The different twists cannot be 
 traced far. There is certainly more than one line of crush. Both limbs 
 of the folds in the contorted part are generally inclined in the same 
 direction : as we look north-west towards the exposure the axes of 
 anticlines generally point south-west, so that there appears to have been 
 a movement along the crush lines of the rocks on the north-west side in a 
 south-west direction over the rocks on the south-east side. This is the 
 opposite direction to that indicated at the crush in the graphite schist at 
 the head of Eas Dubh (see p. 109). 
 
 Quartzose schist below the graphite schist is exposed in the burn from 
 near the limekiln, 200 yards north-east of Leanach, up to where the road 
 crosses the burn. Near the limekiln there are four or five basaltic dykes, 
 running north or N.N.W., and with indications of crushing, either within 
 or near the sides. Some of the crushes are probably accompanied with 
 distinctt hrows, as graphite schist is seen close to the two most westerly 
 dykes, considerably south-east of the strike of the graphite schist mentioned 
 in the preceding paragraph. On the hill side f mile N.N.E. of Leanach, 
 hornblende schist is striking at a green bed on the east. It is probable 
 that part of the disturbances near the limekiln cross between these 
 exposures. To the north, on the coast east of Leak, there are three or 
 four crushes which may continue to the same place. The most westerly 
 crush is accompanied with a camptonite dyke. Both this crush and the 
 next three cause shifts in some irregular lamprophyre intrusions : they 
 appear to downthrow west. The most easterly crush is accompanied by 
 two dykes, one basaltic and the other a fine-grained lamprophyre : the 
 former is chilled against a ferriferous carbonate vein. 
 
 On the north-east side of Meall Reamhar there is a N.N.E. running 
 feature, facing north-west, along which a band of green beds is thrown 
 down north-west. This feature can be traced north-east to a little beyond 
 the "ch" of "Tigh na Criche." A little west of this feature, near the 
 "r" of "Mid Letter," there are four north to south crushes hading west. 
 The two middle crushes are close together, and there is an obscure 
 exposure of green beds between them. 
 
 The Loch Tay limestone is exposed at the hamlet of Glensluan in a 
 quarry which has been extensively worked. This quarry and various 
 veins and crush breccias in it have been described by Mr W. Ivison 
 Macadam (Trans. Edin. GeoL Soc., vol. iv. 1883, p. 101), and a series of 
 analyses is given by him of the limestone and vein rocks, etc. The 
 details of two of these analyses are given on p. 47. None of the crush 
 breccias and slicken-side lines seemed to us to materially displace the 
 
STRUCTURE OF BEINN MHOR DISTRICT. 211 
 
 bed, and owing to the amount of other geological detail, they are not 
 inserted in the map. By the "a" of " Glensluan " there is a thin 
 exposure of limestone 10 to 121'eet above the main outcrop. A similar 
 exposure is also seen ^ mile further south-west. A lenticular band of 
 phyllitic schist, a few feet thick, occurs within but near the top of the 
 limestone. In the limestone below this there is a band of lamprophyre 
 which gradually dies out going south-west. There are two bands of 
 hornblende schist in the limestone : the upper band is at the base of the 
 upper, purer, part of the limestone, and the lower at the base of the 
 calcareous quartzite part. 
 
 In the bend of the River Cur by Tombuidhe a green bed is seen on the 
 south side of a strong crush. The direction of the latter is doubtful : 
 we have drawn it E.N.E. Whether this green bed is the band a 
 little above the limestone at Glensluan is doubtful. Possibly it 
 may be near the top of the main green beds zone and have the Loch Tay 
 limestone above it. Between the crush and the green bed is an obscure 
 exposure of calcareous quartzose schist which might represent part of the 
 lower portion of the limestone. 
 
 One-half mile south-west of the last " n " of " Glensluan " the limestone 
 suddenly comes down into the bed of the burn on the south-west side of 
 three basaltic dykes. The two east dykes are generalised as one in the 
 Map : they are both partly crashed. There is a baud of hornblende schist 
 within the limestone and another at its base, just as at Glensluan. The 
 base of the limestone continues in the north-east bank of the burn for 
 nearly ^ mile south-west of the dykes. Then we meet with a north to 
 south crush, hading west and downthrowing in the same direction, so that 
 the hornblende schist within the limestone on the west side, lies against 
 beds below the limestone on the east side. 
 
 Eighty yards further up stream there is a larger north-west fault, 
 which shifts the limestone some distance on to the south-east side of the 
 burn. Thero is a section showing the upper part of the limestone, the thin 
 phyllitic schist above it, and the hornblende schist within it, in the little 
 burn J mile south of the " h " of " Gleann Dubh." The amount of displace- 
 ment seems about 180 yards. Where the fault crosses the main burn 
 there are two thin bands of green beds on the south-west side of it, opposed 
 to the lower part of the limestone. On the south-west side of the fault 
 in the little burn there are two outcrops of hornblende schist between the 
 limestone and the top of the green beds zone. These are seen at intervals 
 as far as the head of Stralachlan River. Before the limestone gets into 
 the main burn again it meets with another N.N.E. fault probably the 
 continuation of that mentioned, p. 220, in the burn ^ mile east of the 
 "s" of "Creggans." The downthrow is west but not large. On the 
 west side of the fault there is a burn section of the limestone and the 
 leaden coloured phyllitic schist just below it : there is only one hornblende 
 schist in the limestone and this is a little above the base. One hundred 
 yards further up the burn, hornblende schist occurs again in the north-east 
 bank striking at beds below the limestone. There is a crush hading west 
 on the south-east side of the schist, and we therefore presume that it re- 
 presents the band within the limestone. Between this exposure and 
 the burn J mile E.S.E. of the last "n" of "Sith an t-Sluain" the lime- 
 stone is covered by drift, but the green bed a little above the limestone is 
 seen near the middle of this space. In the above burn there are two 
 faults, one running nearly east to west, and the other KN".W., and these 
 let down the beds between them to a small extent. There is a horn- 
 blende schist below the limestone, and below this schist there is calcareous 
 quartzite. On the south side of this burn the limestone makes a con- 
 
212 GEOLOGY OF COWAL. 
 
 spicuous scar with hornblende schist below. Two hundred yards south 
 of Cruach nan Capull (152) there is a prominent bank feature facing south. 
 To the west this twists into a north-west direction, and is accompanied by 
 a throw in a green bed : the south-west side is shifted north-east about 
 60-70 yards. The displacement in the limestone is probably greater 
 than this, but it cannot be accurately determined as there are no rock 
 exposures very near the south side of the feature. 
 
 There are many sections of the limestone and adjoining schists in the 
 small streams S.S.E. of Cruach nan Capull. There must be many faults 
 in the locality, but their exact directions and effects are not always 
 ascertainable, owing to the amount of drift on the hill sides. The horn- 
 blende schists in and at the base of the bed are liable to considerable varia- 
 tion in apparent thickness. One-quarter of a mile south-west of the second 
 "n" of "nan" there are two outcrops of hornblende schist, but neither seems 
 more than a few feet thick. South-west of here the outcrops are always 
 much wider, and there are sometimes 3 of them. Near the head of Stra- 
 lachlan River, about J mile W.JS T .W. of the " u " of " Srou Cruaich " the 
 outcrop within the limestone is about 40 yards wide, and that at the base 
 about 50 yards. The upper part of the limestone is the purest. In the lower 
 part there is a considerable proportion of calcareous quartzite, but good 
 sections of mottled limestone also (see p. 46). In the river J mile N.N.W. 
 of the top of the main limestone outcrop there are two more exposures of lime- 
 stone. These may both be folded inliers of the Loch Tay limestone. The 
 larger, or south-east exposure, contains some mottled bands very like those 
 of this limestone, but most of it is calcareous quartzite : a hornblende 
 schist occurs within it : the foliation dip of the quartzite changes from 
 north-west to south-east near the middle of the exposure. There is a band 
 of green beds 50 yards north-west of the top of the main outcrop of lime- 
 stone. We did not see this green bed again before the higher outcrops of 
 limestone were reached, though the section is a good one. Possibly this 
 absence of repetition may be due to the green bed being at the bottom of 
 a syncline. There are two or three green beds lower down the river before 
 the fields near Leanach are reached : a W.N.W. fault runs along the river 
 course and advances the most north-westerly bed considerably west on the 
 south side of the fault. There are also some thin hornblende schists and 
 epidiorites in the same reach which are at times hard to distinguish from 
 the green beds. South-east of the main outcrop of limestone there are four 
 outcrops of hornblende schist in the river, not counting that at the base. 
 The most south-easterly outcrop, within 70 yards of the boundary of the 
 parish of Stralachlan, is bounded on the west by a N.N.E. crush hading 
 west, but it is possible that this is a reversed hade and that the band is 
 really the same as that on the west side of the fault. Five-twelfths of a 
 mile N.N.E. of this locality there are two N.N.E. faults crossing the lime- 
 stone : one downthrows west, but the other and larger one of the two, 
 though it hades west, has a downthrow in the opposite direction. The 
 larger fault is accompanied by two dykes, one basaltic and the other a 
 lamprophyre. We suppose this fault continues N.N.E. to the crushes 
 in the bum J mile S.S.W. of Mid Letter. 
 
 At the head of Stralachlan River, 50 to 60 yards south-east of the 
 parish boundary, we lose the rock section. Between this place and the 
 limestone we could see no green beds except one band, about 5 feet thick, 
 not far below the limestone : most of the exposure is either hornblende 
 schist or rather massive quartzose schist. We have therefore to draw the 
 top of the main green beds zone further south-east of the parish boundary. 
 Even after allowing for the slope of the ground being in the same direction 
 as the dip, this makes the distance between the limestone and the green 
 
STRUCTURE OF BEINN MHOR DISTRICT. 213 
 
 beds considerably greater than it usually is in the north part of Covval. 
 All the way from here to the burn J mile E.S.E. of the last " u" of " Sith 
 an t-Sluain " the top of the green beds zone is entirely covered by drift. 
 This is also commonly the case through most of the area being described. 
 We have drawn the line in the Map, so as to show where to stop the 
 green beds colour, but it is of little stratigraphical value. 
 
 There are six outcrops of hornblende schist in Garvie Burn below Strath 
 nan Lub. The lowest but two, J mile south of the last " n" of "Strondav- 
 ain," only occurs on the south side of the burn : it conies in on the crest 
 of an anticline with both limbs hading north-west. It is probable 
 that some of the others are also due to repetition by folding. The hill 
 sides near the burn are obscured by drift for long distances, and it is 
 doubtful whether the two outcrops in the bare area east of An Cruachan 
 (162) continue to the exposures to which they have been connected in 
 the Map. 
 
 On the south-east of An Cruachan there is a prominent N.N.E. depres- 
 sion partly occupied by a peat moss. North-west of the hilltop there is a 
 basaltic dyke, with a strong crush at its side, in the same line as the 
 depression. The crush hades west. Neither of the hornblende schists is 
 seen on the south-west side of the depression until we advance a little 
 within 1-inch Map 29, after passing another feature, due to a fault with 
 downthrow N.N.E. 
 
 There are two exposures of hornblende schist in the barn J mile S.S.W. 
 of the " o " of " Caol-ghleann." These probably belong to one band dipping 
 almost with the hill slope. The horizon is apparently much the same as 
 that of the most north-westerly exposure in Garvie Burn. The ground 
 between here and Garvie Burn is obscured by peat on the hill top, and drift 
 in the lower areas, and no other exposure on the same horizon has been 
 noticed in it. 
 
 On the south-east side of Dunans Burn there are small exposures of 
 hornblende schist south-east of the fault running along the burn, at 
 places and J mile north-east of the " D " of " Dunaus." Two other 
 outcrops of similar schist are also seen J mile or more slightly north of 
 east of these. All these are isolated by drift from one another. It is 
 possible they belong to one band. The hill slope being nearly with the 
 dip, the band may make a broad outcrop under the drift. 
 
 There is a hornblende schist in the burn 200 yards south of the last 
 "a" of " Caol-ghleann. A little north of the burn a north-west fault is 
 required, to account for a shift in the outcrop, towards the north-west, 
 of about 200 yards. In a burn north-east of the supposed fault there are 
 two outcrops of hornblende schist. It is probably a continuation of the 
 north-west outcrop which is seen in the burn J mile north of the " h " of 
 " Caol-ghleann," intersected by many parallel basalt dykes. On the 
 south-west side of the dykes the top of the hornblende schist is gradually 
 covered by the overlying schist, but in the stream a little lower down it 
 comes out again, apparently owing to a local flattening of the dip, and 
 keeps in the burn for 70 to 80 yards. After this the base emerges out 
 of the burn. We suppose the exposures just at the foot of the burn belong 
 to the same band: they are cut off on the south-west by the north-west 
 fault mentioned in the beginning of the paragraph. The fault makes a 
 slight shift in a N.N.E. lamprophyre on the north-west side of Caol 
 Ghleann Burn. Many other parallel faults, at least five of them, throw 
 the same intrusion, sometimes in one direction and sometimes in another, 
 between this fault and the alluvium at Caol-ghleann. The most south- 
 westerly exposure of rock in the burn near the north end of this 
 alluvium is dipping south-west, at light angles to the ordinary dip in the 
 
214 GEOLOGY OF COWAL. 
 
 neighbourhood, arid is crossed by red crushes parallel to the strike. This is 
 probably close to the north-west fault, accompanied with basalt dykes, 
 which, in the area 1 mile south-west of Caol-ghleann shifts the base of 
 the green beds zone, the north-east side to the north-west, for \ mile (see 
 p. 215). Accompanying basalt dykes are seeu in a burn \ mile south- 
 east of Coal-ghleann. 
 
 On the west side of the burn by the " G " of " Gaol Ghleann " there 
 are two outcrops of hornblende schist. The higher one is the wider. We 
 suppose it to be the same band as that already mentioned in the burn 
 200 yards south of the last " a " of Gaol Ghleann, etc. Strong crushes, 
 accompanied in part of their course by a basalt dyke, ran up the burn on 
 the north-west side of the exposures, and continue for a long distance 
 N.N.E. to join those with a similiar direction in Ghleann Dubh (see p. 
 211). In the burn f mile S.S.W. of the "h" of "Tom a' Bhiorain" 
 a basaltic and lamprophyre dyke both accompany the crush. On the east 
 side of the same Tom there is a feature facing west, which we suppose to 
 be along the course of the fault. We could not trace the fault satis- 
 factorily on the south-west side of Coal-ghleann, but on the east side of 
 Maol Odhar and An Cruachan there are features in the line of the fault; 
 and in Garvie Burn, along the same direction, there are thin crushes 
 hading west. 
 
 The base of the green beds zone is obscured by drift at the side of the 
 alluvium east of Balliemore. There is a small exposure of green beds in 
 a little stream near the bottom of the wood \ mile E.S.E. of Balliemore, 
 and in a burn not quite J mile south-east. This last exposure is probably 
 near the base of the zone, for all the exposures for some distance east of 
 it are quartzose or phyllitic mica schist. In a little burn f mile south- 
 east of Balliemore there are several thin basaltic dykes, at least four, run- 
 ning north-west with thin schist partings between them. The schist in the 
 partings sometimes strikes parallel to the dykes. Some of the dykes hade 
 south-west. There are crushes near the north-east side of the dykes, and 
 further off, green beds. These crushes and others which probably occur 
 under the drift a few yards north-east of them, must have a downthrow 
 north-east, for 160 yards south-east of the exposure mentioned, and on 
 the south-west side of the direction of the crushes, we see green beds 
 striking far east of the probable base of the green beds on the other side 
 of the crushes. The amount of shift at the surface seems about \ mile. 
 The basement green beds on the south-west side of the fault gradually rise 
 to the south and form a prominent crag Greag Bhaogh. A band of 
 hornblende schist, sometimes 16 feet thick, but not usually so much, 
 is seen about 12 feet above the base for as long as the exposure continues 
 quite bare. The beds under the green beds are alternations of quartzose 
 and other more phyllitic mica schists. Near the " B " of " Bhaogh " 
 there is an outcrop of green beds, about 1 foot thick, 30 feet below the 
 main base. 
 
 In the burn \ mile south-east of the last " r " of " Glen Branter " there 
 is a rather wide exposure of pebbly green beds, about 200 yards south- 
 east of the main base. On the north-east side of this there is a basalt 
 dyke hading west and accompanied with crushes. We could not see any 
 outcrop of green bed on the north-east of the dyke. In a south-west 
 direction the green bed is seen again in several places about J mile east 
 of the last " r " of " Glen Branter." 
 
 The hillside between the base of the green beds zone in the burn near 
 the " r " of " Glen Branter " and \ mile slightly west of south of the 
 " G " of the same words is drift covered. A north-west fault, accom- 
 panied with a basalt dyke, is seeu in the burn near the 
 
STRUCTURE OF BEINN MH6R DISTRICT. 215 
 
 hade south-west, but the amount of shift in the green beds is uncertain. 
 In the burn mile west of the first " r " of " Sron Criche " there are two 
 thin outcrops of green beds not quite J mile up the burn from the main 
 base : the upper one is only 1 foot thick. An outcrop in about the same 
 position with respect to the main zone is seen further south-west, between 
 f mile slightly south of west of the " S '' of " Sr6n Criche " and f mile 
 south-west of the same letter. At one place the band is a good deal 
 folded. 
 
 In the burn running from the north-west near the " L " of " Strath 
 nan Lub " there are two basalt dykes in the general direction of the 
 burn. Is r ear the north-east one there is a fault hading south-west ; 
 on the south-west side of the south-west dyke the schist is reddened and 
 vertical and almost parallel to the dyke. On the north-east side of the 
 upper part of the burn there are good exposures of schist ; a thin green 
 bed is seen about J mile north-west of 'the " u " of " Lub," but the base 
 of the main zone cannot come on until 140 to 160 yards further north- 
 west. In the nearest good section south-west of the dykes, that in the 
 burn running between the " a " and last " n " of " nan," green beds 
 are seen, at intervals, down to near the top of this word. They form the 
 whole of the bottom 100 yards of the exposure, and must be within the 
 main zone. A lower outcrop, corresponding to that on the north-east of 
 the dykes, occurs in the burn a little east of the top of the " L " of 
 " Lub." The amount of shift at the surface along the line of the dykes 
 seems about J mile. The dykes and crushes are known to continue some 
 distance both north-west and south-east. Their indications north-west, 
 near Caol-ghleann, are mentioned on p. 214. Going south-east they run 
 through the Bealach an t-Saic down into Garrachra Glen, and effect a 
 considerable displacement in the top of the greywacke schist horizon 
 mapped on the north-west side of this glen. In the different localities 
 traversed, the foliation near the fault is generally deflected into parallelism 
 with it for a little space. 
 
 In the burn running south-east between the " t " and " h" of " Strath 
 nan Lub " there are occasional exposures, chiefly of quartzose schist, up 
 to nearly half way between the 800 and 900 contour lines. The base of 
 the green beds cannot be below these exposures. On the opposite side of 
 the strath, in the burn that enters the strath near the " S," green beds 
 are seen up to about the same level. These strike considerably south-east 
 of the base line on the north-west side of the strath. "We suppose 
 there is a fault with large downthrow west between the outcrops 
 mentioned. The hill sides are too much obscured with drift to enable us 
 to fix the direction of the fault accurately. The broad hornblende schist \ 
 mile north-west of the " a " of " nan " seems to end suddenly on the west 
 and is perhaps shifted north by a continuation of the same fault. By 
 the side of the wire fence on the hill top between Strath nan Lub and 
 Gaol Ghleann, there is a small exposure of hornblende schist sticking up 
 through the peat. This is perhaps the same hornblende schist, on the 
 east side of the fault. 
 
 In the burn f mile south of the " S " of "Strath nan Lnb " the base of 
 the green beds zone is a little above the 1000 foot contour. One mile 
 south of the same letter there are green beds considerably south-east of 
 the strike of this line, and opposed on their north-west side to quartzose 
 schist. There must be a fault with downthrow south-west, shifting the 
 base line on the south-west side towards the south-east. The amount of 
 surface displacement is 300 to 400 yards. Both north-west and south- 
 east of this locality there are basalt dykes along the line of the supposed 
 fault. 
 
216 GEOLOGY OF COWAL. 
 
 South-east of the green beds there are but few schist lines that 
 have been traced. The top of the apparently thick greywacke schist 
 on the northwest side of "the anticline" comes into the area from the 
 south on the south side of Cam Ban, and keeps fairly well defined as far 
 as the side of the Bealach au t-Saic fault. Below the top there is a 
 large proportion of massive quartzose, often pebbly, schist, all the way 
 down to the alluvium near Garracbra. On the north-east side of the 
 fault the top is not so definite, and going further north-east becomes 
 gradually less and less so, so that we had to cease mapping it. In 
 the steep south-east slope of Creag Tharsuinn we cannot make out 
 that there is any thick zone in which quartzose schists largely prepon- 
 derate over the more phyllitic. We suppose the appearance to be due to 
 a great folding and mixing together of phyllitic mica schists with the 
 greywacke schist horizon. 
 
 The margins of various greywacke schists have been traced on the 
 slopes of Beinn Bheag, Cruach Bhuidhe, 3tc., but none of them continued 
 distinct far. Some of them lose definition in a gradual way, either 
 by the oncoming of phyllitic schists in the greywacke area, or the 
 oncoming of greywacke in the more phyllitic areas. This suggests that 
 the changes are due to gradual intermixing by folding. As examples of 
 this gradual change, we may mention the top of a greywacke schist f 
 mile north-west of Stuck, and the bottom of a similar schist J mile E.S.E. 
 and l mile S.W. of the "B " of "Meall Breac." 
 
 In the want of traceable schists, the numerous lamprophyre sheets in 
 the hills east of Loch Eck have been found useful in finding out faults. 
 In this area faults are exceedingly numerous ; in fact, nearly all the 
 straight parts of the streams and more prominent nicks in crags are 
 occupied by crush lines. The most general direction is slightly north 
 of west, and the downthrow north. Between Cruach Bhuidhe and 
 Bernice Glen ten faults have been mapped, all throwing down north. 
 The fault in Bernice Glen has a downthrow to north of 80 to 100 feet. 
 
 There are also a good number of other faults with a N.N.E. direction. 
 Two of these cross the west side of Meall an-T, and are accompanied with 
 basalt dykes. Two more cross the top of Clach Beinn. They both 
 downthrow east; the west one about 120 feet, and the east one 20 to 
 30 feet. 
 
 A conspicuous feature ranges N.N.E. in Garrachra Glen, and no doubt 
 represents a continuation of one of the faults in Coire No (see p. 222). 
 Near the " G " of " Garrachra " (House) there are several feet of crush 
 rock along the feature. The hade is east. The schist east of the fault 
 is much contorted along axes which are nearly at right angles to the 
 direction of fault (compare the N.N.E. disturbances mentioned on pp. 109, 
 210). -Further north-east the Bealach an t-Saic basalts, or some of them, 
 twist into a south-west direction along the fault for a little distance. By 
 the first "a " of "Garrachra Glen " a lamprophyre sheet affords evidence 
 of a downthrow east, perhaps of about 40 feet. All along the east side 
 of Creag Mholach the fault forms a conspicuous feature facing east. It 
 crosses Glen Shellish between the " h " and " e " of " Shellish," and is 
 accompanied in the burn by a basalt dyke. A basalt dyke is also seen 
 with this fault J mile south-east of Glenshellish farm. 
 
 On the south-east face of Creag Tharsuinn there are prominent 
 joint planes dipping E.S.E. much wikh the hill slope. This is nearly 
 opposite to the foliation dip. On the south side of Clach Beinn there 
 are also prominent joints striking north-east, and hading south-east at 
 about 30. This is the same direction as the foliation dip. 
 
STRUCTURE OF ST CATHERINE'S DISTRICT. 217 
 
 District of St Catherine's. 
 
 This district is iiiclosed by Hell's Glen, the Lochgoilhead valley, the 
 lower part of Lettermay Burn, Curra Lochain, the valley west of Carnach 
 Mar the valley between Bridgend and Straclmr, and part of Loch Fine. 
 
 All the groups of sedimentary schist found on the north-west side of 
 " the anticline " come into this area, and there are also many outcrops of 
 epidiorite, hornblende schist, etc. 
 
 In the Ardrishaig phyllites the schists mapped are epidiorites, horn- 
 blende schist, various outcrops of quartzite schist, and a few thin lime- 
 stones. The quartzite schists have not generally been traced, but are 
 drawn in the burn sections and on the shore of Loch Fine. They are 
 extremely abundant, particularly in the north-west part of the series. 
 
 North-east of Ardchyline there is an unusually wide outcrop of 
 quartzite schist. The width of bare quartzite on the hillside is about J 
 mile, but taking into consideration the sections in the burns on either 
 side, we consider there is about as much more hidden under drift. Most of 
 this outcrop seems to end in three fingers pointing south-west. The most 
 south-easterly finger ends 100 yards north of the "A of "Ardchyline." 
 The middle finger ends, rather bluntly, 200 yards north of the " r " of 
 the same word. The north-west finger is not actually seen to end, 
 but in the burn i mile N.N.W. of the "A" of "Ardchyline" it is 
 only 40 yards wide. This fingering out is no doubt due to folding. 
 In the most northerly of the streams at Ardchyline there are good 
 sections of green-grey phyllite, the foliation of which strikes right at the 
 quartzite. Further north-west there is still a considerable width of 
 quartzite in the burn J mile N.N.W. of the "A." This is bounded 
 on the west by N.N.E. crushes accompanied with a lamprophyre 
 dyke. The effect of the crushes is uncertain. There is no rock seen 
 on the west for some distance. Creag a' Phuill is composed of 
 massive quartzite schist, and this can be traced north-east for several 
 hundred yards. In all probability it is the same bed as the one near 
 Ardchyline. The quartzite mile east of the Creag is underlain by an 
 epidiorite band, on the other side of which more quartzite schist appears. 
 If we look on the two outcrops of epidiorite at St Catherine's as repeti- 
 tions of one bed by folding, which, as stated shortly, is not unlikely, it 
 may also be the case that the quartzites on either side of the epidiorite 
 near the Creag are the same, the epidiorite being in a fold between 
 them. The epidiorite is hidden by drift in the north-east part of its 
 course between the Creag and Ardchyline. It is possible it runs down 
 a dip slope and joins some epidiorite exposures at the back of the raised 
 beach ^ mile north-west of Ardchyline. 
 
 Five-eighths of a mile north-west of Ardchyline a little rocky knoll of epi- 
 diorite appears near the north end of the quartzite schist. The south margin 
 is a gently curving line. Close to the side of the line quartzite schist is seen. 
 The greater length of the margin runs at right angles to the prominent 
 foliation of the district. We suppose the epidiorite to be part of an 
 old intrusive sill, and the south margin to be a folded margin. The 
 epidiorite knob is only about 30 yards wide from south to north. The 
 north face of it is a rough crag which represents a fault line. In the 
 burn to the north, in some places hardly 30 yards distant, there are good 
 exposures, chiefly of quartzite schist, striking at it. The fault is seen in the 
 burn f-inile north of the "A" of "Ardchyline " : the hade is south ; it is 
 accompanied by a lamprophyre dyke 4 to 10 feet thick. In the burn west of 
 the knob a similar dyke is also seen along the supposed f aul t. The epidiorite 
 is shifted by the fault, the north side to west : the amount of displacement 
 
218 GEOLOGY OF COWAL. 
 
 of the east margin of the epidiorite outcrop is about 170 yards, of the 
 west margin rather more than this, the outcrop on the north side of the 
 fault being rather wider than on the south. In the knob south of the 
 fault, the east margin bends round and becomes the west margin. It 
 therefore is probable that on the north side of the fault also, both margins 
 may represent the same line repeated by folding, and we may consider the 
 south-east band of the St Catherine's epidiorite to be the same bed 
 as the north-west band. Whether the south-east band represents an 
 inlier along an anticline or an outlier at the bottom of a syncline is not 
 certain. South-east of the south-east outcrop there is a considerable 
 proportion of quartzite schist which may correspond to that near Ardchy- 
 line. The two bands come very near one another at St Catherine's, 
 and there is less quartzite schist between them than to the south-east : 
 this may be explained by supposing we are dealing at St Catherine's 
 with a less thickness of beds, the mass of the quartzite not being reached. 
 
 Near Ardnagowan Cottage, and between it and Airidh a' Ghobhainn, 
 there are bands of epidiorite which have a habit of gradually thinning 
 and ultimately dying out to the north-east. There are wide exposures 
 of quartzite in the middle of the space between the two outcrops south of 
 Ardnagowan Cottage, but phyllite cornes on on either side of the quastzite, 
 between it and the epidiorite. 
 
 Three-quarters of a mile north-west of Ardchyline a north-west fault shifts 
 the outcrops of both epidiorites, the south-west side to the north-west. The 
 north-west band is well exposed at the back of the raised beach for 
 mile north-east of the fault, but on the south-west side it is only seen on 
 the shore, for about 80 yards. The fault in its course south-east must 
 soon meet with the east to west fault already mentioned f mile north of 
 Ardchyline. A little south-east of their supposed junction there are two 
 lines of fault, both with downthrows south-west, as shown by sheets of 
 lamprophyre and hornblende porphyrite. Indications of the continuance 
 of the south branch occur 1 mile E.S.E. of the first " C " of " Cruach nan 
 Capull," where^a baud of epidiorite is crossed by two closely parallel N.N.E. 
 faults, each with a slight downthrow north-east, and the crushes are seen 
 in the burn to the south-east. The more northerly branch can be traced 
 to Lochgoilhead. Its course will be further described subsequently. 
 
 As already stated, p. 48, the north-west boundary of the garnetiferous 
 schist is not well defined. We have adopted the most north-westerly 
 zone of graphite schist as the boundary. There are crushes, accompanied 
 with severe contortions, running with this graphite schist. Near the 
 head of Eas Dubh there is an interesting section in this crushed schist, 
 at a place about f mile north-east of the "h" of "Dubh." There is 
 a well defined crush line hading north-west. The beds jabove it are 
 mainly quartzose schists with the foliation planes approximately parallel 
 to the crush line, contrasting in this respect strongly with the contorted 
 graphite schist below the crush. As you look north-west, towards the 
 section, the axes of anticlines in the contorted area are seen to have a 
 tendency to point towards the north-east, as if there had been a lateral 
 movement along the crush line of the upper schists towards the north- 
 east over the lower ones. This direction is the opposite to that indicated 
 by the crush in the graphite schist near Leanach (151), mentioned on 
 p. 210. The section is also of interest as indicating that some 
 of the crush movements are earlier than some of the lamprophyres 
 (see p. 109). 
 
 At the head of Eas Dubh there are three W.N.W. faults which shift the 
 north-west graphite schist, the south-west side to the south-east. Owing 
 to these a series of thin epidiorites or chlorite schists, which occur a little 
 
STRUCTURE OF ST CATHERINE'S DISTRICT. 
 
 219 
 
 north-west of the graphite schist, are repeated again and again. The 
 middle fault is seen in a burn, not marked in the 1-inch map, f mile 
 
 E N.E. of the second a " of " Creagan an Eich." It is m two parts both 
 throwing down to south-west. In the space between them there is a lime- 
 stone the same band as that in the burn J mile south-east of Laghngarten. 
 
220 GEOLOGY OF COWAL. 
 
 Ou the north east of this limestone, at the other side of one of the faults, 
 is the hornblende schist which comes "below the limestone. The most 
 southerly fault is seen in the burn f mile E.N.E. of the same letter. 
 
 .____ , _. 
 
 C.T.C . 
 
 p IG 51. 1 inch = 4 feet. Vertical section mile N.E. of "h" of "Ens Dubh," 
 observer looking N.W. [Line " AB " is a crush hading N.W. Above this 
 line is quartzo.se schist. Below is contorted graphite schist. "C" is a 
 lamprophyre sheet. 
 
 The E.N.E. fault a little north of the " h " of " Eas Dubh " is nowhere 
 seen in section. It is inferred from the high level of the limestone and 
 hornblende schist in the burn J mile east of the " h " compared to that 
 in a burn, not marked in the 1-inch Map, f mile slightly north of east 
 of this letter. The hillsides adjacent are thickly covered with drift and 
 it is not possible to determine exactly how the fault runs. At the foot of 
 the east to west burn near the " h " the foliation of the phyllite dips north, 
 probably owing to the proximity of the fault. 
 
 In the burn -J mile east of the "s" of " Creggans " there is a crush 
 hading west and a lamprophyre dyke accompanying it. In the epidiorite 
 J mile S.S.E. of Creagan an Eich the amount of surface displacement is 
 about 70 yards, the west side to south. Graphite schist is seen in several 
 places close on the west side of the fault, between the raised beach and 
 rather more than J mile north of this beach, but we noticed no clear 
 exposure on the east side nearer than the north-east corner of the wood 
 through which the burn runs. From the epidiorite the fault continues 
 N.N.E., forming a bank feature facing west as far as the burn east of 
 Ardnagowan Cottage : in this burn a crush and accompanying lamprophyre 
 are again seen; the foliation of the schist on the west side is vertical and 
 parallel to the crush. Still further north-east this fault probably joins the 
 one in the burn { mile N.N.W. of the " A" of " Ardchyline" (see p. 217). 
 
 The limestone J mile south-east of the highest graphite schist is men- 
 tioned on page 53. As there stated, there is a little difficulty in regard- 
 ing it as an outcrop of the Loch Tay limestone repeated by folding. This 
 limestone is seen in the burn J mile S.S.E. of Ardno, and is associated 
 with hornblende schist as usual. Sixty to seventy yards south-west 
 of this exposure a north-west fault seems required with downthrow 
 north. There is no indication of the limestone in the burn west of the 
 one mentioned, but in the next but one west there is, at a place a little 
 over J mile S.S.W. of Ardno. The outcrop in the last burn is striking 
 west of that in the first mentioned burn. In its course north-west the 
 fault may form the south-west ending of the felsite sheet a little more 
 than J mile south-west of Ardno. The shift in the felsite must be 
 in the opposite direction to that in the limestone. The felsite is an 
 intrusive sheet and not necessarily parallel to the bedding : in this 
 locality the general hade may be different from that of the schists. A 
 third north-west fault, with downthrow north-east, is needed to come 
 between the limestone and hornblende schist outcrops in the two burns 
 J mile east of Laglingarten. 
 
 One-sixth of a mile south-east of Laglingarten a north to south crush, had- 
 
STRUCTURE OF ST CATHERINE'S DISTRICT. 221 
 
 ing west, intersects the top of the limestone. The base of the limestone does 
 not appear west of the fault until we reach the south-west, or downthrow 
 side, of a north-west fault. F^fty and 100 yards south-west of the 
 north-west fault there are other parallel faults throwing in the same 
 direction. The strike of the foliation between these faults is north to 
 south, so that the displacements effected by the faults are soon compen- 
 sated for by this abnormal direction. A little south of the most south- 
 westerly fault the foliation strike gets normal again. South-west of the 
 faults there is no indication of the limestone at the surface until we reach 
 f mile E.S.E. of the "s" of St Catherine's, but the hornblende schist 
 below it is seen mile north-east of this exposure. 
 
 In the burn | mile north-east of the first " C " of " Cruach na Capull " 
 there are two N.N.E. faults, each throwing down to north-west. One 
 is close to the base of the limestone, and the other near the top. 
 
 Five-eighths of a mile slightly north of west of the same " C " the strike 
 seems twisted for about J mile into a south-east direction, almost at 
 right angles to the ordinary one. The change of strike is inferred, partly 
 from the occurrence of the limestone and hornblende schist south-east of 
 where the normal strike should take them, and partly from the section in 
 a burn not marked in the 1-inch Map. The strike in the buru is in 
 some places south-east and in one place sharply twisted along a nearly 
 east to west axis. A felsite sheet occurs in the twisted beds and is itself 
 twisted in the same way. We incline to connect these disturbances with 
 the passage of a fault near their south-west side, probably the same as the 
 east to west one north of Ardchyline (see p. 217). South of the supposed 
 fault we see no good limestone until we reach a burn f mile slightly south 
 of east of the "n"of "Ardchyline." Between this exposure and the dis 
 turbances there is also a N.N.E. crush which is seen in several of the 
 burns south and south-east of Laglingarten : the hade is west and the 
 adjacent schist foliation is sometimes quite vertical and parallel to it 
 This fault is the cause of a prominent feature, facing north-west, all 
 the way from f mile N.N.W. of the "C" of "Creag Dhubh" to 
 | mile W.S.W. of this letter. On the south-east side of the feature 
 there are sections of the limestone and hornblende schist, sometimes in 
 repeated alternations, probably partly due to folding, in the different 
 burns marked in the Map and a few others. 
 
 South-west of the burn f mile slightly north of west of the " C " of 
 " Creag Dhubh " there is nothing seen either of limestone or horn- 
 blende schists until we reach a little burn 1 mile W.S.W, of the above- 
 mentioned letter (see p. 53). It is possible that for a considerable 
 part of this distance the two beds may be faulted out. As the fault 
 is running nearly with the strike of the beds this would not necessarily 
 imply a large throw. In the burn f mile east of the first " u " of 
 " Creagan an Eich " there seem two faults, one running N.N.E. and the 
 other north-east, and both throwing down north-west. The N.N.E. may 
 be a continuation of that we have just been describing. 
 
 The Loch Tay limestone appears in Coire No burn, J mile north-west 
 of the "o" of "No." One hundred and twenty yards lower down 
 the burn there is another limestone outcrop^ much contorted and 
 crushed. Between the two limestones, comes in, among other things, 
 a band of green beds, A calcareous quartzite, with some limestone, 
 is also seen a little above the band of green beds in the burn rather 
 more than J mile north-east of Cruach nan Capull. The Loch Tay 
 limestone in the Coire No burn is no doubt considerably folded ; 
 otherwise the base would corne out of the burn more quickly than 
 it does. A band of hornblende schist occurs within, but near the 
 
222 GEOLOGY OF COWAL. 
 
 top of, the limestone in one place on the west bank of the burn, but 
 seems to be folded out in a little distance. On the north-east side of 
 the limestone there are several north-west faults. They are so near 
 together that it is not possible to show the detail in the 1-inch Map. 
 All the faults hade south-west. On the north-east side of the most 
 south-westerly fault, the limestone is seen in the north-east bank of 
 the burn. The most north-easterly fault must have the largest throw, 
 the limestone not appearing on its north-east side until we reach 
 the burn J mile S.S.E. of Ardno, more than J mile away. Immediately 
 north-east of the burn mentioned there is another subordinate fault which 
 effects a shift in the same direction of 50 to 60 yards. One hundred yards 
 east of the " o " of " No " the different faults appear to be together, and 
 meet with an N.N.E. fault and an accompanying basalt dyke. The 
 N.N.E. fault appears to shift the north-west fault, the east side to south, 
 for perhaps 20 yards, but, as stated on page 229 1 , we are by no means 
 certain the N.N.E. fault is the older of the two. 
 
 The north-west fault in its continuation south-east crosses over into 
 Hell's Glen. Various indications of this continuation are to be men- 
 tioned shortly. 
 
 The N.N.E. fault makes great confusion at the head of Coire No, 
 north-east and east of Cruach nan Capull. In these localities it seems 
 divided into three main branches. There are connections between them, 
 and the beds are considerably twisted. A basalt dyke, not itself crushed, 
 runs with the west branch. This branch must have a considerable down- 
 throw east, for on the west side the hornblende schist below the limestone 
 occurs against the schist overlying the green beds above the limestone on 
 the east side. The middle branch has also a downthrow east in some 
 places, but, owing to the changing dips of the beds on the sides, not 
 always so. The east branch has a downthrow west usually, perhaps 
 always: the limestone is never seen on the east side, though just on the 
 west we may get either it or the overlying beds. On Cruach nan Capull 
 there are several north-east or N.N.E. features, but it is uncertain whether 
 they are accompanied with faults. 
 
 In the River Cur part of the Coire No N.N.E. faults appears 100 yards 
 north-east of the north-east part of the "E" of "ARGYLLSHIRE." 
 It is accompanied by two basalt dykes and a crushed lamprophyre dyke. 
 There is probably another part 150 yards higher up the burn, where there 
 is a feature running N.N.E., with no rock below for a little space. 
 
 Three-eighths of a mile S.S.E. of Cruach nan Capull a fault crosses the 
 green bed above the Loch Tay limestone. The surface displacement is 
 about 30 yards, the south-west side to the south-east. It is probably 
 the fault we suppose to pass near the contortions f mile slightly north 
 of west of the "C" of "Cruach nan Capull" (see p. 221). The effect 
 on the limestone is not seen. In all the burns to the south-west 
 there are sections in the limestone. The general character of it and 
 of the beds near it are described elsewhere (p. 46). One-half mile 
 south of the "D" of " Creag Dhubh " a north to south and an east to 
 west fault meet and let down the beds in the north-west angle between 
 them. The displacements caused by both are seen in the two green beds 
 north-west of the limestone. Just before the north to south fault reaches 
 the most north-westerly of these two green beds it appears to give off 
 a branch in a north-west direction : the branch has a slight downthrow 
 to south-west. One mile S.S. W. of the " D " of " Creag Dhubh " an east 
 to west fault effects a displacement in the limestone and overlying beds, 
 the south side to the west. The amount of shift in the hornblende schist 
 is about 120 yards. A little more than J mile north-east of the "S" of 
 
STRUCTURE OF ST CATHERINE'S DISTRICT. 223 
 
 " Socach " a prominent noith-east feature breaks through the schists. The 
 hill on both sides is largely covered with drift. Probably the downthrow 
 is north-west : massive quartzose. schist, like that usually below the lime- 
 stone, occurs on the south-east side on the same level as the hornblende 
 schist in the limestone on the north-west side. 
 
 The character of the line adopted as the top of the main zone of green 
 beds is described on p. 37. It is covered by drift for a considerable dis- 
 tance on either side of the Coire No north-west fault. In the burn mile 
 north-east of Cruach nan Capull there are some thin green beds above the 
 top of the main zone, but below the Loch Tay limestone. In a little burn 
 f mile E.N.E. of the second "11 " of "Cruach nan Capull" there is also a 
 green bed in this position. There is no exposure of the line south- 
 west of this little burn until we reach the stream J mile south of the last 
 "a" of "Cruach nan Capull," After this the line is frequently seen, 
 keeping at a fairly uniform distance from the Loch Tay limestone, until 
 it is obscured by drift south of the east to west basalt dykes f mile 
 E.N.E. of the "h" of "Strachur." 
 
 The line taken for the base of the green bed zone comes down to the 
 south-west side of the Hell's Glen fault J mile W,S.W. of the "B" of 
 " Gleann Beag." The surface displacement effected by the fault is not 
 quite J mile, the south-west side to the south-east. The line is fairly 
 denned all the way from Hell's Glen to Gleann Canachadan. There are 
 several N.N.E. crushes- going through it, but they seem to have no 
 appreciable throw. The green bed above the line makes a rather wide 
 outcrop. There are subordinate lower outcrops J mile south-east and f 
 mile south of Cruach nam Mult. By the "1 " of " Gleann Cnnachadan" 
 there are three lower outcrops : the top outcrop is 6 feet below the base 
 of the zone, below this is another 3 feet thick, and then a band 5 inches 
 thick. A quartzose pebbly schist occurs immediately below the base of 
 the zone. 
 
 A north-west fault runs up Gleann Canachadan at the base of the green 
 beds, and displaces this base about 30 yards, the south-west side towards 
 the north-west. On the south-west side of this fault there is a subordinate 
 fault close to it, with a shift in the opposite direction. The chief fault is 
 seen in the burn lower down the glen : it lias a tendency to twist the 
 schist into parallelism with itself, with a south-west dip. 
 
 One-quarter of a mile south-west of the " G " of " Gleanu " the base of the 
 green beds is again shifted, this time the south side to west. There are 
 probably two faults converging towards one another as they go west, 
 and continuing to join the one noticed (p. 222), f mile S.S.E. of Cruach 
 nan Capull. South of these faults there are several green beds outcrops, 
 varying in thickness from 2 to 6 feet, below the base of the zone ; in some 
 places there are five such. Most of these can be traced more than J mile. 
 The lowest band is probably more than 100 feet below the main base. The 
 width of outcrop of the band, the base of which we have here taken as 
 the main base, varies from 150 to 300 yards, but there are thin quartzose 
 schists within this outcrop in some places. Above this band comes a 
 wider outcrop of quartzose schist, which we have separated from the 
 green beds zone for a considerable distance south-west. Above this 
 quartzose schist green beds come on again, and extend far down the hill 
 on a dip slope towards the River Cur at least more than J mile. 
 
 The wide green bed at the base of the main zone can be followed pretty 
 clearly along the south-east side of Socach Uachdarach. One-quarter of 
 a mile south-east of the "S" of "Socach Uachdarach" the bed is thrown 
 down north-west by the continuations of the Coire Xo X.N.E. faults. On 
 the shoulder of the hill J mile north-east of Cruach na Cioba, on the east 
 
224 GEOLOGY OF COWAL. 
 
 side of the faults, their is an ill-defined outlier of this bed. Below the 
 outlier are one or two other outcrops of similar schist. Further south- 
 west the bed gradually decreases in width. It is well seen about half 
 way between the " C " and "H" of "STRACHUR," but is hardly 30 
 yards wide. One-half of a mile S.S.E. of the above "C" it is repre- 
 sented by two outcrops, each from 1 to 3 feet thick, and separated by 10 
 to 12 feet of quartzose schist. A little south-west of this it ceases to be 
 traceable. 
 
 Near the " h " of " Leamhanin " the outcrop of green beds above the 
 one we have been describing is hardly 50 yards wide, and is separated 
 from the next overlying green bed by an interval of quartzose and 
 phyllitic mica schist. The interval has been mapped to near the 
 sides of the alluvium f mile east of Ballimore. The last clear section 
 of it is in the burn J mile slightly north of east of Ballimore : here the 
 width of green beds below the interval is less than in Leamhanin and less 
 than that of the interval. 
 
 The top of a greywacke schist horizon occurs on the south-west side of 
 the Hell's Glen fault, between the first " a " and ' d " of " Monovechadan." 
 On the south-east side of Stob Liath, this line, together with the lampro- 
 phyre sheets a little above it, is thrown by a series of north-west faults, 
 all of which shift the south-west side towards the south-east, the same 
 direction as the Hell's Glen fault. One-eighth of a mile south of the first 
 "i" of " Drimsyniebeg " the fault in Gleann Canachadan breaks through 
 the line. The structure is complicated by other N.N.E. faults, some of 
 which are the continuations of those described in Glen Kinglas (p. 233), and 
 the ground is also largely obscured by drift. The line taken for the top 
 of the horizon on the east side of the fault crosses Drimsynie burn 200 
 yards west of the sharp bend to the west. It is not well defined. In the 
 burn at this place there are many crushes and small faults : one runs east to 
 west along the burn, and there are several others almost at right angles to 
 this. One-half of a mile north-west of the " y " of " Drimsynie " the line is 
 better defined : there is a large proportion of quartzose schist below the 
 line down to the fault at the west side of Drimsynie burn. The east to 
 west basalt dyke, \ mile north-east of "s" of "Drimsynie," is crushed 
 and intermixed with ferriferous carbonate strings. The quartzose schist 
 top seems shifted somewhat, the south side to the west, either by it or 
 some line of fault between it and the north basalt dyke. The east to 
 west basalt, \ mile north-east of the second "n" of "Beinn Bheula," also 
 shifts the line in the same direction. 
 
 The fault on the west side of the lower part of Drimsynie burn is seen 
 in the little east to west burn in the wood. It is accompanied by 
 subordinate crushes in the burn, some of them several yards wide. The 
 hade is west. The strike of the schists is made parallel to the faults. 
 Taken together the faults seem to have a large throw, for on the west side 
 massive quartzose schists extend down to the bottom of the wood ; while 
 on the east side there is almost unmixed albite schist up to near the 400 
 foot contour. A little east of the burn there is a parallel fault with a 
 small downthrow in the same direction : the amount of surface displace 
 ment at the top of the albite schist seems 60 or 70 yards. The main 
 fault crushes two basalt dykes at points f mile and a little over \ mile 
 north of the "m" of "Drimsynie." In both there is an apparent shift 
 of 10 to 16 yards, the east side to north. The other dyke north of these 
 is also crushed near the fault, but the direction of shift is not certain : it 
 seems in the opposite direction to that of the other two. We suppose 
 the fault to continue to those in Gleann Cauachadan (see p. 223), and 
 thence to the fault f mile north of the " a " of " Ardchyline " (see p. 217). 
 
STRUCTURE OF LOCHGOILHEAD DISTRICT. 225 
 
 On the hilltop f mile north of the " e " of " Drimsynie," and other 
 places near, there are good exposures of early strain bands (see 
 p. 24) folded sharply by folds of "anticline" type with axes hading 
 north-west. These strains bands hade north-west less steeply than the 
 bedding, or if the bedding be flat, they have a tendency to hade slightly 
 south-east (see p. 28). The folds of anticline age are prominent and 
 acute, and we see repeatedly that it is the under 'or south-east limbs 
 of anticlines that are the most thinned. 
 
 There are good exposures of albite schist on the east side of the 
 lower part of Drimsynie burn and between here and Drimsyniebeg. In 
 various places, e.g., in the band 1 mile south-east of the " n " of " Drim- 
 syniebeg," there are many quartzose portions which have perhaps been 
 formed from quartz veins. These portions are often finely foliated 
 parallel to the axes of " the anticline " folds, but where no such folds are 
 present, they also usually show a fissile structure parallel to that in the 
 schists near. The quartzose portions usually consist essentially of white 
 quartz, and there are gradual passages between the most fissile, with 
 splitting planes at intervals of about T \- inch, and the thicker veins 
 without fissile structure. As we should expect in veins, they vary 
 in thickness and frequency. As a rule they run along the early folia- 
 tion planes, but sometimes are only a few inches in length. At 
 other times they cross the foliation markedly. " The anticline " folds have 
 led to, or been accompanied by, the production of marked differences in 
 the composition of some portions of the schist. The under limbs of 
 anticlines are generally more quartzose than the upper ones. This seems 
 opposed to the general rule in other places (see p. 22). 
 
 District of Lochgoilhead. 
 
 This district is inclosed by Allt Glinne Mohr, the Lochgoilhead valley, 
 Loch Goil, part of Loch Long, and part of the east margin of 1-inch 
 Map 37. 
 
 The schists throughout this area belong to the alternating series of 
 albite or phyllitic mica schists and quartzose, more or less pebbly, schists. 
 The north part of the area is on the north-west side of " the anticline," 
 the south part on the south-east side. In the middle, between Lochgoil- 
 head and Stuckbeg, is an area, perhaps 2 miles in width across the strike 
 of foliation, in which the foliation is nearly flat, the alternating dips, 
 now north-west, and now south-east, about neutralising one another. 
 
 The promontory between Loch Goil and Loch Long, south of Clach 
 Bheinn and Mark, is, with the exception of two bands of albite schist which 
 have been separated out, in the main composed of massive quartzose, 
 often pebbly, schist. This belongs to the greywacke schist horizon the 
 tcp of which has been traced, with some interruptions, for a long distance 
 south-east. At the extreme south end of the promontory, just opposite the 
 Carraig nan Ron, there are good sections of pre-anticline folds with their 
 axes slightly waved. One-quarter of a mile north-east of Mark, a vein in 
 the pebbly schist was found (slide 4198) to consist of quartz, felspar, and 
 a little chlorite: Mr Teall states that the felspar is albite: it is pink 
 macroscopically, like the albite in the pegmatites of the Dunoon shore 
 section (p. 18). 
 
 Near the head of the west of the two burns on the south side of Cnoc 
 Coinnich there is a large proportion of sharply jointed quartzite-like 
 schist, but this is mixed with distinctly pebbly bands. 
 
 The marginal lines of various albite schists have been traced. Often 
 only one of the margins of any particular band was found definite enough 
 
 P 
 
226 
 
 GEOLOGY OF COWAL. 
 
 . tt li- 
 
 u $r 
 
 w* 
 
 to admit of satisfactory mapping. We feel it unwise to make the structure 
 appear clearer than it is on the ground. Some of the margins run parallel 
 
 to the foliation planes in the 
 
 ^ j 1 neighbourhood, but in other 
 
 places there are broad bands of 
 albite schist which die or finger 
 out as we proceed along the 
 foliation. These phenomena 
 we explain by supposing that 
 the beds are often folded along 
 axes which lie parallel to the 
 foliation, the apparent dying 
 out being really folding out. 
 A good instance of this on a 
 large scale occurs on the east 
 side of the valley between 
 Lochgoilhead and Polchorkan. 
 On the west side of the slack 
 which marks the course of the 
 N.N.E. fault near Inveroriich, 
 there are good exposures of 
 albite schist extending from the 
 alluvium to above the 400-foot 
 contour. Close to the slack, 
 practically the whole of the 
 exposure is albite schist. After 
 going north J mile, we see, in 
 the most northerly of the two 
 east to west burns marked in 
 the map, a little quartzose 
 schist from 60 to 100 yards 
 from the edge of the alluvium. 
 The quartzose schist broadens 
 to the north : in the burn 200 
 yards further north it is 100 
 yards wide. The top of it runs 
 north, not far off the 200-foot 
 contour, and between this and 
 the alluvium little else but 
 quartzose schist is seen. Above 
 the 200-foot contour there still 
 continues a wide outcrop of 
 albite schist until we come near 
 the burn mile south-east of 
 the "r" of "Polchorkan." Two 
 hundred yards south of this 
 burn we notice a thin quartzose 
 schist within the albite schist. 
 This band of quartzose schist 
 rapidly increases in width 
 going north. In the burn just 
 mentioned, it is 70 yards wide. 
 North of the burn it widens 
 further, and joins ultimately 
 to the quartzose schists above and below the albite schist. Thus gradually 
 the whole of the thick albite schist, apparently 400 feet thick, on which 
 
 ,1. 
 
 **** *1* c 
 
 ft* 
 
 3 
 
STRUCTURE OF LOCHGOILHEAD DISTRICT. 227 
 
 we started near Lochgoilhead, has, by the time we get to Polchorkan, 
 1 miles away, disappeared. 
 
 Another instance of apparent rapid dying out of albite schist occurs 
 near Stuckbeg (153). In the burn running south-west there is a con- 
 tinuous exposure almost entirely of albite schist from 160 yards 
 north-east of the house to the 700-foot contour. Albite schist is also 
 seen on the shore 100 yards north of the burn foot. There may be a 
 little quartzose schist between the exposures in the burn and on the shore, 
 as a drift area 70 td 80 yards wide intervenes between them. The albite 
 schist on the shore is underlain by a massive quartzose schist. The line 
 between these schists is definite, and readily traced in the bare area by 
 the loch side : it becomes drift covered J mile north of the top of 
 the " S " of " Stuckbeg," and north of this, in the two streams south of 
 Inverlounin, is not so definite as to encourage us to trace it further. 
 The top of the albite schist cannot be traced satisfactorily north of the 
 burn, but the top of another similar, but thinner, outcrop above this, has 
 been carried on as far as the stream mile south-east of Tom nan 
 Gamhna. There is a good section in thi3 stream for J mile below 
 the albite schist, and very little else than quartzose schist is seen. 
 What then has become of the wide outcrops near Stuckbeg? In the 
 burn -f mile south of the last " n " of " Inverlounin " there is a width of 
 about 170 yards of quartzose schist. In a south direction this gradually 
 narrows, and forms a separation within the albite schist. But going 
 north it widens, and the albite schists at the sides become subordinate, 
 until in the burn mile south-east of Tom nan Gainhna we can hardly 
 say there are any representatives of them. 
 
 A well-defined band of albite schist occurs on the side of Loch Long 
 near Dail. This has been traced uphill to the north-east, often making 
 outcrops about 140 yards wide, and it comes into a burn 1 mile W.S.W. 
 of Coilessan. On the north side of the burn we found it impossible to 
 trace the bed, and yet there are no indications of faulting. There is 
 plenty of bare rock in the locality, and it seemed impossible that any 
 great thickness of albite schist could escape notice. 
 
 These suggestions of folding prepare us for the difficulty experienced 
 in matching on Ben Donich the greywacke horizon of which we have 
 mapped the top on the west side of the valley between Lochgoilhead and 
 Loch Restil, etc. From the height of Ben Donich, this greywacke should, 
 after making allowance for the faults, circle all round it, if the beds con- 
 tinued uniformly parallel to the foliation. But no such thick greywacke 
 can as a fact be traced round the hill. At the south-east and east sides 
 there is indeed a thick greywacke, but on the west side this dwindles into 
 insignificance. This is also the case on the north-west side. On the 
 N.N.W. side there is a thick outcrop of greywacke, but this splits up 
 into different bands : the lowest of them appears to run down into Allt 
 Glinne Mhoir, coming into the stream J mile east of the "i" of "Mhoir." 
 
 In Allt Criche (142) the top of the greywacke we suppose to match 
 that traced on the west side of the Lochgoilhead valley, occurs about 
 half way between the 1500-foot and 1750-foot contours. Fifty yards south- 
 east of the burn it is thrown down to north by an east to west fault ; the 
 displacement at the surface is about 30 yards. The line north of the 
 burn is tolerably well-defined for ^ mile, but on the south side the ground 
 is obscure, so that we cannot see what are the effects of the N.N.E. 
 and north to south faults that must cross it; probably, however, 
 the displacements are not large. Seven-eighths of a mile slightly west of 
 south of Ben Donich top, a spur of rock runs south into a drift area, and 
 shows us the line again, close to the 1750-foot contour. In the burn 
 
228 GEOLOGY OF COWAL. 
 
 that comes into Allt Coire Odhar J mile below the first " 1 " of " Allt," 
 the rock exposed is mostly massive quartzose schist from a little below 
 the 1250-foot to the 1750-foot contour. Near the latter contour a north to 
 south crush hading west appears, and the top of the quartzose schist is 
 thrown down to west : the displacement at the surface is about 100 yards. 
 In the burn to the east there is a N.N.W. fault which throws the top 
 down to south-west ; the displacement at the surface is about 40 yards. 
 Between the last-mentioned burns and those that run into Allt Coire 
 Odhar near the " O " of " Odhar," there is a drift area. The level of the 
 line evidently is much lower on the west of this area than on the east. 
 This we suppose is probably owing to the N.N.E. fault which breaks 
 through the crags J mile E.N.E. of the "D" of "Ben Donich"; 
 in the north to south burn J mile S.E. of the "D" of "Donich" a 
 prominent face of rock, like those often marking crush margins, is seen 
 hading east. Near the head of the east of the two burns that come into 
 Allt Coire Odhair near the " O " of " Odhair," a north to south crush is 
 seen. The direction of hade is liable to variation, but is generally west. 
 The downthrow is also west. The top of the greywacke is not reached 
 on the east side of the fault. The base, which is a well-defined line, 
 is shifted at the surface about 200 yards. 
 
 The north-east spur of Ben Donich, from J mile north of the 2250- to 
 a little north of the 1750-foot contour, is practically all albite schist. 
 Below this comes a quartzose schist which we suppose matches the one 
 the course of which we are describing, but its width of outcrop, where 
 best defined, on the east side of the spur, is only about 100 yards. 
 
 The N.N.E. faults on the north side of Ben Donich do not seem to 
 cause much alteration of level in the top of the quartzose schist, but the 
 bottom seems lower on the west side. A want of correspondence in 
 the thickness of the outcrops of the beds at the side of these faults 
 is also noticed near Lochgoilhead. Near the latter place the top of the 
 lowest albite schist is at about the same level at each side of the faults. 
 But the base of it on the east side does riot extend to within 160 yards 
 of the alluvium, though on the west the base must be below the alluvium. 
 The movements along the faults were perhaps more lateral than vertical, 
 and outcrops affected by folding to a different extent may have been 
 brought against one another. In two N.N.E. faults near Strachur there 
 is also evidence of lateral movement (see pp. 210, 218), and in one in 
 Garrachra Glen (p. 216). 
 
 A band of albite schist just north of Polchorkan has been traced east 
 and north-east, and was found useful in disclosing faults which might 
 otherwise have escaped observation. The fault nearest Polchorkan 
 comes into the peat moss at the bottom of the valley near the " h " of 
 " Polchorkan," and runs north-west in a straight line for the Hell's Glen 
 fault (see p. 223). There is no rock in the River Goil in the place where 
 the fault should cross. The outcrop of albite schist is displaced at the 
 surface 200 yards, the south side to east, the same direction as, but much 
 less in amount than, the green beds are displaced by the Hell's Glen fault. 
 North-east of this fault there is another, again effecting a displacement, 
 of about 60 yards, in the same direction. In its course south-east 
 the last fault soon meets another coming from the N.N.E., arid appears 
 to be shifted by it 40 or 50 yards, the east side to south. This N.N.E. 
 fault throws the albite schist, but the displacement, 60 to 70 yards, effected 
 in this schist at the surface is in the opposite direction to the apparent 
 displacement in the fault feature. The hade of the N.N.E. fault is east, 
 but the downthrow in the albite schist is west. Though the north-west 
 fault appears shifted by the N.N.E. one, it is not certain that the latter 
 
STRUCTURE OF LOCHGOILHEAD DISTRICT. 229 
 
 is the later of the two. It may be that the N.N.E. fault was in existence 
 first, and that the north-west one subsequently proceeded along it for a 
 little distance before resuming its normal direction. From the evidence 
 elsewhere procured (see p. 109) we know that some of the N.N.E. faults 
 are of very early date, and we should not like to conclude that the N.N.E. 
 fault in this locality was the later of the two without clear evidence. 
 The appearances are the same as those observed in Coire No (133) 
 where the Coire No N.N.E. fault appears to shift the Hell's Glen north- 
 west fault (see p. 222). We have continued the north-west fault to the 
 south-east to two faults in Allt Criche, near the "h" of "Criche." 
 These throw a lamprophyre sheet down to south-east. The effect on the 
 top of the greywacke on the south side of the burn is uncertain. 
 
 A north to south crush, hading east, is seen on the shore of Loch Goil, 
 100 yards south of Inverlounin. This makes a conspicuous slack or 
 depression at the top of the craggy ground south-east of Lochgoilhead. 
 Part of it may probably be regarded as a continuation of the north to 
 south crush seen in the burn J mile north of the " G " of " LOCH- 
 GOIL." Another part probably runs north-east to join an exposure of 
 shattered schist, 20 to 30 yards wide, in Donich Burn, J mile south-east of 
 the " G." A little more than J mile east of Inverlounin there is another 
 north to south fault. This is not seen at the loch side, but it is probably 
 the cause of the sudden change in direction of the burn J mile S.S.E. of 
 Inverlounin. The fault is traceable north with branchings in places as far 
 as the burn -^ mile north of the " d " of " Lochgoilhead," 
 
 The promontory between Loch Goil and Loch Long is intersected by a 
 prominent feature running north to south which forms the east margin of 
 a drift area immediately north of the loch. Between this drift area and 
 Corran Lochan the feature crosses two bands of albite schist without making 
 any appreciable shift. The length of the lochan lies along the continuation 
 of this feature, a*nd there are also slacks extending from the lochan in 
 the same line. Between Tom Molach and Beinn Reithe the line is 
 continued by a feature facing east. Soon after this the fault divides 
 into two : both branches hade east and pass a little east of Cnoc Coinnich, 
 keeping within 50 to 100 yards of one another. 
 
 Strong crushes occur in the burn south of Stuckbeg, running north- 
 west and hading south. They twist the strike of the foliation into 
 parallelism with themselves and cause it to dip south-west. On the north 
 side of the Saddle they give rise to a conspicuous pass, and then run down 
 the burn that enters Loch Long at Feoileann (1-inch Map 38). In the 
 course of this burn a good many ferriferous carbonate veins occur in and 
 near the crush breccia. 
 
 The outcrop of albite schist at the south end of Corran Lochan grows 
 gradually wider to the east. At the lochan it is only 50 yards across : on 
 the shore of Loch Long it is 300 yards. One-sixth of a mile west of Mark 
 it is shifted by a fault with a general N.N.E. direction : the amount of dis- 
 placement at the surface is about 130 yards, the west side to south. This 
 fault makes a conspicuous feature, facing east, in its course north-east for 
 about 2 miles. Not quite 1 mile south-west of the foot of Allt Guanan it 
 crosses a lamprophyre sheet and throws it : the surface displacement is 
 about 70 yards, the west side to south. On the south side of Allt Guanan 
 it is marked by a slack. In the continuation of the direction of the slack 
 a vertical crush crosses the burn, nearly J mile above its foot. 
 
 On Meall Daraich, the rocky point between Loch Goil and Loch Long, 
 there are a good many ferriferous carbonate veins running almost with the 
 schist strike. One of the veins, J mile N.N.E. of Carraig nan Ron, is as 
 much as 6 inches wide. 
 
230 GEOLOGY OF COWAL, 
 
 District of Cairndow. 
 
 This district is inclosed by Glen Fine, part of Loch Fine, Hell's Glen, 
 Allt Glinne Mohr, and part of the north and east margins of 1-inch 
 Map 37. 
 
 The schists which occur in the district extend from the garnetiferous 
 mica schist to the alternating series of albite and greywacke schists which 
 come below the green beds. Much the largest part of the area is occupied 
 by the latter series : there are good sections of it in Kinglas Water, Allt 
 Glinne Mhoir, and the streams on the south side of Binnein an Fhidleir. 
 There are dip slope exposures of the green beds in nearly all the streams 
 that run north-east between Achadunan and the head of Hell's Glen. 
 The fall of these streams is on the whole rather less steep than the dip of 
 foliation, but for considerable distances the two may coincide. 
 
 There are no quite satisfactory exposures of the Loch Tay limestone. 
 A section in the burn just south of the " o " of " Ardno " is crossed by 
 dykes of lamprophyre and felsite running with the strike and accom- 
 panied by crushing, the effect of which is not exactly known. At the top 
 of the limestone there is calcareous quartzite. Near the base of the lime- 
 stone there is also calcareous quartzite, but the bottom bed is limestone 
 again. There is no hornblende schist except a thin band near the top 
 of the limestone. In the different burn sections further north-east there 
 is always a thick hornblende schist in the middle of the bed : the part 
 below this schist is largely mixed with calcareous quartzite. 
 
 In the north-east corner of the area a portion of the coarse granite of 
 the Meali Breac and Garabal Hill complex (see p. 99), appears, and the 
 schists near it are much altered. The usual strike of the schist is also 
 lost near the granite. For a distance of J mile or more jjhe foliation dip 
 is inwards towards the granite. Further away the dip is in some places 
 away from the granite, towards the south-west : at other places it is 
 almost nil, or towards the west, without any evident relation to the granite 
 boundary. Near Achadunan, more than 2 miles off the granite, the 
 common dip is still east, but south-west of this place, the usual strike and 
 dip prevail. At the east side of Lochan Mill Bhig the foliation is often 
 nearly flat. 
 
 The base of the green beds comes down to the alluvium of Glen 
 Fine J mile north-east of Achadunan. In the burn J mile E.S.E. of 
 Achaduuan a N.N.E. crush is seen with a hade to west. The crush is 
 accompanied with a throw, there being quartzose schist on the west 
 side close against phyllitic mica schist on the east, but the amount of 
 throw is uncertain. It's effect on the base of the green beds is not seen. 
 In the burn J mile south-east of Achadunan there is an E.N.E. fault, 
 hading north, which shifts the base with normal throw. About J mile 
 south-east of Achadunan there are several faults running in the same 
 direction as the last mentioned, but with opposite throws. One of these 
 makes a conspicuous shift in a basic lamprophyre sheet. 
 
 Half-a-mile north-east of Cairndow there are two ochreous weathering 
 lamprophyre dykes which are accompanied with crushes. These can be 
 traced about \ mile, and along their east continuation the base of the 
 green beds appears to be thrown down to south considerably : the 
 lateral displacement effected at the surface is 330 yards. A thin dyke, 
 apparently basaltic, is seen along the course of the fault nearly J mile 
 south of the " oi " of " Upper Clasheoin." 
 
 Between Achadunan and Binnein an Fhidleir the bottom bed of the green 
 beds zone makes a wide outcrop, and there are no subordinate lower out- 
 
STRUCTURE OF CAIRNDOW DISTRICT. 231 
 
 crops which have been noticed. On the hill-top west of Binnein an Fhidleir 
 a thin, tough, green bed, only 1 to 2 feet thick, makes its appearance a 
 little below the base of the zone. Half-a-mile south-west of the " B " of 
 " Binnein " there is an 8-foot green bed about 40 feet below the base : the 
 interval between is mainly massive quartzose schist. Near the last 
 place, on the west side of a little N.N.E. fault, which has a downthrow 
 west of 10 feet, there is a 6- foot green bed about 10 feet below the 
 base : the lower green bed is still apparent. 
 
 In the burn which goes between the "G" and "1" of "Glen King- 
 las " there is a good deal of faulting near the green beds base, and it is 
 hard to show the detail in the 1-inch Map. The fault that runs up the 
 burn has, where it crosses a lamprophyre sheet below the green beds, 
 a throw of about 20 feet down to the south. But when it gets up into 
 the green beds the throw is in the opposite direction. This seems owing to 
 two faults which come in on the west side of the burn, each of them throw- 
 ing the green beds base down to the north. After meeting the fault 
 running with the burn, they keep along it, and more than neutralise its 
 former effect. On the east side of the burn there are two massive pebbly 
 quartzite-like bands about 8 feet thick. One of these is immediately 
 under the green beds base and the other a little lower. A little below the 
 lower one is a band of leaden-coloured phyllitic mica schist 30 feet thick. 
 
 It is a little uncertain where to take the base of the green beds in 
 Kinglas Water. There is a 12-foot band about 120 yards up stream from 
 the line drawn for the main base. On the hillside south of the burn, 
 there is at the base a band of green beds, about 30 yards wide, separated 
 by an approximately similar width of massive pebbly quartzose schist from 
 the overlying green bed. 
 
 The section in the west of the two burns that run into Kinglas Water on 
 the south side near the "G" of "Glen" shows an unusual proportion of 
 massive pebbly quartzose schist. It gives the impression that there is 
 as large a proportion of such schist as anywhere in Glen Kinglas, not 
 excluding the horizon of which the top is mapped on the north side of 
 Beinn an Lochain (134 east). 
 
 Near the course of the east to west basalt on the south side of Kinglas 
 Water there is a sudden alteration of position in the base of the green 
 beds as if it were thrown down south considerably. On the west side 
 of the base there are various crushes hading south or south-west. Some 
 of these are close by the basalt, and others by a thin lamprophyre dyke on 
 the north of the basalt. On the east side of the base there are no certain 
 indications of faulting in the supposed direction. The broad lamprophyre 
 sheets J mile east of the base are not appreciably shifted. This may be 
 because these sheets happen to be nearly vertical. Or it may be that 
 the appearance of faulting further west is really due to folding. 
 
 On the north-east side of Stob an Eas there are two bands of green beds 
 below the line adopted as the base of the zone, and separated from it 
 by massive quartzose schist. The lower of these maks an outcrop nearly 
 100 yards wide in places, but this is on a dip slope. Two outcrops in a 
 corresponding position are seen again in the burns J mile W.S.W. of the 
 "S"of "Stob." 
 
 Owing to drift the base of the green beds is not clearly seen at the side 
 of the road between Lochgoilhead and St Catherine's. In the burn 
 south-west of the line drawn, there is a prominent joint hading south-west, 
 and it is possible that this may be accompanied with a throw. Twenty 
 yards west of the road there are many blocks of green beds just where we 
 have taken the base line, but we cannot be certain we see the rock in 
 place until we have proceeded more than J mile from the road. Sixty 
 
232 GEOLOGY OF COWAL. 
 
 yards south-east of the base line we see, on the south-west side of the 
 road, a green bed, 5 to 6 feet thick, with massive quartzose pebbly schist 
 on either side. 
 
 The big fault on the south-west side of Hell's Glen, and its effect on the 
 green beds outcrop, is described on p. 223. 
 
 The line for the top of the green beds zone is entirely hidden, excepting 
 in three burns. These burns are, taking them in order from north-east to 
 south-west, by the " g " of " Bathaich ban Cottage," J mile east of the " T " 
 of "Tom Dubh," and nearly J mile S.S.E. of the same letter. The Loch 
 Tay limestone and the felsite sheet near it appear to be faulted with a 
 large downthrow to west or south-west a little on the east side of Tom 
 Dubh, but the effect of this fault on the green beds top is not seen. The 
 limestone is not exposed in either burn at the sides of Tom Dubh, but it is 
 certain that it is not south-east of the felsite sheet, for there is a good 
 exposure of schist extending for some distance in this direction from the 
 sheet, and without any limestone. On the east of the supposed fault, or 
 faults, a hornblende schist is seen at the top of the wood f mile east of 
 the "T" of "Tom Dubh." We suppose the main part of the limestone 
 occurs between this hornblende schist and the felsite, as it does in the 
 burn a little north-east. If this is so, the felsite occurs, geologically, 
 below the limestone on the south-west of the fault, but above it on the 
 north-east. 
 
 Above the main zone of green beds there are various other thinner beds 
 of a similar kind. One-third of a mile south-west of Ruclha Bathaich Ban, 
 a band of green beds, a little inland, and on the south-east side of a 
 felsite, is shifted by a fault with downthrow to west. This fault 
 may continue south, and help to separate the two outcrops of lime- 
 stone. The throw between these outcrops is greater than that between 
 the green beds mentioned : perhaps part of it takes a more north-west 
 direction. A green bed still more to the north-west occurs on the shore 
 J mile south-west of Rudha Bathaich Ban. It is crossed by two north- 
 west faults. Two green beds are also seen above the limestone in the 
 burn that goes through the "n" of " Ardno." A band only a few feet 
 thick also occurs in the wood f mile E.N.E. of the "T" of "Tom 
 Dubh " : this cannot be much above the limestone. The schist below the 
 felsite on Tom Dubh is garnetiferous mica schist. This is an instance 
 of the occurrence of garnets S.E. of their usual province. Such instances 
 are common in the north-east part of the area (see p. 48). 
 
 There are strong crushes a little within the high side of the wood 
 between Ardkinglas and Ardno, running- almost parallel to the side. 
 These are seen in the burn that goes through the "ai " of "Bathaich ban 
 Cottage," and the two burns to the south-west that are shown in the 
 1-inch Map. In the first-mentioned burn there are three parallel crushes 
 and the hade is south-east. Judging from the hornblende schist, which 
 occurs above the top of the green beds zone in the two south-west burns, 
 there cannot be much throw with the crushes. 
 
 The top of the schistose greywacke that passes through the second " 1 " 
 of " Hell's Glen " is a good line to adopt as the top of a greywacke 
 horizon, but one cannot be certain that it corresponds with the line 
 adopted on the other side of the Hell's Glen fault. The top of another, 
 higher, greywacke schist, passes by the " e " of " Hell's." The lino by 
 the second " 1 " of " Hell's " continues well marked for some distance 
 north-east. In and near the burn that passes east of the " n " of " Hell's 
 Glen" there are several N.N.E. crushes close together that hade west, but 
 they throw down the top of the greywacke to the east, and must be re- 
 versed faults. In its course north-east these crushes separate. The east 
 
STRUCTURE OF CAIRNDOW DISTRICT. 233 
 
 branch makes a conspicuous feature on the south-east side of the long scar 
 on the south side of Beinn an t-Seilich, and throws a felsite sheet down 
 to the east. The west portion runs west of the long scar, and also throws 
 the felsite down to the east. 
 
 The greywacke top in the burn that joins Allt Glinne Mhoir by the 
 " r " of " Mhoir " is thrown down east by a N.N. W. fault. We suppose 
 there is a more important fault with downthrow west a little on the east of 
 this, and perhaps joining it as it goes south We seem to need such a 
 fault owing to the top of the greywacke on the east side being at a higher 
 level than on the west. The greywacke top is tolerably well marked all 
 along the south and east sides of Beinn an Lochain (134) : it is shifted 
 at least twice by north-west faults, once \ mile south of the "ai" of 
 "Beinn an Lochain" and again T \ mile S.S.E. of the same letters. 
 On the north side of the hill the line is less well marked : in the 
 burn that passes between the "W" and "a" of " Kinglas Water," 
 there is a rather wide outcrop of massive pebbly quartzose schist a little 
 above the line adopted in the Map, and separated from it by albite schist. 
 Above this quartzose schist nearly all the exposures are albite schist right 
 up to the hilltop. A little west of the burn mentioned, the greywacke 
 top is affected by two large faults, which let down between them a strip 
 of higher rocks, chiefly albite schist. The east fault has a tendency to 
 twist the foliation into parallelism with itself. It is accompanied by a 
 lamprophyre dyke in part of it's course. The west fault is inferred from 
 the want of agreement in the schists in the burns that pass on either side 
 of the " W" of "Water." The faults, if continued, should soon meet in 
 a south direction, and probably neutralise one another in throw, but a 
 crush line has been traced, and often makes a conspicuous feature in the 
 landscape, for many miles south-west, far outside the particular area now 
 being described. It makes a slack where it crosses the greywacke top 
 f mile slightly east of south of Beinn an t-Seilich, but has no appreciable 
 throw. 
 
 On the north side of Kinglas Water, near Butterbridge, we are unable 
 to see that there is any thick horizon in which greywacke schist is in 
 distinct excess over albite schist. The only schist mapped in this locality 
 is a massive quartzose schist near the top of the high crags a mile east of 
 Binnein an Fhidleir, and running from these crags to the east margin of 
 the 1-inch Map. 
 
 Various N.N.E. crushes have been already alluded to. There are a few 
 others worthy of mention. The Coire No fault continues under drift 
 to the burn \ mile E.S.E. of the "m" of "Tom Dubh." There is a 
 section of the crush in this burn and the stream changes direction along 
 it for a little distance. The next burn north-east also twists into the 
 crush for a little way. From here we have prolonged it under drift in 
 a straight line for the lochside at Cairndow. There is little doubt that 
 this crush. represents part of the disturbances that cross the west side of 
 Newton Hill (126), and continue to Tyndrum, etc. 
 
 The crush that crosses the west shoulder of Ben Donich (142) perhaps 
 crosses the head of Allt Glinne Mhoir a little below the 900 feet contour 
 line. The schists near are discoloured with a yellow tint and some crushes 
 are also visible, but are not so thick as we should have expected. 
 
 On the east side of Binnein an Fhidleir there are at least three N.N.E. 
 crushes which make prominent features as they cross the hilltop between 
 Glen Kinglas and the head waters of Eas Riachain. The two most westerly 
 ones, about J mile east of Binnein an Fhidleir, are accompanied with a good 
 deal of contortion. In this respect they resemble the one already alluded 
 to, that runs by the second " a " of " Kinglas Water," and they may be 
 
234 GEOLOGY OF COWAL. 
 
 regarded with confidence as continuations of it. One of the crushes in 
 the burn J mile slightly east of south of Binnein an Fhidleir is several 
 yards wide. 
 
 South and south-east of Cairndow, a little above the green bed's base, 
 the foliation dip is, in several places, south-east instead of north-west, 
 Not far off there is a straight feature running nearly with the strike of 
 the foliation. It is possible there is some disturbance along the feature, 
 and that this is the cause of the unusual dip. 
 
 A N.N.E., fault crosses Hell's Glen near the " o " of " or." In the 
 burn by the " o " the hade is west. About J mile up the burn the 
 fault branches. The west part throws a lamprophyre sheet down to west 
 in the burn a littlo over mile south-west of Stob an Eas : the fault 
 makes a prominent feature facing west on the west side of the Stob, and 
 then comes into the east bank of the burn J mile south-west of the " K " 
 of "Kinglas Water"; the hade is still west. A little north of the 
 branching a dark micaceous dyke gets into the east part of the fault and 
 keeps along it for one or two hundred yards at least ; the dyke is itself 
 somewhat crushed. The next clear exposure of the east part is in the 
 burn | mile N.N.E. of Stob an Eas : here a reddish lamprophyre dyke 
 accompanies the fault ; the hade is still west ; we could see nothing of the 
 dyke on the north side of the east to west basalt. In the burn f mile 
 north-west of Beinn an t-Seilich the crush is seen again. The sharp 
 change in direction in the east to west basalt near this exposure is along a 
 subordinate ferriferous carbonate vein hading west. On the north side of 
 Kinglas Water there are several faults which may represent those on Stob 
 an Eas, or branches of them. 
 
 The lamprophyre dyke running slightly north of west along the course 
 of the burn near the " las " of " Kinglas Water " is accompanied by a 
 fault. The dyke hades south and the throw is in the same direction. 
 We lose sight of the dyke at the slight bend in the burn above the " 1 " 
 of " Kinglas Water," but veins of barytes, as much as 1 foot thick, 
 and sometimes hading north, run along the changed path of the burn. 
 Below the " n " of " Glen " two lamprophyre dykes are met with, and 
 are doubtless representatives of the dyke just alluded to. Both hade 
 south and the south one is accompanied by faulting. The dyke in the 
 burn south of the "G" of "Glen" also htfdes south and is probably 
 connected to the others mentioned. 
 
 The nearly east to west fault that runs in the course of the burn below 
 the Eagles' Fall has a downthrow south, probably of at least 60 feet. 
 The crush is often several feet wide, and accompanied with strings of 
 ferriferous carbonate. There are various other crushes which cross this 
 burn at an angle ; one of these, passing through the " F " of " Fall " 
 and running north-west, makes a conspicious nick in the steep crag on 
 the south of the burn ; on the north side of the burn it throws one of the 
 porphyrite sheets down to the south. C.T.C. 
 
235 
 
 CHAPTER XVIII. 
 GLACIAL DEPOSITS. GENEEAL DESCRIPTION. 
 
 In the following description the illustrative details have been chiefly 
 collected from that portion of Cowal which is contained within 1-inch 
 Map 29, and lies on the east side of Gleudaruel and Loch Riddon. The 
 details in other portions are described subsequently. 
 
 Under the head of Glacial Deposits are included boulder clay, many 
 shapeless widespread sands and gravels which exhibit no relation to the 
 present streams but may occur scattered over the hill slopes up to con- 
 siderable heights, more or less definitely shaped morainic mounds, and 
 some beds of finely laminated clay or clayey sand which may contain 
 glacial shells. 
 
 In the 1-inch Maps the localities where the most conspicuous moraines 
 occur are indicated by the word " Moraines " engraved over them, but 
 with this exception no attempt has yet been made to show any of the 
 deposits mentioned. The approximate margins of the thicker and more 
 widespread were, however, drawn on the field-maps,* and also the shapes 
 of many of the more prominent moraines; 
 
 The boulder clay has the usual character of an apparently structureless 
 tough clay wherein are distributed irregularly many rounded and striated 
 boulders. The relative proportion of stones to the clayey matrix varies 
 considerably, and in some cases is so large that the general character becomes 
 more that of a gravel. In other places the matrix is so sandy that the 
 word " clay " is hardly appropriate. This more sandy character of the 
 matrix was, no doubt, original in many cases, and due to the more 
 siliceous character of the rocks from which it was mainly derived, or to a 
 washing out of clayey matter before it reached its present position. But 
 in other cases it is secondary, being produced near the present ground 
 surface by the slow action of water washing away the finer clayey 
 particles : in these cases the colour also usually changes into a brown or 
 ochreous tint owing to more complete oxidation of the ferruginous matter 
 in the clay. In the bank of the raised beach nearly J mile N.N.W. 
 of Hunter's Quay ochreous streaks, about an inch thick and slightly 
 projecting on the weathered face, descend nearly vertically into the 
 boulder clay for 3 or 4 feet. They thin gradually away as they descend. 
 The upper 1 foot of clay is of the same character as the streaks. 
 Individual pebbles lie partly in the streaks and partly in the less ochreous 
 clay at their sides, and so it would seem that the change of colour must be 
 due to the percolation of water. There appear to be thin cracks down 
 the middle of each streak. 
 
 In original colour the boulder clay varies greatly. In certain areas it 
 is a deep haematite red, but, perhaps, a greenish-grey or brown colour is 
 the most general. No attempt has been made to separate the red clay 
 from the other kinds, but many places where it occurs have been noted in 
 the field-maps. Among these are the following : the east shore of Loch 
 Riddon, 170 yards north-west of Springfield House, 1 mile south of 
 Springfield House, and J mile south of Fearn' ach : many places along 
 the shore of the Kyles of Bute between Fearna Bagh and Strone Point, 
 e.g., 1 mile south-east of Fearn' ach, 240 yards N.N.E. of Altgaltraig Point, 
 south-west of Newton, \ mile and f mile south-east of South Hall : on the 
 hillsides 1 mile north-east and east of Colintraive Pier : 250 yards north 
 
 * The sketch map of the superficial geology, near the end of the volume, has been 
 compiled from the Hues and notes on these field-maps. 
 
236 GEOLOGY OF COWAL. 
 
 and 200 yards north-east of South Hall ; in the burn 1 mile north-east of 
 Meallan Riabhach (183 south-west), up^to a height of over 1250 feet : on 
 the west side of Loch Striven, mile north-west of Troustan (a little 
 inland), and J mile S.S.E. of Braingortan : on the east side of Loch 
 Striven, mile south-west of Cnoc Madaidh, a little more than J mile north- 
 west of the Craig, various places on either side of the foot of Invervegain 
 burn, and 240 yards north-west of Inverchaolain Church : in Invervegain 
 Glen by the "i" of " Invervegain," and again a little more than \ mile 
 slightly west of south of this locality ; in the burn nearly f mile north-west 
 of Dun Mor (172 south-east) : in the burn \ mile south-west of A Chruach 
 (172 east) : in Gleann Laoigh a little below the " G," and J mile south- 
 east of Balliemore : \ mile west of Coraddie (182 north-east), at a height 
 over 1350 feet : in Glen Tarsan in many places near the head of the glen 
 and by the shepherd's house : in Glen Lean above the Powder Mills up to 
 the head of the glen, and in particularly clear sections a little south-east 
 of Glenlean Farm : in Coire Athaich (173 north-east), by the " ai " : in 
 various places a little south-west and south-east of Ballochyle (175 south- 
 west) : \ mile north-east of Clachaig Hill (173 east) : in Strath Echaig 
 close by Uig : in Glen Kin in various places near the "G"; in the 
 bum \ mile south-west of Ardentinny Church. It would thus appear from 
 our notes that it is general in the district between Loch Riddon and 
 Loch Striven ; and (on the east side of Loch Striven) on the north-west 
 side of a line between Inverchaolain and Ardentinny, but we cannot be 
 sure that it may not also occur in other areas which have not been noted. 
 This red boulder clay may occur in the same areas as the clays of other 
 colour without any marked physical separation, and is occasionally seen 
 mixed with them in sections : in the burn nearly 1 mile west of Meall an 
 Fharaidh (173 north-west) both red and brown clays occur, and the change 
 of colour is sometimes gradual and sometimes sudden ; in a burn \ mile 
 E.N.E. of Bargehouse Point(194 north-west) red and brown boulder clay 
 are seen within 20 yards of one another : on Strone Point (194 north-west) 
 similar clays occur on the shore, at the same level and not far from one 
 another. 
 
 It is not clear what is the cause of the red colour. The idea of deriva- 
 tion from rocks of the Upper Old Red Sandstone is suggested, but no 
 pieces of these have been noticed in any of the exposures mentioned, and 
 the boulder clays near to them, e.g., near Toward, Inellan, and Dunoon, 
 are not red. It is unlikely that the boulder clay movement was ever 
 from the red rock area in this district on to the schists. The boulders 
 in the red clay do not, as far as has been observed, differ from those in 
 the other clays, and consist either of schist, vein-quartz, or of various 
 igneous rocks granites, basalts, lamprophyres, hornblende schists, etc. 
 none of which seem likely by pounding down to have given rise to the 
 peculiar colour. Thin hematite veins are not uncommon in parts of the 
 schist area, but are not numerous enough to have coloured such widespread 
 deposits. 
 
 Among the boulders in 1-inch Map 29 found in, or in all probability 
 derived from, boulder clay, which have especially attracted our attention 
 as being probably derived from without this Map, are many boulders of 
 epidiorite, hornblende schist, granite with conspicuous porphyritic 
 crystals of flesh coloured felspar, diorites with black mica, and some 
 dark and occasionally much pyritized schists, which sometime contain 
 albite of an unusual reddish brown colour. It is not possible to say 
 with confidence whence the epidiorites and hornblende schists came, 
 because these rocks are common both in this and adjoining maps ; but it is 
 clear that many, in the north-east portion of this map, must have come from 
 
GLACIAL DEPOSITS: BOULDER CLAY. 237 
 
 some distance outside it, as such rocks are locally scarce. The porphyritic 
 granite with flesh coloured felspar can, on the other hand, be referred 
 with certainty to the area between the heads of Loch Fine and Loch 
 Lomond, which has been described by Messrs Dakyns and Teall (Quart. 
 Journ. Geol. Soc., vol. xlviii., p. 104, "* On the Plutonic Rocks of Garabal 
 Hill and Meall Breac)." A granite boulder of this character occurs by 
 the roadside 130 yards slightly west of south of Trinity Church, Dunoon, 
 and there are others on the shore of the West Bay of Dunoon, on the 
 shore near Strone Point (194 north-east), on the shore near Altgaltraig 
 Point (173 south-east), on the shore 70 yards S.S.E. of Toward Lighthouse 
 (at least 4 or 5 cubic feet in contents), and on the east side of Loch 
 Striven J mile south-east of Ardtarag. These granite boulders are much 
 more numerous as we approach their source of origin, and together with 
 the diorite, which has come from the same area, are conspicuous on the 
 sides of Loch Long and Loch Eck, and in Glendaruel. The dark albite 
 schists have only been noticed on the side of Loch Long. A boulder of 
 this kind, measuring about 12 feet by 12 feet by 6 feet, occurs on the 
 shore just south of the rocky point at Ardentinny. A similar rock is seen 
 in place near thehyperite of Donich Burn, Lochgoilhead (1-inch Map 37), 
 and seems to owe its peculiar character to contact alteration by this rock. 
 A similar rock is also seen occasionally near some of the basalt dykes and 
 lamprophyre intrusions. But in none of these cases does the altered rock 
 extend over a large area, and it is probable that the boulders noticed have 
 come from some other district where it is more widespread from the area 
 around the plutonic rocks of Garabal Hill and Meall Breac, etc. 
 
 In some comparatively rare cases the stones in the boulder clay have 
 their longer axes arranged in evident parallelism. On the shore J mile 
 E.N.E. of Cluniter (195 north-west) a stiff grey boulder clay, close to 
 high-water mark, has the stones in it arranged with their longer axes 
 slightly south of east, and lying on their " keels," i.e., with their flat sides 
 approximately vertical. Some 30 yards further north the stones are still 
 on their keels, but are arranged nearly parallel with the coast slightly 
 west of south: 20 yards still further north they lie with their axes E.S.E., 
 and are partly on their keels. On the shore a little more than J mile 
 N.N.E. of Tor Aluinn (184 south-west) a stiff brown clay shows the stones 
 often on their keels and with their axes south-east. In the small 
 stream | mile slightly north of west of Stronchullin (north 174) the 
 flatter sides of the stones incline N.N.E., much with the slope of the 
 hill. In a little burn J mile slightly west of south of the "G" of 
 " Gleann Laoigh " a red boulder clay shows a rough lamination sloping 
 down with the hill towards the west. A stiff laminated clay with 
 stones occurs in the boulder clay in the burn f mile slightly east of north 
 of Cnoc k Mhadaidh (174). On the south-easts ide of Inverchaolain 
 Burn, a little more than \ mile above the church, the boulder clay is both 
 mixed with gravel layers and also has a tendency to lamination in itself. 
 
 Some of the burns run through boulder clay for considerable distances, 
 their pre-glacial courses being still deeply hidden. Brown bonlder clay 
 occurs in the bed of the burn \ mile S.S.W. of "G" of "Glen Kin" 
 (183 north-east), and no rock is seen for \ mile above or 130 yards below 
 this point. In the burn \ mile north-east of Meallan Riabhach (183) 
 there is red boulder clay with a thickness of at least 20 to 30 feet, and 
 for a distance of more than J mile no rock is seen : this is at a height of 
 above 1250 feet. In the burn above Corlarach (194 north-east), from a 
 point due east of Corlarach for a distance of more than \ mile above this, no 
 rock is seen, but only stiff grey boulder clay with a thickness of at least 20 
 feet, and up to a height of 950 feet. Brown boulder clay is seen in the bed 
 
238 GEOLOGY OP COWAL. 
 
 of Tamhnich Burn (172 north-east) near the " c " of " Tamhnich," and also 
 about J mile above the " n " of " Burn : " also in the stream bed | mile 
 south of Cruach nam Mult (172 north-east). From a point f mile N.N.W. 
 of Blairmore Hill (174 north-west), for about J mile up stream, the burn 
 runs through a stiff yellowish-brown boulder clay, at least 40 feet thick : 
 this clay is overlain by loose sandy and gravelly material which is at times 
 developed into good morainic shapes. Near the junction of the burns 
 J mile east of the Badd (183 north-east) we see at least 70 feet of boulder 
 clay without reaching the rock below : the clay is generally brown near 
 the top and greyer below : in one place, near the top, thin bands of red 
 and brown alternate. The burn I mile W.S.W. of Kilbride Hill (183 
 south-west) shows, on its south side, a thickness of at least 60 feet of 
 boulder clay, but there are rock exposures in parts of the burn. The burn 
 J mile north-east of Kilmarnock Hill (194 and 183), for a distance of 
 200 yards, runs through reddish brown boulder clay overlain by a greyish- 
 green more stony clay : the total thickness seen is 50 or 60 feet : the 
 height above sea-level is 800 to 900 feet. 
 
 No rock is seen in Ardyne Burn (194) more than 50 yards below the 
 main road, with the doubtful exception of a small exposure about J mile 
 N.N.W. of Killellan, but exposures of boulder clay and other glacial beds 
 are not uncommon. The shores on either side of the foot of this burn 
 show a similar absence of rock for a long distance, and though now 
 spread over by beach gravels, it is probable that glacial deposits underlie 
 these gravels, and are indeed, from their readiness to yield to denudation, 
 the cause of them making such a prominent show in this locality. The 
 original rock floor of the mouth of the glen is clearly below the present 
 sea-level, and is still covered by glacial deposits. Being under the sea 
 no fluviatile or atmospheric denudation can now effectively work to free 
 it from the overlying beds, and restore the old outlines : and during the 
 times of the different raised beaches this protection from denudation must 
 have been still more perfect. There are many other glens which are 
 at their seawards ends entirely occupied by boulder clay or later deposits, 
 e.g., Strath Echaig, Glendaruel, Gleann Laoigh, the valley of the burn 
 which runs into the West Bay of Dunoon, and that of the burn between 
 Ardballow and Clyde View (184 south-west). There must be rock 
 hollows under the present sea-level in each of these cases, for rock is seen 
 at either side of their mouths, and if we suppose the hollows to have been 
 formed by river denudation, the land must in preglacial times have stood 
 at a higher level relatively to the sea than it does now. 
 
 It is probable that the sea lochs themselves, however modified by sub- 
 sequent glacial action,* represent glens originally formed by river action. 
 We do not know in what proportion the floors of these are of rock or 
 boulder clay, but the shallower parts near the shore are often of the latter. 
 In these places the clay is often partly obscured by the shifting shingle 
 of the shore, and therefore the exposures at one time noted may not be 
 observable subsequently, but may be represented by other similar ones. 
 Very commonly, e.g., in the West Bay of Dunoon, north-east of Tor 
 Aluinn (184), near Strone Point (194 north-west), and north-west of 
 Inverchaolain Church, these boulder-clay exposures are covered, near 
 high-water mark, by the gravels of the raised beaches, from which 
 numerous fresh-water streamlets descend and trickle down across the 
 partly shingle-hidden boulder clay. 
 
 * For the contours under sea-level see Trans. Roy. Soc. Edin., vol. xxxvi., "The 
 
 2 
 
 Clyde Sea Area," by Dr H. R. Mill. Also Admiralty Chart, Sheet 2131. 
 
 DE 
 
GLACIAL DEPOSITS : SAND AND GRAVEL. 239 
 
 Sand and gravel beds are not uncommon within or under boulder clay. 
 Examples occur on the east side of Inverchapel Burn (164 south-west), 
 nearly J mile above the bend, and J mile above the bend ; in the east 
 to west burn 1 mile west of Meall an Fharaidh (1 73 north-west) ; by the "ai" 
 of " Coire Athaich " (173 north-west) ; in a little burn (not marked in the 
 Map) about \ mile south-east of Ballochyle (173 east); \ mile N.N.E. of 
 the last " n " of " Inverchaolain Glen " ; on the east side of the burn a 
 little more than \ mile north-east of Inverchaolain Church ; J mile W.S.W. 
 of Ardnadam Farm ; -^ mile south-west of " G " of " Glen Kin," in a 
 section on the south side of the burn. 
 
 In the section J mile south-west of Ballochyle, only the 6 or 7 feet of 
 coarse gravel at the top seem referable to the high-raised beach ; 
 below this at the west end of the section, are sand layers, sandy gravel, 
 and stiff laminated stony clays; at the north-east end, just under the 
 gravel at the top, there are 10 feet of deep red boulder clay, and below this 
 indications of sand and gravel. 
 
 In the two burns west and south-west of Ardentinny there is a con- 
 siderable thickness of sand and gravel lying over boulder clay. The sand 
 is in part very fine and evenly laminated ; on the east bank of the burn, 
 a little more than \ mile south-west of the church, it is overlain by a stiff 
 clayey sand with striated pebbles and boulders, and without lamination. 
 Over this is a 4-foot bed of ochreous gravel and boulders, the base of 
 which undulates but is rudely parallel to the present ground surface : it 
 has a somewhat smooth flat top and may belong to an old burn 
 deposit, but has not been mapped as such. 
 
 In the burn nearly 1 mile west of Meall an Fharaidh (173 north-west) 
 the boulder clay contains irregular pockets of gravel, and a small fault 
 runs vertically through it. 
 
 Much more commonly seen than the sands and gravels below boulder 
 clay are those above it. These last are so abundant over the hill slopes 
 that it is not necessary to cite particular examples. Should you notice 
 on any burnside a line of springs and wet ground you will find this due, 
 in nine cases out of ten, to a coarse gravel or sand overlying the boulder 
 clay, the line between the two being sharp and usually straight. Even 
 on the hillsides it is often possible to distinguish with confidence the lines 
 between such beds, by the drier character of the ground where the sand 
 and gravel occur ; but no general attempt has been made to separate them. 
 
 These deposits are generally very irregularly bedded : sometimes when 
 lying on steep slopes they are seen to be bedded roughly parallel with 
 the slope. They spread over the hills far away from any streams, and 
 up to heights where there are now no streams of any magnitude. They 
 form surfaces usually not distinct in the distance from those of the 
 boulder clay, but in other cases well-defined mounds and morainic shapes 
 of a recognisable character. It has been suggested that these well-defined 
 mounds are of later age than the other gravels and sands, and that the 
 great age of the last is the cause of their want of mound-shape, denudation 
 having destroyed the original outlines. But in absence of clear sections 
 it is not possible to say that one gravel is younger than another, or 
 younger even than a certain boulder clay ; the sands and gravels without 
 mound-space do not, as far as is known, differ in character from other 
 beds seen under the boulder clay, and it is possible that some of them 
 are overlain by boulder clay in some areas. 
 
 On the east bank of the Ruel, 300 yards north of Ardacheranbeg, a 
 section shows a wedge-shaped exposure of fine sand, with occasional 
 fine gravel bands, lying in coarser gravel. The sand shows distinct and 
 repeated contortions. The folds are very sharp, and their axes, as seen 
 
240 
 
 GEOLOGY OF COWA.L. 
 
 in the section, which runs nearly north to south, are approximately 
 horizontal. There are some lines which appear like horizontal " thrusts," 
 but perhaps they are only lines of sharp twist. The sand layers that 
 show the contortions are a little variable in thickness, their outcrops 
 not being exactly parallel. Above the contorted beds comes a red 
 sandy clay with stones ; the matrix of this is stiff, but we did not see 
 any striations on the stones ; it is a good deal mixed with irregular 
 patches of fine yellow sand. At the top of the section are 3 or 4 feet of 
 evenly stratified gravel and sand which clearly belong to a river terrace. 
 The underlying beds are probably all glacial, and the contortions may be 
 due to the passage of ice over them. 
 
 f. T.C 
 
 FIG. 53. x-rV Section on E. bank of river Ruel 300 yards N. of Ardacheranbeg. 
 Fine sand and gravel, with nearly horizontal folds and thrust-like lines, 
 surrounded by gravel. Over the last is red sandy clay with stones. 
 
 A little further up the same river, J mile E.N.E. of Glendaruel 
 House, stratified clays, sands, and fine gravel, occur in a series of false- 
 bedded sands and gravels. The clay layers are at times sharply folded 
 with both limbs of the fold inclining in the same direction. A little 
 below the folded layers is a 6-inch band of dark clay which is traversed 
 by a reversed fault, of about 6 inches throw, the direction of which is 
 the same as that of the axes of fold. 
 
 In a little bum 260 yards south-west of Ardnadam Pier 4 feet of gravel, 
 presumably belonging to the raised beach, overlie 5 feet of finely lami- 
 nated clayey sand with occasional stones, which is much contorted. This 
 sand rests on brown boulder clay. 
 
 On the east shore of Loch Striven, \ mile N.N.W. of Finnart, a lami- 
 nated stoneless clay shows occasional contortions. 
 
 It is possible that the contorted beds described belong to the same 
 series as the beds containing glacial shells. Some of them closely re- 
 semble the last in character, excepting for the fact that no shells have yet 
 been observed in them : and we know that the shell beds do not unfre- 
 quently exhibit similar contortion. 
 
 The localities for some of the best morainic shapes are indicated in the 
 Map, but it was not possible to show all, and as moraines are not so 
 common in this district as in the higher parts of the Highlands, we 
 give below a list of them : at the north part of Gleann Laoigh (163 south- 
 west), on either side of the burn ; the south-west side of the Massan (163 
 
GLACIAL DEPOSITS: MORAINES. 241 
 
 south-west), west of Glenmassan, and on the north-east side (rarer) ; the 
 head of the glen If mile east of Glenmassan, and extending down from 
 here to within about J mile of the foot of the burn of this glen ; the 
 hillside { mile north-west of Cnocan Sgeir (172 north-east), at a height 
 of 500 or 600 feet, and extending hence north-east ; the east side of 
 Glendaruel just above the river terraces near Auchateggan ; the hillside 
 south and south-east of Duillater (162), at a height of from 500 to 800 
 feet ; by the junction of the burns nearly J mile slightly west of south of 
 Corrachaive (173 south-west) ; a little north of Corrachaive, separated by 
 alluvial deposits; the north-east side of burn T ^ mile north-east of 
 Ballochyle (173 south-east), and hence extending up stream for more than 
 J mile ; about J mile slightly east of north of Leacann nan Gall (173 
 and 183); near the "c" of "Coire Athaich " (173 north-east); near the 
 junction of the burns f mile N.N.W. of Blairmore Hill; mile west of 
 Ardbeg (183 north-west) ; north-east side of Glen Kin, J mile north-west 
 of the Bishop's Seat (183 north-east) ; hillside between \ and J mile 
 E.N.E. of Blar Buidhe (183 south-west) ; east side of the north to 
 south burn 1 mile north-east of Blar Buidhe, and on the west side (rarer). 
 
 The semi-circular shape is rare in the moraines of this district. Com- 
 monly they consist of mounds rather longer in one direction than another, 
 and at times slightly curved. The longer axes are usually roughly 
 parallel to what appears to have been the course of the glaciers which 
 produced them : this is seen at the head of the glen If mile east 
 of Glenmassan, and on the east side of the north to south burn 
 1 mile north-east of Blar Buidhe : in the last locality two of them 
 extend north and south for a distance of \ mile, though they do not 
 often exceed 30 yards in breadth. Individual mound shapes are less 
 common than more or less confluent banks with rather indefinite margins. 
 
 In the typical moraines the material consists of an irregular mixture of 
 huge boulders, sand, and gravel, the fine and coarse matters lying to- 
 gether without any sorting, and their tops are strewn over with angular 
 blocks of schist. But there are also other mounds which do not contain 
 such big blocks, and the sides of which are smoother. About \ mile 
 north-east of Corlarach such a mound occurs, about 150 yards long and 
 80 broad, at a height of about 600 feet : a section near the top shows 
 stones varying from 1 to 3 inches in diameter, and not very rounded in 
 outline. 
 
 On either side of the burn which runs into the West Bay of Dunoon 
 there are moraines running much in the direction of the burn, and these 
 descend to a level of 280 feet. The morainic material lies over grey 
 boulder clay, and about J mile east of the last "d" of "Badd" the 
 surface is strewn with huge blocks of hornblende schist. 
 
 In the more hilly areas moraines are seen at a lower level even than this. 
 Near the foot of the Massan, just before it joins the Echaig, thers are 
 four morainic mounds which stand out like islands in a wide gravel flat. 
 The gravel probably belongs to one of the old raised beaches more or 
 less modified by river action. The bottoms of the mounds are at a 
 height of about 40 feet. This low elevation was long ago called 
 attention to by Mr Charles MacLaren (Edin. New Phil. Journal, 1855, 
 "Notices of Ancient Moraines, etc."). That some moraines are of 
 later date than the raised beaches is clearly made out in some areas of 
 Scotland (L. W. Hiiixman, Trans. Geol. Soc. Edin., vol. vi. p. 249, " On 
 the Occurrence of Moraines later than the 50-foot beach in the North- 
 West Highlands "), but in the Glenmassan locality we think it doubtful 
 whether this relation obtains. We should prefer to suppose that the 
 gravel flat is of later date, and lying on the sides of or over morainic 
 
 Q 
 
242 GEOLOGY OF COWAL. 
 
 material. At all events, we are not aware of any section that shows the 
 reverse relation. 
 
 In 1-inch Map 37 there is an absence of the highest raised beaches 
 near the heads of the sea lochs in the more hilly districts, and it is suggested 
 that these areas were occupied by ice while the terraces were being formed 
 in the less mountainous parts, but we have not seen any instance of con- 
 tortion of the beach deposits, as if by the advance of ice, and there is too 
 a general absence of coarse boulders within or on them. 
 
 The glacial sands and gravels, when near sea-level and not showing 
 morainic shape, may be hard to distinguish from the deposits belonging to 
 the 100-foot beach, these latter being occasionally so worn by denudation 
 that they no longer possess a rudely flat or evenly-sloping surface. East 
 and north-east of Altgaltraig Point (182 south-east), stratified sand and 
 gravel, sometimes showing a reddish tint, cover the slopes above the 20- 
 foot beach. These beds ascend considerably above the 100-foot contour line, 
 and we have not mapped any as beach deposits, but it is quite possible that 
 they are partly so. On the east side of Loc.h Striven, between Brackley- 
 more and Tighnuilt, and a little on the south of Brackleymore, there is a 
 considerable spread of sand and gravel, the character of which is doubt- 
 ful. Some of it has been taken as beach deposit, and some as glacial. 
 
 The steeply-dipping sands and gravels below the gravel of the top of the 
 100-foot and lower beaches may possibly be glacial. Their edges are often 
 seen to be cut across by the gravel at the top, and there may be a great 
 difference in age between the two. The sands and gravels alluded to are 
 seen in the relation described in the following places, in the burn bank 
 J mile north-west of Colintraive Pier ; on the west side of Loch Striven, 
 60 yards south-west of Troustan (the lower gravels dipping steeply down 
 the burn, and overlain unconformably by coarser gravel) ; on the east 
 side of Loch Striven, on the east side of the foot of Invervegain Burn 
 (the lower sands and gravels with a regular dip seawards of about 25, 
 and overlain by a coarser and less regular gravel dipping seawards at 
 about 11), and at Tighnuilt (the lower gravels dipping seawards at 24, 
 and cut across at the top by more nearly level bands of gravel). One-sixth 
 of a mile north-west of Brackleymore, gravel layers incline seawards at 
 20, and are cut off by the more nearly level gravel of the 20-foot beach. 
 
 The drift gravels are not uncommonly stained, and partly cemented, 
 by some black material probably the black oxide of manganese. On 
 the hillside, 1 mile 8.S.W. of Coraddie (182 east), the cement binds the 
 little stones into small lumps. * 
 
 In various sections of drift, particularly the looser and more permeable 
 varieties, we are struck by the very soft, decomposed condition of some 
 of the contained blocks, such as basalt, epidiorite, green beds, and 
 granite. These may even be quite friable to the fingers. It is clear the 
 decomposition, and resulting softness, must have been brought about 
 since the formation of the beds in which the boulders occur, and since 
 these beds were in their present position : the boulders in their present 
 condition could not keep their shape while they were being dragged or 
 rolled about in rapid streams. Boulders of basalt sometimes 6 to 8 inches 
 in diameter may now be only represented by concentric rings of soft brown 
 crumbly rock. The schistose laminae of the green beds sometimes flake 
 off from one another on the slightest touch. The bank on the east side 
 of the river Cur about 1 mile east of Glensluan (141) shows at the top 
 layers of sand and gravel almost flat. These perhaps represent an old 
 
 * Similar occurrences in the north part of Cowal are mentioned on p. 258. 
 Reference may also be made to the black manganese staining found in the recent 
 freshwater alluvia of the district (p. 271). 
 
GLACIAL DEPOSITS: STRIATIONS. 243 
 
 river terrace. Below these come in order, coarser gravel, which contains 
 tongues and lenticles of stiff greenish-grey laminated clay with rare small 
 stones, then stiff grey stony boulder clay, then laminated sand and gravel. 
 In one part of the boulder clay we noticed a boulder of the green beds 
 which was cavernous all through, with bits of vein quartz and chlorite 
 projecting into irregular hollows. The boulder seemed to represent part 
 of a green bed which had been crossed by veins of ferriferous carbonate, 
 quartz and chlorite, such as are so common in these rocks. The ferriferous 
 carbonate is now all dissolved away. The boulder broke up at a slight 
 tap of the hammer, but on incorporation in the bed was probably quite 
 sound, and with carbonate still connecting the other constituents of the 
 veins. The boulder clay is very stony, and allows of the percolation of 
 water to some extent. Porphyritic granite boulders, in a much decom- 
 posed condition, occur in the same bed. Granite boulders occur also in 
 the gravel below the clay. The section is also of interest in some other 
 respects, and is alluded to again (p. 259). 
 
 Three-quarters of a mile E.N.E. of Ballemeanoch (141) the morainic drift 
 at the side of a little stream contains various granite boulders about 8 
 inches long, which crumble readily under the fingers; the porphyritic 
 felspars break up also, so that their shapes cannot be isolated. 
 
 The widest spreads of drift, including in this term both boulder clay 
 and glacial sands and gravels, occur in Inverchaolain Glen, Glen Fyne 
 (194 and 183), on the hill-slopes near Toward, in tne glen leading into 
 the West Bay of Dunoon, Glen Kin, between this glen and the head of 
 the Holy Loch, and in the glens that open into Loch Long by Gairletter 
 Point and Blairmore. If we were speaking of the boulder clay apart 
 from sands and gravels, it is not probable that any of the above localities 
 would have to be omitted. The arrangement of the boulder clay on the 
 different sides of the glens not unfrequently bears witness to the usual 
 rule, that the greatest development is on that side from which the 
 "carry" has been. The head of Glen Kin, in which the ice carry as 
 shown by glacial striations was from north-west to south-east, shows this 
 well. But the carry was down rather than across the more important 
 glens and sea lochs, and therefore this feature is not brought out strongly. 
 
 It is certain that all this district, up to the highest hilltops, was over- 
 ridden by ice, for, even in cases where no striations have been found, we 
 may still see boulders which have been derived from, or which have 
 travelled across lower areas, e.g., on the top of the hill 1 mile south of 
 Glenlean, at a height of 1988 feet (only 7 feet below the highest point in 
 the 1-inch Map 29) there are a good number of basalt pebbles ; these have 
 not necessarily come far, but they must have come from a lower position, 
 as there is no basalt on this hilltop. 
 
 In some areas the hillsides have been polished so smooth that a first 
 glance suggests that they are covered by drift, but closer examination 
 shows that the covering may be merely a few inches of turf, or at most a 
 foot or two of drift, lying on a polished rock surface. Examples of 
 this occur on the east side of Kilmun Hill ; on the slope 200 yards 
 slightly west of south of Trinity Church, Dunoon ; and mile slightly 
 east of north of South Hall (194 north-west). 
 
 The glacial striations are marked in the Map, and so need not be 
 mentioned in detail. The general direction along the bottoms of the 
 more important glens is nearly with these glens,* the depth having been 
 enough to determine the flow locally ; thus, in parts of Glen Lean, it is 
 nearly east to west ; in the lower areas of Glen Massan, south-east ; in 
 
 * For an early reference to the glaciation of Glendaruel, see Sir A. Geikie, 
 Scenery of Scotland (1865), p. 157. 
 
244 GEOLOGY OF COWAL. 
 
 Glen Tarsan, S.S.W. On the higher grounds, away from the influence 
 of the valleys, the most general direction is perhaps from north-west or 
 N.N.W. This is so on the hill between Bishop's Seat and Strone Saul ; 
 on the south side of Cruach nan Capull (183) ; on the south-east side of 
 Sgarach Mor (173 north-east) ; and on the hills east of Loch Eck. 
 
 Different sets of striations crossing one another are not uncommon, but 
 it is not generally clear which set are the earlier. In the Burnt Islands 
 of the Kyles of Bute there is one set trending south or a little east of 
 south, and another set trending east or a little south of east. On the 
 south-west side of Glen Massan, above Stronlonag, several occur which 
 point slightly east of north, about at right angles to the general direction 
 of the glen and most of the striations in it. Perhaps we may regard 
 these as later than the others, and due to local ice descending directly 
 down the steep side of the glen. The striations on the still higher ground 
 to the south-west of these run south-east again, like those in the 
 glen generally. On the hill slope nearly 1 mile slightly south of west 
 of Ardeiitinny there is also a set pointing straight down the slope, and 
 almost at right angles to the general direction in the neighbourhood. 
 
 Perhaps the most distinct striations occur between tidemarks, e.g., on 
 the Gantcocks, near Dunoon, on the Bull Rock, 1 J mile south of Dunoon, 
 and in many places on the west side of Loch Striven. But in higher 
 areas they are also often wonderfully fresh, and we are repeatedly coming 
 across little vertical scars which are deeply scored, and may be existing 
 now in essentially the same state as when the ice left them. Numerous 
 small hollows can be proved to be of glacial or preglacial origin, the rocky 
 walls being striated on both sides : e.g., Iriverchapel Burn (164 south- 
 west) is running along such a hollow, which is still partly covered by 
 boulder clay. 
 
 Few freshwater lochs occur in this area, but it is certain various others 
 formerly existed which are now filled by alluvium or peat. Some sites of 
 this character are referred to in chapter xx. There is no rock seen in 
 the bottom of Strath Echaig between Loch Eck and the Holy Loch. 
 The barrier at the foot of the former loch consists, as far as seen, of gravel 
 and sand which show a fairly flat surface, and may be referred to a raised 
 beach deposit. The barrier reaches to a height of about 90 feet. On the 
 east side of the outflow the surface is, for an acre or two, uneven and 
 moundy, and reminds us of morainic outlines partly washed down ; and 
 it is very probable that the more even surfaced area also represents an 
 original morainic surface, which has had its inequalities levelled up by 
 rearranged material. 
 
 Loch Loskin, between Dunoon and Sandbank, is perhaps a rock basin. 
 The barrier is formed, on the east side, by a massive hornblende schist, 
 which displays striations pointing slightly east of south. West of the 
 outflow only alluvium, and the gravel and sand of the 100-foot beach, are 
 seen, but it is possible that a rock barrier may occur on this side also, 
 hidden under the beach deposits. 
 
 Lochan na Leirg, on the hill between Loch Riddon and Loch Striven 
 at a height of over 1500 feet, is surrounded by rock on all sides. 
 
 Parts of the areas of the Clyde and of the neighbouring sea-lochs would, 
 if raised sufficiently, form land-locked water basins, the bottoms of some 
 of the more inland parts being known to reach a greater depth than those 
 more seaward. Particulars of these basins are given by Dr H. R. Mill 
 in his work on "The Clyde Sea Area" (Trans. Roy. Soc. Edin., vol. 
 xxxvi. p. 641). From this we gather that a basin, called the Dunoon 
 basin, extends from the north end of Great Cumbrae up to the junction 
 of Loch Goil and Loch Long. On the south side of this is another 
 
GLACIAL DEPOSITS : SHELL BEDS. 245 
 
 basin, the Arran basin, an extension of which runs up Loch Fine as far 
 as Otter. In upper Loch Fine there is another basin extending from 
 Minard to Inveraray. At Minaro! Narrows the depth is 18 fathoms : near 
 Creggans it is 83 fathoms. In Loch Goil there is also a well-marked 
 basin. The deepest part, opposite Stuckbeg, is 45 fathoms : the depth at 
 the mouth of the loch is only 7 fathoms. 
 
 Contortions of schist planes due apparently to the drag of the ice sheet 
 are occasionally observed. On the shore J mile north of Blairmore Farm, 
 J mile south-east of Kilmun Established Church, and north-east of Glen- 
 acre (195 north-west), the schists seem to dip north-west instead of south- 
 east, and have probably had their edges twisted back by the ice coming 
 from the north and north-west. On the shore J mile east of Hafton 
 House (174 south-east) thin yellow schists show a reversed dip, and are 
 churned up and mixed with boulder clay. In a small burn (not marked 
 in Map) J mile slightly north of east of Corlarach (194 north-east), and 
 in Corlarach Burn itself, -% mile N.N.E. of Beinn Ruadh, the schist is 
 much twisted near the surface. 
 
 Beds containing glacial shells have long been known in the district. 
 Such were first described by Mr Jas. Smith (of Jordanhill) in his paper 
 " On the Phenomena of the Elevated Marine Beds of the Basin of the 
 Clyde," Mem. Wern. &oc., vol. viii. More recently Messrs Crosskey and 
 Robertson have examined them in great detail, and given lists of the 
 fossils procured from them ("The Post Tertiary Fossiliferous Beds of 
 Scotland," Geol. Soc. Glasgow, vol. v., p. 29, 1875). 
 
 In Cowal these beds have only been noticed up to a height of a few 
 feet above high-water mark ; frequent exposures occur on the shore by 
 this mark, or between it and low-water. They generally consist of very 
 finely-laminated clays or sandy clays, of a reddish-brown or yellow colour, 
 alternating layers differing slightly in tint. At other times the clay is 
 grey and shows no signs of lamination. The proportion of stones in 
 the clay varies considerably, and in some places is so large that 
 probably half the bulk of the bed is of stones, while in others stones are 
 almost absent. The stones rarely exceed 3 or 4 inches in diameter, and 
 are generally somewhat angular in shape : we have not noticed any with 
 striated surfaces. 
 
 We are not aware that any of the beds in this district lie within boulder 
 clay, though in other areas shell-bearing beds can be seen in this position, 
 e.g., in Tangy Glen, near Campbeltown, described by Messrs Robertson 
 and Crosskey (Trans. Geol. Soc. Glasgow, vol. iv.), and in the south of 
 Ai-ran, described by the Reverend R. Boog Watson (Trans. Roy. Soc. 
 Ed<'n., vol. xvi. p. 523). 
 
 In the bay at Port an Eileiu, east side of Loch Riddon, a reddish 
 shelly clay occurs which contains many small Tellinas. Mr J. Bennie, 
 who collected from this and other localities, informs us that many of the 
 small shells had a bright epidermis, and had evidently been well preserved, 
 but that others were much weathered. 
 
 In the bay J mile W.S.W. of Fearn'ach (182 south-east), close under the 
 raised beach, there is a stiff shelly clay which contains Pecten Islandicus. 
 Mr Bennie found here a great number of Littorinas, many in a broken 
 condition, suggesting that they had had a "squeeze," but none showed 
 marks of abrasion. 
 
 On the shore J- mile or so south of Fearn'ach, at various places for a 
 distance of 80 yards, a stiff chocolate-brown clay, somewhat sandy in 
 parts, is seen 3 or 4 feet above high water mark. The clay is full of 
 rootlets and vegetable fibres descending from the ground surface. It is 
 overlain by rather fine gravel belonging to the raised beach, and there 
 
246 GEOLOGY OF COWAL. 
 
 is a wet line between the two deposits, the clay being evidently 
 much less permeable to water than the gravel. The clay shows no 
 lamination on the weathered faces, and is sticky, moulding well to 
 the trowel and fingers. It contains many shells, but they are some- 
 what brittle and readily broken : among them Pecten Islandicus is 
 abundant, and attains a length of 4 or 5 inches : the two valves of one 
 individual sometimes occur in close apposition. The large arctic barnacle 
 is also common, sometimes fixed on stones and sometimes on the larger 
 shells. A sea urchin was also found, the plates fitting exactly together 
 but only kept in position by the clay. The same bed forms the shore 
 below high water mark, and seems hsre to contain shells in a less brittle 
 state. 
 
 On the shore J mile north-west of Colintraive Pier the shell bed again 
 occurs a few feet above high water mark. It is here much harder to dig 
 than south of Fearn'ach, as it is very full of stones. Mr Bennie found 
 Myas frequent and most of them with both valves in contact, but they 
 were soft and easily broken : Littorinas frequent : Pecten Islandicus 
 small, only J inch, but perfect, not rubbed or worn. 
 
 The north bank of the Ruel, J mile slightly east of north of Ormidale 
 House, shows a section as below : 
 Grass. 
 Three to four feet gravel becoming coarser downwards : stones of 
 
 8-inch diameter not uncommon near the base. 
 One foot sandy clay with nests of shells and big barnacles. 
 Six feet finely laminated greenish-grey sandy clay, apparently stoneless 
 
 and shell-less, and conformably under the bed above. 
 The sand and gravel at the top probably belong to a river terrace. No 
 unconformity is seen here between them and the underlying deposits> but, 
 at a point J mile south-east of Ormidale House, in the west bank of the 
 Ruel, a laminated blue sandy clay dips down stream rather steeply, and 
 the edges are cut off by gravel of the overlying river terrace. In the 1 
 foot of sandy clay Mya truncata was found in abundance, and often in 
 the habit of life with the mouth uppermost. The shells are brittle and 
 easily broken near the surface, but stout and well preserved further in : 
 they are generally filled with coarser sand ; the epidermis is in a good 
 state in all, except where weathered. The Cyprinas are large and stout, 
 occasionally with the valves together, but many single : about half the size 
 of those in the Loch Long localities south of Ardentinuy : the epidermis is 
 preserved. The barnacles are 1 J inch long, often in clusters adhering to- 
 gether, and generally free from attachment to shells or stones. One stone 
 had apparently serpulae on it. The clay at the bottom reminds Mr Bennie 
 very much of the white mud found under the shell beds of the Clyde, 
 in which, after much search, Mr David Robertson found some foraniinifera : 
 near Ormidale the mud was sometimes dyed black from decaying matter, 
 from the shells in the bed above. 
 
 One hundred and twenty yards E.N.E. of the cottage at the foot of 
 Ardyne bum (194, south-east), a section on the west bank of the stream 
 shows (March, 1893) the section below : 
 
 Six to seven feet sand and gravel, horizontal and evenly stratified, 
 
 belonging to the 20-foot beach. 
 Three feet of dark grey boulder clay. 
 
 Similar boulder clay is also seen under the water of the burn. The line 
 between the gravel and the clay is perfectly sharp and nearly horizontal. 
 A few yards south of this section a change takes place, and, just at the 
 edge of the water, a finely laminated stoneless clay, in alternating yellow 
 and reddish-brown colours, overlies the boulder clay, the line between 
 
GLACIAL DEPOSITS : SHELL BEDS. 24? 
 
 being quite sharp and distinct. The laminae of the clay are not conform- 
 able to its junction with the boulder clay, and, further under the water, 
 more of it comes on, until the thickness reaches 2 or 3 feet. The laminae 
 dip 10 to 12 in a direction about 20 west of south. It is clear that the 
 20-foot beach gravel is unconformable to the laminated clay, and must cut 
 across its inclined edges, so as to rest on boulder clay below it. About 20 
 yards above the section the same clay is seen in the burn bed, from a point 
 about 10 yards below the new suspension bridge to 6 or 7 yards above. 
 We could see no shells in the laminated clay either in the bank section 
 or the burn bed, but 6 or 7 yards above the bridge, on the west side of 
 the burn, this clay dips east at a gentle angle, and is overlain by a dull 
 brown or dark grey clay, which is full of shells : perhaps there is one 
 shell for every 16 to 18 square inches of surface. This clay does not show 
 any lamination : it is only seen under the ordinary water level of the 
 stream, and no specimens have been obtained from it. It is stated by 
 Sir Arch. Geikie ("On the Phenomena of the Glacial Drift of Scotland," 
 Trans. Geol. Soc., Glasgow, vol. i. p. 133) that a laminated brown or 
 reddish clay, without stones and shells, is almost always found between 
 the shelly clay and the boulder clay in Bute and the Clyde district. 
 Further up the burn, mile south-west of Killellan, a yellow shelly, 
 nearly stoneless, clay was seen under the river terrace on the east side 
 of the burn : 220 yards north-west of Killellan a similar shelly clay was 
 seen in the burn bed, the laminae dipping down stream in a southerly 
 direction : and in several places a little further up the burn, on either 
 bank, similar ciay occurs, but without shells as far as noticed. 
 
 A laminated shelly clay is exposed on the shore just north of the rocky 
 point at Toward Quay. It is very stiff, and coloured yellow and reddish- 
 brown in thin alternating layers. The layers often dip steeply, as much 
 as 45, and make curved outcrops on the shore, as if the strike was 
 contorted. Pecten Islandicus, sometimes 3 to 4 inches long, is abundant, 
 stout, and well preserved. Astarte, a big barnacle, and a stony seaweed, 
 growing attached to boulders, are also common. The deposit is largely 
 obscured by shingle, and is overlain at high water mark by the gravel 
 of the raised beach, from which numerous fresh-water streamlets descend. 
 
 On the west side of Loch Long several exposures of shelly laminated 
 clay occur. About J mile south of Ardentinny church this clay is seeu 
 to overlie a reddish-brown boulder clay. About 1J mile south of the 
 church the Myas were good, the Pecten Islandicus, Cyprinas, and Astartes, 
 large, and Mr Bennie considers these localities very promising for further 
 search. 
 
 Laminated clays, but as far as known without shells, occur on the shore 
 J mile E.S.E. of Altgaltraig Point (182 south-east) ; on the shore T 5 o mile 
 north of Port an Eilein ; and on the west side of Loch Striven, nearly 
 | mile N. of Strone Point. In the first mentioned locality the clay clearly 
 overlies boulder clay. 
 
 Lists of the shells collected in the different localities are given in the 
 Appendix, but we reproduce here the substance of some observations 
 Mr Bennie made on concluding his researches. Nothing was observed 
 differing much from what is generally seen in the Clyde glacial shell beds, 
 excepting for the great number and large size of the barnacles near Ormi- 
 dale House, and also the entire absence here of the stones and shells to 
 which they must once have been attached : this suggested that they may 
 have been transported, but the place from which they came could not be 
 far off, as there are no marks of travel-wear upon them. In most of the 
 beds there is a mixture of shore and shallow water shells with those that 
 inhabit deep water : this also is a common feature in the Clyde beds, 
 
248 GEOLOGY OF COWAL. 
 
 where Littorinas and mussels are often found in clay which must have 
 been deposited in water of some depth. 
 
 It has been already mentioned that the Toward Quay bed shows indica- 
 tions of contortions. It is perhaps reasonable to suppose this due to the 
 drag of ice. In this locality a block of calcareous freestone, measuring 
 about 5 feet by 4 by 2, lies on the shore within 4 or 5 yards of a clear 
 exposure of the bed, and is in all probability lying on it ; it is somewhat 
 angular in shape. Beside this, blocks of schist, attaining a length of 5 
 feet and a breadth of 2 to 3, occur within 2 or 3 yards of some of the 
 exposures. From 260 yards north-west of the west gates of Toward 
 policies the shore to the westwards, at mean tides, is covered by gravel, 
 and shows no boulders so big that they may not have been derived from 
 the raised beaches, or brought as ballast, or derived from a wrecked sea- 
 wall. This applies to the shore as far west as Ardyne Point, and for at 
 least a little distance north of the point. With the exception of the 
 blocks from the old sea-wall, there are none much more than 1J foot in 
 length, and very few as large as this. Blocks of the size of those on the 
 shelly clay do not occur among the gravels of either the present or the 
 old beaches in this locality. 
 
 Along the shore between Ardyrie Point and Toward Quay, small blocks 
 derived apparently from areas lying south or south-east occur, e.g,, Upper 
 Old Red sandstones, magnesian limestones, crush-rocks like those near 
 the schist boundary, and fine-grained purple andesite-like rocks. 
 
 Between Toward Quay and Toward Lighthouse, there is an abundance 
 of large boulders on the rock exposures, and on the tidal flats which may 
 be formed out of boulder clay, but they do not occur on the raised beach 
 gravel, excepting when this is within a few yards of the margins of the 
 other formations : the boulders in this situation seem in some cases to be 
 resting firmly on beach gravel. 
 
 The shore just east of Colintraive Pier shows an abundance of boulders, 
 as much as 3 feet in length, some of which seem to rest firmly on the 
 beach gravel. Good sections of the old beach occur near, and show no 
 stones so large as these : the largest are about 9 inches long. 
 
 In various other localities we find stones on the shore which are not 
 noticed in the boulder clays, and which seem confined to the shores, and 
 to have been derived from areas lying south or south-east. In Fearna 
 Bagh there are many rather soft, coarse-grained freestone boulders, 
 containing small quartz pebbles and few or none of schist : we did not 
 notice any exceeding 1 foot in length : they are not very rounded. There 
 are also small boulders of fine-grained hard white sandstones, coarse 
 chocolate-coloured freestone with clayey lenticles, conglomerate of quartz 
 pebbles, with the pebbles as much as 2 inches in length, and purple 
 andesite-like rocks. To the north also, as far as Springfield House, red 
 freestone blocks have been noticed. 
 
 In the West Bay of Dunoon there are a good number of boulders, 
 about 6 or 8 inches long, of green serpentinous rock like that at the 
 schist boundary, and of purple andesite-like rock. 
 
 The garden walls about Blairrnore contain so many blocks of reddish 
 freestone, often several feet long, that we examined the shore to see if 
 they did not occur as boulders on it. We found a good number both 
 of red and yellow blocks, sometimes quite coarse and not the kind 
 that would be chosen for good building stones : in one place, about J 
 mile south of the pier, there is a boulder of calcareous false-bedded free- 
 stone measuring 4 feet by 2 by 2 : in another, J mile north of the pier, 
 there is a grit boulder with a length of 3 feet and a breadth of 2 : but it 
 is rare for them to exceed 1 foot in length. C.T.C. 
 
249 
 
 CHAPTER XIX. 
 
 GLACIAL DEPOSITS (continued). DESCRIPTION OF 
 PARTICULAR DISTRICTS. 
 
 District of Tighnabruaich. 
 
 This district includes that part of Cowal which lies west of the lower 
 part of Loch Riddon, and the west Kyle of Bute, and south of a line 
 that runs east to west between Eilean Dearg and Drum Point. 
 
 There are no wide spread areas of glacial drift in the peninsula south 
 of Kilfiuau. The boulder clay or till, always of a bright red colour, 
 generally occurs in small irregular patches in the hollows and slopes 
 between the numerous rock exposures, and seems nowhere to be thick 
 except in some of the burns and valleys. Perhaps the drift areas are the 
 largest in the Acharosson valley. In Allt Dubh to the north-east of 
 Beinn Capuill at a height pf 950 feet above the sea, the till is 15 to 20 
 feet thick. It is very thick in the lower part of the Acharosson burn : a 
 thickness of 20 to 30 feet may be seen in the north bank near Auchan- 
 askioch, and it is probably much thicker thau this. A similar thickness 
 of drift may be seen in the most westerly branch of the stream that runs 
 into Loch na Melldalloch. Thick red clay was observed at Tighuabruaich 
 reservoir, and it may be seen on the shore in many places from the east 
 side of Tighnabruaich Pier, round to south of Kames Pier. There is a 
 good thickness of red clay at Rudhaban, Port Driseach, underlying the 
 gravel of the 100 feet beach, and also in the Craignafeich Burn, 200 
 to 400 yards below the lowest dam. Red till may be seen about Stillaig 
 Farm and in the burn to the north-east, and there is a good section of it 
 in the small stream near Asgog Farm. It may also be noticed up the 
 valley of Allt Osda in several places, under the high beach gravels and 
 sand, and about Millhouse. In addition to these localities may be men- 
 tioned the neighbourhood of Ardlamont and Corra, especially a small 
 stream west of the bend of the road on the west of Corra. 
 
 There is a patch of gravel, probably glacial, to the west of Allt Mor, 
 and about J mile north-west of the Established Church, Tighnabruaich. 
 The gravel, in which there are small pits, is dirty-looking and subangular, 
 and covers an area about 100 yards long by 50 yards broad. It appears 
 to overlie schist. 
 
 Glacial striae have been noted on the 6-inch Map in this district about 
 50 times, but all of these are not placed on the 1-inch Map. They vary 
 in direction from north-west round to N.N.E., the most numerous direc- 
 tions being about due north, and north 10 west, in nearly equal propor- 
 tions. The northerly direction prevails along Loch Riddon, but over the 
 greater part of the area the general direction is west of north. The 
 places where the direction is to the east of north are nearly all on the 
 coast, e.g., at Callow and Rudhaban, Loch Riddon, on the shore opposite 
 Tighnabruaich, and to the south of Kames Pier, and on Loch Fine, south 
 of Black Harbour. Some of the strias most to the west of north must 
 be regarded as abnormal, e.g., one which is about north-west, by the road- 
 side on the way to Kilfman to the south-west of the lower dam, is on a 
 nearly vertical face of rock, which has evidently influenced the direction 
 of the ice at that point. The same explanation must be given of one to 
 the north of Callow, which points about north 40 west, nearly parallel 
 
250 GEOLOGY OF COWAL. 
 
 to the direction of the cliff there. Sometimes we meet with more than 
 one set of striae on the same surface, as, for instance, by the side of the 
 upper road, 300 yards south of Tighnabruaich Established Church, where 
 they vary in direction 20 to 40 west of north ; and north-west of Stillaig 
 Farm, where they vary from 10 to 30 west of north. 
 
 Not many noticeable boulders were observed in this area. A large 
 block of white granite, .8 feet long by 4 or 5 feet broad, was seen on the 
 shore on the west side of Ardlamont Bay near Rudha na Peilige, and 
 boulders of granite are built into the wall bounding the plantation 1000 
 yards north-east of Ardmarnock House. A boulder of serpentine, 6 feet 
 by 5 feet by 3 feet 6 inches high, occurs on the moor, 1000 yards north- 
 east of Loch na Melldalloch, and 800 yards north of the upper dam. 
 About \ mile N".N".E. of Ardlamont House, there is a group of large 
 schist boulders, one of which is 15 feet long by 7 feet broad. 
 
 W.G. 
 
 District of Kilfinan and Stralachlan. 
 
 This district is bounded on the east side by Newton Bay, Gaol 
 Ghleann, Glendaruel, and the upper part of Loch Riddon. On the south 
 side the boundary is the Tighnabruaich District. 
 
 This area is comparatively poor in glacial deposits. Boulder clay and 
 drift are only met with in isolated patches among rock hollows, and 
 are generally only a few feet in thickness. In the high ground but 
 few striated surfaces of rocks have been observed. As the lower ground 
 is approached towards Loch Fine on one side and Glendaruel on the other, 
 such markings become more numerous, and when the coast is reached 
 they are discovered in abundance. Those on the coast have the same 
 general direction as those found on the hilltops and slopes, and indicate 
 a movement of the ice-sheet from a north-easterly direction. 
 
 The area that lies between Stralachlan Glen and Loch Fine is well 
 glaciated, the rock surfaces preserving the rounded outlines that have 
 been impressed on them by the passage of the ice-sheet. In this district 
 most of the rocks consist of massive epidiorites, which, by their power of 
 resisting the processes of weathering more than the rock masses in which 
 they have been intruded, have been the means of indicating the degree 
 of glaciation to which the whole district has been subjected. Besides the 
 general smoothness of the surface, good striations are met with up to the 
 summits of these epidiorite ridges, at heights between 500 and 600 feet. 
 
 The direction of movement of the ice-sheet corresponded nearly to 
 the general trend of Loch Fine, and to the upper portions of Glendaruel 
 and Gaol Ghleann. Where, however, the valley of Glendaruel deflects 
 from this course, as at Ballochandrain (172), the glacial striae at the lowest 
 parts of the valley likewise deflect. At Ballochandrain (172) stria? by 
 the roadside have been noted in a direction nearly north and south. At 
 the head of Loch Riddon on the western side of the Ruel estuary (172) 
 north and south striae have been observed. On the published Map (sheet 
 29) striae have been shown on the coast at Lochead on the seaward margin 
 of a raised beach ; the striae are preserved on mica schist. About 200 
 yards further south along the shore another set of striae occurs with a 
 similar trend, the scorings being well preserved on the surfaces of a 
 massive quartzose schist. North and south striae have also been observed 
 on the west shore of Loch Riddon opposite Eilean Dearg. On reference 
 to the Map, it will be noticed that the north and south direction of these 
 glacial scorings between Lochead and Eilean Dearg corresponds almost 
 exactly to the trend of Loch Riddon and the Ruel estuary near these 
 localities. It is evident, therefore, that these striae were produced by 
 
GLACIAL DEPOSITS I KILFIN AN " DISTRICT. 251 
 
 the advance of an ice-sheet from Glendaruel into Loch Riddon, the course 
 of which was determined by the trend of the valley of Glendaruel and 
 its extension into Loch Riddon. While the bulk of the strise along 
 Loch Riddon conform to this general direction, a few have been observed 
 somewhat oblique, but in these cases they follow the unevenness of the 
 coast-line. 
 
 As stated previously, the general trend of the ice-sheet that once 
 covered the area was in a direction from north-east to south-west. Some 
 instances, however, occur, in which the rock surfaces have been striated 
 from a direction nearly due east. These are well shown on some of the 
 epidiorite masses between Stralachlan Glen and Loch Fine at elevations 
 of 500 to 600 feet. 
 
 The nature of the boulder clay has already been treated of. Two dis- 
 tinct types of boulder clay occur differing from one another in colour ; 
 the prevalent colour of one type is greyish to blue when fresh, and 
 yellow to yellowish-brown when weathered ; the colour of the second type 
 is red to chocolate. In this district the red boulder clays do not occur 
 north of Otter Ferry (171) on Loch Fine; the boulder clays in the 
 northern part of the area are of the grey-blue type. 
 
 It is quite clear that the difference in colour of the boulder clay cannot 
 be ascribed to difference of composition of the rocks on which it now 
 lies. The rocks underlying the red clay are similar to those underlying 
 the blue clay. Neither can the difference be accounted for by ascribing 
 one variety to the more elevated regions and the other to the lower 
 country. In the areas peculiar to each clay these deposits are found 
 from sea-level to the most elevated situation. 
 
 In this district sandy and gravelly beds in the boulder clay are rare. 
 The boulder clay is sometimes laminated : more usually, however, it is 
 devoid of structure. The majority of the contained boulders are semi- 
 rounded, and a small proportion show striations. 
 
 The bulk of the area consists of an irregular hill slope dipping away 
 from the high ground that rises precipitously out of Glendaruel down to 
 Loch Fine. Boulder clay is seldom met with on this hill slope, and when 
 it does occur the deposit is usually thin and covered by peat. It i 
 common, however, for the slope to be thickly strewn with a coating of 
 blocks and rubbish, which appear to have been left behind on the hill 
 slope after the drift deposits in which they were embedded had been 
 denuded away. This is a common feature of the slopes in the Stra- 
 lachlan area. 
 
 The raised beaches on the coast of Loch Fine are generally found rest- 
 ing on a boulder clay floor. At Barnacarry (151) the gravel of the 20- 
 foot beach rests on a stony stiff blue boulder clay. A mile further 
 south two small raised beaches consisting of sand and gravel are found 
 resting on blue boulder clay. In fact, without further enumeration in 
 detail, it may be said that in nearly the whole of the raised beaches 
 within this area sections are exposed, revealing boulder clay below the 
 beach deposit. 
 
 At the roadside leading south-west from Lephinmore (162) just beyond 
 the upper limit of tbe 50 foot beach there is a section of blue boulder 
 clay showing contortions. The section is 40 feet above sea-level, and the 
 contortions were evidently produced before the formation of the 50 foot 
 beach. In this area sections of contorted boulder clay are rare, but it 
 must be borne in mind that such contortions can only be detected when 
 the boulder clay happens to be laminated. From its position the con- 
 tortion may very well have been brought about by floating ice. 
 
 Where the raised beaches rest upon the boulder clay, the beaches are 
 
252 GEOLOGY OF COWAL. 
 
 unconformable to the boulder clays. The gravel frequently overlaps the 
 boulder clay and rests on the rock. 
 
 Erratics and perched blocks are common over the whole district : the 
 latter are often found on the summits of the ridges. As a rule the 
 boulders have not come from any great distance. Where the original 
 locality of the boulders can be made out, they invariably indicate their 
 transport from a general north-easterly direction. The boulders comprise 
 every type of rock which the district contains, and in addition some rocks 
 which are not found in the area. Boulders of the Glen Fine granite are 
 often met with as well as fragments of coarse garnet schist, which have 
 probably been derived from the same area. No boulders have been found 
 which correspond to rocks peculiar to the north-western side of Loch Fine, 
 nor any of the Lome Andesites, which lie about 11 miles to the north- 
 west of this area. Although the Lome Andesites are not found on the 
 eastern side of Loch Awe, they are nearer this district than the Glen Fine 
 granite. 
 
 The glaciatiou must be referred to a great south-westerly movement 
 of the ice-sheet, which spread over a large area of which this district 
 forms but a part, the area extending across Loch Fine to Loch Awe. The 
 highest points of this area have been covered by the ice-sheet, which 
 must have had a thickness of at least 2000 feet. 
 
 Moraines are scarcely ever met with in this area, except near the 
 extreme north-east boundary where numerous moraines occur in the upper 
 part of Gaol Ghleann, resting on a deep deposit of boulder clay. This is 
 the most extensive deposit of boulder clay in the area. As these moraines 
 are described in the description of another area (see page 257), they will 
 not be further alluded to. They occur here and there the whole way 
 down the glen as far as Dunans, and along the sides of the Kilbridemore 
 Glen (162). J.B.H. 
 
 District of Strachur and Lochgoilhead. 
 
 This district includes most of the north part of Cowal. It includes that 
 portion of the area being described which is contained in 1-inch Maps 
 37 and 38, with the exception of the part which lies west of Newton 
 Bay, Gaol Ghleann, and Glendaruel. 
 
 Near the tops of the higher hills in the northern part of Cowal, e.g., 
 on Sgor Coinnich, Beinn Bheula, Cnoc Coinnich, Benin Eeithe, Carnach 
 Mor, the two Beinn Lochains, Ben Donich, Binnein an Fhidleir, etc., 
 the glacial striations point south-east or S.S.E., though on the lower 
 ground they are either parallel to the glens, or to Loch Fine. The south- 
 east direction is not found at heights much under 1500 feet, and in some 
 places, e.g., on the north-west side of Stob an Eas, just over the 2000 feet 
 contour, and mile east of Binnein an Fhidleir, over the 2250 feet contour, 
 a movement in a south-west direction is indicated at higher levels than 
 this. There is no ground so high as the hills mentioned in exactly the 
 direction whence some of the striae point, anywhere between Loch Fine 
 and the Firth of Lome, though Ben Cruachan (3689 feet) is not much 
 off the direction. The south-east striss are not abundant, and to some of 
 them exception might be taken, but of the most of them there can be no 
 doubt : they are usually on the surfaces of quartz veins in the albite 
 schists. From the carry of the boulders we suppose the movement was 
 from the north-west and not the south-east. Sometimes boulders are 
 found not far off the striations, which do not occur anywhere on the south- 
 east side of the striations, e.g., \ mile north of Cruach nam Miseag (153), 
 there are many angular bits of garnetiferous schist mixed with others of 
 
GLACIAL DEPOSITS: STRACHUR DISTRICT. 253 
 
 quartz ite schist and lamprophyre, at a height of about 1900 feet. The 
 garnet schist is like the schist which occurs on the north-west side of 
 the Loch Tay limestone. There is no rock like it in the area south-east. 
 Also, there is a total absence of boulders of the less altered beds which 
 are found near the south-west boundary of the Highlands. The boulders 
 of garnet schist occur at an elevation greater than the supposed parent 
 rock. In the north-east corner of 1-inch Map 37, the same rock occurs 
 at higher elevations : this is in a direction north or slightly east of north 
 of the boulders. But as the nearest striae indicate a movement in a 
 north-west direction, it is perhaps unnecessary to go so far for the source 
 of the boulders. 
 
 On the lower areas we meet again and again with boulders, such as 
 those from the green beds on the north-west side of "the anticline," which 
 have come from a north-west direction, but this is along the course of 
 glens, such as Hell's Glen and Gleann Canachadan. 
 
 In spite of the striations running north-west on the higher hills, we 
 cannot point to any boulders that have been brought from the north-west 
 side of Loch Fine on to the south-east side. The absence on the south- 
 east side of any boulders of the andesitic traps of Lome, and the com- 
 parative rarity of quartz felsite boulders, seems to negative the supposition 
 of any great ice movement across the loch from the north-west side. It 
 may be that at the same time as the ice-sheet was moving down Loch 
 Fine, and the lower areas near it, from the north-east, a portion of the 
 sheet near the high hills mentioned was shedding itself off in a south-east 
 direction. 
 
 On the south side of Drynain Glen, about mile west of the " T " of 
 "Tom nan Con" (164), and J mile south-east of the "n" of "Con," 
 there are striations pointing north-east, almost at right angles to the 
 general direction in the neighbourhood. We suppose these due to a 
 movement from the high ground on the south-west, at a time subsequent 
 to the general glaciation. They are clearly of the same type as those a 
 little south of here, west of Ardentinny (see p. 244). 
 
 The boulders of porphyritic granite derived from the Garabal Hill and 
 Meall Breac complex (p. 96) are much more abundant in the north 
 part of Cowal than in the south part. This is, of course, but natural, 
 as the north part is so much nearer their source. It is needless to 
 detail where these boulders may be seen : suffice it to say, that both 
 on the shores of Loch Fine, Loch Goil, Loch Long, Loch Eck, and on 
 the hillsides near Loch Restil, Socach, and Gaol Ghleann, they cannot but 
 attract attention. The clean-washed boulders on the shores of Loch 
 Fine are, quite apart from their glacial interest, worthy the attention of 
 any who is studying the rock masses from which they came. We see, 
 mixed with the boulders of granite, others of diorite, of granite with 
 diorite inclusions, junction specimens of diorite and schist, altered albite 
 schist, and schist with opaque spots of white felspar about the size of peas. 
 We are informed by Mr Dakyns that a rock like this last mentioned 
 forms nearly the whole of Ben Damhain and the south face of Troisgeach. 
 This assemblage of boulders can only have come from a north-east 
 direction from the complex already alluded to. At the point J mile north- 
 east of Rudha Bathaich Bhain, we estimated these boulders to form quite 
 one-quarter of the boulders on the shore. The following list of places, 
 nearly the highest in their respective localities, at which the granite 
 boulders have been seen, will indicate to what an extent the granite- 
 bearing drift has overridden this country : 240 yards north-east of the 
 Ordnance Station on Beinn an Fhidleir, at a height of 2600 feet ; J mile 
 E.N.E. of the same station, at a height of about 2450 feet; 170 yards 
 
254 GEOLOGY OF COWAL. 
 
 north-west of the same station, at a height of over 2500 feet ; close to 
 the top of the water-shed J mile and T 5 2- mile E.N.E. of Mullach Coire a' 
 Chuir, at heights of over 1750 feet ; by the top of the " h" of " Beinn 
 Tharsuinn," at a height of 1750 feet ; a little more than J- mile N.N.E. of 
 the " B " of the same words, at a height of over 1500 feet ; 260 yards 
 south-west of -the top of Cruach nan Capull, at a height of 1800 feet; 
 nearly J mile slightly north of west of Sith an t-Sluain, at a height of 
 a little more than 1000 feet this boulder is unusually large, 8 feet by 6 
 feet by 5 feet. The highest point at which this granite occurs in place 
 is on Meall Breac, in the north-west corner of 1-inch Map 38. The 
 height is 2115 feet. It is clear, therefore, that all the boulders mentioned 
 on Beinn an Fhidleir must have been derived from areas lower than their 
 present positions. 
 
 Some boulders of felsite, like the sheets of this rock, which occur in 
 abundance on the sides of Loch Fine, particularly the north-east side, 
 have been noticed within the Clyde watershed, but we cannot be certain 
 that these have come from the Loch Fine watershed, as a band of this 
 rock also occurs on the south side of Stob an Eas and Beinn an t' Seilich 
 (134), and along the course of the N.N.E. disturbances which pass on 
 the east side of Cruach nan Capull (133). One such boulder was noticed 
 J mile north of An Crnachan (162) ; another on the watershed nearly 
 | mile north-west of Meall Dubh (163), at a height of over 1700 
 feet ; another by the road a little more than mile south-east of Drim- 
 syniebeg (142) ; and others in Donich Burn below Donich Lodge, and 
 on the shore of Loch Goil near Ardnahien (153). 
 
 A boulder over 5 feet long, seemingly nearly all composed of large 
 crystals of hornblende, was found J mile east of the second " n " of 
 " Beinn Tharsuinn " (142), at a height of about 1 250 feet. Other boulders 
 rather like this, but not quite so basic, were noticed f mile south-west of 
 Mark (143) and J mile below the foot of Criogan (141). Mr J. R. Dakyns 
 thinks the boulder near Mark is like the rock of some diorite bosses 
 which occur east of Glen Falloch, and Mr J. B. Hill says the Criogan 
 boulder is like some of the deformed basic rock on Beinn Buidhe (1-inch 
 Map 45). 
 
 There are several boulders of the coarse dolerite of Sith an t-Sluain 
 about J mile south-west of this hill. There is no other rock like this in 
 the neighbourhood with which it could be confused. We noticed no 
 boulders carried in any other direction. The glacial striations in the 
 district are all running north-east to south-west. 
 
 At various places north-west of the large albite schist areas, boulders 
 of this rock were found: e.g., on the shore near Tighe Claddich (133), 
 in the burn J mile S.S.E. of Laglingarten (133), by the road a little more 
 than J mile S.S.W. of Ardno, and 80 yards above the road a little more 
 than J mile east of Socach (141). In the last place, the height is about 
 400 feet, and the boulder is 5 feet long. It is suggested that there was a 
 carry in a north-west direction from the albite schist hills down to the 
 lower ground by Loch Fine. But it is not necessary to suppose this, for 
 tlie same movement which carried the granite boulders south-east, would 
 carry albite schist, and, as the strike of the schists is rather nearer north 
 and south than the " carry," might, after carrying it a long distance, leave w 
 it on green beds or other rocks which lie on the north-west side of the 
 strike of the albite schist. There are some exposures of albite schist 
 which lie on the north-west side of the main outcrop of green beds, but 
 these are only small, and not likely to be the source of the boulders 
 mentioned. 
 
 A similar explanation may be given for the boulders of garnetiferous 
 
GLACIAL DEPOSITS: STRACHUR DISTRICT. 255 
 
 mica schist that are sometimes seen resting on rocks which lie north-west 
 of the strike of this schist. 
 
 The deep red boulder clay so common in the south part of Cowal 
 (p. 235) extends also into 1-inch Map 37. It is seen near the head of 
 Glen Fiuart (164) ; in sections by the roadside on Larach Hill there are 
 sharp junctions between it and overlying ochreous morainic drift. In 
 Strath nan Lub (163) the boulder clay is sometimes brown and some- 
 times red ; in the river bank near the " a " of " nan " both colours are 
 seen in the same section ; near the top of the clay there is a close wavy 
 lamination. Red boulder clay also occurs in a bum at the south margin 
 of 1-inch Map 37, f mile south-east of the last "n " of "An Cruachan " 
 (162) ; on the side of Loch Eck, by the foot of the little stream south of 
 Rudha Garbh ; in a drift area west and south-west of Tom Soilleir (163), 
 generally overlain by loose morainic drift ; on the south side of Drynain 
 Glen (164) between the "Drynain" and "Glen"; mile S.S.W. of 
 the " C " of " Tom nan Con " (164). We have not noticed any red clay 
 within the Loch Fine watershed. The general colour of the clay both 
 on the shores and in the glens that lead down to this loch, is pale 
 greenish-grey or pale buff. These colours seem to pass gradually into 
 one another, also at times into more decided brown. 
 
 Signs of lamination in the boulder clay are not uncommon. One-half 
 mile south-east of the "r" of " Laglingarten " (133), a stiff grey 
 boulder clay shows a lamination inclining down hill. In the glen west 
 of Creag Dhubh (141), a thickness of over 30 feet of drift is sometimes 
 seen : the under part is boulder clay with laminae sloping south-east 
 much with the hill. In a burn % mile south of St Catherine's Pier stiff 
 buff boulder clay, containing granite boulders, shows lamination dipping 
 north-west, again down hill. A greenish-grey clay in the burn J mile 
 south of the "h" of "Bathaich ban Cottage" (134) also shows lamina- 
 tion in a north-west direction. 
 
 A section on the east side of "Coire No" (133), by the last "o" of 
 " Coire No," shows laminated sand and gravel, at least 30 feet thick, 
 under stiff boulder clay, probably about 60 feet thick, under morainic 
 drift, 
 
 In the burn 120 yards below the basalt dyke in Leamhaniu (141) 
 there is at least 50 to 60 feet of drift. The lower part is stiff grey or 
 buff boulder clay, the upper part looser morainic. There are good 
 sections for some distance above the basalt, and in more than one place 
 the till is seen below the water of the burn : the stones in the till are 
 sometimes lying with their broader sides approximately horizontal. 
 
 In the burn south of Corrow (142), there are good drift sections; at 
 the top is loose morainic stuff; under this comes a tough grey or brown, 
 rather sandy till ; below this again is looser sand and gravel. 
 
 In Sugach Aodainn (152), | mile slightly east of north of Invernoaden, 
 40 feetof sand and gravel is seen under loose bouldery drift. The 
 sand and gravel contain somo more clayey pieces, which are very irregularly 
 distributed, almost as if they were pebbles, and with a lamination some- 
 times at right angles to that in the gravel. Lower down the burn there 
 are sections of stiff grey till under loose sand and gravel. 
 
 In the burn J mile S.S.W. of Meall au-T (163), there is 10 feet of 
 sandy or gravelly clay and reddish-brown almost stoneless clay, with a 
 lamination dipping S.S.E. at 24, under coarse morainic drift. A little 
 further down the burn, 8 feet of sand and gravel, with boulders and 
 roughly horizontal bedding, is seen to overlie stiff brown till. 
 
 The areas of thick and wide-spread drift have been mapped, but it is 
 impossible to give a satisfactory idea of them by verbal description. We 
 
256 GEOLOGY OF COWAL. 
 
 must, until the margins are engraved in the 1-inch Maps, be content with 
 enumerating a few of them, as follows : the west side of Gaol Ghleann 
 (152), and the tract to the north passing over into the Loch Fine water- 
 shed ; both sides of Strath nan Lub (163), and the tracts extending, 
 south-west to the large peat moss on the south-east side of An Cruachan, 
 and north-east over into Glen Branter ; the west side of Garrachra Glen, 
 above the second " a " of " Garrachra," and extensions thence in scattered 
 patches to join wide deposits in Glen Shellish ; both sides of Eas Dubh 
 (141), and the area crossing over the watershed into Coire No; the Coire 
 No, and the ground on the east side of it over which the road passes 
 between Lochgoilhead and St Catherine's ; the south-east side of the River 
 Cur (142), and the area extending up Glen Leamhanin to a little east 
 of Curra Lochain, and also far up Liogan and Criogan ; the south-east 
 side of Lettermay Burn (142), and the tract extending over the watershed 
 into Coire Ealt ; both sides of Donich Burn and Coire Odhair, and the 
 sides of the streams 1 mile east of Lochgoilhead ; the north side of Glen 
 Kinglas (134), f mile below Butterbridge ; and the south side 2 miles 
 below the same place ; the sides of Eas Riachain (126) and its tributaries 
 this area is connected by a narrow strip with another wide area on either 
 side of the glen north of Meall Beag. 
 
 In most of these areas the surface is occupied by loose morainic drift, 
 and well-defined banks and heaps of coarse bouldery material are common. 
 In some places there are definite boundaries to the areas occupied by the 
 better-shaped moraines. The moraines west and south of Loch Restil 
 pass over the watershed into Glinne Mhor : the upper limit of good 
 moraine shapes is a fairly regular line gradually descending as it goes 
 west from 1200 to 900 feet; it never gets more than about 200 yards 
 from the roadside. The ground north arid west of this line is for some 
 distance occupied by smoother surfaced drift, with isolated rock exposures 
 in places. 
 
 The moraines on the top of the watershed between Hell's Glen and 
 Loch Fine cannot but attract the traveller's attention as he passes on the 
 coach road. Hell's Glen itself is comparatively free of drift, but just on 
 the watershed moraines appear, and extend for a long distance by the 
 roadside. They spread up the west slope of Stob an Eas to a little above 
 the 1250 feet contour. The shapes on the south-west side of the road 
 usually take the form of banks running north-east to south-west, and 
 with their steep sides facing north-west. Near the sides of Coire No, the 
 south-west margin of the morainic area is well defined : the boundary 
 crosses the burn by the " C " of " Coire " : on the east of the burn it runs 
 almost due east for a little over J mile : on the west side it forms a 
 curved line which can be traced about mile in a north direction. 
 There is drift further up the Coire, almost to the head, but there 
 are no well-deiined moraine shapes. 
 
 Moraine shapes are prominent on the sides of Glen Branter (152) ; some 
 of them on the east of the gleu have a long axis almost at right angles to 
 the course of the glen. The best shapes end near the head of the glen, 
 along a line running south-west from the "S"of " Srou Criche " ; the 
 ground beyond this line is for some distance much smoother, but ill- 
 defined hummocks appear again on the higher ground to the east and south- 
 east, between the 1250 feet and 1500 feet contours, and the surface 
 drift at the south end of the moss on the watershed between Glen Branter 
 and Strath nan Lub is morainic in character. The best moraines along the 
 lower part of this strath have the form of banks with a direction roughly 
 parallel to that of the strath. Such are seen near the "W" of 
 "COWAL," and J mile south and S.S.E. of Maol Odhar: the last run 
 
GLACIAL DEPOSITS: STKACHUR DISTRICT. 257 
 
 W.S.W., bending as it were down the glen to Garvie. The valley which 
 continues in the direction of Strath nan Lub, S.S.W., from the junction 
 of this strath with Garvie Burn, is occupied by moraines on both sides 
 until the peat moss, J mile E.S.E. of An Cruachan, is reached. 
 Moraines are particularly prominent near the moss, and there is one 
 long bank, running in a rough semi-circle with convex side facing south, 
 which has clearly caused the formation of the moss by damming 
 the drainage outlet. This bank is smoother than typical moraines, and 
 a section at the south side shows fine yellow sand layers, inclining in 
 places at a considerable angle. Another section in the burn J mile E.S.E. 
 of the last " n " of " An Cruachan " shows coarse bouldery drift intermixed 
 with sand and false-bedded laminated clay, and it seems impossible to 
 separate this bank from the others a little further north, which also show 
 occasional sand layers mixed with coarse angular gravel and boulders. 
 South of the bank which margins the moss there are no good moraine 
 shapes, though loose moraiuic drift is still seen in various sections, at 
 times overlying deep red boulder clay. 
 
 Dunans (162) probably takes its name from the multitude of small 
 moraine heaps (dun = a heap or castle), which occur in the glen near 
 this place and to the north-east. Such are prominent all the way from 
 about 1 mile above Dunans to the head of Gaol Ghleaun, and, on the east 
 side of the valley, extend over the watershed to a little beyond the 
 boundary between the parishes of Stralachlan and Kilmodan. North-east 
 of this the ground is still drift-covered for a considerable distance, but the 
 surface is much smoother, and stiff grey boulder clay is seen close under 
 the turf in several places. 
 
 On the west side of Gleann Dubh (152 and 141) the boundary of the 
 more lumpy drift surface is fairly definite, between the head of the glen and 
 | mile of the hamlet of Glensluan ; below this the moraines rest directly 
 on rock, and this continues to be the case at intervals until we get north 
 of the hamlet. From the hamlet to within a few hundred yards of 
 Tombuidhe the boundary of the moraines runs evenly, a little higher 
 than the 200 feet contour ; here and there on the east side of this line 
 stiff grey boulder clay is exposed to day. On the east side of Gleann Dubh 
 moraines extend to higher levels than the west, but they become gradually 
 smaller and less definite on the higher grounds. Mr C. MacLaren (Edin. 
 New. Phil. Jour., vol. i. p. 189, 1855) mentions the moraines near 
 Glensluan; he supposes them to be terminal moraines belonging to 
 the glen. 
 
 The watershed between Eas Dubh, which flows into Loch Fine, and 
 the Cur, which flows into Loch Eck and thence into the Clyde, is very 
 low, and is occupied partly by a peat moss and partly by drift, with one 
 or two small rock exposures near the north end of the moss. The drift 
 generally exposed is stiff greenish-grey boulder clay, but there are also 
 some mounds of sandy material with rabbit burrows. Mounds are 
 much more prominent on the east side of the Cur near Ballemeauoch, 
 and extend south to Invernoaden. Many of these are quite smooth, and 
 have been ploughed over. One, at the edge of the alluvium ^ mile 
 south of Ballemeanoch has been artificially levelled at the top, and the 
 sides evenly graded, to make an old burying ground. The slacks and 
 low parts between the mounds are often occupied by alluvial wash which 
 passes gradually down into the alluvium of the Cur, so that this alluvium 
 has the appearance of fingering off between the mounds, or of quite isolating 
 them. We suppose the mounds to approximately represent original shapes, 
 and that the side streams have, as a rule, merely taken advantage of the 
 original hollows between them, without modifying them largely. There 
 
 R 
 
258 GEOLOGY OF COWAL. 
 
 are moraines a little up the west side of the Cur J mile north-west of 
 Bridgend, running almost at right angles to the course of the river ; stiff 
 grey boulder clay underlies the morainic material. 
 
 Mounds occur on the north-west side of the Cur J mile above 
 Ballemeanoch, with a north-east to south-west direction. About J mile 
 further up the river there is a large one which has a direction almost 
 at right angles to the adjacent Cur. On the north-west side of the 
 river 1 mile above Ballemeanoch, a section on the roadside shows 
 loose morainic drift lying irregularly on, or vertically at the sides of, 
 boulder clay. There seem also to be some patches of the latter enclosed 
 in the morainic drift. It is clear that there has been some erosion 
 between the deposition of the two beds. In the same locality, in a little 
 burn J mile south-west of Socach, 66 yards from the foot of the burn, 
 there is an interesting section of a somewhat similar nature. A coarse 
 bouldery gravel cuts through a buff, finely-laminated, almost stoneless 
 clayey sand. The laminae dip north-west, nearly with the stream and 
 hillslope ; they are cut sharply through on the south side of the section by 
 the coarse gravel, and are also overlain by a thin band of it. The junction 
 line between the two beds is in places overhanging. Twenty yards above 
 this section, a similar gravel is seen, lying with an irregular junction on a 
 stiff laminated sand with occasional stones. This sand is no doubt a 
 continuation of the laminated sand above mentioned, but with more 
 stones. 
 
 There are two mounds a few hundred years east of Glenshellish farm, 
 which are probably morainic in origin, though some people regard them 
 as artificial. 
 
 On the south-east side of the Kiver Fine the deltas of the side streams 
 have spread out irregularly among moraines, and there are moraine 
 shapes quite isolated by alluvial gravel. The old mound fort J mile 
 N.N.E. of Achadunan may possibly be a modified moraine. 
 
 In the angle between the Cur and the Cab there is a well-marked 
 boundary to the good moraine shapes. This boundary makes a curve 
 300 yards north of the " C " of " Cab," corresponding roughly to the 
 angle between the two rivers. From the curve it runs E.S.E. until it gets 
 to the " i " of " Liogan," and N.N.E. for nearly mile. Loose sand 
 and gravel beds often cover the hillslopes outside of, and at higher levels 
 than, this boundary. Good sections of these beds occur in a little stream 
 j- mile and \ mile north-east of the bottom of the " L " of " Liogan." 
 In the first place we see layers of fine and coarse gravel, inclining south- 
 east nearly with the stream and hillslope ; the layers are occasionally 
 cemented with some black cement, probably in part the black oxide of 
 manganese (see p. 242). In the second place there is no clear stratifica- 
 tion. The north-east side of Leamhanin is ridgy and banky, and usually 
 shows a sandy drift at the surface. There are comparatively few boulders 
 on the ridges. A pronounced mound runs from near the sharp bend in 
 the burn J mile north-west of Carnach Mor in a south-west direction, and 
 this too has a smooth surface. 
 
 There are a few good moraines close at the sides of Loch Eck : on 
 the east side, J mile north-east of Dornoch Point, and on either side 
 of Rudha Croise : and on the west side, from the north side of the Ber- 
 nice delta for J mile north, and for a little distance on the south side of 
 the same delta. All these have directions parallel with the loch. Mr C. 
 MacLaren mentions them (op. cit.) and supposes them to be remnants of 
 lateral moraines. Other moraines occur in the coires on the east side of 
 Beinn Mh6r, but these are generally small. 
 
 The moraines are particularly rough, with boulder-strewn tops and 
 
GLACIAL DEPOSITS: STRACHUR DISTRICT. 259 
 
 sides, on the north side of Kinglas Water near Butterbridge, on the sides 
 of the different tributaries of Eas Riachain, in the glen north of Meall 
 Beag, in the glens north and south of Carrick Castle, and the glen south 
 of Cruach nam Miseag (153). In these localities they sometimes consist 
 of great heaps of schist boulders with little or no fine soil between. 
 There are heaps of large boulders too on the east side of Glen Shellish, 
 about J mile and f mile below the burn fork near the head of the glen. 
 There are several island-like knolls in the alluvium T %- mile east of Butter- 
 bridge : some are rock, but others are heaps of boulders, probably rem- 
 nants of moraines. On the high delta on the south side of the foot of 
 the glen south of Cruach nam Miseag, there are some large isolated schist 
 boulders ; these are also probably remnants of moraines which the stream 
 has not had power to clear away. In the alluvium J mile south-east of 
 Drimsyniebeg (142), and in the river near this place, there are also great 
 boulders of probably the same character. 
 
 A very large block occurs on the south slope of Ben Donich at a point 
 }i mile north-east of the " h " of " Inveronich." It forms a prominent 
 object in the view of the mountain from near Lettermay, and goes by 
 the name of " Clach a' Bhreatunnaich " (the Briton's stone). The slope 
 above the stone is comparatively gentle, and we saw no indications of land- 
 slips near. Probably the stone must be regarded as ice-borne. The height 
 of it is about 20 feet, and the sides 18 and 30 feet respectively. It is 
 composed of albite schist, and a little on the south side of it, there is a 
 bank which is thickly strewn with smaller blocks of the same rock. 
 
 Some glacial gravels cemented in part by black cement have been 
 already mentioned (p. 258). Such have also been noted J mile slightly 
 north of east of " h " of " Strath nan Lub," in a stream J mile slightly 
 west of south of " S " of the same words, and in a stream a little more 
 than J mile E.S.E. of Socach ; in a specimen from the last place the 
 presence of manganese was proved. In the east bank of the stream \ mile 
 E.N.E. of the first "n" of "Cruach nan Capull (133), there are small 
 nodules in the top drift soil with a black binding material. 
 
 A section on the roadside 30 yards south of the burn south of Cruach 
 nam Miseag (153) shows 3 to 4 feet of fine sand lying between coarse 
 gravel. The top gravel is probably part of the raised beach. The sand 
 varies in fineness in different layers, and in places the bedding is sharply 
 contorted and folded, with both limbs dipping the same direction. 
 
 The section in the bank of the Cur a little more than \ mile east of 
 Glensluan has already been alluded to (p. 242) for some points of 
 interest. It has to be further mentioned that the lenticles of laminated 
 clay enclosed within the coarse gravel sometimes contain lamina which 
 are sharply twisted, though the boundaries of the lenticles are not so. 
 The ends of the twisted laminae sometimes end suddenly at lines which 
 rather resemble thrust lines. The axes of the folds always incline up 
 stream, towards the N.N.E. . . The lowest gravel may include or 
 overlie stiff laminated clay, like that of the lenticles ; sometimes it cuts 
 across the Iamina3 slightly. Small faults or slips occur in this gravel, 
 and they are filled, for a breadth of an inch or two, with fine sand. 
 
 Lochan Mill Bhig (126) is surrounded by moraines, except where there 
 are two small rock exposures, near the north-east end. The other smaller 
 lochans near this are also mostly surrounded by rnorainic drift. Curra 
 Lochain (141) has morainic drift all round it ; the burn that runs from 
 the moss at its west end shows no rock till you get more than \ mile west 
 of the loch. Lochan nan Cnaimh, south-east of Beinn Bheula, is surrounded 
 by a narrow margin of drift, except in one place near the alluvium at the 
 head. There is a drift-covered strip extending from the lochside, south of the 
 
260 GEOLOGY OF COWAL. 
 
 outlet, to the east side of Lettermay burn. The various peat mosses a 
 little more than 1 mile south of Carrick Castle, east of Tom Molach (153) 
 and J mile north-west of Cruach nam Miseag, probably represent old lochs. 
 Many of the sudden expansions of alluvium at the sides of the streams 
 may also do so. 
 
 In two places on the side of Loch Fine the boulder clay contains broken 
 shells. One of these, 90 yards south-west of Ard na Gailich (133), 
 shows a stiff greenish-grey boulder clay overlain by the raised 
 beach gravel. Close under the gravel the colour of the clay gets brown. 
 The line between the two colours may abut against the middle of an en- 
 closed boulder, and probably represents the advance of water and oxi- 
 dising agents. Shell fragments occur in both the grey and brown clay ; 
 they are in an extremely friable condition, crumbling readily under the 
 finger, and are in pieces which rarely attain \ inch in length. They 
 are in fair abundance, there being perhaps one fragment visible on the 
 average for every square foot of exposure. One bit, a little over \ inch 
 long, showed clear glacial striations. The clay is full of well-smoothed 
 rounded boulders of Glen Fine granite ; there is an obscure lamination 
 in it for a few inches near the top. 
 
 Two hundred yards south-west of the sharp bend in the shore at Airidh 
 a' Ghobhainn (133 and 141), a stiff grey boulder clay, with lamination 
 dipping north, contains broken shell bits. 
 
 In contrast with the above, some glacial shell-bearing beds occur in 
 various places on the coast, in which the shells are probably in approxi- 
 mately the position of growth. None of these have yet been searched by 
 the Survey collectors. In the little burn by the lodge ^ mile E.N.E. of 
 Rudha No (133) 1 to 2 feet of greenish-grey sandy laminated clay is seen, 
 with a gentle dip down stream. This is only a few feet above high- water 
 mark. About 30 yards above the lodge the clay is exposed again, rather 
 more distinctly; it is clearly laminated, but contains stones as much as 7 
 inches in length, in the arrangement of which we could discern no order. 
 The colour of the weathered clay is buff or greenish, but internally the 
 clay is dark-grey, and contains many shiny spangles, probably of minute 
 mica flakes. Shells occur scattered through it near the water-level of the 
 burn, sometimes singly and sometimes in discontinuous streaks as much 
 as J inch broad. The shells are often much broken : we noticed several 
 Astartes among them. 
 
 A greenish-grey laminated clay with shells occurs on the foreshore J 
 mile and nearly \ mile north-east of Creag nam Faoileann (141). In 
 one place the laminae dip south-east at 30, in another north-west, and we 
 thought there were signs of contortion. A stiff buff clay is also seen on 
 the shore in several places to the south-west, nearer to the Creag. Old 
 exposures are no doubt often covered up and new ones exposed, owing to 
 the shifting of the shore gravel. At the time of the Survey, the clay was 
 seen within a few yards of some of the big boulders near the Clach Dubh 
 na Criche (a little more than \ mile north-east of Creag nam Faoilean), and 
 we have little doubt that both they, and the Clach Dubh itself, are resting 
 on it. If this is so, the case is parallel to that mentioned near Toward 
 Quay (p. 248). The Clach Dubh and the other boulders are referred to 
 again (p. 261). This shell-bed is described by Mr W. Ivison Macadam, 
 ("Preliminary Notice of a Clay Shell-bed between Newton and Strachur, 
 Loch Fine, Argyllshire," Trans. Edin. Geol. Soc., vol iv., 1883, p. 94, 
 and " Further Notice of the Tigh-na-criche Shell-bed, Loch Fine, 
 Argyllshire," op. cit., p. 232). He gives lists of the sheila collected by 
 him from the bed, and also an analysis of the clay in which they are 
 found. The analysis is as follows : 
 
GLACIAL DEPOSITS : STRACHUB DISTRICT. 261 
 
 Ferric oxide, Fe 2 O 3 , . . . 16*08 
 
 Aluminic oxide, A1 2 3 , . . . 22 -83 
 
 Calcic oxide, CaO, . . . . 2-55 
 
 Magnesic oxide, MgO, . . . 1-96 
 
 Silica, etc., Si0 2 , .... 56-58 
 
 100-00 
 f 
 
 It is stated that the clay is employed by the people of the locality to 
 whiten the hearthstones before the fire. 
 
 One hundred and thirty yards south-west of Corriesyke (142, close to 
 Douglas Pier, which is not shown on the 1-inch Map) a laminated stone- 
 less clay clips steeply seawards. Similar clay also occurs on the shore 
 1 mile and J mile north-west of this place, and ^ mile south-east. On 
 the side of Loch Long, 100 yards south of the foot of Allt Guanan 
 (142) a laminated clay is seen near high-water mark. All the clays 
 mentioned in this paragraph look like glacial shell clay, but no shells were 
 actually observed in any of them. At the locality J mile south-west of 
 Corriesyke the edges of the clay laminae are distinctly cut off by the 
 raised beach gravel. 
 
 The Clach Dubh na Criche (Black Stone of the boundary, so called 
 because it marks one end of the boundary between the parishes of Stra- 
 lachan and Strachur) is said to have been slightly shifted by shore ice 
 during a severe frost 50 or 60 years ago. Upper Loch Fine is distinctly 
 less salt than the open sea (Dr H. R. Mill, " The Clyde Sea Area," Tram. 
 Roy. Soc. Edin,, vol. xxxvi. p. 697), owing to the number of large burns 
 which empty into it, and freezes with comparative readiness. The Clach 
 Dubh is a boulder of epidiorite, about 10 feet long. The height and 
 breadth we have no note of, but we think they are each about 5 feet. The 
 rock type is very like that of the epidiorite bands near Creggan's Point. 
 The sides are rather rough, but the top is smoothed and striated in a 
 direction 4 east of south. There are some other rather large epidiorite 
 boulders on the shore a little south-west of the Clach Dubh ; one of them 
 is striated at the top in a direction 30 west of south, but it is rough at 
 the sides ; on another one there are striations both on the top and the 
 sides, but the directions vary. If the Clach Dubh, one of the largest 
 boulders on the coast, was moved by shore ice so recently, it is still more 
 possible for the smaller ones, so abundantly scattered on the shore, to have 
 been so. But perhaps most of the large ones occupy much the same 
 positions as they did ages ago when the climate was much more severe 
 than now. On the shores of Loch Fine there is generally a marked absence 
 of large boulders at the mouths of the more gently-flowing burns, both 
 on the fore-shore, on the deltas now in process of formation, and on the 
 deltas of raised beach times. So that it would seem that there have been 
 no boulders left in these places by ice since the deltas mentioned were 
 formed. At the foot of steep running mountain torrents, on the contrary, 
 large boulders may be found, but these have probably come down in 
 flood time, and are no larger than others in the courses of these torrents. 
 
 In Strachur Bay there is neither rock nor boulder clay, and the raised 
 beach deposits extend for some distance inland. Here we saw no boulders 
 on the shore which much exceeded 8 inches in length. But on either 
 side of the bay, where we get on rock or the laminated shelly clay, 
 boulders are abundant. Near Eudha No (133) there are no big boulders 
 on the shore for a distance of about J mile, but at either side of this tract, 
 where the raised beach is represented in the main by a bare shelf of 
 erosion, in rock or boulder clay, boulders are abundant. 
 
262 GEOLOGY OF COWAL. 
 
 The above instances certainly follow the usual rule, but there are some 
 exceptions which deserve notice, e.g., on the shore south-west of Airidh 
 na Gobhainn, there are boulders of granite 3 to 4 feet long which are 
 surrounded by, and seem resting on gravel ; boulder clay is seen on the 
 bank of the raised beach within a little distance. 
 
 We examined the shore of Newton Bay, and found two pieces of red 
 sandstone like that of the Upper Old Red sandstone, but both these were 
 small. The dimensions of the larger were 1 foot by 6 inches by 4 inches; 
 this was a rather pebbly sandstone, with some well rounded quartz pebbles 
 as large as a blackbird's egg, and a greenish-grey matrix. The other 
 was 7 to 8 inches long, and contained pieces of greenish-grey shale 
 nearly 1 inch long. Both might well have been brought as ballast to the 
 bay. They are not the kind of rocks likely to be used for building stone. 
 They are too small to compare with the boulder mentioned (p. 248) near 
 Toward Quay. The largest and most abundant boulders in the bay 
 consist of Glen Fine granite, epidiorite and hornblende schist. Pieces of 
 quartz porphyry with rare quartz crystals, like the rock of the quarries 
 at Furnace on the opposite side of the loch, are common, but they are 
 generally angular, and with fresh fractured sides, and most of them have 
 probably been brought across the loch for building purposes. This is still 
 a common practice. C. T. C. 
 
 CHAPTER XX. 
 
 MAEINE AND FRESHWATER ALLUVIA.* 
 Marine Alluvia. 
 
 There is in many cases no satisfactory distinction between the high 
 gravel and sand deposits taken as marine and freshwater. Shell remains 
 are rarely observed in either, and we may be left to judge of the character 
 of a deposit merely from the distance from the sea at which it now occurs. 
 In the same way at the present day the gravel in the burns passes quite 
 gradually as they approach the sea-level into the gravel under the sea, 
 below the burn mouths. 
 
 In cases, however, in which the deposits can be traced running approxi- 
 mately level along the shores, far away from any burn mouth, it seems 
 clear that the terrace shape must be due to sea action, and the gravel and 
 sand on such terraces are no doubt marine in most cases. It is not certain 
 that all of them are, for the terrace may originally have been one of 
 erosion merely, unaccompanied by deposition, and, long after its formation, 
 little burns coming down the steep hillsides may partly cover the terrace 
 with alluvial material, the more gentle slope of the terrace largely helping 
 to this result. There is, too, a doubt whether some of the deposits now 
 seen below the terrace tops may not be of earlier age than the terrace 
 itself, may be glacial sand and gravel, the edges of which have been 
 abraded by later sea action. The way in which the lower beds in terrace 
 sections may have their edges cut across unconformably by a more gentle 
 sloping, and generally coarser bed, the top of which approximately 
 represents the slope of the terrace, certainly suggests that the lower beds 
 
 * A sketch map of the superficial geology is inserted near the end of the volume. 
 
MARINE ALLUVIA. 263 
 
 may be separated by a long interval from the upper, and have been 
 formed under different conditions. The best instances of these apparent 
 unconformities are given elsewhere, p. 242. 
 
 The greatest breadths of these deposits generally occur near the 
 mouths of glens, a fact which indicates that the material in them has 
 not been produced on a large scale by wave action along the shore, but 
 rather brought down ready formed into gravel, etc., by rivers, though by 
 the sea it has been subsequently rearranged and spread out. For 
 examples of this, we may refer especially to the deposits at the foot of 
 Ardyne Burn (194), at the head of the Holy Loch, at the foot of Glen- 
 daruel, and to the smaller beds at the mouths of the different burns 
 that flow into Loch Striven. 
 
 Shell remains are very rare in beds which we can with certainty refer 
 to the terraces. It is said that such are occasionally ploughed up in the 
 field near Colintraive Pier, within the area of the lower raised beach, and 
 also in the higher terrace near Ardentraive farm, but we do not know the 
 particulars. In some of the small wave worn hollows at the back of the 
 old beach in the garden of Buthkollidar, 2 miles south of Dunoon, sea 
 'shells are also said to have been found mixed with hazel-nuts. 
 
 The highest terrace shape usually seen is that known as the 100-foot 
 beach. This title passes current from its brevity, and perhaps expresses 
 sufficiently well the general height of the surface of the bed, but there 
 are many places, even apart from the neighbourhood of burn courses 
 along which the level might naturally be supposed to rise as we go inland, 
 where the height of 100 feet is considerably exceeded. On the south- 
 west side of Dunoon the height is about 120 feet. Close to Dunloskin 
 farm (180) it is about 130 feet. And near Creag na Cailliche (194) 
 it is even higher still. The surface of it, and also of all the lower 
 beaches, including the present beach among these, has generally a dis- 
 tinct slope towards the adjacent sea margin. It has often been so 
 carved out and denuded by the burns that the terrace shape is no longer 
 clear, and we may doubt whether a certain bed belongs to it, or to an 
 earlier series of glacial deposits. The landward margins near Hafton 
 House (174) and Brackleymore (183) are very uncertain. 
 
 The deposits on the different terraces on the east side of Loch Riddon 
 and the Kyles of Bute possess generally an even stratification. We have 
 seen no sharp contortions in them such as the drag over of ice might be 
 supposed to cause, nor inclusion of boulders enormous in size in comparison 
 to the pieces among which they occur, such as might have been dropped 
 by floating ice. Xo glacial shells have been seen at a height of more 
 than a few feet above the present high water mark, though many of the 
 varieties found in the glacial beds belong to littoral forms. Hence it 
 seems probable that these beds belong, not to the period of the 100-foot 
 beach, but to an earlier and probably colder age.* It should be stated, 
 however, that, as mentioned elsewhere, p. 242, nothing of the 100-foot 
 beach is seen at the heads of Loch Goil or Loch Fine, in the more 
 mountainous district lying in 1-inch Map 37, and it has been suggested 
 that this may be due to the heads of these lochs having been still filled 
 with ice at the time the sea stood at the 100-foot level. The terrace at 
 this level is not known for certain further up Loch Goil than J mile north 
 of Gairletter Point : this is about 10 miles south of the head of the loch. 
 The highest distinct flat in Glen Finart does not much exceed 40 feet in 
 height. That at Ardnahein is about the same height at its landward 
 margin. Those at Corrow and Lochgoilhead are rather lower than this. 
 
 * Mr J. B. Hill is inclined to dissent from this opinion. There is certainly room 
 for different conclusions about the matter. 
 
264 GEOLOGY OF COWAL. 
 
 At Stuckbeg (153) the terrace rises over 40 feet, but this is close to the 
 mouth of a large stream, and the terrace slopes steeply down towards the 
 sea : just east of the terrace there is a section showing evenly stratified 
 sand and gravel between coarser unstratified gravel, but there is no even top 
 to the ground surface, and we cannot safely class these beds with the 100- 
 foot beach. C. T. C. 
 
 In Loch Fine the 100-foot terrace does not appear above Largiemore 
 (171), about 20 miles below the head of the loch. The high flat at 
 Strachur reaches to 100 feet or even more inland along the burn side, and 
 its height near the sea averages perhaps 20 to 40 feet. The high flats 
 at Ardno (133), and Ardkinglas (134), increase in height inland in much 
 the same way. C. T. C., J. B. H. 
 
 At the foot of the burn J mile north-west of Carrick Castle, well-shaped 
 boulder strewn moraines come down to a level of about 50 feet, and are 
 in close contact with the high flat. There is no section to show the 
 relation in age of the one to the other. We suppose the moraines are 
 earlier than the flat : on the south side of the stream the flat extends up 
 it to form the apex of a " v " shape, and there are some huge boulders on 
 the top of it which may be remnants of morainic material which the 
 stream has not had the power to carry away. On the north side, 
 the landward margin of the flat tapers off between moraines to some 
 extent in the same way as the high river terrace in Glen Fine, and 
 south of Ballemeanoch (see p. 257). 
 
 At the foot of Loch Eck the surface of the beach at the east of the out- 
 flow is uneven and moundy, and may represent an old morainic surface 
 which has had its inequalities partly washed down. The surface on the 
 east of the loch is also moundy in places : north of the north end of it 
 there are some smaller patches of gravel which may also belong to it, but 
 the stratification in these is very irregular, and they are not shown in the 
 Map. On the west side of the loch, close to the north margin of 1-inch 
 Map 29, the bed has a somewhat flat surface, but resting on it are two 
 large schist boulders : the adjoining hill slope is not very steep, and it 
 hardly seems that the boulders can be ordinary tumblers. Perhaps in this 
 area the ice was still mantling the hills while the 100-foot beach was 
 being formed. 
 
 A section on the north of the Little Echaig J mile south-west of Bal- 
 lochyle shows 6 to 7 feet of coarse gravel at the top, overlying, 
 at the south-west end of the section, sand, sandy gravel, and tough 
 laminated reddish clay. This laminated clay may represent some of those 
 seen within the boulder clay occasionally (see p. 237). We are inclined to 
 refer the upper bed only to the 100-foot beach. At the north-east end of 
 the section there comes under the gravel some thickness, at least 10 feet, 
 of tough red boulder clay : this boulder clay is at a higher level than the 
 sand and clay in the south-west part, and very likely is really of later age 
 than them, for just under it undoubted signs of sand and gravel occur. 
 
 C. T. C. 
 
 On the east shore of Loch Fine from Newton Bay to Kilfinan Bay, 
 marine terraces are fairly abundant wherever the nature of the ground has 
 favoured their formation and subsequent preservation. They are most 
 numerous at the mouths of the old river valleys where they have escaped 
 the destructive influences of marine erosion. In these cases they have to 
 a large extent been modified by river action, and their partial destruction 
 has furnished material for building up the river terraces with which they 
 
MARINE ALLUVIA. 265 
 
 are associated. The raised beaches at Kilfinan offer a good illustration. 
 They occupy an area of about ^ square mile at the mouth of Kilfinan 
 Burn. On the south side of the burn their upper boundary between 
 Otter House and Kilfinan attains a height of rather over 100 feet, from 
 which there is a gradual slope towards the river. The corresponding 
 terrace on the north side of the burn has been cut into at two or three 
 places by tributary streams and its surface broken up. The ground 
 between these two exposures of the 100-foot beach has been occupied at 
 different times by Kilfiuan Burn, and the marine beaches are entirely 
 replaced by subsequent river terraces. The 100-foot beach on the north 
 side of the burn is continuous east of Lindsaig with a deposit that at the 
 side of the river reaches a height of 200 feet. It is possible, however, 
 that the upper portions of this deposit may be fluviatile, and that we 
 have here an instance of a freshwater terrace passing insensibly into one 
 of marine origin. The deposits are made up of stratified sand and gravel. 
 At Otter Ferry, a few miles further north, a set of terraces occurs, the 
 upper limits of which reach a height above sea-level varying from 170 to 
 200 feet. It is possible these higher portions may be of glacial origin, 
 but we were unable to find sufficient grounds for separating them from 
 the deposits at lower levels into which they merged. J. B. H. 
 
 Near Ardyne Point (194) there are besides the 100-foot beach no less 
 than six different flats at the following approximate levels: 10 feet, 18 
 feet, 23 to 30 feet, 36 feet, 50 to 64 feet. In cases like this where there 
 are many different levels it is impossible to show them all by different 
 tints, and several have to be coloured the same. The lines between them 
 are, however, still engraved. 
 
 Near South Hall (194) four terraces can be made out. At Ardtarag 
 (173), Ardbeg (183), Invervegain (183), Couston (183), Colintraive, 
 Dunoon, and many other places three. In all these places the 100-foot 
 beach is present. 
 
 The lowest raised beach that is generally found is called the 20-foot 
 beach. This forms an almost continuous fringe around the shore, though 
 in places, especially in the more rocky areas, it is represented by a terrace 
 of erosion merely. This is so, for instance, for considerable distances on 
 both sides of Loch Striven, for a little space near Strone Point (Holy 
 Loch), on the south side of Gairletter Point near the basalt dyke, J mile 
 and J mile south of Ardentinny, between Ardentinny and the entrance to 
 Loch Goil, on the east of Loch Goil, from J mile north of Woodlands to 
 near Stuckbeg, on Loch Fine side between Leak and Stucreach, and be- 
 tween Aird Cottage and Creggans. In these cases the landward margin 
 of the terrace is alone intended to be coloured burnt sienna, but the 
 terraces are sometimes so narrow that it is hard to leave an area free from 
 this colour between these margins and the sea line. A similar style of 
 colouring is also used to distinguish the terraces of erosion without deposi- 
 tion on the higher levels, but there are not many instances of these known. 
 On the south-east side of Castle Toward there is a terrace, in part higher 
 than 20 feet, which is bare for some distance. Near Toward farm, on 
 the east of the burn, there is a feature apparently referable to a high 
 terrace, reaching to 70 feet or more, and there may be no gravel on the 
 flatter area below. 
 
 Even when the terrace is of boulder clay there may be little or no 
 deposit on it. This is seen well at Strone Point (Kyles of Bute). 
 
 As an illustration of the common fact that the terraces slope downwards 
 to the sea, even when quite away from any large burn, we may mention 
 the low terrace at Toward Point. The landward margin of this is in one 
 
266 GEOLOGY OF COWAL. 
 
 place 45 feet above sea-level, but the surface near the sea is only 11 or 
 12 feet. Probably every terrace shows this to some extent, just as the 
 present beaches do. 
 
 It is readily noticed that the same physical causes which give rise to 
 features, indents, or points, on the present sea margin, have acted in a similar 
 way in the times of the raised beaches. The same dykes that project 
 prominently on the shores of to-day did so also on the shores of long ago. 
 The same crush lines which form lines of weakness for the waves to 
 advance along and form galleys did so also in old beach times. Often the 
 old beach margins are partially obscured by the slipping of soil over 
 them, so that the smaller gulleys and caves are hidden, but in some of 
 the gardens near Dunoon, e.g. y at Ardfillayne and Buthkollidar, the old 
 sea caves and wave-worn hollows have been carefully cleared out and the 
 old features restored. 
 
 It is probable that the lowest flat at Ardyne Point is to some extent a 
 storm bank. The third beach, too, is of a very uneven surface, and may 
 be due to older storm banks. The raised beach on the south side of the 
 Echaig near Kilmuri Cottage is also very uneven, partly perhaps owing 
 to storm banks, and partly to old river channels. The lowest flat on the 
 east side of the burn in the West Bay of Dunoon is banked up close to 
 the sea-margin, so that in very high tides pools of sea-water form in the 
 gardens, between the outer bank and the edge of the next higher flat. 
 
 C. T. C. 
 
 Near Drum Point south of Kilfman are two terraces of erosion with 
 well-defined margins landward, but rocky and rough toward the sea. At 
 a higher level are two curved gravel ridges meeting at a point storm 
 beaches of the olden time and still higher, rising to above 100 feet is an 
 extensive flat which is probably an old erosion terrace. At Port Leathan 
 to the southward are gravel beaches at three different levels ; these are 
 rocky in places toward the sea and not everywhere distinct from one 
 another. There is a gravel pit in the middle one. In Auchalick Bay 
 there are two old beaches, well defined, but probably somewhat modified 
 by the stream. There is a section of the higher one in the bank ^ mile 
 from the mouth, and on the east side of the valley at Melldalloch and 
 Auchanaskioch there are patches of the 100-foot beach. At Ardmarnoek 
 the second beach is pretty extensive, and there is a patch of the highest 
 beach also. The second beach north of Bagh Buic is covered with peat. 
 Patches of the two lower beaches occur in several places to the south of 
 this, and between Portavaidue and Derybruich there is a fine example of 
 the 100-foot with a good section in the banks of the burn. To the 
 east of Low Stillaig the 50-foot forms an extensive peat-covered flat, and 
 there are traces of higher terraces both to the north-west and to the south- 
 east of this, in the latter case often small gravelly patches interspersed 
 among rocky knolls covered with wood. There are others east of Asgog 
 Bay, and gravel patches of the highest beach about Stillaig Farm, and on 
 either side the little stream to the north-east. The lower beaches up A lit 
 Osda, north of Kilbride Bay, are largely composed of sand, and there is a 
 fine section in the banks of the stream west of Kilbride Farm. Higher 
 up the valley the gravel of the higher raised beaches occurs interspersed 
 with the modern alluvium of the stream, with patches of glacial drift, and 
 some outcrops of rock. The 100-foot beach runs up beyond the powder 
 works at Millhouse, and there is a section of it in a pit near the road-side 
 opposite Auchagoyl Cottages. We heard that shells had been found in this 
 pit, but could not be satisfied of the truth of the rumour. There is a pit 
 in sand and gravel on the west side of the valley near the old mill, and 
 
MARINE ALLUVIA. 267 
 
 another at the north end of the plantation in which are the powder mills, 
 which gives the following section : 
 
 Gravel rather fine, in beds approximately horizontal, 15 feet or more. 
 Layers of sand, dipping steeply, seen below in places. 
 Where the road to Tighnabruaich passes through the plantation, the old 
 beach rises to nearly 120 feet above the sea, and south of the road seems 
 made up mainly of sand, sections of which may be seen in the banks of 
 the stream and in a pit near it, where was observed the following : 
 Soil, 1 foot. 
 
 Sandy laminated clay, 1 foot 6 inches. 
 Brown sand with irregular layers of gravel, 5 to 10 feet. 
 South of the plantation the sand is seen to rest on red till. 
 The greatest extent of the highest beach in the south-west part of 
 Cowal is shown at Ardlamont where it reaches over 100 feet above the 
 sea, though the gravel is not very thick in places, and there are peaty 
 hollows in it. North of Carry Point for some distance the beaches are 
 inconspicuous being only small patches on the solid rock here and there. 
 From Blair's Ferry the lower beach is nearly continuous, but narrow, 
 round to Port Driseach, and patches of the higher beaches are seen 
 occasionally as at Over Inens in Tighnabruaich, and near Rudha Ban. At 
 the latter place they mount up to 130 feet above the sea aod the gravel 
 was seen resting on 10 feet of boulder clay. In Loch Riddon beaches are 
 found at West Glen, Callow and Upper Callow. They are most conspicu- 
 ous at the latter place where there are pits in the highest one. W. G. 
 
 In a good many places on the coast we find rock knolls surrounded by 
 old beach deposits, or by them and the present beach. These must have 
 formed islands in olden times. Examples occur in many places on the 
 east side of Loch Riddoii : between Loch Riddon and Colin traive : at 
 Ardyne Point : at Dunoon (including the conspicuous Castle Hill) : in 
 Loch Long, at the foot of Knap Burn, J mile south-west of the " P " of 
 " Port an Lochan," J mile east of Feoileann, 1 mile S.S.W. of Coilessan : 
 in Loch Goil, the Carrick Castle Hill, 1 mile south-east of Cruach nan 
 Miseag : in Loch Fine, at Leak, Stucreach, a little north-east of Creag a' 
 Phuill, and St Catherine's. C. T. C. 
 
 At the period of greatest submergence the coast line on the west side of 
 Loch Riddon and the west Kyle of Bute, presented much the same 
 appearance as now, but in Loch Fine all the adjacent islands disappeared 
 beneath the waters, except perhaps the east part of Eilean Aoidhe, and 
 new islands were formed south of Black Harbour, north of Bagh Buic, 
 west of Low Stillaig, East of Low Stillaig, east of Asgog Bay and north of 
 Ardlamont Point (two) : and the sea ran up Allt Osda to near Craignafeich 
 making a long narrow peninsula between it and the Kyles. At the 50-foot 
 level of the present islands, would still remain, but much reduced in size, 
 Eilean Buic, Eilean na Beithe, and Eilean Dubh (Loch Riddon), while 
 Eilean Aoidhe would have been two islands, and new islands would have 
 appeared west of Kilbride Bay and north of Port a' Mhadaidh. W. G. 
 
 Where the large burns discharge into the lochs we can generally see 
 that delta-shaped deposits are being formed below the sea line and 
 between tide marks. These marine deposits are in direct continuation of 
 those formed by the burn at higher levels. The tides in the lochs are 
 not strong usually, and so the material deposited under the water is not 
 spread out to great distances from the burn mouth. In upper Loch 
 Fine we have noticed that the deltas at the mouths of streams are 
 
268 GEOLOGY OF COWAL. 
 
 generally composed of finer material than the raised beach deposits on 
 either side of them ; this is seen, e.g. , at Rudha No. and J north-west of 
 Ardkinglas House. 
 
 In most parts of the area the present beaches are free from large 
 boulders where the entire thickness of the shore bank is composed of 
 raised beach material or of the delta deposits of the present streams. 
 But if the terraces are represented by shelves of erosion merely, or by only 
 a thin covering of gravel overlying rock or boulder clay, large boulders 
 may be abundant, in size far exceeding any commonly seen in the sections 
 of the raised beach beds. The deltas of very steeply-flowing burns may 
 in places include boulders as large as these, but, as already intimated, 
 many of the delta deposits are finer than the raised beach deposits near 
 them. There are places, however, and at some distance from the burn 
 mouths, where large boulders are abundant on the shore quite surrounded 
 by, and apparently resting on, gravel. 
 
 In the bay south of Creag a' Phuill (133), and for a little dis- 
 tance south-west of it, their are many boulders, chiefly of Glen Fine 
 granite, sometimes 3 or 4 feet long, and these seem to be lying on gravel; in 
 various places in the shore bank, however, boulder clay is seen underlying 
 the gravel of the raised beach, and at a higher level than the boulders. 
 In some districts where the foreshore is very free from boulders it is 
 possible that this is due to artificial clearance to make sea walls, etc. 
 There are many big boulders on the foreshore south-west of Strachur Bay. 
 The raised beach here is represented by an erosion shelf merely, and so 
 this is in accordance with the usual rule. Exposures of stiff finely lamina- 
 ted, and somewhat contorted, clay with glacial shells, occur close to 
 several of them. The largest boulder called " Clach Dubh na Criche," is 
 an epidiorite block about 10 feet long and about 5 or 6 feet high ; it is 
 striated at the top in a direction 4 west of south. This big boulder is 
 said according to information kindly supplied by the late Mr Khyncl of 
 Strachur, to have been slightly shifted by shore ice at the break up of a 
 severe frost some fifty-two years ago. 
 
 A big landslip, the slipped material of which descends to the shore line 
 1 mile south-west of Kilmarnock Hill (194) breaks the line of the 20-foot 
 beach, and must be of later date than it. C. T. C. 
 
 Freshwater Alluvia. 
 
 There are no broad spreads of freshwater alluvium in this district, the 
 glens being all somewhat narrow, or else filled at their broader seaward ends 
 with deposits which, in part, are marine. There is no sharp line in 
 nature between the old marine and the old freshwater desposits, any more 
 than between the gravels of the present beaches and of the streams which 
 come down to the beaches. In the maps we are obliged to start the 
 conventional colours of these deposits at some line, but lines already in the 
 maps, such as road sides, have been utilised for this purpose, and they 
 are not supposed to indicate more than the approximate positions of change. 
 
 It is probably that part, perhaps a large part, of the gravels spread over 
 the different sea-margins is not marine, but freshwater, and of later date 
 than the flats on which the gravel rests, having been deposited by the 
 various little side streams which come laden with material from the steep 
 sides of the lochs, but have their rapidity checked as soon as they get to 
 the old sea flats, and so lose part of their load on them. Instances of this 
 occur at the foot of the burn f mile E.S.E. of Meallan Glaic (194 north- 
 west), at Inverlounin (west side of Loch Goil), and on either side of 
 Rudha nan Eoin (entrance to Loch Goil), etc. 
 
FRESHWATER ALLUVIA. 269 
 
 Strath Echaig contains a breadth of freshwater alluvial deposits which 
 reaches to \ mile, and shows, by adding to these the probably marine 
 alluvia, a spread from side to side of nearly 1 mile of flat land composed 
 of sand or gravel. The river flat in Glendaruel has, above the bridge 
 near Ballochandrain, a very uniform breadth of about J mile. In Glen 
 Massan the greatest width is about \ mile, but this continues for hardly 
 the length of a mile, and in the lower part the river runs for some distance 
 through rock, or between rock and moraines without any alluvium. In 
 the lower part of Glen Finart (163), there is sometimes a breadth of J mile ; 
 outside this breadth the soil is also sandy or gravelly in character, but we 
 refer it to glacial deposits. At the heads of Loch Eck and Loch Goil, 
 and along the river Cur between Ballimore and Ballemeanoch (141), the 
 breadths average about J mile. In the valley of Stralachlan (151), the 
 freshwater deposits are over 1 mile in length and \ mile in breadth. In 
 parts of Glen Tarsan and Glen Lean there is a breadth of 200 to 300 
 yards. In Glen Kin and Glen Fyne (183 and 194), the breadths are less 
 than that amount, and so much divided among terraces of different eleva- 
 tions, with occasional separations of drift banks, that a first sight fails to 
 give an adequate impression of their extent. C. T. C., J. B. H. 
 
 It is probable that in some of the glens the greater breadths occupy the 
 sites of old loch basins which are now filled up. The lower part of the 
 river Massan above Corrarsk is a rapid-flowing stream with but little 
 alluvium, but above the rapids \ mile south-east of Stonefield there is a 
 flattish area extending for about mile, and no more rock in the river 
 for this distance, except in places where it is running just at the side of 
 the flat area. 
 
 This absence of rock in the river beds, excepting where they are just 
 at the sides of the flat areas is not at all uncommon. It occurs, e.g., in 
 the higher part of Glen Massan above Stronlonag, in Glendaruel above 
 Ballochandrain bridge, in Glen Tarsan " between the " t " and the " n " 
 of " Tarsan," and in Glen Lean from a little above Glenlean Farm to \ 
 mile north-west of Corrachaive. 
 
 In the south-western part of Cowal there is nowhere any great extent 
 of alluvium. There is some near the head of the Acharosson Burn at a 
 height of over 1000 feet above the sea, and lower down the same bum 
 near Acharosson in several places there is a high alluvial terrace. The 
 alluvium which forms a narrow strip below this expands considerably 
 in width near the sea, where it merges into the raised beaches. The 
 only other strips worth noticing are those along the streams running into 
 Asgog Bay and Kilbride Bay. The latter stream is called Allt Osda, and 
 its continuation the Creag-an-fhithich burn. In the lower part of this 
 valley it is not always easy to distinguish between the more modern fresh- 
 water alluvium and that of the raised beaches which run up the valley to 
 beyond the Kames Powder Works. There is a pretty extensive alluvial 
 flat partly overgrown with moss opposite Craignafeich, and there is 
 another a good distance further up, above the upper dam, which may have 
 been the site of an old lake like that above Loch na Melldalloch. 
 
 W. G. 
 
 The extension of the flat on the east side of Polchorkan, above Loch- 
 goilhead, is occupied by a peat moss, and we suppose this to be of earlier 
 date than the alluvium of the adjoining river, and that this alluvium is in 
 large part spreading over the old extension of the moss. 
 
 The extension of the flat on the north-east side of Ballemeanoch towards 
 Strachur is also occupied by a peat moss. The boundary between the 
 
270 GEOLOGY OF COWAL. 
 
 peat and the alluvium is not well denned, but it is not far from the 
 " mor " of " Strachurmore." The alluvium would not, in all probability, 
 have extended so far as this, had there not been a flat area lying ready 
 for it to spread over. The rise between the north-east end of the moss 
 and the boundary of the adjacent flat in the Loch Fine watershed by 
 Strachur is very slight, and mostly drift covered. Perhaps at one time 
 the river Cur may have discharged into Loch Fine, instead of the Clyde 
 as it does now. The west edge of the flat for \ mile south of Ballerneanoch 
 spreads out along peaty slacks between moraine-like mounds ; in all 
 probability the whole flat was once occupied by ground of this character 
 peaty areas here and there divided by drift mounds. One of the mounds 
 | mile slightly west of south of Ballerneanoch has been artificially 
 levelled at the top, and smoothed at the sides, but we regard it as natural 
 in origin. Five-eighths of a mile south-east of Baltimore there are many 
 small moraines surrounded by alluvial material. This material is probably 
 more due to small side streams and rainwash than to the river itself. We 
 suppose the moraine shapes are approximately as they were originally, and 
 that the side streams have taken advantage of the low ground between 
 them. 
 
 The east margin of the flat in Glen Fine between the "g" of " Glen," 
 and Eas Riachain tapers out in an indefinite way between moraines, and 
 one moraine shape is quite isolated by alluvium. There is no rock seen 
 in the river between the head of Loch Fine and f mile south-west of the 
 "G" of " Glen." 
 
 In Glen Lean the stream running through the broad alluvial area is an 
 extremely small one, and the alluvial deposits have clearly come in the 
 main from the numerous side streams which descend the glen sides. This 
 is no doubt the case to a large extent in some of the other glens also. 
 Where each side stream begins to lose its steepness it forms a more or less 
 prominent delta, the outer margins of which sometimes merge insensibly into 
 the alluvium of the main stream, e.g., on the north-east side of the Massan 
 near Stonefield. In other cases the deltas of the side streams are cut 
 through by the main stream, and have their outer margins passing gradu- 
 ally into one of the higher flats of the valley. 
 
 The deltas or cones on the west side of the river Fine J mile S.S.W. of 
 the " R " of " River," and above the " v " of " River " are very steep, and 
 composed of unusually coarse torrential material ; their upper margins are 
 not easy to distinguish from screes and drift. 
 
 The alluvium in Hell's Glen consists in the main of coarse delta de- 
 posits brought down by the steep streams on the south-west side of the 
 glen. 
 
 For a great part of Glen Kinglas the higher margins of the cones of 
 material brought down by the numerous side streams are very prominent, 
 but the detrital material does not extend down as far as the Kinglas 
 Water, excepting in the case of the larger streams. 
 
 The different side streams flowing into Loch Eck show good delta de- 
 posits. The head of this loch is also rapidly silting up with the materials 
 coming in with the River Cur. 
 
 Not unfrequently steeply-sloping deltas lie at the foot of crags high 
 among the hills, their material being brought down in wet seasons along 
 little gulleys which are too small to be named or marked in the map, e.g., 
 at the foot of the crags J mile north-east of the top of Stronchullin Hill 
 (164 south-west), on the south-west side of the burn rather more than \ mile 
 south-west of Stronchullin Hill, and J mile W.S.W. of Cnoc Breamanach 
 (182 north-east). On the top of the watershed between Gaol Ghleann 
 and Stralachlan River there are delta deposits brought down by the 
 
FRESHWATER ALLUVIA. 271 
 
 streams from Tom a' Bhiorain. There are sand and gravel deposits filling 
 up part of the old peaty slacks on the north-east side of Leanach ; 1 
 mile north-west of Leanach these are not less than 9 feet thick. 
 
 The deposits along some of the steeper streams consist of coarse 
 and irregularly bedded gravel and boulders, but such as these are usually 
 narrow, and have not often been mapped. The broader deposits all lie 
 
 beside less steeply-flowing streams, and consist of less coarse material, 
 
 gravel, sand, or laminated sandy clay. The upper parts of the flats at 
 present liable to floods usually consist of this last material. 
 
 The alluvium on the south-east side of Glen Lean (172 north-east) is 
 often a fine clay of a deep-red colour. The hillsides are partly covered 
 with a deep red boulder clay, and it is clear that the red alluvium has 
 been derived from it : on wet days we have often seen the road, in places 
 where it passes close under the steep glen sides, traversed by little streams 
 carrying red clayey matter in suspension. A similar red alluvial clay 
 occurs also J mile east of Rashfield (173 north-east). 
 
 The high terrace on the east side of Tamhnich burn, ^ mile west of 
 A'Chruach (172 north-east), consists of gravel which is partly cemented 
 by some black material. A similar black cement is not uncommon else- 
 where, and, judging from examination of a sample obtained from J mile 
 east of Baltimore (141 south) consists largely of the black oxide of man- 
 ganese,* mixed with iron ores. 
 
 We have been often obliged to group several terraces under one sign 
 and tint, owing to the impossibility of clearly distinguishing more than 
 three tints of one colour, while the number of flats in any area may 
 exceed this number. In such cases we have still had lines engraved to 
 separate the different flats, where the scale of the Map allows it. 
 
 In some places the separating bank between two flats becomes quite 
 indefinite, and is replaced by a gradual slope. In these cases we cease to 
 draw a line between them, but keep the colour difference in a straight 
 line, until we come to the next locality where there is a distinct bank 
 between the two, provided this is not too far away. 
 
 Of the cultivated areas Glendaruel has a specially bad reputation for 
 flooding, the coincidence of a high tide and a heavy spate leading almost 
 inevitably to this result. We have also seen a large part of Glen Lean 
 below the farm under water, also portions of the valleys above Loch Eck 
 and Loch Goil, in spite of the earthen mounds built along the river sides 
 to keep the water within bounds. 
 
 The flat by Balliinore(141) is in places only 3 feet above the ordinary 
 water level, and for J mile to the north-west it averages only about 5 feet 
 above. Up the River Cur between Strachurmore and Ballemeanoch 
 the slopes of the terraces increase, and their tops rise to a greater 
 
 * Dr John Murray and Mr Robert Irvine state ("On the Manganese Oxides and 
 Manganese Nodules in Marine Deposits," Trans. Roy. Soc. Edin., vol. xxxvii. p. 
 721), that manganese dioxide has been very commonly observed by them as a coating 
 on the pebbles and sand in the channels of the river Clyde and its tributaries, and 
 that traces of manganese were found in Glen Morag burn, both in a state of solution 
 and also in an insoluble condition. In the different streams examined it was a rule 
 that the manganese in solution was more abundant towards the head of the stream, 
 especially near deposits of peat. They attribute its less abundance near the mouths 
 of the streams to the oxidation of the carbonate of manganese in the solution, and 
 the consequent deposition of the black manganese dioxide on the stones of the bed of 
 the stream, etc. For the original source of the manganese, whether in freshwater or 
 marine deposits, they look to the rocks composing the earth's crust, and show how 
 widely spread manganese is in these rocks. They give (op. cit., p. 723) a list of rocks 
 in which they have found manganese, including among these a mica schist from Glen- 
 morag. This schist is stated to contain from 0*1 to 0'5 per cent, of manganous oxide 
 (MnO). See also analysis of chlorite from St Catherine's, p. 64. 
 
272 ' GEOLOGY OF COWAL. 
 
 height above the present stream surface. It seems therefore that the 
 stream must once have had a steeper fall than it has now ; its course 
 within the hilly area has been eroded and deepened while that in the 
 more level parts has been less eroded, or even filled up in part by the 
 material brought down from the hills. 
 
 The terraces between Glenmassan and Garrachra (163), slope more 
 steeply than the course of the present burn, so that what is the lowest 
 flat at Glenmassan becomes the second at Garrachra. 
 
 The surface of the flat between Loch Eck and the foot of Glen Branter 
 burn is only 4 or 5 feet above the ordinary river level. The lower parts 
 of the banks of the river are generally composed of fine even layers of 
 sand, while the parts just above these, and the shoals and travelling 
 material in the burn bed, are of gravel. 
 
 The alluvium above Loch Goil is in most places only a few feet above 
 the ordinary river level. The materials in the flats always become coarser, 
 as we should expect, when we approach the entrances of the more steeply 
 flowing side streams. 
 
 A slight horizontal feature of erosion, about 2 feet above the ordinary 
 surface of the loch, may be seen in places at the side of Loch Eck, e.g., 
 between Dorrioch Point and the foot of Coire Ealt. 
 
 Between 100 and 250 yards sonth-east of Inverchapel (163, south east) 
 a flattish area extends in a south-west direction from Inverchapel burn. 
 It is partly covered by gravel, and seems to have been used in times of 
 flood as a channel into the river Echaig. 
 
 At the foot of Kinglas Water there are excellent examples of old river 
 channels cutting through the higher flat. In the gardens a little more 
 than J mile south-west of Cairndow Church ship's anchors are said to have 
 been found, thus testifying to the amount of silting up there has been. 
 
 Small outliers of higher flats surrounded by a lower one are not un- 
 common : an example occurs J mile above Garrachra (163). C. T. C. 
 
 In the Glendaruel valley between Achanelid and Glendaruel House 
 (162) some curious gravel mounds occur; they are noted on the published 
 1-inch Map 29 by the engraving of the words " gravel mounds." They vary 
 in size from long serpentinous mounds to isolated hillocks. The River 
 liuel before reaching Achanelid flows in a south-westerly direction. 
 Between Achanelid and Glendaruel it sweeps round and takes an 
 approximate southerly course, and it is in the vicinity of the river bend 
 that these mounds are met with. They have an average breadth of about 
 15 to 20 yards, and some of them attain a length of 150 yards. They 
 attain a height of about 12 feet above the alluvial terrace. At present 
 they are all planted with timber, and good sections cannot be observed. 
 Their surface is however free from blocks, and where small sections can 
 be seen they are seen to consist of rounded gravel similar to that of 
 the terrace. 
 
 It has been suggested that these mounds may be glacial, but at present 
 there is not sufficient evidence to decide the point. J. B. H. 
 
273 
 
 CHAPTER XXI. 
 
 PEAT, LANDSLIPS, BLOWN SAND, PREHISTORIC 
 REMAINS. 
 
 Peat. 
 
 The amount of peat, especially in the north-east part of Cowal, is less 
 than in many Highland areas, the sides of the hills being generally too 
 steep and too rapidly drained to be favourable to its growth, and their 
 tops often narrow and somewhat ridgy. 
 
 Peat areas are not coloured in the Maps except where they occupy 
 basin-shaped or fairly well defined hollows. Among the wider, gently 
 sloping hill tops which are covered with some thickness of peat, we may 
 mention the following, those between the head of Glen Tarsan and Gleann 
 Laoigh ; by the north margin of the 1-inch Map 29 near the "Creachan" 
 of " Creachan Mor" (163); on the north-west side of Stronchullin Hill; 
 on the south-west of the hornblende schists on Cruach Mhor (162); between 
 Beinn Bhreac and Meallan Riabhach (183) ; on the top of Meallan Sithean 
 (183) ; on the south side of Kilbride Hill (183) ; between Dunans burn 
 (162) and Gaol Ghleann on one side and Strath nan Lub, Eas Davain, 
 and the heads of Glen Branter and GJeann Dubh on the other ; north of the 
 head of Eas Dubh (141). A peaty area about 5 miles in length extends 
 from Garbhallt Lochain (151) to Lochan Chuilceachan (162), with a slope 
 towards Loch Fine : it is J mile wide at its north extremity and widens 
 out to 1 mile on the south side, and sends offshoots in various places 
 along the dip slope towards Loch Fine. A mass of thick peat occurs 
 between Cruach nan Gearran, and the main road between Otter Ferry 
 and Glendaruel, which extends for about f mile on the slope towards 
 Loch Fine. In the part of Cowal between Loch Fine and the Kyles of 
 Bute the hill peat is thicker and more extensive than usual on the west 
 side of Beinn Capuill, the north side of Cnoc Dubh, and between this 
 hill and the Acharosson Burn. 
 
 Some of the peat areas contain stems, etc., of birch at elevations con- 
 siderably higher than any trees now growing in the neighbourhood, e.g., 
 the areas J mile north-west of Stronchullin Hill (163) at a height of 
 1500 feet or more, near the Horse Seat (183) at a height of about 1250 
 feet, J mile north-east of Maol Odhar (162) at a height of over 1000 feet. 
 
 Basin-shaped areas which are well-defined all round are not common. 
 Many of the mosses mapped are well-defined on two or three sides, but 
 thin away gradually in the other directions along gentle slopes. At the 
 sides of most of them there are, in places, small delta deposits of alluvium 
 brought down by side streams and partly spread over the peat. It is not 
 usually possible to separate these deltas from the peat, the slope from 
 the head of the delta down to the moss top being quite gradual. 
 
 Numerous peaty hollows have been mapped in the south west part of 
 Cowal. Some of these have not well-defined margins on all sides, and 
 may consist partly of ordinary hill peat overlying flat spreads of drift, 
 especially those at or near the heads of streams, e.g., both north and 
 south of Cnoc na Carraige (Kilbridej ; at the head of Loch na Melldalloch 
 stream ; south of Creag Mhor, by the side of the stream running into 
 Glenan Bay ; both north and south of Achanlochan (Tighnabruaich), etc. 
 Some again consist probably of ordinary stream alluvium with a growth 
 
274 GEOLOGY OF COWAL. 
 
 of peat above. There is a well-defined basin of peat to the east of Black 
 Harbour and S.S.W. of Ardmarnock House, which possibly overlies a 
 raised beach. There are several fairly well-defined peaty hollows between 
 Low Stillaig and Loch Asgog, and north-west of Achanlochan. In the 
 big moss between Kames and Millhouse stumps of trees were to be seen. 
 Other noticeable mosses lie east and south-east of Kilbride Church. 
 
 W.G., C.T.C., J.B.H. 
 
 There are cases where large streams have cut through mosses and formed 
 distinct gravel terraces in them at a lower level than the moss surface. 
 In other cases there is quite a gradual slope between the moss and the 
 terrace surface, the alluvium having spread over the moss to some 
 extent, or having been formed cotemporaneously with it. The mosses 
 at the flat sides of streams have probably in great part grown on old 
 alluvia, the flatness of the surface prepared by the stream having furthered 
 the growth of moss. In cases where we feel some confidence that this 
 has been the process of events, we omit any special indication of the peat 
 and map the whole area as alluvium. 
 
 The mosses earlier than, or cotemporaneous with, the river deposits at 
 their sides, have grown since the commencement of post-glacial times in 
 the hollows of uneven drift deposits or in rock basins. For example, the 
 moss J mile east of Polchorkan (142) makes an angle to the north, so 
 opposed to the general direction of the river adjacent, that it does not seem 
 likely that the flat which it occupies has been formed^by this river's action. 
 The sudden expansion of the alluvium near Polchorkan seems to indicate 
 that there was here some area specially easy for the river to wind about 
 in and overflow, i.e., some low area of soft material. We may either 
 regard the moss as a remnant of a once larger moss which has escaped 
 destruction by the river, because it lies so far off its natural path towards 
 the sea, or the moss and the alluvium may have been gradually formed 
 together, the moss in the part of the old hollow that lay out of the river 
 path and the alluvium in the part nearer that path. 
 
 The low watershed between Glen Lean and Glen Tarsan is partly 
 occupied by a peat moss. The west side of the moss is separated from 
 the alluvium of Glen Tarsan burn by a well-defined margin, caused 
 apparently by the cutting action of the burn. Part of the east margin is 
 also well defined from the deltas, etc., of some small side streams. The 
 position of the moss, so near the watershed between the two glens, makes 
 it unlikely that since glacial times any large stream has traversed the area 
 occupied by it so as to denude a previously uneven site down to the flatness 
 favourable to peat growth. More probably the flat area was there, much 
 as it is now, at the close of glacial times. 
 
 The moss on the watershed between the valley of Loch Eck and 
 Strachur, on the north side of the alluvium at Strachurmore, is another 
 instance of much the same kind, except that the boundary between 
 the alluvium of the Cur and the moss is less definite. The shape of the 
 moss, the narrow constriction at the middle, together with the absence of 
 any signs of river deposits at its sides, excepting in a direction towards 
 the Cur, make it unlikely that any large stream has passed over the 
 watershed and prepared the site for the moss since glacial times. We 
 .would say rather that the surface features which led to the growth of the 
 moss are of glacial origin. This is the more likely since there are a con- 
 siderable number of peaty slacks or depressions to be noticed at the east 
 edge of the alluvium of the Cur south of Strachurmore. These slacks are 
 not due to denudation by the river, but are hollows essentially due to the 
 uneven surface of drift deposits, moraines, etc., though some of them have 
 
LANDSLIPS. 275 
 
 probably been subsequently modified by small side streams, or covered 
 with alluvium by these streams.- 
 
 The mosses a little more than 1 mile south of Carrick Castle, east of 
 Tom Molach (153) and J mile north-west of Cruach nam Miseag, probably 
 represent sites of old lochs. The large moss on the watershed between 
 Glen Laoigh and Strath nan Lub is also perhaps of this character. The 
 north end of this is a prominent moraine-like mound (see p. 257). 
 
 The mosses on the kill tops J mile S.S.W. of Dun Mor (173), J 
 mile slightly west of north of Kilmarnock Hill (183), at the head of Curra 
 Lochain, on the watershed between Strath nan Lub and Glen Branter, are 
 none of them surrounded by higher ground on all sides. 
 
 At the head of Loch Restil there is a peat moss extending for about 
 100 yards from the loch end. Probably this does not represent an in-filled 
 old bay for there is no stream near to have filled in such a bay. The 
 peat has probably grown in an old hollow in the moraine drift edging the 
 loch. There are peaty hollows of much the same character at the side of 
 Lochan nan Cnaimh (153). The peaty flat at the head of Loch Loskin 
 (184) is probably due in part to the in-filling of part of the loch. This 
 case differs from the last mentioned in that there is a considerable burn 
 near, bringing down alluvium into the . loch, and still continuing to fill 
 it up. But it is not likely that the loch ever extended as far as the north- 
 west margin of the peaty area shown in the map, for the rise from the 
 loch in a north-west direction is considerable, and the height of the sur- 
 face becomes greater than that of the barrier at the south end of the loch. 
 
 C. T. C. 
 Landslips. 
 
 The position of the more important landslips have been indicated by 
 writing on the maps.* In the 6-inch maps the boundaries of the slipped 
 material were roughly drawn. The sites of these are formed by great 
 hummocks and irregular ridges of slipped material covered by scattered 
 blocks, and they have a very wild appearance in the landscape. It is 
 perhaps most usual for the displaced schist masses to dip into the hill 
 from whence they have come. This is seen at the head of the slip west 
 of Carnach Mor (141). In the slip north-east of Strone Dearg{183), 
 a little lochan, about 150 yards long and 40 broad, has been formed, 
 and in another, in Hell's Glen, there is a narrow pool 50 yards long ; but 
 generally there is a very ready drainage through the slipped material, 
 so that slip sites afford better feeding for the sheep than the adjacent hill 
 slopes, and give rise near their bases to good springs of water. Such 
 springs occur, e.g., in the slips on the north-west side of Beinn Mh&r, 
 the south-east side of Gaol Ghleann, the west side of Carnach Mor. 
 They are also well fitted for rabbit warrens, the banks in some of them 
 seeming to be quite alive with these animals. 
 
 The lower parts of the slipped material are elevated in a rubbish bank 
 above the surrounding hill slopes. At the top there is usually a somewhat 
 coombe shaped hollow in the crag, often itself in a somewhat shaken con- 
 dition, and with deep narrow cracks at the back which the pedestrian has to 
 be on his guard against. These cracks and also those in the lower material 
 may extend underground for some distance, and form caves, some of which 
 have been used in old time for dwellings, e.g., Paul's cave in Gaol Ghleann, 
 or as places of concealment for treasure and valuable documents, e.g., on 
 Clach Beinn (163). Some of the caves in the parish of Lochgoilhead 
 are described in the "New Statistical Account of Scotland," Argyle 
 section, p. 703. 
 
 * See also one of the sketch maps at the end of the volume. 
 
276 GEOLOGY OF COWAL. 
 
 The following list gives the more important slip localities. The west 
 side of Creachan Beag (163), sloping down to Glen Massan. The north 
 side of Am Binnein (173). One-third of a mile north-west of Clachaig 
 (173). The east side of Ballochyle Hill (173). The south-west side of 
 Meallan Sithean, with its head extending for f mile along the 1000 foot 
 contour. The east side of Sgian Dubh (183). The north-east side of Strone 
 Dearg (183), with the head extending T 7 ^ mile at the level of 1500 feet or 
 more, arid the slipped stuff reaching down to Inverchaolain burn. The south- 
 west and south-east sides of Kilmarnock Hill (194). The north side of 
 Clach Beinn (163), extending down to the Coirean T burn. North-west, 
 J mile north, and \ mile north-east of Beinn Mhor ; the head of the first 
 is about 220 yards north-west of the hill top and the slipped material 
 descends to the burn in Garrachra Glen. South-east side of Gaol Ghleann 
 from 1 mile north of Maol Odhar for \ mile north-east. North-west side 
 of Clach Bheinn (153). One-third of a mile south-west of Cruach a' Bhuic. 
 South side of Sugach Aodainn (152) between the "h" and " A." South- 
 east side of Cnoc Coinnich (142), from between the 2250 and 2000 foot 
 contours down to Loch Long, a distance of 1J mile. North side of 
 Mullach Coire a' Chuir, the head extending nearly a mile from east to 
 west, and up to the top of the ridge west of the Mullach. Five-eighths of 
 a mile S.S.W. of Mullach Coire a' Chuir. South side of Allt Coire Odhair, 
 near the "Allt." At the sides of Allt Criche (142). South side of 
 Liogan, J mile west, and close at the side of the " L" of "Liogan." 
 West and north sides of Carnach Mor. The south-west side of Hell's 
 Glen from near the top of Stob Liath. North and west sides of Beinn 
 an Lochain (134). Three-quarters of a mile east and mile slightly south of 
 west of Beinn Fhidleir. North side of Beinn an t-Seilich. One-half mile 
 W.S.W. of the "1" of "Glen Kinglas." One-quarter mile north-east of 
 Upper Clasheoin (126). f mile S.S.E. and 1 mile north-east of Achadunan. 
 
 Many of the slips e.g. those on the north-east side of Strone Dearg, the 
 south-east side of Kilmarnock Hill, north-west side of Beinn Mhor, south- 
 east side of Caol Ghleann, south-east side of Cnoc Coinnich, south side of 
 Allt Coire Odhar, and near Upper Clasheoin and Achadunan, are on hill- 
 sides the directions of slope of which agree with that of the foliation, a 
 circumstance which must have helped towards the occurrence of the slip. 
 But there seem at least an equal number which have descended down hill 
 slopes at right angles to the foliation dip, e.g., the one in Hell's Glen, and 
 that on Mullach Coire a' Chuir. And in some cases the slip is in a direc- 
 tion opposed to that of the dip, e.g., f mile east of Binnein an Fhidleir, and 
 J mile north-east of Beinn Mhor. The margins of some of them are along 
 basalt dykes from which the slipped material has broken away in a some- 
 what clean cut, e.g., the south margin of the slip on Strone Dearg ; or 
 along lines of vein or crush, e.g., the head of the slip \ mile south-east of 
 Lochgoilhead, portions of the north-east side of the slip J mile north-east 
 of Upper Clasheoin, and, apparently, the north-east side of the west slip 
 on Carnach Mor. 
 
 The coombe shaped crags at the top remind us of those we may 
 frequently see elsewhere, where now there is no trace of slipped material 
 crags high on the hills with conspicuously smoother areas below and 
 at the sides, of which no satisfactory explanation can be given. Is it 
 possible that these localities are sites of older slips, glacial or pre-glacial, 
 the rubbish of which has now all been cleared away by glacial action ? 
 
 The slipped material on the south-west "side of Kilmarnock Hill 
 (194) breaks the line of the 20 foot beach, so that the slip must be 
 later than it. There is a tradition that the slip on the south side of 
 the Kinglas, \ mile W.S.W. of the "1" of "Glen Kinglas," took place a 
 
BLOWN SAND. 277 
 
 little more than 200 years ago. From the slipped masses J mile north-east 
 of Beinn Mhor large masses still occasionally slip. A large block, about 11 
 yards by 7 yards by 7 yards, by the side of the stream f mile E.N.E. of 
 Beinn Mhor, was said by Mr Proudfoot, the late shepherd at Bernice, to 
 have descended with others in 1885. It is very probable that portions of 
 many of the other slips are also still liable to break away now and then, 
 being in a state of equilibrium which is easily disturbed. 
 
 Small slips along the drift banks at the sides of streams and steeper 
 hill slopes are very common. These generally take place after a time of 
 unusually heavy rain. At the time the Survey was in progress, the coach 
 road in Hell's Glen was blocked for several days by a small slip of this 
 kind, and we noticed in more remote places various other slips which 
 appeared to have taken place during the same wet season. C. T. C. 
 
 Blown Sand. 
 
 The only area of blown sand noticed in the Cowal district occurs in 
 Kilbride Bay or Bagh Osde (203), west of Ardlamont Point, on the 
 east of the mouth of the stream called Allt Osda. It extends along the 
 bay for nearly half a mile from the stream, and its greatest breadth is 
 about 150 yards. The sand, as is usually the case, forms a series of 
 irregular shaped mounds, but none of these attain to any great height, 
 probably not more than 10 or 12 feet. It has been accumulated on the 
 lowest raised beach, part of the 20-foot. W. G. 
 
 Prehistoric Remains. 
 
 Mr MacNaughton, the gamekeeper at Craigbrac (152), informed us that 
 some years ago he found in the delta a little below Craigbrac House, a 
 polished wedge-shaped instrument of stone, perhaps an old axe-head. The 
 length was about 2J inches, and the extreme breadth about 1J inches. 
 The stone was fine in grain and pale grey in colour, and according to our 
 informant, not unlike some of the finer grained lamprophyre sheets of the 
 neighbourhood. 
 
 In the National Museum of Antiquities of Scotland there is preserved 
 (AF 138 in catalogue of 1892) a polished stone axe-head, 5J inches long 
 by 2 inches broad, which is said to have been found at Strachur. The 
 stone of which it is composed is a fine grained buff whinstone with a good 
 number of amygdules, some of which are distinctly elongated. The sharp 
 edge of the instrument is not symmetrical. Perhaps it has been worn 
 back more at one side than another, and subsequently re-edged. In the 
 same Museum there is also a stone knife (AA 12) from Strashur. The 
 dimensions are 2 J inches by J inch. It is ground to a sharp cutting edge 
 from both faces. 
 
 In the policies of Strachur House, there is a large standing stone of 
 epidiorite. This is marked on the 6-inch Map. A little north-west of 
 this there is another smaller standing stone, and it seems as if there 
 may originally have been a group of such. At the head of Garrachra 
 Glen (163), there is an old cairn about 100 yards east of the " n " of 
 " Glen." Five-twelfths of a mile north-east of Strachur House there is a 
 large mound by the side of the River Cur, which is supposed to be the site of 
 an old fort. Another mound of very similar appearance occurs on the 
 south-east side of the River Fine, J mile N.N.E. of Achadunan There 
 seemed to be no mason work now remaining in either of these mounds. 
 It is possible that both are natural in origin, though they have been sub- 
 sequently modified and used as forts. 
 
278 GEOLOGY OF COWAL. 
 
 There is a round fort near the top of the wood, 1J mile slightly east of 
 north of Castle Toward, at a height of over 1100 feet. The fort is called 
 Buachailean in the 6-inch Map 194. We are informed by Mr D. "Whyte, 
 of Glasgow, that a number of stones from this fort were removed and 
 used in erecting the farmstead at Killellan. Another round fort occurs 
 on a knoll, called Cnoc nam Fiantain in the 6-inch Map, 174, on the 
 shoulder of the hill T 8 ^ mile KN.W. of Strone Point. Mr Whyte states 
 that a flagstaff once stood on this knoll, and that at the time of its erection 
 a large quantity of wood cinders was discovered at a depth of 2 feet. It 
 seemed as if the hillock had formerly been the site of an old signal station. 
 The position commands extensive views, particularly over the different 
 sea lochs adjacent, both up and down the Clyde, and up Loch Long and 
 the Holy Loch. C. T. C. 
 
 There is an unusual number of old forts and cairns in that part of 
 Cowal which lies within 1-inch Map 29 and borders the east side of 
 Loch Fine. Those that occur on the north side of Kilfinan are detailed 
 in the following list : 
 
 One-third of a mile north-west of Cam al Tilgidh (161). A cairn con- 
 sisting of a big heap of stones at a height of 634 feet overlooking 
 
 Loch Fine. 
 One-third of a mile north of Largiemore. Carn Evatiachan. A circular 
 
 heap of stones on the beach below high water mark. 
 Two-thirds of a mile E.S.E. of Largiemore. Cairn on hill slope flanked 
 
 by two gorges. 
 
 One-quarter mile east of Otter Ferry. Site of cairn. 
 One and a half mile E.S.E. of Otter Ferry. Cairn Ban. A small cairn. 
 One hundred and fifty yards south-west of Ballimore House. Fort on 
 
 round gravel mound. Cnoc na Eoghainn. Since used as a private 
 
 burial ground. 
 
 One mile east of Ballimore. Fort on hill, Bkrr lola. The best pre- 
 served fort in the district ; part of the circular enclosing walls being 
 
 still standing. 
 Two miles east of Ballimore House. Cairn at Meall Keamhar. This 
 
 and the two preceding forts are in a line. 
 One and a quarter mile south of Ballimore. Two forts within J mile 
 
 of one another in a north and south line, on a ridge of limestone. 
 
 Both within J mile of Loch Fine. 
 One and one-sixth mile south-east of Ballimore. Cairn and standing 
 
 stone. 
 
 One and one-third mile south-east of Ballimore. Fort. 
 One-half mile north-west of Kilfinan. Cairn and standing stone on the 
 
 50 foot raised beach. 
 Nearly J mile N.N.E. of Glendaruel House. Dun an Oir. Now used 
 
 as a family burial ground. J. B. H. 
 
 There is a group of standing stones south of Polphail (192), one of them 
 10 feet high, another only a little over 2 feet. There is another standing 
 stone among the woods -east of Low Stillaig, and several to the west of 
 Kames. Cairns are to be found to the S.S.E. of Ardmarnock House and 
 on the raised beach north of Eilean Aoidhe. 
 
 There is a vitrified fort on one of the Burnt Islands in the Kyles of 
 Bute, and another on an island in Loch Fine called Caisteal Aoidhe, near 
 Rudha Preasach. The wall of the first-mentioned fort consists of pieces 
 of the mica schist of the district fused together. A black or dark 
 coloured glass cements the schist pieces into a firm mass and also runs 
 
PREHISTORIC REMAINS. 279 
 
 into these pieces in thin layers, about ^j- inch thick. A specimen of the 
 partially fused rock was sent to Mr Tea 11 for microscopical examination 
 (slides 5083 and 5084), and he reported in it as follows: "The 
 specimen consists of agglutinated fragments of the granulitic biotite- 
 schists of the neighbourhood. The layers of biotite have fused to a 
 dark coloured glass containing vesicles. Under the microscope the two 
 principal constituents are seen to be glass and quartz. The glass varies 
 from deep brown to colourless. It contains minute octohedra (spinelle). 
 The quartz occurs in grains which have been strongly corroded by the 
 glass." The vesicles in the specimen sometimes attain the size of peas, 
 and are generally quite spherical in shape. Ordinary forts without 
 vitrified walls are to be found one in a plantation east of the road 
 nearly a mile to the north of Ardmarnock House, and another, unmapped, 
 over 20 yards in diameter, on the west side of Allt Osda, opposite Kil- 
 bride, at the western edge of a wood, and 200 yards from the stream. There 
 is a fort called Creag a' Chasteil, at the edge of a crag 600 yards to the 
 north-west of Low Stillaig, and another fort at Camp Cottage, Ardlamont. 
 There are no less than three crannogs or lake-dwellings in Asgog Loch. 
 That nearly opposite the ruins of the old castle and about 70 yards from 
 the shore is shortly described by Dr Robert Munro, in a paper in the Proc. 
 Soe. Antiquaries of Scotland, vol. xv. pp. 205-222 (Notes on Crannogs or 
 Lake-dwellings in Argyllshire, 1892-93). He states that this is known 
 by the natives as crannaig, and that bars and huge beams of timber ap- 
 peared in 1836, when the powder factory was started, the water being 
 then at a lower level than ever before. He seems to have heard of the 
 two others, but not to have seen them. They occur near the west end of 
 the loch and were noticed by us in 1888, when the loch was unusually low. 
 One of them is near the south-west end of the loch, and is 70 yards from 
 the shore, nearly opposite the centre of that narrow side of the loch. We 
 were able to walk out to it and found it 35 yards in diameter, nearly 
 circular, and the piles distinctly visible, as was also a double row of 
 piles leading for some yards from it towards the shore, but no piles 
 were seen close to the loch side. Along the south-east side of the loch 
 200 yards from its southern outlet occurs another about 90 yards 
 apparently from the shore, but we were unable to reach it though we 
 could see it distinctly, and also the double row of piles leading to it. 
 
 W. G. 
 
 CHAPTER XXII. 
 
 GEOLOGICAL ASPECTS OF THE SCENERY. 
 
 The " anticline " schist area even when of low elevation, as between 
 Colintraive and the head of Loch Riddon, makes a much rougher, more 
 craggy country than that at either side. Perhaps the greater alteration 
 of the rocks may have made them harder and less readily subject to 
 atmospheric wear. But, besides this, it seems possible that the crump- 
 ling of the prominent planes may have contributed to the same result, 
 water and other decomposing agents not having so many straight running 
 channels to advance along. In this area the more micaceous and the 
 more quartzose pebbly schist make about equally prominent crags, and as 
 their colour is also much the same in the landscape, they cannot be 
 confidently distinguished except on close approach. 
 
280 GEOLOGY OF COWAL. 
 
 On and near Cruach Tuirc the albite and greywacke schists within J 
 mile of the granite edge make a steep craggy slope on the south-east side 
 of Glen Fine. The schists in question have, at equal distances from 
 the base of the green beds, a common habit of forming rough rocky 
 ground even far away from the granite, e.g., on the two Beinn Lochains, 
 Beinn Bheula, etc., and so it is doubtful to what extent we may attribute 
 the roughness of Cruach Tuirc to the special mineral metamorphisin in the 
 vicinity of the granite. The schists near Achadiman make a smoother 
 slope on the glen side than at Cruach Tuirc, but near the former 
 place the foliation IB in nearer agreement with the slope of the hill, and 
 this of itself would make a considerable difference in the look of the 
 slopes. Though Glen Fine is straight it does not always make the 
 same angle with the foliation of the rocks traversed. Owing to the twist 
 near the granite edge, the strike of foliation near Cruach Tuirc is nearly 
 at right angles to the glen. 
 
 The granite weathers in large tabular blocks with rounded edges. It 
 crumbles somewhat readily into a gravel-like soil which may form a 
 covering of considerable thickness on the slopes below some of the crags. 
 The approximate line between the granite and the schists is not easy to 
 discern on first inspection. This is no doubt due partly to the alternation 
 of granite and schists which occurs for a little breadth, there being no 
 absolutely sharp line at which the main granite mass begins. The 
 granite is crossed, too, by prominent regular joints which split the 
 rock up into bands a few feet thick, and give the impression at first 
 that we are dealing with bedded rocks. The general strike of the joints 
 in the crags T ^ mile slightly east of north of Cruach Tuirc and in the 
 river near the "F" of " Fine" is about north-east, and the dip to north- 
 west at an angle of 28 but sometimes as low as 12. As a matter of fact, 
 of course, the bedding in the schists is nowhere dipping so steadily as 
 these joints. 
 
 The Ardrisbaig phyllites and the garnetiferous mica schists form 
 together an unusually smooth area, the smoothest on the north-west side 
 of " the anticline," and we think, too, smoother than that of the Dunoon 
 phyllites on the south-east side. They are more shivery under the 
 hammer than the Dunoon phyllites and are cut into more deeply by the 
 burns, e.g., by the burns that enter Loch Fine between Creag a' Phiull and 
 St. Catherine's. In the Ardrishaig phyllites the close intermixture of thin 
 calcite layers and grains no doubt helps to this result. The agreement in 
 direction also of the foliation and the chief hill slopes is closer than that in 
 the Dunoon area. If the formation of the garnets and actiuolites in the 
 garnetiferous schist was originally attended with hardening of the schist, 
 such as we commonly find in the neighbourhood of large igneous masses, 
 it is clear that the extra hardness has now disappeared. Perhaps the 
 shearing action which the garnets and actinolttes have undergone since 
 their formation would itself bring the schist back to a softer condition, sup- 
 posing it had been hardened before then. It is curious that the same band 
 of garnetiferous schist begins to form much rougher ground almost 
 directly it reaches the north-west side of Loch Fine, on the slopes of the 
 Brannie, Clachan Hill, and the hills further north-east. At the same 
 time the garnets become larger and the actinolites more abundant. The dip 
 being into the hill instead of down the hill would inevitably tend to pro- 
 duce the more rugged appearance, but the rock also becomes harder of 
 itself as we go north-east, breaking less readily under the hammer and with 
 more ring. It would seem that we are getting nearer the influence of 
 some special altering and hardening agent, the effect of which in Cowal 
 was either very much less or has been subsequently destroyed. 
 
GEOLOGICAL ASPECTS OF SCENERY. 281 
 
 The hornblende schists and epidiorites usually form the more 
 rocky exposures among the schists, and can often be distinguished by 
 this means even at some distance. For examples we may refer to the 
 fir-clad ridge on the east side of Loch Loskin (184) and the continuation 
 of this band on the west side of this loch ; the outcrops on Kilmarnock 
 Hill (194), near Blaii-more and Strone Saul (173 and 183), Ardnagowan 
 Cottage (141), Creggans, and St Catherine's ; the ridges between Loch 
 Fine and the valley of Strathlachlan (151). 
 
 It is probable that the degree of roughness of the different outcrops is 
 to some extent dependent on the amount of schistosity developed in the 
 rock. The less schistose the rock, the more it projects. The more 
 schistose it is, the more planes there are for the entry of water and other 
 decomposing agents, and the more readily it weathers away. Some of 
 the highly sheared chloritic bands on Loch Fine side are hardly to be 
 distinguished in roughness from the other schists with which they are 
 associated. 
 
 When the green beds are free from drift and peat, but not actually 
 crag forming, they make rather greener and richer looking ground than 
 the greywackes and phyllites. It is possible that they contain a rather 
 greater proportion of lime and the alkalies, being presumably formed 
 in greater proportion from old igneous rocks. For examples we may 
 refer to the hill slopes south-east of Ardkinglas wood (134), and near 
 Cairndow and Upper Clasheoin (126). In the south west part of Cowal 
 the green beds form somewhat lower and less rugged ground than the 
 mica schists on their south-east side, and it is easy to follow the boundary 
 between them. W. G., C. T. C., J. B. H. 
 
 The limestones of the Dunoon phyllite series never make swallow holes, 
 nor, as far as we can call to mind, any green bands on the hillsides. 
 
 In some rare cases the Loch Tay limestone makes small incipient 
 swallow holes, e.g., on the watershed a little more than J mile slightly 
 south of east of Cruach nan Capull (133), -J- mile S.S.E. of Cruach nan 
 Capull (152), doubtfully, and J mile north of Cruach an Lochain (151). 
 The part above the hornblende schist in the north part of Cowal makes 
 steep banks with small limestone exposures near the top, and green grassy 
 slopes below. The prominence of the bank is no doubt increased by the 
 hornblende schist, which almost invariably accompanies the limestone. 
 The best crags are those on the south side of the burn J mile E.S.E. of 
 the last "n" of " Sith an' t- Sluain" (152), 1 mile west of the "s" of 
 "Socach Uachdarach " (141), and in Glendaruel. The limestone readily 
 dissolves away in some positions near the surface and far in along joints, 
 and gives rise to a soft ochreous residue, covering for a few inches or 
 more the sounder heart of the rock. We have noticed this particularly 240 
 yards E.S.E. of Cruach nan Capull (152). Such ochreous residue, partly 
 mixed with or colouring the local drift or soil cap, may be the first 
 indication of the presence of the limestone. C. T. C., J. B. H. 
 
 There is a sharp distinction between hillsides according as they slope 
 with or opposite to the dip of the foliation; the latter are much the 
 steeper and more craggy. This is seen well on the sides of Glendaruel, 
 on the north-west and south-east sides of the Bishop's Seat, on Creag 
 Tharsuinn, Beinn Bheula, Cruach nan Capull (133), Stob ail Eas, and 
 many other hills. In Bishop's Seat, the difference is accentuated by the 
 carry of the ice having been roughly at right angles to the hill crest, 
 from the north-west to the south-east, so that the south-east side is, in 
 accordance with the usual rule, more drift covered than the other. 
 
282 GEOLOGY OF COWAL. 
 
 As we steam down the Firth of Clyde, we cannot but be struck with 
 the smooth aspect of the nearer Highlands, those near Dunoon, Blair- 
 more, and Inellau, when compared with those in the distance, near the 
 heads of Loch Long, Loch Goil, or in the direction of Loch Eck. More 
 than one cause no doubt contributes to the contrast. The rougher areas 
 are composed of the more altered and more crumpled anticline schists, 
 the general rough weathering of which has already been spoken of. 
 Besides this, it is only their more elevated and drift-free portions that 
 can be seen in the distance, while in the nearer hills, the low drift covered 
 slopes strike the eye at once, and in parts above the drift, it is to dip 
 slopes chiefly that the observer is turned. It is quite possible, also, that 
 the greater amount of glaciation to which the nearer and lower ground has 
 been subjected as compared with the highest, may have tended to give 
 them a smoother aspect. 
 
 The foliation strike is very steady in the district generally, and the 
 main crag faces keep roughly on the same lines or parallel to one another. 
 If we look from some commanding point on the north-west side of the 
 " anticline," in a direction rather nearer east to west than the strike, we 
 see bluff after bluff advancing with bold front to the south-east, like 
 great waves one after the other, until in the far distance, they "go 
 from less to less and vanish into light." Points of view which may 
 be specially mentioned as bringing out this structure are those near 
 the foot of Allt Glinne Mhoir (134), and on Benin Dubhainn looking 
 towards Creag Tharsuinn. In the area between Ardmarnock and Porta- 
 vaidue (192), some of the more gritty and pebbly bands form features 
 or even crags for short distances. The features are accentuated by a 
 series of small streams that run nearly along the strike. 
 
 But features which run with the general strike of foliation cannot be 
 considered to represent bedding without actual examination of the rock on 
 either side. As a matter of fact the great majority of features of this 
 kind, which at a distance, in the early days of the Survey of the district, 
 led one to expect they might indicate margins of beds, turned out on 
 closer approach not to do so : they were due generally to crush lines, thin 
 lamprophyre intrusions, or joint planes. The joint planes in this district 
 are, however, not generally so prominent or so constant in direction, as to 
 deceive one in this way. We have recorded them as unusually strong 
 for a little space on the south side of the Coire Athaich bum (173) 
 near Corrarsk ; here they incline north-west, directly opposite to the 
 foliation dip, at an angle of about 29. About two miles slightly 
 west of north of Corrarsk, there are prominent joints dipping in the 
 opposite direction at about 30. On the south-east face of Creag 
 Tharsuinn (163) there are prominent joints dipping south-east, nearly 
 with the hill slope. 
 
 Joints sloping nearly with the prominent foliation have at times acted 
 as lines for the entry of lamprophyre intrusions (see p. 108). Such in- 
 trusions often form little vertical scars, weathering in retreat from the 
 schist above and below, or narrow grassy ledges with steep schist crags 
 on either side. At other times they have given rise to the formation of 
 crags above them, e.g., in Creag an Fhithich (193). All these appearances 
 are due to the more ready wearing away of the lamprophyres, compared 
 with the schists in which they occur. 
 
 The basaltic dykes often form prominent features in the landscape. 
 Owing to their superior hardness many of them stand up, as their name 
 implies, in a wall-like way, particularly along coast lines, whether of the 
 present day or of old beach times, and they have not unfrequently been 
 mistaken for artificial structures. The wall-like form is often less marked 
 
GEOLOGICAL ASPECTS OF SCENERY. 283 
 
 inland, because, in cases where the dyke runs nearly with the contours, 
 the hollow at one of the sides, that facing the upward slope of the locality, 
 becomes gradually filled in by movements of the soil cap, etc. Other dykes 
 resist weathering less than the surrounding rocks, and these form hollows 
 and the lower parts of features. Why they should do so is not always 
 clear, but the reason is probably often connected with the grain of the 
 dyke rock, as suggested on p. 127, the coarser grained being more readily 
 penetrated by water and > other decomposing agents. Sufficient examples 
 of these two classes of dykes are given in the place just cited. The 
 more readily decomposed dykes often also form dry smooth banks and 
 mounds clothed with short sweet grass, which form a striking contrast 
 to the peaty and *' benty " ground on either side. The broad east to west 
 Dunoon Castle dyke affords good examples of this. We may suppose 
 it due, partly to their porous character, and partly to their richness in 
 lime and the alkalies. 
 
 Except in the north-east and south-west portions of Cowal, the basalt 
 dykes are extremely abundant. The difference expresses itself somewhat 
 markedly in the coast scenery of the Clyde and Loch Striven, as com- 
 pared to that of Loch Long, Loch Goil, and the part of Loch Fine above 
 Strachur; also, but to a less extent, on the hillsides adjacent to these 
 lochs. 
 
 A short examination of any area where dykes and crush lines are 
 abundant, e.g.> the sides of Glendaruel and Glen Tarsan, will reveal what 
 an important part these play in directing the course of the minor streams. 
 The crush rocks and decomposing dykes are acted on more readily by de- 
 nuding agents than the rocks at their sides ; so they would form hollows 
 in early times, and these would get gradually deepened by the waters 
 running down the hill, until at last deep burns are formed. In some 
 districts, we can hardly find a burn which is not running along either a 
 dyke or a crush ; and by a careful examination of the plain Ordnance Map 
 before visiting the ground, we can usually make a good guess as to what 
 burns, or parts of burns, are running along dykes or crushes, th3se being 
 almost invariably straighter than the others. These straight burns are 
 sometimes so deep and so steep sided, that one can hardly advance along 
 them except in the driest seasons. 
 
 If we take position on some hillside on a fine clear day, and carefully 
 scan the bare crags on the opposite side of the glen, we are struck with 
 the immense number of small nicks and features, which traverse them 
 in almost every direction. The crags on the north-west side of Glen 
 Massan show good examples of these. We do not suppose that the 
 generality of these are due to dykes or faults; in fact, in the particular 
 instance alluded to, it is certain they are not ; but even a strong joint or 
 the thinnest crush line, without any appreciable throw, may be enough 
 to give rise to them. 
 
 Some of the larger features coincide with lines of important fault, 
 and, we have little doubt, may be attributed indirectly to them; 
 eithsr to their having thrown together rocks of different degrees of 
 hardness, or to the softness of the crush rock itself. The boundary 
 line of the Highland schists, as far as it occurs within this district, is a 
 conspicuous example of this, and the courses of some of the other fault 
 lines mentioned in ch. XV.-X\II. afford further illustrations. We may 
 mention especially the north-west fault on the north-east side of the 
 Saddle (133), the KN.E. fault on tha west shoulder of Ben Donich, the 
 north to south fault J mile east of Lochgoilhead, the N.N.W. fault on the 
 west side of Am Binnein (164), the Corran Lochan north to south fault, 
 the Hell's Glen north-west fault, the Bernice Glen and Stuck burn faults. 
 
284 GEOLOGY OF COWAL. 
 
 (163). None of the above mentioned are accompanied by dykes. At least 
 an equal number could be mentioned accompanied by basalts, for in the area 
 where basalts are abundant, nearly all the faults are also filled with them. 
 
 In considering the origin of some of the larger river valleys, such as 
 those of Glen Massan, and Glendaruel, it does not seem that we can 
 ascribe them to fault lines. There is often some breadth of obscure ground, 
 free from rock exposures, in the bottoms of these glens, but the tracing of 
 the beds on the glen sides is sufficient to show that no large faults exist 
 along them. The direction of these glens depends perhaps on the slopes 
 and ready direction of drainage of some old schist tableland, before it was 
 carved out into separate hill shapes. It would seem that to the geologist's 
 eye these valleys are not of very great age, or that at all events they have 
 been greatly deepened in late times, for if they had existed at their 
 present depth at the time of the intrusion of the tertiary dykes, the 
 material of some of these could hardly fail to have been poured out on 
 the surface and signs of it would still remain. (See p. 147.) 
 
 In the Loch Eck valley it is curious that a considerable fault (see 
 p. 179) can be traced for some distance parallel to the loch, on its east side. 
 At the north end of the loch there is a large fault (see p. 214) running 
 from Baltimore to the alluvium near the first "a" of " Creag Bhaogh." 
 The fault should, if continued south-east, run along the loch as far as 
 Whistlefield. At Whistlefield there are crushes proceeding south-east 
 from the loch in the direction of the pass over into Glen Finart. In a 
 north-west direction the fault may continue across the low watershed 
 between the Loch Eck valley and the valley that leads down from 
 Ballemeanoch into Strachur Bay. This watershed is very low I think 
 only about 20 feet above the level of the Cur at Ballemeanoch and 
 is occupied partly by a peat moss and partly by drift with one or two 
 small rock exposures near the north end of the moss. 
 
 The lowness of the watersheds separating some other of the important 
 burns and glens, e.g., Glen Lean and Glen Tarsan, Glen Tarsan and Glen 
 Massan, Lettermay burn and Leamhamn, Garrachra Glen and Glen 
 Shellish, Gaol Ghleann and Stralachlan River, is also notable. If we 
 look on the sea lochs as representing old land valleys which are now sub- 
 merged, we may add to the above the two Kyles of Bute : the deepest 
 channel connecting these is that on the south side of the Burnt Islands, 
 
 / Sheet 2 \ 
 
 but this is only 3J fathoms near its centre ^Admiralty Chart as* J 
 
 the channel on the north side of these islands is 2 fathoms ; the west 
 Kyle is the natural continuation of Loch Eiddon, and west of the Burnt 
 Islands attains a depth of from 21 to 27 fathoms. 
 
 Perhaps we may suppose in the above cases that two adjacent streams 
 have gradually denuded backwards towards one another, and thus grad- 
 ually lowered the surface of the area between. We know of no special 
 lines of weakness at the three first mentioned watersheds, but the last 
 two are partly traversed by N.N.E. crushes. C. T. C. 
 
 The upper part of Loch Fine between Otter Ferry and Ardno runs 
 almost with the strike of the beds, lying in the comparatively easily 
 eroded Ardrishaig phyllite series. A set of prominent N.N.E. faults come 
 down to its south-east shore, e.g., the Coire No fault, the crushes 
 accompanying the north-west graphite schist, the N.N.E. fault near 
 Ardchyline, the faults J mile west of An Carr, but we have no reason to 
 suppose that anyone of them continues along it for more than 3 to 4 miles 
 this is the distance the Coire No fault continues along the loch, and the 
 alluvium at the head of it, before it reaches the north-west side of the 
 
GEOLOGICAL ASPECTS OF SCENERY. 285 
 
 valley, between Achadunan and Xewton Hill. The Coire No fault (see 
 p. 222) is the south-west extension of the great Tyndrum fault, the course 
 of which has probably determined the line of drainage which has resulted 
 in the excavation of the upper part of the valley of Glen Fine, within 
 1-inch Map 46. C. T. C., J. B. H. 
 
 The north-west fault near the Saddle may be supposed to be the same 
 as that which enters Loch Goil near Drimsynie. The part of the loch 
 between Stuckbeg and Drimsynie runs in much the same direction as the 
 fault and perhaps the original formation of it was influenced by the fault. 
 A little north of Stuckbeg there are several north to south faults coming 
 down to the loch from the north. South of these, and after the Drim- 
 synie-Saddle fault has reached the east side of the loch, there is a slight 
 bend in the direction of the loch almost into parallelism with the north 
 to south faults. The changed path continues as far as Carrick Castle, 
 where one of the north to south faults comes out of the loch again. 
 
 Our former colleague, Mr H. M. CadelL, has called attention ("The 
 Dumbartonsnire Highlands." Scottish Geographical Magazine, vol. 2., p. 
 336) to the number of large valleys in Cowal and Dumbartonshire which 
 run south-east or S.S.E., in directions often continued across watersheds, 
 as that of the upper part of Loch Eck and Glen Finart, or across both low 
 watersheds and valleys which run in different directions, as the valley of 
 Loch Goil and the Gareloch, Coilessan burn and the Douglas water (1- 
 inch map 38). He looks back to a time when perhaps the original water 
 parting in this district between the east and west coasts of Scotland was 
 a tract of ground in the neighbourhood of what is now Loch Fine. He 
 says " Before Loch Lomond and Loch Long came into existence all the 
 country east of Inverary, and northwards to the Arrochar Highlands and 
 Glen Falloch, was probably drained by the Forth, and not as at present 
 by the Clyde." He supposes the direction of original slope of the table- 
 land out of which the valleys were carved was nearly south-east, somewhat 
 oblique to the strike of the rocks. The different bands of soft rock 
 were more easily worn away in a south-west direction than in a north- 
 east direction, because the slope of the ground more nearly coincided with 
 the former than the latter. Hence the general direction of some of the 
 valleys is S.S.E., or even south, rather than south-east. It is further 
 suggested that Loch Long is of comparatively recent origin compared to 
 Loch Goil and the Gareloch, and is due to erosion by ice. 
 
 The well marked fringe of raised beaches along the coast cannot fail to 
 attract attention. These have rendered it easy to make good level roads, 
 and also formed convenient sites for the villas and gardens which abound 
 along the Clyde, etc. But the frequent alteration of level indicated by 
 them has had the effect of interrupting the cutting action of the sea, and 
 setting it to work again at new levels, so that high cliffs have rarely been 
 formed. This limitation of height is from a geological point of view 
 somewhat to be regretted, as the coast sections are on a smaller scale than 
 they would otherwise have been. 
 
 Owing to the "carry" of the ice having been down rather than across 
 the more important glens and sea lochs one does not see so clearly as in 
 some districts that the greater spreads of boulder clay are on the lee 
 sides of the carry. An instance is afforded by the upper part of Glen Kin 
 (174), but even here the extra smoothness of the north-west side is 
 not solely due to the drift distribution, but also to the structure in the 
 schists, the north-west side having a slope in the same direction as the 
 dip of foliation. 
 
 As stated, p. 243, it is not safe to attribute all the smooth slopes 
 
286 GEOLOGY OF COWAL. 
 
 without rock exposures to boulder clay or other drift. It is clear that 
 even when there is no drift the rock on the hillsides has often been 
 so planed and polished, that it now presents a smooth grass covered face 
 and one would not suspect how near the surface it really is. 
 
 Moraines have quite a different influence on the landscape than the 
 boulder clay. Instead of the smooth slopes of the latter we see a con- 
 gregation of rather steep sided ridges and hummocks with very little 
 order in their arrangement, and often strewn over with blocks lying in 
 fantastic positions, the whole assemblage presenting a scene of disorder 
 and dreariness. 
 
 The moraines in the south-west part of the area are not numerous and 
 do not affect the scenery to any marked extent. In the north-east part 
 the hills are higher and the rainfall is greater, and we may suppose that in 
 glacial times the snowfall was also greater. The later glaciation in this 
 part was on a much more extensive scale than in the south-west, but still 
 hardly came up to that in some part of the Highlands. The main areas 
 of the occurrence of moraines are detailed on pp. 240, 241, 256-259. 
 Good examples are seen by the traveller on the coach roads between 
 Lochgoilhead and St Catherine's, Arrochar and Cairndow, the head of 
 Loch Eck and Strachur. Those by the side of the first-mentioned road 
 are particularly rough and boulder strewn. 
 
 The torn crags at the head of landslips, and the huge banks and masses 
 of fallen rock below them, make some of the wildest scenery in the 
 district. The two big crags on the north side of Beinn an Lochain (134) 
 are both the heads of landslips. So too are the crags on the north side of 
 the glen, f mile east and f mile slightly south of west of Binnein an 
 Fhidleir (134). The smaller but better defined slip on the south side 
 of the same glen, about J mile W.S.W. of the "1" of "Glen" is still 
 more prominent, being so near the roadside. This is the slip that is said 
 to have taken place about 200 years ago. One quarter of a mile north- 
 east of Upper Clasheoin (126) another comes down almost to the raised 
 beach, from about the 1250-foot contour. 
 
 The south-west side of Hell's Glen, from near the top of Stob Liath, is 
 one great mass of tumbled blocks. The rock at which the coach horses 
 stop to drink, out of " Moses' well," is one of these blocks, but not nearly 
 so large as some. The bottom of the slipped material is nearly J mile 
 long. The sharp vertical face of An Stiobull (The Steeple) \ mile south- 
 east of Lochgoilhead is the head of a slip. 
 
 The north-east side of Loch Long is particularly marked by landslips. 
 On the south-east side of Cnoc Coinnich there is one, both sides of which 
 can be traced to the loch side from between the 2250 and 2000 foot 
 contours a distance of 1J mile. Outside the area being described, the 
 Brack and Ben Arthur (The Cobbler) are in a still more ruinous con- 
 dition. 
 
 On the west side of Loch Eck there is a very rough slip on the north 
 side of Clach Beinn. One can see the large tumbled blocks quite clearly 
 from the steamer deck. 
 
 The above form only a small proportion of the whole lot of slips, and 
 have been selected for mention merely because they are the most readily 
 discerned from the common tourist routes. A detailed list of the others 
 is given on p. 276. The causes which appear to have led to the formation 
 of some of them are also mentioned. C. T. C. 
 
287 
 
 CHAPTER XXIII. 
 
 ECONOMIC RESOURCES. 
 
 The fault breccias, qnish lines, and veins in the schists are rarely 
 accompanied with useful mineral, and, as far as known, never in 
 quantities to repay working. Three trial levels were driven by Mi- 
 Duncan, the former proprietor of Ben more, into crush lines near Blair- 
 more burn, but met with such little success that they may well act as 
 deterrent examples. The adits are engraved in the published 1-inch Map 
 29 : one occurs just on the north side of Blairmore burn, another on the 
 hillside mile slightly east of north of this, and the third at the west side 
 of the south branch of Stronchullin burn J mile slightly south of the " S " 
 of " Stronehullin." A fourth has been unfortunately engraved, owing 
 to an error which escaped notice, a little north of that last mentioned. 
 We have to thank Mr Wood, Mr Duncan's factor, for particulars about 
 the trials, and for accompanying us into two of them after their abandon- 
 ment. The level in Stronehullin was driven for 858 feet, along a crush 
 line the whole way, and various short cross cuts were also made where 
 subsidiary crushes seemed to be coming in. A small wheel for crushing 
 the ore was erected near the mouth, but did not appear to have been 
 ever used. In both the other levels small specimens of argentiferous 
 galena were found here and there, about half an inch long ; the main 
 crushes in each appear to be the same ; the more northerly level follows 
 the crush for 104 feet ; the south level cuts the main crush at a distance 
 of 225 feet from the mouth, but another at half this distance. 
 
 In the schist quarry -fa mile south of the " y " of " Trinity " (Duiioon) 
 there is a thin vein, hading north-west, which contains small specks of 
 galena mixed with quartz and calcite. 
 
 Veins of galena were formerly worked near Tyndrum (1-inch Map 46) 
 along the N.N.E. disturbances which pass by there. It is interesting to 
 observe that some of the N.N.E. crushes which continue into this area 
 from Tyndrum are also accompanied with small strings of this mineral, 
 though never in such quantity as to have induced trial of them. Three- 
 quarters of a mile N.N.E. of Bridgend (141 and 152) a N.N.E. crush about 
 6 feet wide, hading west and accompanied with a felsite dyke (see p. 104), 
 is said to contain strings of argentiferous galena. We did not observe 
 any, but we think the information was correct. We noticed one or two 
 thin strings of this mineral too, in the Loch Tay limestone in the upper 
 part of Coire No (133). 
 
 In the north part of the area, not far from the edge of the granite, 
 there are some galena veins which appear rather more promising than 
 those yet mentioned. In a steep crag mile slightly south of west of the 
 Eagles' Fall, at intervals for a breadth of about 4 feet in the lower part 
 of the scar, there are veins of barytes, nearly vertical, and running north- 
 west. Some of these also contain a ferriferous carbonate, small specks of 
 copper pyrites as large as small shot, and galena in isolated crystals or 
 short ribs. The best of the veins noticed was 6 to 8 inches wide, and 
 the ribs of galena in it were in places rather over 1 inch in breadth. 
 
 In the course of a streamlet (not marked in the Map), f mile slightly 
 south of east of Achadunan (126) there is a vein of barytes about 1 foot 
 thick, which contains little strings of galena J inch wide. The direction 
 is apparently north-east. This occurrence was kindly called to our 
 
2"88 GEOLOGY OF COWAL. 
 
 attention by Mr Brodie, the chief game-keeper on the Ardkinglas 
 estate. 
 
 In the green beds f mile W.S.W. of the " M " of " Garbh allt Mor " 
 (126) there is a 1 foot east to west vein of calcite and ferriferous 
 carbonate, and thinner parallel veins in which there are occasional specks 
 of galena. 
 
 On the shore of Loch Long 120 yards north-east of Mark (153), 
 there is a north to south crush with a ferriferous carbonate in a phyllitic 
 mica schist. A few yards east of the crush there are flattish strings, 
 about 1 inch thick, which cross the foliation of the schist. These are 
 composed of quartz, specular iron, magnetite, pyrrhotine and chal- 
 copyrite. 
 
 The pyritous schist in the Ardrishaig phyllite series on the shore of 
 Loch Fine 70 yards N.N.W. of M'Phun's Cairn and south east of 
 Creggans Point (141) is mentioned on p. 58. In the first locality 
 small proportions of galena, blende, silver and gold also occur. The 
 results of an assay of a sample are given on the page quoted. The 
 occurrences seem quite an integral part of the schist series and not de- 
 pendent on the proximity of any crush line. They are perhaps more 
 promising than any other of the metalliferous veins in the district, and it 
 might in certain circumstances be worth while to further explore them. 
 
 The occurrences of copper ore in Glendaruel, and the Kyles of Bute, 
 are mentioned elsewhere, p. 81. They are interesting from their mode 
 of occurrence, forming apparently an integral portion of the schist, but 
 are on far too small a scale to be of economic value. The copper pyrites 
 found here and there along veins and crush lines is also generally in very 
 small specks. Three such occurrences have been already mentioned, one 
 in the fault rock in the burn J mile W.N.W. of the Ordnance Station 
 697 (184) (p. 173), another in the quarry in the Bull Rock greywacke 
 on the south of Dunoon, p. 178, and another in the galena vein J mile 
 slightly south of west of the Eagles' Fall. The most easterly crush rock 
 in the burn J mile south-east of the "Badd" (184), also contains small 
 specks of this mineral mixed with quartz and ferriferous carbonate. 
 
 Small quantities of ferriferous carbonate and specular iron are found 
 along many of the fault lines and in thin veins. Of the former we may 
 mention especially a vein about 1 foot thick that occurs near the head of 
 the burn on the north-east side of Cruach na Capull (183) : in one place 
 a good deal of iron pyrites is mixed with this. A thick rib of quartz and 
 ferriferous carbonate with iron pyrites crosses the stream just below the 
 junction of the three burns f mile east of the Badd. Small quantities 
 also occur in crushes in the following places, f mile north-east of Rash- 
 field (174), J mile S.S.W. of Garrachoran (crush not engraved), f mile 
 S.S.E. of the top of Cruach nan Capull (183), between Mark and Carraig 
 nan Ron (6 inches wide at a point j mile N.N.E. of the Carraig), in thin 
 " flats," sometimes 6 inches thick, near the north-west crush J mile E.S.E. 
 of the Saddle (153), in the north-east crush \ mile north east of the " c " 
 of "Beinn Bhreac" (153), in the N.N.E. crush J mile S.S.W- of 
 Corriesyke (142), in the Cur 130 yards east of Socach (141), in Liogan 
 by the "g," in the burn north of Criogan by the "g," in the N.N.E. 
 crush in Durians burn, in the N.N.E. crush \ mile north-east of An 
 Cruachan (162), and many other places. 
 
 Specular iron is seen in the veins mixed with quartz and other minerals 
 on the shore near the Bull Rock, south of Dunoon, in the greywacke quarry 
 near the Bull Rock, and in the veins with chalcopyrite, etc., 120 yards 
 north-east of Mark. It is probably common in veins at a little depth under 
 the surface, and the staining derived from it is the cause, we may suppose, 
 
ECONOMIC RESOURCES. 289 
 
 of the deep red colour often seen in the crush lines of the district, e.g., 
 on the west side of Meall Buidhe (173), J mile south-east of Uig (173), 
 and J mile south-west of the "e 3> of " Coire Athaich" (173). 
 
 lu spite of the scantiness of these ores it is not impossible that in old 
 times some of the better exposures among them may have been used by 
 the clans for smelting down into claymores, etc. Here and there small 
 slag heaps of old bloomeries can still be recognized. Two such occur 
 near together on either side of the burn by the " e " of " Gleann Laoigh " 
 (163) : there is plenty of wood charcoal lying about near the east heap. 
 Others were noticed close to the shore ^ mile north-east of Eilean Dearg 
 (Loch Riddon), by the first "n" of "Glen Fiuart" (164), by the burn at 
 the 400 foot contour E.S.E. of Leak (151), in the wood ^ mile north of 
 the "s" of "Creggaus" (141), and J mile W.S.W. of the "g" of Gleann 
 Laoigh."* But we cannot say that in any of these cases we could find 
 any signs of old mining, or promising veins in the neighbourhood, so that 
 it may be that ores foreign to the district have been imported, and 
 smelted with the help of charcoal from the native wood. It is stated 
 (W. I. MacAdam. Trans. Geol. Soc. Edin., vol. iv., 1881, p. 95, "Notice 
 of veins of Specular Iron Ore at Strachur, Argyleshire "), that so impor- 
 tant was the oak wood that used to grow all over the lower ground, that, 
 long after the use of native ores had been given up, red iron ore was 
 shipped from Cumberland to Furnace (1 inch map 37) for smelting. 
 And from this the name " Furnace " is no doubt derived. Mr MacAdam 
 gives analyses of two specimens of specular iron ore from Strachur. The 
 exact locality is not stated. Specimen 1 was picked ore, as pure and free 
 from rock as possible. Specimen 2 was the ore as found in the veins. 
 To these are added analyses of mica schist close to the veins (3), and 6 
 feet from the veins (4). The results are as follows : 
 
 1234 
 
 Fe 2 3 88-83 37'51 16'03 1518 
 
 CaO trace 0'28 0'38 0'36 
 
 MgO trace trace 0'98 0'84 
 
 0-16 0-25 0-12 0-09 
 
 , aiid Silicates 10'92 6179 82'49 83'53 
 
 99-91 99-83 lOO'OO lOO'OO 
 
 Barytes sometimes occurs with the fault breccias, but not commonly. 
 In the south part of the area the thickest rib noticed was in the crush cross- 
 ing Gleann Laoigh burn about 50 yards north of where the dyke uear 
 the " g " of " Laoigh " leaves the burn. This is 4 inches wide. Small 
 strings and plumose aggregates of it also occur in the crush rock on either 
 side of the above dyke, at the side of the dyke J mile north-east of Meall an 
 Fharaidh (173), aiid in the burn in Drynain Glen (164), south of the "a." 
 In the north part of the district, near the granite, it is perhaps 
 commoner than elsewhere. Some instances of its occurrence have been 
 already mentioned in association with galena and copper pyrites. 
 
 A magnesian limestone in the Upper Old Red Sandstone near Toward 
 was ijuarried by Messrs Merry and Cunningham, in 1886, for lining their 
 basic Bessemer steel converters, but as the sample lot of some 30 tons 
 showed 10 '8 per cent, of siliceous matter they did not use any of it. 
 
 * Since the above was written Mr Charles Mackintosh, the borough surveyor of 
 Duuoon, has mentioned to us two heaps apparently of the kind under description, 
 which were met with in extending the Diuioou Waterworks. These are both near 
 together about mile west of the bottom of the "D" of "Dunooii." Mr James 
 Tod of Rashtield has also reminded us of a similar heap on the hillside ^ mile 
 E.N.E. of Rashfield (173 and 174). 
 
 T 
 
290 GEOLOGY OF COWAL. 
 
 For particulars of the locality quarried, and for the analyses kindly 
 furnished by Mr Main of Messrs Merry and Cunningham, refer to p. 94. 
 We were informed by Mr Main that the samples broken by hand made 
 him think that a purer stone might yet be got in bulk, and that it was in 
 contemplation to make arrangements for further trials on the west side of 
 the burn the opposite side to that from which che stone was quarried. 
 
 The Dunoon limestones do not appear to have been ever quarried 
 except in one place, by the junction of the little burns i mile W.N.W. of 
 the " D " of " Dunoon " (town). Even the quarries in the thicker and much 
 better limestone of Glendaruel, etc., the Loch Tay limestone, which used 
 to be extensively worked for lime burning, are now very generally disused. 
 The amount of lime used for agricultural purposes is much less now 
 than formerly, and is generally imported ready made. The old lime 
 kiln on the roadside south-west of Glenleaii was never used for local stone, 
 but limestone was imported from Ireland, brought to the head of Loch 
 Striven by ship, and thence carted to the kiln. Judging from the 
 abundant chalk flints still noticed on walking over the old ploughed 
 fields this source must once have been largely drawn on. C.T.C. 
 
 The Loch Tay limestone at the hamlet of Gletislnan (141) is .still 
 occasionally burnt into lime for agricultural use, at an adjacent kiln. 
 Most of the limestone now quarried seems to be used for road metal. 
 There are 2 quarries on the north-west side of the burn, and another, -i- 
 mile above the hamlet, on the south-east side. The latter has evidently 
 been long since abandoned. At the time of the Survey only the quarry 
 nearest to the hamlet was being used. Mr W. I. Macadam (" On the 
 Chemical Composition of certain Limestone Beds at Baltimore, Argyll- 
 shire." Trans. Edin. Geol. Soc., vol. iv., 1883, p. 101) gives some 
 analyses of certain bands in the limestone, and vein rocks going through 
 it. Two of these analyses are quoted on p. 47. The main band contains 
 65*44% of carbonate of lime, a little iron and magnesia, and 29*63% of 
 silica and silicates. Mr Macadam states that, beside the kiln at present 
 used, " there are several old and disused ones, the formation of which is 
 peculiar, they being so formed that a continuous process is impossible and 
 thus the tires had to be lighted before each charge, the contents burned, 
 and the whole cooled before removing the charge." There are several old 
 quarries in the Loch Tay limestone south of Kilfinari (181) and it seems 
 to have been formerly burnt for lime as there is an old limekiln near the 
 roadside north of Drum. A big quarry has been opened in the limestone 
 at Otter Ferry : this provides an excellent road metal and the roads in 
 this district are almost entirely repaired from this source. There are 
 various old limestone quarries, now abandoned, at the sides of Kilbride- 
 more burn (162), which formerly were largely wrought for agricultural 
 purposes by the farmers of Glendaruel. 
 
 Some of the old slate quarries in the Dunoon phyllite series and the 
 adjoining phyllites are elsewhere mentioned, pp. 30, 32. None of these 
 are now worked, as they cannot compete with the slates imported from 
 other districts. The cheapness of freight at the present day has brought 
 into such close proximity and rivalry districts which are geographically 
 far apart, that only those best fitted for their respective products find 
 industries can retain even the local market. 
 
 To state this is almost a truism, but still we were hardly prepared for 
 the great extent to which some of the local products have consequently 
 fallen into neglect. In spite of the numberless basaltic dykes of the 
 district a good deal of the road metal used in the south-east part of 
 Cowal is shipped from Gourock, and the cost is considered to be lessened 
 
ECONOMIC RESOURCES. 291 
 
 by this means. The Gourock stone is readily distinguished from the 
 various local whin stones, and is carted up for considerable distances from 
 its landing places. Among the basaltic dykes which have been quarried 
 \ve may mention the following, those J mile south-west of the foot of 
 Loch Eck, J mile south of Auchateggan (172), T V mile east of Auchen 
 breck (172), J mile slightly west of north of Ardtarag (173), on the raised 
 beach j- mile slightly north of west of Toward cottages, at the landward 
 margin of the 20-foot beach, 1 mile E.S.E. of Cluniter (195), 200 yards 
 E.X.E. of Leanach (151), by the roadside near Drum (181) and Craigna- 
 feich (191 and 192), and on the west side of Loch Riddon south of upper 
 Callow. 
 
 We cannot call to mind many instances of lamprophyres having been 
 quarried in this area. We should suppose that many of them would 
 make good metal, but only few of them crop out conveniently for use 
 along the roadsides. The baud in the limestone quarry nearest to the 
 hamlet of Glensluan is quarried together with the limestone, and a mix- 
 ture of the two rocks applied to the roads near. A band near Auchan- 
 askioch (181) has also been quarried. A clay, apparently formed from a 
 crushed decomposed lamprophyre, occurs in a line of fault f mile east of 
 Socach (141), and was formerly known locally as a good pottery clay 
 (see p. 109). 
 
 The sheet of felsite near St Catherine's has been quarried, both for 
 road metal and field dykes, a little below the road near the top of the 
 " h" of "Tighe Claddich " (133), and on the hill J mile south-east of the 
 " s " of St Catherine's. Half a mile slightly north of east of Ardno (133) 
 a felsite sheet has been quarried, and metal from it is carried over the 
 watershed for use on the Hell's Glen road. The extensive quarries in 
 the somewhat similar rock lower down Loch Fine, at Furnace and Crarae, 
 are all on the north-west side of the loch and so outside Cowal. There are 
 no exposures on the south-east side at all so extensive, or so conveniently 
 situated for shipping. There is a fair sized quarry in the felsite south of 
 Loch na Melldalloch (181), which is worked for the roads. 
 
 The granite has not been quarried anywhere. The nearest part of it is 
 3 miles from the head of Loch Fine. Some varieties would probably 
 serve well for ornamental purposes, being rather like the Shap Fell 
 granite of Westmoreland, but with even larger porphyritic felspars. 
 
 The hornblende schist in the fir-clad ridge east of Loch Loskin has 
 been extensively quarried in several places, and supplies most of the road 
 metal used in the town of Dunoon. 
 
 The north-west outcrop of epidiorite at St Catherine's has been largely 
 quarried, and is said to have supplied most of the stone used in building 
 Inveraray Castle. The rock is evidently liable to vary in character a good 
 deal, both structurally and in chemical composition. The more schistose 
 and fissile parts are not so suited for building purposes. The microscopical 
 characters of the variety preferred are described on p. 64. The rock is 
 called by Mr Teall a tremolite-chlorite-rock. It is said in the neighbour- 
 hood that the new quarry, close to the road leading south-east from the side 
 of the inn, did not furnish such good stone as the old quarry in the 
 garden on the west side of the ruined chapel of St Catherine's. Besides 
 these quarries, there are others at the back of the raised beach south and 
 south-west of the old chapel. The stone has a great local reputation. It 
 is soft and easy to cut, but yet offers great resistance to atmospheric 
 weathering. Many of the bridges in the neighbourhood are built of a 
 rather schistose variety of it, or some similar stone, and the depths of the 
 names cut into them, and the dates added, show how easy the stone is to 
 cut and how long it retains tool marks. These varieties remind one 
 
292 GEOLOGY OF COWAL. 
 
 somewhat of the stone of which the old crosses of lona and Kilchoman 
 (Fslay) have been formed. 
 
 The somewhat similar epidiorite bands near Creggaus (141), have been 
 worked for building stone near the west end of the wood, and in some 
 older quarries further inland. There are also small quarries for general 
 purposes in the epidiorites south of Kilfinan (181). 
 
 Small quarries for road metal are not unfrequently opened out in 
 schist outcrops which happen to be conveniently situated at the road side. 
 One third of a mile N.N. W. of Inveronich an albite schist has been exten- 
 sively quarried, partly for this purpose and partly for building stone. 
 
 The more massive schists, quartzose or pebbly beds, or the green beds, 
 are generally used for building purposes in the schist area. Some of 
 the latter may tool with comparative facility, but with the other 
 rocks mentioned it is hard to prepare even an approximately smooth 
 face, and so the outsides of buildings are usually covered with cement 
 or fine concrete, and subsequently painted. For the same reason 
 imported freestone is used for window sills, door lintels, etc. Most of 
 the stone used in building Dunans Castle (162), was procured from a 
 tough pebbly green bed in the north-west banks of Dunans burn J mile 
 south-west of Caol-ghleann. It is said to have given great satisfaction. 
 The building stone chiefly used in Dimoon conies from a quarry in a 
 massive portion of the Bull Rock greywacke schist, a little north of the 
 Bull Rock. There are various large quarries of pebbly schist within the 
 phyllite series near the town. One of these lies near the "d" of 
 "Castle Crawford," another in the wood J mile north of the first "o" of 
 "Dunoon," another just north-east of the same letter' "o," another y 1 ^ 
 mile south of the u y"of "Trinity." Of these four the second was the 
 only one in active work at the time the Survey was being carried on. In 
 the south-west part of Cowai the more gritty schists have been quarried for 
 building purposes in several places, but not on a large scale ; among the 
 more important, are those of Ardlamont west of Point Farm, and between 
 Corra and Craig Cottage, at Acharosson, north-east of Auchanaskioch, 
 Kilbride, Auchagoyl, 400 yards north of Ardmarnock House, Tighna- 
 bruaich, etc. 
 
 The red sandstone near Inellan and Toward is generally too full of 
 bits of schist and other rock to make good building stone, particularly as 
 these bits are not firmly cemented in. It has been quarried close to 
 Toward Church, together with a basalt dyke, and we think also at the back 
 of the raised beach near Chapel Hall. 
 
 The main areas of peat are detailed on pp. 273-274. Nearly all these are 
 some distance off the farms in the glens, and at the time of the Survey we 
 think there were only 3 houses in the part east of Glendaruel where peat 
 was in common use for fuel. These were the shepherd's house at the head 
 of Glen Tarsan, Upper Duillater, the house near the "t" of " Duillater " 
 (164), and Caol-ghleann (152). It is perhaps worth mentioning that in 
 Ardrishaig, 1-inch Map 29, but just without Cowal, the peat that the whisky 
 distillery used was at the time of the Survey imported from Ireland. 
 Along the south-west coast of Cowal bordering on Loch Fine peat is pretty 
 generally used, and there is abundance of it in the peat flats marked in the 
 Map, and elsewhere. 
 
 The clay shell-bed which occurs on the shore between Newton and 
 Strachur is stated (p. 261) to be sometimes used locally as a hearthstone, 
 to whiten the hearths before the fire. Various other exposures of similar 
 beds are mentioned on pp. 245-247. These beds are often formed of a fine 
 stiff clay, fairly free from stones, and pale grey in colour. They might, 
 perhaps, make good pottery clay. 
 
ECONOMIC RESOURCES. 293 
 
 The sand in the present beach at the head of the Holy Loch was at the 
 time of the Survey being shipped for making the moulds for iron castings. 
 The gravel in the beach of the west bay of Dunoon is largely used for 
 the garden paths of the numerous villas adjoining. Excellent gravel is 
 also obtained from the beaches of Kilfinan Bay and Otter Ferry. At Sand- 
 bank (174) slightly more than J mile south-east of the " k " of " Sand- 
 bank " there is an extensive pit in the gravel and sand of the 100-foot 
 beach. Pits in the same beach have also been opened out about J mile 
 south of Gortanansaig (194) and near Blairmore Farm. There is a good 
 section of fine sand within the 100-foot beach on the south side of 
 Dunoon, ^ mile south east of the " y " of ' Trinity," and this sand has 
 sometimes been used for mixing with lime for building purposes. In the 
 south-west part of Cowal sand and gravel pits have been opened in the 
 raised beaches at Upper Callow, several places near Millhouse and in the 
 valle} 7 of Allt Osda, near StillaigFarm, Port Leathan, Ardmarnock Ho., etc. 
 
 The reservoir that supplies the towns of Dunoon and Kirn with water 
 is situated on the course of the burn that runs into the west bay of 
 Dunoon : the centre of the embankment is about J mile south-west of 
 the " D " of " Dunoon " and the reservoir extends up the barn for 
 about 330 yards. With the exception of some narrow burn channels the 
 site is in drift, the lower part stiff boulder clay and the upper part 
 morainic. We understand that at present (1896) an additional reservoir 
 is being constructed further up the burn. The reservoirs that supply 
 Inellan and Sandbank are along the burns J mile south-west of Garrow- 
 choran Hill, and J mile south-east of Finbracken Hill respectively. Both 
 these reservoirs and also the one at Dunoon have been constructed since 
 the Ordnance Survey of the district was completed, and they are not 
 shown on the 6 inch or 1-inch maps. We believe that a storage reservoir 
 for the district of Blairmore and Strone is now being constructed. 
 
 There are two dams or reservoirs used at the Kames Powder Works 
 (193), on the Creag-an-fhithich burn E.S.E. of Loch na Melldalloch. 
 and the water of Loch Asgog is also made use of for the same purpose. 
 The Tighnabruaich reservoir for the supply of water to the town is partly 
 in boulder clay, on the stream called Allt Mor, west of Barr Liath, and 
 there is another reservoir further down the same stream near Middle Ineus. 
 There is another reservoir in red till on the moor Jinile south of Kames Farm. 
 
 The amount of arable land is small, nearly all of the area being 
 given over to sheep farming. The winter climate is generally mild and 
 snow does not lie long except near the hill tops, but there is little 
 feeding in the winter, and near the end of autumn the lambs of the 
 preceding spring have to be sent away fur wintering, or the death-rate 
 among them is excessive. On some of the hills in the north-east part of 
 the district there is very little heather, and even the sheep farmers 
 sometimes express a wish there were rather more of it, for the sake of 
 the mixed feeding it affords. In this part the grouse shooting is of little 
 value. Red deer are often seen on the hills north of Kinglas Water and 
 occasionally considerably further south, but these have wandered in from 
 neighbouring forests on the north. There is no area from which sheep 
 are excluded for the sake of the deer. 
 
 The patches of arable land are generally on the marine terraces 
 or alluvial flats, or the expanses of boulder clay adjoining these areas. 
 Among the larger patches we may mention the valley of the Echaig, the 
 Lochgoilhead valley below Polchorkan, the lower part of Glen Finart, 
 the valley between Baltimore and Strachur Bay, the valley between 
 Bridgend^aml the head of Loch Eck, the head of Loch Riddon and the 
 valley of Glendaruel, the sides of Ardyne burn below Knockdow (194), 
 
294 GEOLOGY OF COWAL. 
 
 and the vicinity of Toward Point. The alluvial flats in Glendaruel, the 
 Lochgoilhead valley, and at the head of Loch Eck are often flooded, and 
 receive deposits of fine silt, which add greatly to their fertility. At 
 Kilfinan there is a considerable area of land under cultivation extending 
 from Kilfinan Bay to a little past the village of Kilfinan. The various 
 raised beaches between Ballimore and Largiemore (171), and the river 
 terraces of Stralachlan, are also under cultivation. On the south side of 
 Kilfinan there is some tillage land between this place and Ardmamock, 
 and again to a larger extent on the south side of the road between 
 Tighnabruaich, Millhouse, and Portavaidue, in the low lying ground 
 about Ardlamont, and in the valleys of the streams running into Kilbride 
 Bay and Asgog Bay. 
 
 At the time of the Survey there were only two crofters in the area east 
 of Glendaruel, but it is not very long since the glens were thickly peopled 
 with them, and their old ruined houses and field dykes can still be seen 
 in some places, e.g., near the edge of the alluvium J mile east of the " 1 " 
 of "Glen Tarsan" (173), on the north-west side of A lit Glinne Mhoir 
 (134) a little north of the ' i " of " Mhoir," in Glen Shellish by the " n " 
 and "s," in Glen Branter 100 yards north of the "R" of "Robuie." 
 Remains of higher lying, more isolated dwellings remind us of times when 
 it was customary to remove for the summer time to distant shielings and 
 tend herds on the small bits of pasture near the mountain tops as the 
 Norwegians still resort to the " seters " with their goats. Such remains 
 occur J mile south-east of the the Eagles' Fall (126), mile E.N.E. of the 
 "c" of "Beinn Bhreac" (153), in Glen Branter 100 yards east of the 
 "G" of "Glen," in Garrachra Glen 100 yards south-east of the "h" of 
 " Garrachra Glen" (163). In those days there were comparatively few 
 sheep kept, but many Highland cattle. The large sheep farms are said 
 to be a later introduction. 
 
 In the south-west part of Cowal, there are ruins of farm buildings at 
 Inveryne on the north side of the Acharosson burn, and on the south 
 side of the same burn are others at Upper Auchalick, Upper Auchana- 
 skioch, and at another place | mile north east of the latter. Glenan is 
 now unoccupied, as also Creag-an-fhithich cottages and Strone-duich, 
 west of Kilbride. As examples of moorland which was once cultivated 
 may be mentioned a tract 300 to 400 yards east of Kilbride church, and 
 another on the moor J mile east of Auchagoyl cottages. There are also 
 many old fences on the moor west of Stillaig Farm near the ruins of the 
 old chapel. 
 
 Some of the older inhabitants tell you tales of these old times, and 
 speak of them with regret. They were humble and simple days, but 
 it was more possible then for the young people to find employment at 
 home, and in comparatively healthy surroundings. Each little feature in 
 the glen was well known and had a Gaelic name distinctive of its 
 peculiarities, and gradually acquired a corner of affection in their hearts. 
 
 The population is now nearly all concentrated in the coast villages and 
 towns. These have either sprung up or largely increased since crofter 
 days, and afford a pleasant and convenient outlet for the holiday makers 
 of Glasgow and the other large towns near. The summer population of 
 the coast places is very much larger than that in the winter, many of the 
 houses being closed at the latter time of year. In the case of Dunoon 
 it is said (1894) that the winter population may be taken as 6000, while 
 in the height of the summer it amounts to 35,000. But even the winter 
 residents, including the business men, who in yearly increasing numbers 
 go up to Glasgow or other towns day by day, probably considerably 
 exceed in number the population of old crofter days. 
 
 W.G., C.T.C., J.B.H. 
 
295 
 
 APPENDIX. 
 
 I. General Remarks on the Petrography of the Cowal District. By Mr J J H 
 
 Teall, F.E.S. 
 
 The main interest of the Cowal district, so far as petrographical questions are 
 concerned, centres in the fact that it is largely composed of sedimentary deposits 
 which have been converted into crystalline schists by metamorphic agencies operat- 
 ing on a regional scale. It has been shown in the body of the memoir that the least 
 altered rocks, consisting mainly of phyllites and schistose grits or greywackes, occur 
 in the south-eastern portion of the district, and that, as we proceed towards the 
 north-west, across the general strike of the formations, the metamorphism is seen 
 to increase until we reach, near the centre of the "anticline," an extensive area of 
 typical crystalline schist. No abrupt change can be observed ; at the same time it 
 may be regarded as certain that the rocks of the most highly altered area are not 
 simply the metamorphosed representatives of those which occur in the least altered 
 area : new petrographical elements are introduced into the complex as we advance 
 towards the north-west. 
 
 Another point which has been clearly brought out by a study of the rocks in the 
 field is that all portions of the district have been profoundly affected by earth move- 
 ments of different types and of different ages. Structures produced by one set of 
 movements have been subsequently modified or even obliterated by a later set. 
 
 In comparing the rocks of the most highly altered with those of the least alteied 
 areas the most striking feature, however, is not a difference in the apparent amount 
 of movement, but in the nature and relative abundance of the minerals which have 
 been developed in sitii, or, in other words, of the authigenic constituents. An 
 unaltered mechanical sediment consists wholly of allothigenic constituents, whereas 
 a typical crystalline schist consists wholly of authigeuic constituents. Between 
 these two extremes every intermediate stage may be found, and many, though not 
 all, of these occur in the district in question. The initial stages are absent, for the 
 least altered rock belonging to the Highland series shows a certain amount of new 
 mineral development. 
 
 It is well known that in studying the metamorphism of a complex series of strati- 
 fied deposits the coarser grained sediments retain traces of their original character 
 long after all such traces have disappeared from the finer grained deposits. It is 
 also known that rocks which can be clearly recognised, in the field or in hand speci- 
 mens, as of clastic origin, often so closely resemble crystalline schists in microscopic 
 structure that if we had to depend on the microscope alone it would be impossible 
 to form any definite conclusion as to their origin.* 
 
 These points are well illustrated in the Cowal district by a widely distributed 
 rock to which the terms gneissose grit, biotite-gueiss, and grauulitic biotite-gneiss 
 have been applied during the progress of the Survey. f This rock is found not only 
 in the district in question but in many other portions of the southern Highlands, 
 along a belt of country stretching from the coast north of Stonehaven to the 
 peninsula of Kintyre. Although distinctly gneissose in structure and composition it 
 differs markedly from igneous gneisses in its relation to the other rocks with which 
 it is associated, and frequently contains relics of original grains of quartz, often 
 bluish in colour, and felspar. The main mass of the rock is a granulitic mosaic of 
 quartz and felspar with which definite flakes of biotite and flakes or confused 
 aggregates of white mica are associated. 
 
 * L. Milclt, Beitnige zur Lehre von der Regional-metamorphose. Seues Jahrbuch. Beilage 
 Band ix. (1894), p. 101. 
 
 t In the body of this memoir, however, they have been called simply schistose grits, or schis- 
 tose greywackes. C.T.<'. 
 
296 
 
 GEOLOGY OF COWAL. 
 
 A very common type of this rock is represented by a specimen from Fearna Bagh 
 (3834). It is formed of fine-grained, irregular, quartzo-felspathic layers separated 
 by thin dark streaks which have a tendency to run into each other, and so cut out 
 
 FIG. 54. x 1. Granulitic biotite gneiss. Fearna Bagh 
 
 the broader granulitic folia of quartz and felspar. The above diagrammatic sketcli 
 of the cut surface of this specimen represents the relation of the dark laminre to the 
 light coloured folia. 
 
 In this particular specimen the original clastic character has been almost entirely 
 obliterated. The rock tends to split along the dark laminae, and the planes of 
 schistosity are coated with plates of black mica. Under the microscope the light 
 coloured folia are seen to be composed of quartz, felspar, a carbonate, and here and 
 there a flake of biotite. Of these constituents quartz is by far the most abundant. 
 It forms a mosaic of interlocking grains. The felspar and the carbonate are present 
 only in small quantity, but they interlock with the individuals of the quartz mosaic 
 in the same way as these do with each other. All the constituents are authimorphio, 
 and most, if not all, are authigenic. The plates of biotite are isolated, and are 
 idiomorphic so far as the basal plane is concerned. One and the same plate may lie 
 in two or three individuals of the quartz-mosaic. This fact is important because it 
 has been suggested that the idiomorphism of the biotite is a distinctive character of 
 gneissose rocks of igneous origin. 
 
 The dark laminpe are extremely rich in micas of two kinds. One is strongly 
 pleochroic in light brown and deep brown or green tints ; the other is nearly, but 
 not quite, colourless. The dark mica occurs in flakes which usually show definite 
 extinction, but it is not so markedly idiomorphic as the plates which lie in the 
 granulitic folia. The white or pale green mica sometimes shows definite extinction, 
 but is more apt to form sericitic aggregates. Iron ores occur sparingly in the dark 
 layers. 
 
 In addition to the constituents above described there are a few larger grains of 
 quartz and felspar. These, like the other constituents, are authimorphic, but they 
 are probably relics of original clastic (allothiclastic) grains which have not been 
 completely absorbed into the granulitic mosaic ; in other words, they may be in 
 part allothigenic. The felspars sometimes appear to have been fractured ; the 
 different portions of what was probably an original grain being now separated by 
 veins of granulitic material. It is clear, however, that the amount of allothigenic 
 material in this particular specimen is extremely small. 
 
 Another specimen from Tom an lasgaire (5295) belonging to the same type of 
 rock has preserved its original character in a much more perfect manner. More or 
 less deformed grains of blue quartz and pink felspar, often measuring '5 mm. in 
 diameter, are clearly recognisable in the hand specimen. The bed of grit has been 
 bent into a fold, and, although all the grains have been deformed, those which occur 
 near the axial plane have suffered less than those which occur in the limbs. The 
 composition of the rock is the same as the last. The constituents are, for the most 
 part, authimorphic, but the amount of allothigenic material is much greater. The 
 specimen furnishes a striking illustration of the difference in behaviour of quartz and 
 felspar under the influence of the deforming stresses. The former changes its shape 
 by granulitisation, the latter by fracture. Under the microscope detached authi- 
 clastic fragments of felspar which clearly belonged to the same grain are often seen 
 to be separated by veins of microcrystalline quartz. Folia of microcrystalline 
 material and micas sweep round the lenticles or phacoidsof quartz and felspar. The 
 
PETROGRAPHICAL REMARKS. 29? 
 
 mosaic produced by the deformation of the large quartz grains is much coarser than 
 that of the matrix. 
 
 The extensive series to which these two specimens belong consists of foliated 
 crystalline rocks essentially composed of quartz, felspar, and one or two micas 
 They are, therefore, gneisses in the usual sense in which that term is employed 
 Where conspicuous traces of their clastic origin remain they may be termed gneissose 
 grits ; when all or nearly all such traces have disappeared they may be termed 
 granuhtic gneisses. They pass by insensible gradations into felspathic mica schists 
 
 The rocks in the area of least metamorphism consist of phyllites and greenish 
 schistose grits or greywacikes. The latter are composed of more or less deformed 
 grams of quartz and felspar in a matrix of micro-crystalline quartz, sericitic mica 
 and chlorite. The rock possesses under the>icroscope a marked flaser structure, and 
 the larger grains of quartz frequently have " tails " of granulitic material which 
 merge themselves in the micro-crystalline matrix. The streaks of sericitic mica wind 
 round the larger constituents and thus produce the characteristic flaser structure 
 
 The rocks grouped as " green beds " vary in character. Many specimens have the 
 appearance of greenish, more or less schistose grits, others are finer in grain and more 
 markedly schistose. A special feature is the almost constant occurrence of granular 
 epidote. Chlorite and a dark green or brown biotite are usually present, and a white 
 mica, in well developed flakes, is not uncommon. The coarser grained rocks are 
 light in colour, and are mainly composed of quartz, felspar, and epidote. 
 
 The quartz and felspar appear in many cases to represent clastic fragments, but some 
 of the felspar, especially in the finer grained schists, is albite and undoubtedly authi- 
 genic (3831). In some rocks large plates of authigenic white mica may be seen under 
 the microscope lying at right angles to the plane of foliation. Rutile and tourmaline 
 occur as accessory constituents in some specimens. The more gritty looking varieties 
 have a marked flaser structure under the microscope, the larger grains apparently 
 representing clastic quartz and felspar, the matrix being composed of the ubiquitous 
 micro-crystalline mosaic with which more or less granular epidote is associated. 
 
 The recks with authigenic albite, grouped as albite-schists, are sufficiently 
 described in the body of the memoir and in the Appendix No. II. It is, therefore, 
 only necessary, in this connection, to refer to other rocks of a similar character! 
 Albite-gneisses are recorded as occurring at several localities along the northern border 
 of the central zone of the eastern Alps. The rocks from the north-eastern prolonga- 
 tion of this border, south of Wiener Neustadt, have been described by Bohm.* He 
 divides the rocks of the district, according to the dominant mineral, into mica-rocks, 
 chlorite-rocks, and hornblende-rocks. The rocks containing albite belong to the first 
 group which he further subdivides into albite-gueiss, granulitic albite-gneiss, mica- 
 schist, epidote-niica-schist, and quartzite-schist. His detailed petrographical 
 descriptions show that there are many points of resemblance between the rocks of the 
 Wechselgebirge, and those of the Cowal district. Amongst these points may be 
 mentioned the occurrence of a green mica, and epidote as well as that of albite. 
 Bohm regards the rocks as a transitional group between the old crystalline schists and 
 the true phyllites. 
 
 Rocks of a similar character occur in the upper part of the Ennsthal and in the 
 Radstadter Tauern.t 
 
 Rocks, termed albite-phyllites, have been described by the officers of the Geological 
 Survey of Saxony as belonging to the lower portion of the phyllite-formation of the 
 Erzgebirge.:t They consist of a white potash mica referred to damourite, chlorite, 
 and a variable quantity of quartz and albite. The albite occurs sporadically, as it 
 does in the Cowal district, and where abundant the rock may be termed albite- 
 gneiss. Dr Credner lias examined hand specimens of the Cowal rocks, and states 
 that they can be exactly matched by specimens from Saxony. The upper portion 
 of the "phyllite-formation" of the Erzgebirge is referred in part to the Cambrian. 
 It is less crystalline than the lower portion, and contains rutile needles. It is there- 
 fore the petrographical equivalent of the Dunoon phyllites. 
 
 Rocks closely allied to the albite-schists of the Cowal district occur in the Green 
 Mountains of Massachusetts, where they are said to be of later date than quartzite 
 containing Olenellus. The albite-schist of Hoosac Mountain overlies a meta- 
 morphosed grit or conglomerate containing blue quartz and having other points of 
 resemblance to the gneissose grits of the Cowal district. The albites often give a 
 porphyritic character to the microscopic section ; but they contain the other minerals 
 as inclusions. " The groundmass is composed of muscovite and biotite, or muscovite 
 alone, chlorite, grains and aggregate lenses of quartz, magnetite in octahedra or 
 grains, apatite, tourmaline, and rutile." u The main difference between these rocks 
 
 - L'eber die Gesteine des Wechsels. TschermaK'g J/t. u. Petro. Mitth. v. 201. 
 t Von Foullon. Jahrb. K. K. geoL Reichsatust, 1883, xxxiii. 207 ; and 1884, xxxiv. 635. 
 I See K. Dalmer. Erlauterungen zvr geologischen Specialkarte, Section Lossnitz. 
 Geology of the Green Mountains by Pumpelly, Wolff and Dale. Monograph of the U. S. 
 GeoL Survey, xxiii. (1894). , 
 I! Op. eft., p. 61. 
 
298 GEOLOGY OF COWAL. 
 
 and those of Cowal appears to lie in the relation of the albite to the micaceous 
 minerals. These have not been observed as inclusions in the Cowal schists. 
 
 It will thus be seen that a considerable amount of doubt remains as to the age and 
 mode of origin of the different occurrences of albite-schist and gneiss. These re- 
 markable rocks sometimes undoubtedly form a kind of transitional zone between normal 
 crystalline schists and unquestionable sedimentary deposits ; and those who still 
 believe that this transition in space corresponds to a transition in time refer the 
 rocks in question to the " transitional period." The albite-gneisses of the Alps have 
 been in part referred to the carboniferous and in part to this " transitional period " ; 
 the albite-phyllites of Saxony are supposed to belong to a continuous series, the 
 upper part of which is Cambrian, while the albite-schists of the Green Mountains 
 are said to be Cambrian or Silurian. 
 
 The Cowal district furnishes no satisfactory evidence as to the age of the rocks in 
 question, but it shows that they ^belong to a series of highly metamorphosed stratified 
 deposits which cannot be sharply separated from another series, far less highly meta- 
 morphosed and consisting of phyllites or clay -slates, schistose grits, and limestones. 
 
 The rocks of the hornblende-schist and epidiorite group probably represent in all 
 cases basic igneous intrusions. The type to which they belong is so well known and 
 so widely distributed that it is unnecessary to refer to special localities where similar 
 rocks are to be found. They were in existence before the movements which have 
 so powerfully affected the district had commenced, or at any rate before these move- 
 ments had ceased. 
 
 The granitic rocks were, on the other hand, intruded after the movements. They 
 vary in character from granitites to quartz-diorites, and often contain clove-brown 
 crystals of sphene which may be easily recognised in hand specimens. Basic patches 
 richer in ferro-magnesian constituents and sphene than the main mass are not un- 
 common. Both in macroscopic and microscopic characters the specimens (6113- 
 6116) bear a very close resemblance to rocks from the Galloway district and especi- 
 ally to those from the Criffel mass. They are also allied to rocks occurring in the 
 neighbourhood of Ballachulish. 
 
 The hyperites (4743, 4744) are extremely interesting as furnishing another bond of 
 union between the later intrusive rocks of the Cowal district and those of Galloway. 
 The description of these rocks which has been given in the text may be compared 
 with that of the Galloway hyperites already published in the Memoir on Sheet 5. 
 
 A word or two is necessary as to the use of the term lamprophyre. Professor 
 Rosenbusch says* : " I adopt Giimbel's term lamprophyre for a group of dyke-rocks 
 which occur in folded districts, and which, in respect of mineralogical composition, 
 belong in part to syenitic and in part to dioritic types. They are characterised 
 macroscopically by a fine grained, compact or porphyritic structure, by a grey or 
 black colour when in a fresh condition, and by a great tendency to decomposition 
 accompanied by a rich development of carbonates. In the porphyritic varieties, 
 apart from certain rare exceptions and some transitional forms, the phenocrysts 
 belong to ferriferous minerals of the mica-, augite-, and hornblende-families .... 
 felspar rarely occurs as a phenocryst." 
 
 In the rocks of the Cowal district which answer in a general way to the above 
 description the dioritic types prevail. Of the three minerals, augite, biotite, and 
 hornblende, the first is the one most commonly found, although it is frequently not 
 the most abundant. Unlike the common type of augite in dolerites and diabases it 
 is colourless or nearly so in thin section, and shows a strong tendency to idiomorph- 
 ism, frequently occurring in large phenocrysts. Hornblende and biotite occur 
 separately or together, and seem more or less to replace each other. The former is 
 often developed in long brown prisms. These three minerals occur in a felspathic 
 matrix. 
 
 Plagioclase is seen to be the dominant felspar when the rocks are sufficiently well 
 preserved to allow of the determination of the mineral. It may occur in large 
 irregular grains, or in zoned and more or less idiomorphic individuals. In the latter 
 case a little interstitial quartz may. occasionally be detected (3417). When the 
 darker rock contains pink patches (4012) these are largely composed of orthoclase, 
 and it is probable that this mineral is frequently present, in small quantities, in many 
 of the other rocks. 
 
 Names such as diorite, camptonite, augite-diorite, mica-dolerite or diabase, kersau- 
 tite, and vogesite might be applied to different varieties ; but as these varieties can- 
 not be systematically separated in the field, and as the state of preservation of the 
 rocks is often such as to render their precise determination impossible, even with the 
 aid of microscopic sections, it has been found necessary to group them together under 
 the comprehensive but somewhat ill-defined term lamprophyre. 
 
 The porphyrites of the Cowal district are essentially similar to those of Galloway 
 described in the Memoir on Sheet 5. They represent the porphyritic phase of a 
 
 Mikroskopische Physiographic der massigen ttesteine. II. Edition 1887, p. 308. 
 
DESCRIPTION OF AN ALBITE SCHIST. 299 
 
 hornblende -granitite or quartz -mica-diorite. The ground-mass may be micro-granitic 
 felsitic, or even microhtic, as in some andesites. 
 
 In addition to the normal porphyrites, with numerous phenocrysts of plagioclase 
 biotite, and hornblende, there are many light coloured rocks for which the term 
 felsite is retained. These rocks are often so much altered that their precise deter- 
 mination is impossible. In many cases they are merely altered porphyrites but one 
 specimen from the north-west side of Loch Fine, belonging to this group (4806) 
 contains large Carlsbad trains of altered orthoclase similar in form and size to the 
 crystals of sanidine in the J)rachenfels trachyte. It is probable, therefore, that some 
 ortho-felsites are included in this group. True quartz-porphyries appear to be absent 
 but the porphyrites occasionally contain a few scattered phenocrysts of corroded 
 quartz, and such varieties must be classed as quartz-porphyrites. 
 
 II. DESCRIPTION OF AN ALBITE SCHIST NEAR ARD A' CHAPUILL. 
 BY Mu TEALL. 
 
 Slide 3418. | mile E.N.E. of Ard a' Chapuill (182). 
 
 Macroscopically this rock consists of narrow wavy folia of white granulitic quartz 
 and a grey highly micaceous schist. The micaceous portions of the rock contain 
 numerous crystals of a glassy -looking mineral, having well-marked cleavages. These 
 crystals measure on the average about 1 mm. across. They give a porphyritio 
 aspect to the rock. Isolated grains, tested by Szabo's method, give a strong soda 
 colouration to the flame of a Bunsen's burner ; but it is impossible to obtain frag- 
 ments sufficiently large to yield perfectly satisfactory results by this method. So far 
 as they go, they point to a felspar rich in soda. 
 
 More satisfactory results are obtained by examining crushed grains under the 
 microscope. AVhen mounted in hard balsam, and examined in parallel light, the 
 refractive index of the mineral is seen to be almost exactly that of the balsam, which 
 is about 1*536. A crushed albite mounted in the same way shows precisely the 
 same refractive phenomena. In both cases the flakes which show the somewhat 
 oblique emergence of a positive bisectrix, and which therefore contain approximately 
 the greatest and mean axes of elasticity, nearly disappear when viewed by rays vibrat- 
 ing at right angles to the trace of the optic axial plane, but stand out distinctly when 
 viewed by rays vibrating parallel to the trace of the plane. From this it follows that 
 the mean and least refractive indices of the mineral are the same as those of albite, or 
 at any rate that the difference is less than 2 in the third place of decimals (refractive 
 indices for albite n g T540, n m 1-534, ni 1-582). Another point of agreement with 
 albite is the extinction angle in flakes which show the oblique emergence of a 
 positive bisectrix. This varies from 19 to 21 in the positive direction. 
 
 An attempt was made to isolate the mineral, but it was found impossible to obtain 
 it in a pure state, in consequence of the inclusions which are especially abundant in 
 the central portions of the individuals. The material analysed floated in a solution 
 of sp. gr. 2'643. It yielded the following result : 
 
 SiOo, 81-4 
 
 Hfc I 
 
 CaO, 
 
 MgO, 
 
 Na 2 0, 
 
 Ignition, 
 
 99-1 
 
 It is evident from this that the substance analysed consisted essentially of a 
 mixture of albite and quartz, in about equal proportions. The analysis was merely 
 undertaken for the purpose of verifying the results obtained by the other methods. 
 
 When the rock is examined in thin section under the microscope it is seen to 
 consist of albite, quartz, white-mica, chlorite, magnetite, and tourmaline. 
 
 The albite occurs as more or less idiomorphic crystals, and also as grains with some- 
 what irregular boundaries. Sometimes a patch" of albite consists of four or five 
 individuals. The substance of the albite is water clear, and never shows a trace of 
 alteration. The cleavages are often well marked in the section. The individuals are 
 
300 GEOLOGY OF COWAL. 
 
 generally simple, and the sections are of fairly uniform dimensions in the different 
 directions. Binary twins may occasionally be observed. Lamellar twinning is 
 entirely absent. Magnetite occurs as inclusions, especially in the central portions 
 of the individuals, but the grains are smaller and less numerous relatively to the 
 enveloping matrix than those occurring in the groundmass of the schist. It is 
 especially worthy of note that the foliation of the rock, as defined by the stream-like 
 arrangement of the grains of magnetite, is seen in the central portions of the 
 albite crystals. In addition to the magnetite, we rind also numerous minute and 
 nearly colourless prismatic microlites occurring as inclusions in the albite. 
 
 The quartz occurs in irregular grains of variable size, and is for the most part singu- 
 larly free from inclusions. 
 
 "White-mica is present both in large and small plates. There is a considerable 
 amount of confusion in its mode of arrangement ; and plates may not unfrequently 
 be seen having their broad flat surfaces oblique or even at right angles to the general 
 plane of schistosity. 
 
 The chlorite is not a very important constituent of the rock. Sections at right 
 angles to the flat surfaces of the scales are strongly pleochroic. The colour for rays 
 vibrating at right angles to the basal plane is yellow, that for rays vibrating parallel 
 to the basal plane is green. Cross sections polarise in the neutral tints of the first 
 order, and the minor axis of depolarisation is always at right angles to the length of 
 the section, i.e., to the basal plane. Observations on the flakes of the chlorite from 
 an allied rock show that it is uniaxial. It belongs therefore to the pennine group, 
 and the double-refraction is positive. 
 
 Magnetite occurs abundantly in the form of opaque grains. That the grains are 
 magnetite has been proved by isolation and treatment with acids and a weak magnet. 
 Small grains of rutile are often associated with the magnetite. 
 
 Tourmaline occurs as an accessory constituent. It is present in the form of small 
 prisms. The larger individuals are pleochroic in pale rose-colour and deep bluish - 
 grey tints. They often lie with their longer axes at right angles to the plane of schis- 
 tosity, as if they had been developed in sitd after the schistosity had been produced. 
 
 The minerals above described are not uniformly distributed throughout the rock. 
 A section at right angles to the general trend of the foliation is seen to be made up 
 of wavy lenticular bands which vary in composition. Thus we have folia which 
 consist almost entirely of quartz, and others which consist mainly of large flakes of 
 white-mica. These alternate with bands composed of smaller scales of white-mica, 
 magnetite, chlorite, and a little granulitic quartz and felspar. It is in these bands 
 that the albite occurs. The white-mica ends oif abruptly where it comes against the 
 albite, and never occurs as inclusions in that mineral. The streams of magnetite, on 
 the other hand, are continued through the albite. The foliation planes between the 
 individual crystals of albite are often puckered, and it is possible that this may be a 
 result of the crystallisation of the albite. In the thin section the total space occupied 
 by the albite is about equal to that occupied by the schistose groundmass in those 
 bands in which the albite occurs. The foliation of the rock is not even and regular, 
 but wavy and of the flaser type. 
 
 III. LIST OF MICROSCOPE SLIDES. 
 
 Schists S.E. of the Bull Rock Greywacke. 
 
 2834. Near Toward schist-boundary (194). 
 
 2835. Near schist-boundary S. of Indian pier. 
 
 4840. $ mile E. of Indian Hill. 
 
 4841. J mile W. of Toward schist-boundary. 
 Bull Rock Greywacke. 
 
 3823. Bullwood, Dunoon. 
 
 3824. Same locality. 
 Dunoon Phyllite Series. 
 
 3825. Bullwood, Dunoon. 
 
 3826. Same locality. 
 
 3827. Same locality. 
 
 Schistose Grits and Greywackes N. W. of Dunoon Phyllites. 
 
 3828. 1 mile E.S.E. of Lephinkill (172). 
 3834. Fearna Bagh (182). 
 
 4731. 1 mile N.N.W. of Ben Donich (134) : with tourmaline. 
 5295. Tom an lasgaire (152). 
 Pegmatites, with Albite, in Schistose Grit. 
 4198. i mile N.E. of Mark (163). 
 7314. 50 yards S. of the Bull Hock (184). 
 
LIST OF MICROSCOPE SLIDES. 3 01 
 
 " Green Beds." 
 
 2830. 1 mile S.W. of Ardnadani Farm (184). 
 
 2831. Burn \ mile N. of Bishop's Seat (183). 
 
 3791. 150 yards W. of Conchra (162). 
 
 3792. 200 yards S.E. of Ardiiadam Farm (174). 
 
 3793. \ mile S. of Ardnadani Farm. 
 
 3794. \ mile N. W. of Blairbuie (183) : with (?) albites. 
 
 3795. Tighnuilt, Inverchaolain (183). 
 
 3829. Lephinkill (172). 
 
 3830. Same locality \ with garnets. 
 
 3831. | mile slightly N. of E. of Lephinkill : with albites. 
 
 3832. \ mile S. E. of Lephinkill : with albites. 
 
 4726. \ mile N.W. of Mullach Coire a Chuir (142) : with albites. ~ . 
 
 4727. 1 mile slightly S. of E. of Dundarave Castle (133) : with albites. 
 
 4728. \ mile S.E. of Crunch narn Mult (134). 
 
 4729. Same locality. 
 Albite Schist. 
 
 2957. i mile N. of Cruach iiam Cuilean (172) : pegmatite. 
 3418. * mile E.N.E. of Ard a' Chapuill (182). 
 
 3833. Nearly 1 mile E. of Lephinkill (172). 
 3866. Coast f mile N.N.E. of Knap (164). 
 
 4197. i mile N.W. of Ben Reithe : junction of lamprophyre sheet with albite 
 schist. 
 
 4732. A little over \ mile N.N.E. of Ben Lochain (142) : thiu band in 
 
 albite schist. 
 
 4733. Beiun Tharsuinn (142) : altered near basalt. 
 
 4734. \ mile W.S. W. of Drimsynie (142) : altered near basalt. 
 
 4738. H mile slightly W. of S. of Carrick Castle (153) : altered near basalt. 
 
 5214. Head of Stuck Burn (152). 
 
 5215. Same locality. 
 
 5432. $ mile slightly N. of E. of Mid Letter (141). 
 
 6101. River Fine a little over \ mile N.W. of Chruac Tuirc (126): altered 
 
 near granite. 
 
 6102. Garbh Allt Mor \ mile S.E. of Achaduiiau (126) : with garnets. 
 8111. \ mile N.W. of Lochan Mill Bhig (126) : with ganiets. 
 
 Loch Tay Limestone and Bands in it. 
 
 4730. Not quite \ mile E.N.E. of Bathaich ban Cottage (134). 
 5133. Not quite \ mile E.N.E. of Bathaich ban Cottage (134). 
 
 5135. Not quite \ mile S. of Cruach nan Capull (141). 
 
 5136. Not quite | mile S. of Cruach nan Capull (141). 
 6213. 1 mile slightly E. of N. of Socach (141). 
 
 5546. Same locality. 
 
 5547. Same locality. 
 Garnetiferous Mica Schists. 
 
 4739. i mile W. of Bathaich ban Cottage (133 and 134). 
 
 6103. | mile slightly S. of W. of the Eagle's Fall (126). 
 Graphitic Schists. 
 
 5053. H mile S.E. of St Catherine's pier. 
 
 5054. % mile slightly N. of W. of Cruach nan Capull (133) : knotted schist. 
 
 5055. Burn 1 mile slightly S. of E. of St Catherine's pier. 
 Ardrishaig Phyllite Series. 
 
 5053. \\ mile S.E. of St Catherine's pier. 
 
 5054. | mile slightly N. of W. of Cruach nan Capull (133) : knotted schist. 
 
 5055. Bum 1 mile slightly S. of E. of St Catherine's pier. 
 Andalusite Hornfels. 
 
 6098. Top of Chruac Tuirc (126). 
 
 6099. Near above locality. 
 
 6112. & mile S.E. of Cruach Tuirc. 
 Quartz-horntlende Schist. 
 
 6100. River Fine | mile slightly N. of W. of Cruach Tuirc, 
 Schist altered near Basalt. 
 
 4737. 1 mile S.W. of Benin Mhor (163). 
 Schist Crushed near Intrusion in Donich Burn. 
 
 4735. Stream mile E.X.E. of Ben Donich Lodge (142). 
 Hornblende Schist and Epidiorite Group. 
 
 2832. 230 yards N.N.W. of Hunter's Quay (174). 
 
 4000. Stralachlan (151). 
 
 4003. Kilbride Chapel, Stralachlan : "eye" in the schist. 
 
 4005. Kilbride Chapel, Stralachlan. 
 
 4006. N. of Kilbride Chapel, Stralachlau. 
 
302 GEOLOGY OF COWAL. 
 
 4008. i mile N. of Stralachlan. 
 
 4740. i mile E.N.E. of Cruach nam Mult (134). 
 
 5056. T \ mile N.E. of Ardchyline (133). 
 
 5057. T V mile S. W. of St Catherine's pier (133). 
 
 5058. From spoil heap of quarry 50 yards N. of St Catherine's old chapel. 
 
 5059. T \ mile S.W. of St Catherine's pier. 
 
 5060. 130 yards E. of St Catherine's pier. 
 
 5061. Block in low sea wall mile N.E. of St Catherine's. 
 
 5062. Loose block near St Catherine's. 
 Serpentine and Allied Bocks. 
 
 2833. S. of Inellan pier (195). 
 
 4004. Glendaruel (162). 
 
 4369. Near Kilbridemore (162) : interior of mass. 
 
 4370. Same locality : dyke-like band in serpentine complex. 
 
 4837. I mile S.W. of Chapel ton (194). 
 
 4838. Toward schist-boundary fault : ferriferous dolomite with patches of 
 
 serpentine. 
 
 4839. Same locality : schistose crush rock of carbonates and talc. 
 Granitite. 
 
 6113. River Fine T \ mile slightly S. of E. of Newton Hill (126). 
 
 6114. River Fine mile S. E. of Newton Hill. 
 
 6115. River Fine ^ mile E.S.E. of Newton Hill : with inclusion. 
 
 6116. Boulder by road mile N.E. of Achadunan. 
 Hornblende -porphyrite. 
 
 6109. mile slightly N. of W. of Cruach Tuirc (126) : middle of sheet. 
 
 6110. Same locality : 2 inch off top of sheet. 
 
 6117. & mile S.W. of Cruach Tuirc : altered near a crush. 
 Felsite. 
 
 4013. Acharosson Burn, Kilnnan (182). 
 
 4741. f mile S.S.W. of Stob an Eas (134). 
 
 5063. 230 yards slightly E. of S. of Ard na Slaite (133). 
 5066. i mile S.E. of St Catherine's pier (133). 
 
 Hyperite. 
 
 4743. Donich Burn 1 mile above Donich Lodge (142). 
 
 4744. f mile N. of Ben Donich (134). 
 The (?) Intrusive Andesite near Inellan. 
 
 2837. Near Inellan Perch (195) : the most northerly exposure of this ruck. 
 Trachytic Dykes. 
 
 2960. N.N.E. dyke in Allt na Airidh Loisgte (burn | mile E. of Cruach Mhor, 
 
 162) : spherulitic edge. 
 
 2961. i mile S.E. of Dun Mor (172). 
 
 2962. 200 yards W. of Craigendaive (172) : spherulitic edge. 
 
 3452. Judge's Chair, Dnnans Burn, 162 ft mile S.E. of the "D" of 
 
 " Dunans"). 
 
 3921. 200 yards W. of Craigendaive (162) : spherulitic edge. 
 
 3922. I mile S.E. of Dun Mor (172). 
 
 a. Next to selvage. 
 
 b. Intermediate portion. 
 
 c. Furthest from selvage. 
 
 Pebble of Igneous Eock from the Upper Old Red Conglomerate. 
 
 2836. i mile W. of Toward Point (194). 
 Partially fused Biotite Schist from a Vitrified Fort. 
 
 5083. Island 1 mile N.W. of Colintraive. 
 
 5084. Same locality. 
 
 Lamprophyre Group. 
 
 2838. \ mile S.S.W. of Cnoc Madaidh (173): with hornblende. 
 
 2839. 300 yards N. of the Craig (183) : with malacolite and hornblende. 
 
 2840. 160 yards N.W. of Doire Dairach ft mile E.N.E. of Drynain, 164). 
 
 2958. i mile S.W. of Glenmassan (163). 
 
 2959. 1J mile S.S.E. of Craigendaive (172). 
 
 3417. Old Chapel, Cnoc Dubh (182) : allied to kersantite. 
 
 3453. % mile S. of " I " of "Tom an lasgaire " ft mile N.N.W. of the " P " of 
 
 " Dornoch Point," 152) : with hornblende. 
 3835. J mile N.E. of Ben Bhreac (153) : with hornblende. 
 
 4011. Stralachlan (151) : kersantite. 
 
 4012. Barnacarry, Stralachlan : kersantite. 
 4015. Craig Lodge, Loch Riddon. 
 
 4197. i mile N.W. of Ben Reithe v (142) : spherulitic; junction withal bite schist. 
 
LIST OF MICROSCOPE SLIDES. 303 
 
 4369. Kilbridemore Burn (162). 
 
 4742. \ mile slightly AY. of S. of Bathaich ban Cottage (134) : mica trap. 
 
 4745. | mile N. of Ben Donich. 
 
 4746. A little over \ mile S. of Bathaich ban Cottage (134) : phenocrysts 
 
 of malacolite. 
 
 4752. The most W. of the two dykes ^ mile E.N.E. of Cruach nani Mult (134) : 
 
 augitic mica trap. 
 
 4755. f mile N.N.E. of Stob an Ens (134) : biotite dolerite. 
 5067. % mile S.W. of St Catherine's pier (133). 
 
 5064. 1 mile slightly E. of S. of St Catherine's pier (133). 
 
 6107. * mile W.N.W. of the Eagle's Fall (126). 
 Camptonite Type. 
 
 4747. 100 yards S.E. of Bathaich ban Cottage (134). 
 
 4748. mile W.X.W. of Loch Kestil outlet (134). 
 
 4749. ^ mile E. of Mouovechadan (134). 
 
 4750. Not quite mile S.S.E. of Bathaich ban Cottage (134). 
 
 4751. $ mile W. of Loch Restil outlet (134). 
 
 4753. Portion of upper sheet mile S.E. of Loch Restil head (134). 
 
 4754. Lower portion of lower sheet, same locality. 
 
 5065. Y V mile slightly N. of E. of St Catherine's (133). 
 Crushed or Foliated. 
 
 6104. ^ mile W.N.W. of Cruach Tuirc (126). Hornblende-mica-schist. 
 
 6105. i mile less 50 yards N.E. of Achaduuan (126) : calc-chlorite-schist. 
 
 6106. | mile E.N.E. of Achadunan (126). 
 
 6108. i mile E.S.E. of Achaduuau. 
 
 Basaltic Group. 
 
 Sith an' t-Slnain (152) Dolerite Boss. 
 
 5438. Interior of intrusion. 
 
 5439. Edge of intrusion. 
 
 5440. Felspar-augite vein. 
 Early E. to W. Dykes. 
 
 2841. a. The broad dyke in Easau Biorach (the stream \ mile S.W. of Bodach 
 
 Bochd, 183). 
 b. Red vein in above dyke. 
 
 2843. The broad dyke S. of Larach Hill (164). 
 
 4199. f mile E. of Donich Lodge (142). 
 
 4200. Reddish less basic band in above dyke. 
 
 4756. Not quite f mile S. of Bathaich ban Cottage (134). 
 Later Dykes. 
 
 2842. By the big bend in Inverchapel Burn (164). 
 
 2844. The N.W. running dyke S. of Larach Hill (164): porphyritic olivine 
 
 dolerite. 
 
 2845. 200 yards S. of Brackleymore school (194) : porphyritic olivine dolerite. 
 
 2846. Same locality : companion dyke. 
 
 2847. Same locality : companion dyke : glassy basalt. 
 
 2848. f mile above foot of Invervegain Burn (183) : edge of dyke ( ? basalt). 
 
 2849. mile W. of Toward Lighthouse (194) : hard band in dyke in old beach : 
 
 porphyritic basalt. 
 
 2850. Kasau Biorach (stream f mile S.W. of Bodach Bochd, 183) : most N. of 
 
 the N.W. running dykes : tachylite. 
 
 2851. i mile S. of the foot of Easan Biorach : perlitic tachylite. 
 
 2852. i mile E. of Cloiueter Hill (100 yards N. of the "i" of " Buthkollidar," 
 
 184): tachylite. 
 
 3268. i mile slightly N. of E. of the Clachau of Glendaruel (172) : part of a 
 
 " core" : andesitic glass. 
 
 3269. i mile slightly N. of E. of the Clachau of Gleudaruel : part of a " sheath " : 
 
 andesitic glass. 
 
 3270. N.E. corner of 172 N.E. W . (i mile S.W. of Cruach Mhor) : andesite, 
 
 tholeite type). 
 
 3271. | mile S.E. of Lower Duillater (162) : audesite, tholeite type. 
 4014. Near Glendaruel House (162) : porphyritic dolerite. 
 
 4016. Otter 3| miles N.E. of (171) : pyroxene audesite glass. 
 
 5435. Not quite \ mile X.E. of Tigh na Cliche (141): dolerite with zeolite 
 
 amygdules. 
 
 5436. 100 yards W.S.W. of Mid Letter (141): dolerite with chlorophaeite 
 
 amygdules. 
 
 6437. 250 yards N.N.E. of MTlmu's Cairn (141): dolerite with olivine pseudo- 
 niorphs. 
 
304 
 
 GEOLOGY OF COWAL. 
 
 IV. LIST OF GLACIAL FOSSILS. 
 
 The collections of glacial fossils from the different localities were made by Mi- 
 James Beunie of the Geological Survey, aud we have been much indebted to the late 
 Dr David Robertson, the veteran naturalist of Cumbrae, for their determination. A 
 list of glacial fossils previously noted in the district is given by Messrs Crosskey and 
 Robertson in their paper 011 the "Post-Tertiary Fossiliferous Beds of Scotland" 
 (Trans. Geol. Soc. Glasgow, vol. v. p. 29, 1875). See also the Catalogue of Western 
 Scottish Fossils, compiled by James Armstrong, John Young, M.D., and David 
 Robertson, 1876. 
 
 We give first a list of the exact localities from which the collections were made, 
 and then the list of fossils. In the last list there are ten columns at the right hand 
 side, a column for each locality. The localities at which each fossil was collected are 
 denoted by crosses in the columns belonging to these localities. 
 
 Localities. 
 
 1. mile above Ormidale on N.E. (left) bank of River Ruel, and 70 yards up the 
 
 river above this locality, on same side of the river : about 5 miles N.N.W. of 
 Colin traive. 
 
 2. By Springfield House (182), below high-water mark: 3 miles N.N.W. of 
 
 Colintraive. 
 
 3. Port an Eilein (182), below high-water mark : 2 miles N.W. of Colintraive. 
 
 4. N. side of Fearna Bagh : H mile N.W. of Colintraive. 
 
 5. | mile S. of Fearn'ach (182) : 1| mile N.W. of Colintraive. 
 
 6. \ mile N.W. of Colintraive pier. 
 
 7. Balnakailly Bay, N. end of Bute. 
 
 8. 80 yards N.E. of Toward Quay (194). 
 
 9. | mile N. of Gairletter Point (174), a little below high-water mark. 
 10. \ mile S. of Ardentinny (164), below high-water mark. 
 
 
 
 I 
 
 
 
 
 
 
 
 
 
 n 
 
 1 
 
 f c . 
 
 w 
 
 ' 1 
 
 S ' ^" 
 
 . 
 
 
 1 
 
 d 
 
 1 
 
 1 
 
 cD 
 
 m 
 
 ol 
 
 ! 1 
 
 i 
 
 1 
 
 1 
 
 
 "fl 
 
 
 
 S 
 
 | 
 
 i 
 
 cs | a 
 
 "3 
 
 1 
 
 *8 
 
 1 
 
 
 Q 
 
 02 
 
 
 N 
 
 * 
 
 
 
 W 
 
 H 
 
 o 
 
 *! 
 
 
 1 
 
 2 
 
 3 
 
 4 
 
 5 
 
 6 
 
 7 
 
 8 
 
 9 
 
 10 
 
 Plantce. Algce. 
 
 
 
 
 
 
 
 
 
 
 
 Melobesia, Linne. 
 
 
 
 
 
 
 
 
 
 
 
 $P 
 
 
 
 
 
 
 X 
 
 
 
 
 
 Protozoa. Foraminifera. 
 
 
 
 
 
 
 
 
 
 
 
 Miliolina. 
 
 
 
 
 
 
 
 
 
 
 agglutinans, D. Orb., 
 
 X 
 
 
 
 
 
 X 
 
 
 
 
 secaus, D. Orb., .... 
 
 
 
 
 
 
 X 
 
 
 
 x 
 
 
 oblonga, Montague, .... 
 
 
 
 
 
 
 X 
 
 
 
 X 
 
 
 semimulum, Linn., .... 
 
 
 
 
 
 
 X 
 
 X 
 
 X 
 
 x 
 
 X 
 
 subrotunda, Montague, 
 
 
 
 
 
 
 
 X 
 
 
 
 
 fusa, Brady, ..... 
 
 
 
 
 
 
 
 x 
 
 
 
 
 bicornis, Walker and Jacob, 
 
 
 
 
 
 
 
 
 X 
 
 
 
 Biloculina, D. Orbigny. 
 
 
 
 
 
 
 
 
 
 
 
 ringens, Lamk., .... 
 
 
 
 
 
 
 
 x 
 
 X 
 
 
 Lagena, Walker. 
 
 
 
 
 
 
 
 
 
 
 Isevis, Montague, .... 
 
 
 
 
 x 
 
 
 
 
 X 
 
 
 striata, D. Orb 
 
 
 
 
 
 
 X 
 
 
 
 
 semistriata, Will., .... 
 
 
 
 
 
 x 
 
 
 
 
 
 
 ,, var. apiculata, Reuss., . 
 
 
 
 
 
 
 
 X 
 
 
 
 x 
 
 distoma, Parker and Jones, . . < 
 
 
 
 
 
 
 X 
 
 
 
 
 marginata, W. and B., . . 
 acuticosta, Reuss., .... 
 
 
 
 x 
 
 
 
 X 
 X 
 
 
 x 
 
 
 lucida, Williamson, .... 
 
 
 
 
 
 
 X 
 
 
 
 
 Cristellaria, Lamarck. 
 
 
 
 
 
 
 
 
 
 
 
 rotulata, Lamk., .... 
 
 
 
 
 
 
 
 
 X 
 
 
 
LIST OF GLACIAL FOSSILS. 
 
 305 
 
 
 
 
 
 j. 
 
 
 
 
 
 
 
 ^ 
 
 
 oa 
 
 
 
 
 
 
 
 
 
 
 
 I 
 
 1 
 
 f^ 
 
 
 
 1 
 
 
 
 
 
 
 
 JS 
 13 
 3 
 
 1 
 
 8 
 
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 1 
 
 1 
 
 1 
 
 1 
 
 j 
 
 
 
 1 
 
 1 
 
 1 
 
 CC 
 
 1 
 
 ^ 
 
 1 
 
 1 
 
 1 
 
 08 
 
 1 
 
 
 9 
 < 
 
 
 1 
 
 2 
 
 3 
 
 4 
 
 -5 
 
 6 
 
 7 
 
 8 
 
 9 
 
 10 
 
 Protozoa. Foraminifera continued. 
 Polymorphina, D. Orbigny. 
 
 
 
 
 
 
 
 
 
 
 
 ovata, D. Orb., .... 
 
 X 
 
 
 
 
 
 
 
 
 
 
 lanceolata, Reuss., .... 
 
 
 
 
 X 
 
 
 
 
 
 X 
 
 X 
 
 augustion, Egger 
 
 
 
 
 
 
 
 X 
 
 
 
 
 Textularia, Defrance. 
 
 
 
 
 
 
 
 
 
 
 
 agglutiuans, D. Orb., 
 Bulimina, D. Orbigny. 
 
 
 
 
 
 
 
 X 
 
 X 
 
 
 
 elegantissima, D. Orb., 
 marginnta, D. Orb., .... 
 
 
 
 
 
 
 
 X 
 X 
 
 
 
 
 Bolivina, D. Orbigny. 
 
 
 
 
 
 
 
 
 
 
 
 punctata, D. Orb., .... 
 
 
 
 
 . 
 
 
 
 X 
 
 
 
 
 Discorbiiia, Parker and, Jones. 
 
 
 
 
 
 
 
 
 
 
 
 rosacea, D. Orb., .... 
 
 
 
 
 
 
 
 
 X 
 
 
 
 globularis, D. Orb., .... 
 
 
 
 
 
 
 
 
 X 
 
 
 
 Cassidulina, D. Orbigny. 
 
 
 
 
 
 
 
 
 
 
 
 crassa, D. Orb., .... 
 
 
 
 
 
 
 
 X 
 
 
 
 
 Trancatulina, D. Orbigny. 
 
 
 
 
 
 
 
 
 
 
 
 lobatula, Walker and Jacob, 
 
 
 
 
 
 
 
 
 X 
 
 
 
 Rotalia, Lamarck. 
 
 
 
 
 
 
 
 
 
 
 
 Beccarii, Linn., .... 
 
 
 
 
 X 
 
 
 X 
 
 X 
 
 X 
 
 X 
 
 X 
 
 Polvstomella, Lamarck. 
 
 
 
 
 
 
 
 
 
 
 
 macella, Fichtel and Moll, 
 
 
 
 
 
 
 
 
 X 
 
 
 
 crispa, Linn., ..... 
 
 
 
 
 
 
 
 
 X 
 
 
 
 striata-punctata, Fichtel and Moll, . 
 
 X 
 
 
 X 
 
 X 
 
 X 
 
 X 
 
 X 
 
 X 
 
 X 
 
 X 
 
 Arctica, Parker and Jones, 
 
 
 
 
 
 
 
 X 
 
 
 X 
 
 X 
 
 Nonionina, D. Orbigny. 
 
 
 
 
 
 
 
 
 
 
 
 depressula, Walker and Jacob, . 
 
 X 
 
 
 
 X 
 
 
 X 
 
 
 X 
 
 
 X 
 
 orbicularis, Brady, .... 
 
 
 
 
 X 
 
 X 
 
 
 X 
 
 X 
 
 X 
 
 >* 
 
 stellavia, D. Orb., .... 
 
 
 
 
 
 
 
 
 
 
 X 
 
 Spirobulina. 
 
 
 
 
 
 
 
 
 
 
 
 limbata, D. Orb., .... 
 
 
 
 
 
 
 
 
 X 
 
 
 
 Caecum. 
 
 
 
 
 
 
 
 
 
 
 
 glabrum, Mont., .... 
 
 
 
 
 
 
 
 
 X 
 
 
 
 Ech inodermata. Echinoidea. 
 
 
 
 
 
 
 
 
 
 
 
 Echinus, Linne. 
 
 
 
 
 
 
 
 
 
 
 
 Drobachiensis, Muller, 
 
 X 
 
 
 X 
 
 X 
 
 
 X 
 
 X 
 
 
 X 
 
 X 
 
 
 
 
 
 
 X 
 
 
 
 X 
 
 
 
 Spatungidfe. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 X 
 
 
 
 
 
 X 
 
 
 
 Annelida. Tubicola. 
 
 
 
 
 
 
 
 
 
 
 
 Serpula, Linne. 
 
 
 
 
 
 
 
 
 
 
 
 tiiijuetra, Martin, .... 
 
 
 
 
 
 
 X 
 
 
 
 
 
 vennicularis, Ellis, .... 
 
 
 
 
 
 
 X 
 
 
 
 X 
 
 
 Spirorbis, Lamarck. 
 
 
 
 
 
 
 
 
 
 
 
 communis, ..... 
 
 
 
 
 
 
 
 X 
 
 
 X 
 
 X 
 
 Crustacea. Ostracoda. 
 
 
 
 
 
 
 
 
 
 
 
 Cythere, Muller. 
 
 
 
 
 
 
 
 
 
 
 
 pellucida, Baird, .... 
 
 
 
 
 X 
 
 
 X 
 
 X 
 
 
 
 X 
 
 
 
 
 
 
 
 X 
 
 
 
 
 
 
 X 
 
 
 X 
 
 X 
 
 
 X 
 
 X 
 
 X 
 
 X 
 
 X 
 
 ,, =varidis, .... 
 
 
 
 
 
 
 
 X 
 
 
 
 
 ,, =reniformis, Baird, 
 
 
 
 
 
 
 
 
 x 
 
 
 
 albo-maculata, Baird, 
 
 
 
 
 
 
 
 
 X 
 
 
 
306 
 
 GEOLOGY OF COW At. 
 
 
 
 i 
 
 a 
 s 
 
 4 
 
 
 (jj 
 
 >> 
 
 i 
 
 B 
 
 
 
 Ormidale. 
 
 Springflelc 
 
 Port an Ei 
 
 - 
 
 1 
 
 
 Balnakaill 
 
 Toward Qi 
 
 Gairletter 
 
 Ardentinn 
 
 
 1 
 
 2 
 
 3 
 
 4 
 
 5 
 
 6 
 
 7 
 
 8 
 
 9 
 
 10 
 
 Crustacea. Ostracoda continued. 
 
 
 
 
 
 
 
 
 
 
 
 Cythere, Mutter. 
 
 
 
 
 
 
 
 
 
 
 
 cuneiformis, Brady, .... 
 
 
 
 
 
 
 
 
 x 
 
 
 
 
 x 
 
 
 x 
 
 
 
 X 
 
 x 
 
 X 
 
 x 
 
 x 
 
 angulata, G. 0. Sars, 
 
 x 
 
 
 
 X 
 
 
 X 
 
 x 
 
 X 
 
 x 
 
 X 
 
 tuberculata, G. 0. Sars, . 
 
 
 
 x 
 
 
 
 X 
 
 X 
 
 X 
 
 X 
 
 X 
 
 Dunelmenais, Norman, 
 
 x 
 
 
 
 
 
 
 
 
 
 
 con f usa, Norman and Brady, . 
 
 
 
 X 
 
 
 
 X 
 
 X 
 
 X 
 
 
 
 
 
 
 
 
 
 
 
 x 
 
 
 
 Cytheridea, Bosquet. 
 
 
 
 
 
 
 
 
 
 
 
 papillosa, Bosquet, .... 
 
 X 
 
 
 X 
 
 
 
 X 
 
 X 
 
 X 
 
 
 X 
 
 punctillata, Brady, .... 
 
 X 
 
 
 X 
 
 
 
 
 X 
 
 X 
 
 x 
 
 X 
 
 Loxoconcha, G. 0. Sars. 
 
 
 
 
 
 
 
 
 
 
 
 impressa, Baird, .... 
 
 
 
 
 
 
 
 
 X 
 
 
 
 tamarindus, Jones, .... 
 
 X 
 
 
 X 
 
 x 
 
 
 X 
 
 
 
 
 
 Cytherura, G. 0. Sars. 
 
 
 
 
 
 
 . 
 
 
 
 
 
 nigrescens. Baird, .... 
 
 X 
 
 
 
 
 
 x 
 
 
 
 
 
 similis, G. 0. Sars, .... 
 
 
 
 
 X 
 
 
 X 
 
 
 
 
 
 undata, G. 0. Sars, .... 
 
 X 
 
 
 
 
 
 X 
 
 
 
 X 
 
 X 
 
 clathrata, G. 0. Sars, 
 
 
 
 
 
 
 X 
 
 
 
 
 
 Cytheropteron, G. 0. Sars. 
 
 
 
 
 
 
 
 
 
 
 
 latissimuin, Norman, 
 
 X 
 
 
 x 
 
 
 
 X 
 
 
 
 X 
 
 X 
 
 declevis, Norman, .... 
 
 
 
 
 
 
 
 
 
 
 X 
 
 Sclerochilus, G. 0. Sars. 
 
 
 
 
 
 
 
 
 
 
 
 contortus, Norman, .... 
 
 X 
 
 
 
 
 
 
 
 
 X 
 
 
 Polycope, G. 0. Sars. 
 
 
 
 
 
 
 
 
 
 
 
 orbicularis, G. 0. Sars, 
 
 
 
 
 
 
 
 
 
 
 X 
 
 
 
 
 
 
 
 
 
 
 
 
 Cirripeda. 
 
 
 
 
 
 
 
 
 
 
 
 Balanus, Lister. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 x 
 
 
 
 x 
 
 X 
 
 
 
 
 
 X 
 
 
 
 X 
 
 
 
 
 
 X 
 
 
 porcatus, Da Costa, .... 
 
 X 
 
 
 
 
 
 
 
 
 X 
 
 
 Verruca, Schumacher. 
 
 
 
 
 
 
 
 
 
 
 
 stromia, Midler, .... 
 
 X 
 
 
 
 
 
 
 
 
 
 
 Mullusca. Conchifera. 
 
 
 
 
 
 
 
 
 
 
 
 Anomia, Linne. 
 
 
 
 
 
 
 
 
 
 
 
 ephippium, Linn., .... 
 
 X 
 
 
 X 
 
 x 
 
 
 X 
 
 
 
 
 
 ,, v&r. aculata, Linn., 
 
 X 
 
 
 
 
 
 
 
 
 
 
 Pecten, Pliny. 
 
 
 
 
 
 
 
 
 
 
 
 Islandicus, Mull., .... 
 
 X 
 
 
 
 X 
 
 
 X 
 
 
 
 X 
 
 X 
 
 Mytilus, Linne. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 x 
 
 
 
 
 
 
 
 
 modiolus, Linn., .... 
 
 X 
 
 
 
 
 
 X 
 
 
 
 
 
 Nucula, Lamarck. 
 
 
 
 
 
 
 
 
 
 
 
 tenuis, Mont., 
 
 
 
 
 
 
 
 
 
 
 x 
 
 Leda, Schumacher. 
 
 
 
 
 
 
 
 
 
 
 
 pygmse, Miinst., .... 
 Lucina, Bruguiere. 
 
 x 
 
 
 
 
 
 
 
 
 
 
 borealis, Linn., .... 
 
 
 x 
 
 
 
 
 
 
 
 
 
 Axinus, Sowerby. 
 
 
 
 
 
 
 
 
 
 
 
 
 X 
 
 
 X 
 
 
 
 X 
 
 X 
 
 
 
 
 Cardium, Linne. 
 
 
 
 
 
 
 
 
 
 
 
 Sn., , 
 
 
 
 
 
 
 
 
 
 x 
 
 
 
 
 
 
 
 
 x 
 
 
 
 
 
 
 
 
 
 
 
 
 x 
 
 
 
 
 Cyprina, Lamarck. 
 
 
 
 
 
 
 
 
 
 X 
 
 X 
 
 
 X 
 
 
 
 
 
 
 
 
 
 
LIST OF GLACIAL FOSSILS. 
 
 307 
 
 
 
 1 
 
 3 
 
 
 
 
 1 
 
 
 a 
 
 
 / 
 
 
 
 w 
 c 
 
 
 1 
 
 1 
 
 .d 
 
 2 
 
 i 
 
 I 
 
 I 
 
 fe 
 
 1 
 
 
 1 
 
 1 
 
 
 
 C8 
 g 
 
 08 
 
 1 
 
 1 
 
 1 
 
 1 
 
 1 
 
 
 | 
 
 
 1 
 
 cS 
 
 1 
 
 1 
 
 1 
 
 
 o 
 
 1 
 
 
 1 
 
 2 
 
 3 
 
 4 
 
 5 
 
 6 
 
 7 
 
 8 
 
 9 
 
 10 
 
 Mollusca Conchifera continued. 
 
 
 
 
 
 
 
 
 
 
 
 Astarte, Soiverby. 
 
 
 
 
 
 
 
 
 
 
 
 sulcata, Da Costa, .... 
 
 
 
 
 
 
 X 
 
 
 
 
 X 
 
 ,, var. elliptica, Brown, . 
 
 
 
 
 
 
 
 x 
 
 
 x 
 
 X 
 
 compressa, Mont., .... 
 
 
 
 
 
 
 
 
 
 X 
 
 X 
 
 Venus, Linne. 
 
 
 
 
 
 
 
 
 
 
 
 exoleta, Linn., .... 
 
 
 x 
 
 
 
 
 
 
 
 
 
 fascia ta, Da Costa. 
 
 
 
 
 
 
 
 
 
 
 
 Tellina, Linne. 
 
 
 
 
 
 
 
 
 
 
 
 calcaria, Chcmn., .... 
 
 x 
 
 
 x 
 
 x 
 
 
 X 
 
 X 
 
 X 
 
 X 
 
 X 
 
 Mya, Linne. 
 
 
 
 
 
 
 
 
 
 
 
 Sp. , . 
 
 
 
 
 X 
 
 
 
 X 
 
 
 
 
 truncata, Linn., .... 
 
 X 
 
 X 
 
 
 
 
 X 
 
 
 
 X 
 
 X 
 
 ,, var. Uddevallensis, . 
 
 
 x 
 
 
 X 
 
 
 
 X 
 
 
 X 
 
 X 
 
 Saxicava, Fleurain de Bellevue. 
 
 
 
 
 
 
 
 
 
 
 
 
 X 
 
 
 
 
 
 x 
 
 X 
 
 
 X 
 
 
 Gasteropoda. 
 
 
 
 
 
 
 
 
 
 
 
 Chiton, Linne. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 X 
 
 
 
 
 
 Tectura, Citvier. 
 
 
 
 
 
 
 
 
 
 
 
 virginea, Mull., .... 
 
 X 
 
 
 
 X 
 
 
 X 
 
 
 
 X 
 
 
 Puncturella, R. T. Lowe. 
 
 
 
 
 
 
 
 
 
 
 
 Noachiua, Linn. t .... 
 
 X 
 
 
 
 
 
 
 
 
 
 
 Trochus, Rondeletius. 
 
 
 
 
 
 
 
 
 
 
 
 Sv . 
 
 
 
 
 X 
 
 
 
 
 
 
 
 helicinus, ..... 
 
 
 
 
 
 
 x 
 
 X 
 
 
 
 X 
 
 Grcenlandicus 
 
 
 
 
 
 
 X 
 
 
 
 
 
 cinerarius, Linn., .... 
 
 
 
 
 
 
 X 
 
 
 
 
 
 Mblleria, Jeffreys. 
 
 
 
 
 
 
 
 
 
 
 
 costalata, ...... 
 
 
 
 
 
 
 X 
 
 X 
 
 
 X 
 
 
 Lacuna, Turton. 
 
 
 
 
 
 
 
 
 
 
 
 divaricata, Fabr., .... 
 
 X 
 
 
 
 
 
 X 
 
 
 
 x 
 
 
 Littorina, Fenissac. 
 
 
 
 
 
 
 
 
 
 
 
 
 X 
 
 
 X 
 
 X 
 
 
 V 
 
 X 
 
 
 
 X 
 
 obtusata, Linn., .... 
 
 
 
 
 
 
 X 
 
 
 
 
 
 Rissoa, Freminville. 
 
 
 
 
 
 
 
 
 
 
 
 striata, Adams, .... 
 
 x 
 
 
 
 
 
 X 
 
 
 
 
 
 sereata, ...... 
 
 
 
 
 
 
 
 
 
 
 X 
 
 Xatica, Adamson. 
 
 
 
 
 
 
 
 
 
 
 
 affinis, Gmelin, .... 
 
 
 
 X 
 
 
 
 
 
 
 x 
 
 
 Groenlaudica, Bed., .... 
 
 X 
 
 
 
 
 
 
 
 
 
 X 
 
 Purpura, Bruguiere. 
 
 
 
 
 
 
 
 
 
 
 
 lappillus, Linn., .... 
 
 
 
 
 x 
 
 
 
 
 
 
 
 Trophon, De Montfort. 
 
 
 
 
 
 
 
 
 
 
 
 truncatus, Strom., .... 
 
 
 
 
 X 
 
 
 
 
 
 
 
 Pleurotoma, Lamarck. 
 
 
 
 
 
 
 
 
 
 
 
 pyramidalis, Strom., 
 turricula, Mont., .... 
 
 X 
 
 
 
 
 
 x 
 
 X 
 
 X 
 
 
 
 X 
 
 Since the above list was made up, Mr James Tod of Rashfield, Kilinun, has 
 informed us of two additional exposun s of glacial shell beds. One of these lies about 
 1 mile east of Rashfield, near the school-house, and the other is in the bed of the 
 river Echaig less than $ mile above Rashfield. From the former locality Mr Tod 
 forwarded some specimens, among which Mr James Bennie has determined the 
 following : Echinus, spines; Serpula vermicularis ; Balanus, plate ; Pec ten 
 Islandicus ; Cyprina Islandica ; Mya ; Astarte ; Leda ; Littorina littorea ; Littorina 
 rudis ; Purpura lapillus. 
 
308 GEOLOGY OF COWAL. 
 
 V. BIBLIOGRAPHY. 
 
 1800. JAMESON, ROBERT (Prof.). Mineralogy of the Scottish Isles. 2 vols. 4to. 
 Edinburgh. 
 
 1819. MACCULLOCH, JOHN, M.D. A Description of the Western Islands of Scotland 
 
 and the Isle of Man. London. 2 vols. 8vo, and 1 quarto vol. of 
 Plates. 
 
 1820. BOUE, AMI. Essai geologique sur L'Ecosse. 8vo. Paris (no date, but 
 
 probably 1820). 
 
 1823. SMITH, JAMES (of Jordauhill). ' On the Vitrified Forts on one of the Burnt 
 Islands, Kyles of Bute,' Trans. Antiq. Soc. Edin. and Trans. Roy. Soc. 
 Edin., vol. x. 79. 
 
 1839. SMITH, JAMES (of Jordanhill). 'On the Phenomena of the Elevated Marine 
 
 Beds of the Basin of the Clyde,' Mem. Wern. Soc. t vol. viii. p. . (Shells 
 of Balnakaille Bay.) 
 
 1840. MACCULLOCH, JOHN, M.D. A Geological Map of Scotland, with Memoir on 
 
 do. (published several years after Macculloch's death). 
 
 1844. NICOL, JAMES (Prof.). Guide to the Geology of Scotland. 8vo. Edin- 
 
 burgh. 
 
 1845. MACKAY, Rev. M. New Statistical Account of Scotland, Argyllshire, 
 
 Parishes of Duuoon and Kilmun, pp. 579-581. 8vo. Edin. and London. 
 
 1850. -MACLAREN, CHARLES. 'On Glacier Moraines in Glen Messan, Argyllshire,' 
 
 Rep. Brit. Ass. Trans, tint., vol. xix. p. 90, and Edin. New Phil. Jour., 
 vol. xlix. p. 330. 
 
 1851. HOPKINS, W. ' On the Granitic Blocks of the South Highlands of Scotland,' 
 
 Quart. Jour. Geol. Soc., vol. viii. p. 20. 
 
 1852. SHARPE, D. ' On the Southern Border of the Highlands of Scotland,' Quart. 
 
 Jour. Geol. Soc., vol. viii. p. 126. 
 SHAUPE, D. 'On the Arrangement of the Foliation and Cleavage of the Rocks 
 
 of the North of Scotland,' Phil. Trans., vol. cxlii. p. 445. 
 
 1855. MACLAREN, CHARLES. ' Notices of Ancient Moraines in the Parishes of 
 Strachur and Kilmun, Argyllshire,' Edin. New Phil. Jour., vol. i. New 
 Series, p. 189, and Proc. Roy. Soc. Edin., iii. 279 (1850-1857). 
 
 1858. NJCOL, JAMES (Prof.). Geological Map of Scotland. 
 
 1859. BRYCE, JAMES. The Geology of Clydesdale and Arran. 8vo. Glasgow. 
 
 1861. HARKNESS, Prof. R. ' On the Rocks of Portions of the Highlands of Scotland 
 
 South of the Caledonian Canal and on their Equivalents in the North of 
 Ireland,' Quart. Jour. Geol. Soc., vol. xvii. p. 256. 
 
 JAMIESON, T. F. ' On the Structure of the South- West Highlands of Scot- 
 land,' Quart. Jour. Geol. Soc., vol. xvii. p. 133. 
 
 1862. JAMIESON, T. F. 'On the Iceworn Rocks of Scotland,' Quart. Jour. Geol. 
 
 Soc., vol. xviii. p. 164. 
 
 SMITH, JAMES (of Jordanhill). Researches in Newer Pliocene and Post- 
 Tertiary Geology. 8vo. Glasgow. 
 
 MURCHISON, Sir R., and GEIKIE, A. First Sketch of a New Geological 
 Map of Scotland, with Explanatory Notes. 
 
 1863. NICOL, JAMES (Prof.). 'On the Geological Structure of the Southern 
 
 Grampians,' Quart. Jour. Geol. Soc., vol. xix. p, 180. 
 SORBY, H. C. 'On the Original Nature and Subsequent Alteration of Mica 
 
 Schist,' Quart. Jour. Geol. Soc., vol. xix. p. 401. 
 GEIKIE, A. (Sir). ' On the Phenomena of the Glacial Drift of Scotland,' 
 
 Trans. Geol. Soc. Glasg., vol. i. part ii. 
 1865. GEIKIE, A. (Sir). The Scenery of Scotland viewed in connection with its 
 
 Physical Geology. 8vo. London and Cambridge. (2nd edition, 1887.) 
 BRYCE, JAMES. The Geology of Arran and Clydesdale. 8vo. Glasgow. 
 
 New Edition of Work of 1859. 
 CROSSKEY, Rev. H. W. 'Glacial Deposits of the Clyde District,' Trans. 
 
 Geol. Soc. Glasg., vol. ii. p. 45. (Kyles of Bute.) 
 1868. ARGYLL, DUKE OF. ' On the Physical Geography of Argyllshire in connection 
 
 with its Geological Structure,' Quart. Jour. Geol. Soc., vol. xxiv, p. 255. 
 ARGYLL, DUKE OF. ' On Six Lake Basins in Argyllshire,' Quart. Jour. Geol. 
 
 Soc., vol. xxiv. p. 508. 
 HASWELL, JAMES.' On Columnar Structure developed in Mica Schist from 
 
 a Vitrified Fort in the Kyles of Bute,' Proc. Geol. Soc. Edin., vol. i. 
 
 p. 229. 
 1871. YOUNG, J. WALLACE. 'Miscellaneous Notes on Chemical Geology,' Trans. 
 
 Geol. Soc. Glasg., vol. iii. p. 28. (Read in May 1868.) 
 BELL, DUGALD. 'On the Aspects of Clydesdale during the Glacial Period,' 
 
 Trans. Geol. So;. Glasg., vol. iv. p. 63. 
 
BIBLIOGRAPHY. 309 
 
 874. BELL, DUGALD. ' Notes on the Glaciation of the West of Scotland with 
 reference to some recently observed instances of Cross Striation,' Trans. 
 Geol. Soc. Glasg., vol. iv. p. 300. 
 
 1875. CROSSKEY, Rev. H. W., and ROBERTSON, D. ' The Post-Tertiary Fossiliferous 
 
 Beds of Scotland' (Tighnabruaich, Kyles of Bute, and Loch Riddon), 
 Trans. Geol. Soc. Glasg., vol. v. p. 29. 
 
 GLEN, D. 0. ' On a Magnetic Sand from East Bay, Rothesay,' Trans. Geol. 
 Soc. Glasg. , vol. v. p. 158. 
 
 1876. ARMSTRONG, JAMES, YOUNG, JOHN, and ROBERTSON, DAVID. Catalogue of 
 
 the Western Scottish Fossils, with Introduction by Prof. Young, M.D., on 
 
 the Geology and Palaeontology of the District. 8vo. Glasgow. 
 1880. SORBY. H. C. Anniversary Address to the London Geological Societ} r , 
 
 vol. xxxvi. p. 46. 
 1883. MACADAM, W. IVISON. ' Preliminary Notice of a Clay Shell-Bed between 
 
 Newton and Strachur,' Trans. Geol. Soc. Edin., vol. iv. p. 94. (Read in 
 
 1881.) 
 MACADAM, W. IVISON. 'Further Notice of the Tigh-na-Criche Shell-Bed, 
 
 Loch Fyne,' ibid., vol. iv. p. 232. (Read 1882.) 
 MACADAM, W. IVISON. ' Notice of Veins of Specular Iron Ore at Strachur, 
 
 Argyllshire,' ibid., iv. 95. (Read in 1881.) 
 MACADAM, W. IVISON. 'On the Chemical Composition of certain Limestone 
 
 Rocks from Baltimore (Argyllshire),' ibid., vol iv. p. 101. (Read in 1881.) 
 1886. CADELL, H. M. 'The Dumbartonshire Highlands,' Scot. Geoyrapli. Mag., 
 
 vol. 2, p. 336. 
 ARGYLL, DUKE OF. ' Onr Highland Mountains,' Good Words for 1886, pp. 32 
 
 and 119. 
 
 1888. GEIKIE, Sir ARCHIBALD. ' The History of Volcanic Action during the 
 
 Tertiary Period in the British Isles,' Trans. Roy. Soc. Edin., vol. xxxv. 
 p. 21. 
 
 1889. ARGYLL, DUKE OF. 'On certain Bodies, apparently of Organic Origin, from 
 
 a Quartzite Bed near Inveravay,' Proc. Roy. Soc. Edin., vol. 21, p. 39. 
 1892. GEIKIE. Sir ARCHIBALD. Geological Map of Scotland reduced chiefly from 
 the Ordnance and Geological Surveys, with Explanatory Notes. Edin. 
 
 MILL, Dr HUGH ROBERT. 'The Clyde Sea Area,' Trans. Roy. Soc. Edin., 
 vol. xxxvi. p. 641. (Read May 1891.) 
 
 DAKYNS, J. R., and TEALL, J. J. H. 'On the Plutonic Rocks of Garabal 
 
 ill and Meall Breac,' Quart. Jour. Geol. Soc., vol. xlviii. p. 104. 
 1892-93. MUNRO, Dr ROBERT. 'Notes on Crannogs or Lake-dwellings in Argyll- 
 shire,' Pro. Soc. Antiq. Scotland, vol. xv. pp. 205-222. (Notices some in 
 Loch Askaig, near Tighnabruaich.) 
 
 1894. MURRAY, JOHN, and IRVINE, ROBERT. 'On the Manganese Oxides and 
 
 Manganese Nodules in Marine Deposits,' Trans. Roy. Soc. Edin., vol. 
 xxxvii. p. 721. 
 
 1895. BKLL, DUGALD. 'On the Origin of certain Granite Boulders in the Clyde 
 
 Valley,' Trails. GeoL Soc. Glasg., vol. x. p. 16. (Read in 1892.) 
 
 1896. In February, before Glasgow Geol. Soc. 
 
 MACNAIK, PETER, read a paper on 'The Altered Basic Rocks of the Highlands 
 as Exemplified by the Sill of Hornblende Schist underlying the Loch Tay 
 Limestone.' (Reported in Glasgow Herald for Feb. 18, 1896.) 
 
 ANDERSON, JAMES. ' Evidences of the Most Recent Glaciers in the Firth of 
 Clyde District,' Trans. GeoL Soc. Glasg., vol. x. p. 198. (Read Oct. 1894.) 
 
310 
 
 GEOLOGY OF COWAL. 
 
 INDEX 
 
 N.B. The figures in brackets after the names of places refer to the 6-inch Maps in 
 which these places occur. 
 
 ABEEFOIL, 83, 85, 89. 
 
 A' Chreachan (173), 182, 183. 
 
 A' Chruach (163), 183. 
 
 (172), 131, 146, 236. 
 
 (172), alluvial gravels near, 271. 
 
 (182), 40, 45, 77, 78, 80, 81, 121. 
 
 Ach Chreagach (181), 188, 189. 
 
 Achadalvory (193), 195. 
 
 Achadunan (126), 36, 43, 60, 98, 102, 
 
 122, 140, 159, 230, 280, 285, 287. 
 
 landslip near, 276. 
 
 old fort near, 258, 277. 
 
 Achanelid (162), 75. 
 
 (162), gravel mounds near, 272. 
 
 Achanlochan (193), 195. 
 
 (193), peat near, 273, 274. 
 
 Acharosson, 102, 151, 189, 190, 191, 192, 
 
 193, 292. 
 
 drift near, 249. 
 
 Burn, 3,105, 151, 190, 191, 192, 
 
 194. 
 
 alluvium of, 269. 
 
 peat near, 273. 
 
 ruined farm buildings near, 
 
 294. 
 
 till in, 249. 
 
 Actinolite, chlorite pseudomorphs after, 
 
 in garuetiferous schist, 50, 51, 77, 91, 
 
 280. 
 chlorite pseudomorphs after, in 
 
 foliated lamprophyre, 125. 
 - in epidiorites and hornblende 
 
 schists, 62, 63, 64, 180. 
 Admiralty Charts, 238, 284. 
 Agalmatolite, 103. 
 Agate, 130. 
 Aird Cottage (141), 54, 56, 57, 59, 60, 79. 
 
 (141), erosion terrace near, 265. 
 
 Airidh a' Ghobhaiim (133), 218 
 
 (133), boulder clay with shells near, 
 
 260. 
 
 (133), boulders on shore near, 262. 
 
 Alban, 4. 
 
 Albite crystals, age in relation to anda- 
 
 lusites, 101. 
 
 age in relation to garnets, 52, 91. 
 
 age in relation to movements in 
 
 schist, 39, 40, 41, 42, 76. 
 increase of size near anticline, 23, 
 
 41, 42, 43. 
 in "green beds," 34, 35, 37, 44, 
 
 86. 
 - -gneiss of the Alps, 297, 298. 
 
 Albite pegmatites, 10, 17,18, 34, 40, 43, 
 
 76, 149, 225. 
 
 -phyllites of Saxony, 297, 298. 
 
 schists and associated schists, 
 
 general descriptions of, 39-45, 295- 
 
 298, 299-300. 
 incidental references to, 5, 8, 
 
 23, 76, 77, 78, 79, 87, 88, 122, 123, 
 
 149, 156, 158, 279-280, 282. 
 in Beinn Mhor District, 208, 
 
 216. 
 
 in Blairmore District, 177, 180. 
 
 in Caniek District, 200-208. 
 
 in Cairndow District, 230, 
 
 233-234. 
 in Lochgoilhead District, 225- 
 
 229, 292. 
 in St Catherine's District, 230, 
 
 233-234. 
 altered by basaltic dr kes, 101, 
 
 149, 157, 158, 237. 
 
 altered by lamprophyres, 1 14. 
 
 near the granite, 91, 98, 99, 
 
 100, 101. 
 boulders, 236, 237, 253,254, 
 
 259. 
 of the Hoosac and Greylock 
 
 Mountains, 40, 297-298. 
 
 strise on veins in, 252. 
 
 with garnets, 48, 51, 52, 99. 
 
 Allothiclastic fragments in schists, 296. 
 
 See also Pebbles. 
 Allothigenic constitutents of schists, 295. 
 
 296. See also Pebbles. 
 Allt a' Chapuill (182), 186. 
 
 a Chaoruinn, 197. 
 
 an Eas, 194. 
 
 Buidhe (162), 154. 
 
 Coire Odhair (142), 228. 
 
 (142), landslip near, 276. 
 
 Criche (142), 229. 
 
 (142), landslip near, 276. 
 
 Dubh (182), 151, 195, 196. 
 
 (182), boulder clay in, 249. 
 
 Glac na maill (182), 23, 10S, 113, 
 
 18(5. 
 Glinne Mhoir (134), 42, 227, 230, 
 
 233, 283. 
 
 (134), ruined dwellings in, 293. 
 
 Guanan (142), 229. 
 
 (142), laminated clay near 
 
 foot of, 261. 
 Mor (182 and 193), 192, 195. 
 
INDEX 
 
 311 
 
 Alt Mor (182 and 193), glacial gravel 
 
 near, 249. 
 (182 and 193), reservoirs on, 
 
 293 
 
 Garbh (126), 43. 
 
 Osda (193), 3, 188, 197. 
 
 (193), alluvium of, 269. 
 
 (193), blown sand near, 276. 
 
 (193), in time of 100-foot 
 
 beach, 267. 
 
 (193), raised beaches near, 266. 
 
 Alltan nam Breac, 194. 
 
 Alluvium, freshwater (including deltas 
 
 and terraces), general description of, 
 
 268-272. 
 incidental references to, 182, 
 
 188, 200, 202, 210, 212, 224, 226, 228, 
 
 230, 240, 241, 243, 244, 246, 257,258, 
 
 259, 260, 261, 262, 264, 265, 266, 267, 
 
 273, 274, 275, 284, 293, 294. 
 marine (see also raised beaches), 
 
 general description of, 262-268. 
 incidental references to, 5, 
 
 189. 
 
 ALLPORT, S., 156. 
 Alps, albite-gneiss of, 297, 298. 
 Altgaltraig Point (182), 81. 
 
 (182), boulder clay near, 235. 
 (182), glacial sands and gravels 
 
 near, 242. 
 
 (182), granite boulders near, 237. 
 
 Am Binnein (164), 206, 207, 283. 
 
 (173), landslip on, 276. 
 
 AMI BOUE, 6. 
 
 Amphibolite, 65, 68. 
 
 Amygdules, doubtful, in foliated larap- 
 
 rophyres, 122, 123. 
 
 -in basaltic dykes, 107, 128-130, 
 
 137, 161, 162, 170, 194. 
 in lainprophyres and mica traps, 
 
 107, 114, 120-121. 
 
 in polished stone implement. 277. 
 
 in porphyrite, 105. 
 
 in Sith an t-Sluain dolerite, 164. 
 
 in trachytic dykes, 168, 170-171. 
 
 An Carr (141 and 152), 49, 51, 53, 63, 
 
 209, 284. 
 
 Cruachan, 62, 213, 214, 288. 
 
 boulder clay and drift near, 
 
 255, 256, 257. 
 
 boulder near, 254. 
 
 peat, 257. 
 
 Gnob (203), 150, 197. 
 
 Leacann (172), 141. 
 
 Stiobull (142),' landslip of, 28G. 
 
 t-Suil(172), 82. 
 
 Analcime, 93. 
 
 Analyses : of albite schist, 39. 
 
 of albite schist (portion of), 299. 
 
 of chlorite, 64. 
 
 of glacial shell clay, 261. 
 
 of Loch Tay limestone, 47. 
 
 of magnesiau limestone, 94. 
 
 of mica schist, 55. 
 
 of mica schist near iron ore veins, 
 
 289. 
 
 of phyllite, 39. 
 
 of pyritous ore, 58. 
 
 of specular iron ore, 289. 
 
 of trachyte, 170. 
 
 Analyses: partial, of Duuoon Castle dyke, 
 
 139. 
 
 of larnprophyre, 117. 
 
 of mica schist, 271. 
 
 of red strings in Dunoou Castle 
 
 dyke, 139. 
 
 Andalusite, 91, 98, 99, 100, 101. 
 ANDERSON, DANIEL, 1. 
 Andesite, Augite, 6, 126. See also Ba- 
 saltic Dykes. 
 
 boulders, 248. 
 
 doubtful intrusive, 6, 162-163. 
 
 Hypersthene-, of Cheviots, 155. 
 
 lavas of Bute, 92, 94, 163. 
 
 of Lome, no boulders from. 252, 
 
 253. 
 "Anticline," general accounts of, 8, 9, 
 
 82-83, 84-87. 
 incidental references to, 7, 61, 62, 
 
 79, 80, 81, 82, 89, 171, 179, 183, 186, 
 
 192-193, 194, 197, 200, 208, 216, 217, 
 
 225, 280, 281. 
 
 boulders from N.W. side of, 253. 
 
 increase of metamorphism u^ar, 
 
 7, 8, 22, 26, 27, 28, 39, 42, 43, 78, 
 
 90-91, 295-297. 
 
 structure of, near Carrick, 201-205. 
 
 movements, influence of, on earlier 
 
 structures, 9, 23, 26, 27, 83, 90, 208, 
 
 295. 
 schists, 23-29, 39-45, 76, 279-280, 
 
 282, 295-297. 
 absence of pieces of, in Upper 
 
 Old Red breccias, 92. 
 in Blah-more District, 179. 
 
 180. 
 in Cairndow District, 230, 
 
 233-234. 
 
 in Carrick District, 200-208. 
 
 in Colintraive District, 184, 
 
 185-187. 
 
 in Dunoon District, 171. 
 
 in Glen Massan District, 181- 
 
 183. 
 
 in Kilfinan District, 197, 198. 
 
 in Lochgoilhead District, 225- 
 
 229. 
 
 Antigorite, 74. 
 Apatite in albite-schist of Massachusetts, 
 
 297. 
 
 in albite schist zone, 44. 
 
 in igneous rocks, 67, 97, 156, 158. 
 
 Arable ground, 293. 
 
 Arbutus, 3. 
 
 Ard a' Chapuill (182), 40, 77, 79, 299. 
 
 na Gailich (133), 56, 64, 65, 105, 
 
 217. 
 (133), boulder clay with shells 
 
 near, 260. 
 
 na Slaite (133), 105, 140, 159. 
 
 Ardacheranbeg (172), 77. 
 
 (172), section in glacial deposits 
 
 near, 239-240. 
 Ardbeg (183), 88, 132, 143, 144, 145, 186. 
 
 (183), moraines near, 241. 
 
 (183), raised beaches at, 265. 
 
 Anlchyline (133), 56, 60, 64, 65, 84, 21 7, 
 
 218,. 220, 221, 224, 284. 
 Ardentinny, 2, 29, 38, 41. 61 , 81, 83, 
 
 108, 140, 171, 181. 
 
312 
 
 GEOLOGY OF COWAL. 
 
 Ardeiitinny, boulder clay near, 236. 
 
 boulder on shore at, 237. 
 
 erosion terrace at, 265. 
 
 glacial shell bed neur, 246, 247, 
 
 304-307. 
 
 sand and gravel near, 239. 
 
 section in schists south of, 18-22, 
 
 23, 26, 90-91. 
 Ardentraive (182), raised beaches at, 
 
 263. 
 Ardfillayne (184), 32, 33. 
 
 (184), cliff of raised beach at, 266. 
 
 Ardhallow (184), 178. 
 
 (184), superficial deposits near, 
 
 238. 
 Ardkinglas (134), 1, 33, 62, 78, 82, 88, 
 
 104, 110, 159, 132, 281. 
 
 (134), deltas near, 268. 
 
 (134), raised beaches, 264. 
 
 Ardlamont (203), 150, 196. 
 
 (203), boulder clay near, 249. 
 
 (203), old fort, 279. 
 
 (203), raised beach, 267. 
 
 (203), tillage ground near, 293. 
 
 Bay, 150. 
 
 granite boulder in, 250. 
 
 east and west basaltic dyke, 150- 
 
 151, 196, 197. 
 House, 150. 
 
 boulders near, 250. 
 
 Point, 150, 188, 191, 196. 
 
 islands near, in time of 100- 
 
 foot beach, 267. 
 Ardmarnock (192), 282. 
 
 (192), raised beaches at, 266. 
 
 (192), tillage ground near, 293. 
 
 Bay, 190, 191. 
 
 House, 191, 192, 292. 
 
 cairns near, 278. 
 
 granite boulders near, 250. 
 
 old forts near, 279. 
 
 peat near, 273. 
 
 sand and gravel pits near, 
 
 293. 
 Ardnadam, 33, 173, 176. 
 
 superficial deposits near, 239, 240. 
 
 Ardnagowan Cottage (141), 54, 57, 218, 
 
 220, 231. 
 Ardnahien (153), 203, 206, 207. 
 
 (153), boulders near, 254. 
 
 (153), raised beach, 262. 
 
 Ardno (133), 50, 51, 52, 53, 63, 104, 220, 
 
 222, 230, 232, 284, 291. 
 
 (133), boulders near, 254. 
 
 raised beaches, 264. 
 
 Ardrishaig, peat imported into, 292. 
 phyllites, general description of, 
 
 54-60. 
 incidental references to, 5, 
 
 7, 37, 52, 66, 67, 81, 85, 89, 280, 284, 
 
 288. 
 in Beinn Mhor district, 208, 
 
 209. 
 in Kilfinan District, 197, 198, 
 
 199. 
 in St Catherine's District, 
 
 217, 219. 
 
 Ardtarag (173), 80, 145, 171, 291. 
 (173), granite boulders near, 237. 
 
 (173), raised beaches, 265. 
 
 Ardyne Burn (194), 176, 177. 
 (194), arable ground near 
 
 293. 
 
 (194), boulder clay in, 238. 
 
 (194), glacial shell bed, 246. 
 
 (194), raised beaches at foot of, 
 
 263. 
 
 Point, 31, 178. 
 
 boulders on shore near, 248. 
 
 raised beaches, 265, 266. 
 
 267. 
 
 Arenig rocks of S. of Scotland, 89. 
 ARMSTRONG, JAMES, 304. 
 Arran Basin of the Clyde, 245. 
 
 glacial shell beds, 245. 
 
 Arrochar Highlands, 285. 
 
 moraines near, 286. 
 
 Asbestus, 64. 
 
 Ascog Point (Bute), 150. 
 
 Asgog(192), 195. 
 
 (192), boulder clay near, 249. 
 
 (192), tillage ground near, 294. 
 
 Bay (202), 196. 
 
 (202), raised beaches, 266, 
 
 267. 
 
 Loch (192), 188, 193, 194. 
 
 (192), crannogs, 279. 
 
 Assynt, camptonites of, 116, 122. 
 
 Astarte, 247, 260, 307. 
 
 Auchagoyl (193), 195, 292. 
 
 Cottages, moors once cultivated 
 
 near, 294. 
 
 raised beach at, 266. 
 
 Auchalick Bay (181), 49, 61, 188, 189 
 
 190. 
 
 Upper, ruined buildings at, 294. 
 
 Auchanaskioch (181), 190, 191, 291. 
 
 292. 
 (181), boulder clay near, 249. 
 
 (181), 100-foot beach, 266. 
 
 Upper, ruined buildings near, 
 
 293. 
 Auchateggan (172), 138, 185, 291. 
 
 (172), moraines near, 241. 
 
 Auchenbreck (172), 87, 185, 186, 291. 
 
 Auchnagarran (172), 184. 
 
 Augen (eye) structure, 34, 36, 62, 65, 
 
 66, 67, 69, 70, 71, 72, 73, 74. 
 Augite andesite, 6, 126. See also 
 
 Basaltic Dykes. 
 
 in hyperite, 105, 106. 
 (malacolite) in lamprophyres, 111, 
 
 112, 113, 115, 116, 117, 118, 124, 125, 
 
 297. 
 ophitic, 115, 130, 142, 154, 158, 
 
 164, 165. 
 Ausvveichung, or strain slip, foliation, 
 
 9, 12, 14, 19, 22, 25, 27, 41, 54, 59, 
 
 88, 204. 
 
 folding of, 14, 20, 23, 24, 28. 
 
 of "anticline" age, 14, 20, 
 
 24-28, 40, 60. 
 Authiclastic fragments in schists, 296. 
 
 See also Cracking. 
 Authigenic constituents of schists, 295, 
 
 296, 297. 
 Authimorphic constituents of schists, 
 
 296. 
 
 Axis of fold, pitch of, 59, 87. 
 use of term, 10, 59, 87. 
 
INDEX. 
 
 313 
 
 B 
 
 BADD, The, (183), 33, 130, 147, 175, 176, 
 
 177, 288. 
 The, (183), boulder clay near, 
 
 238. 
 
 The, (183), moraines near, 241. 
 
 Bagh Buic (192), 192. 
 
 (192), raised beaches, 266, 267. 
 
 Osde (203), blown sand in, 277. 
 
 See also Kilbride Bay. 
 Balanus or barnacle in glacial shell beds, 
 
 246, 247, 306, 307. 
 Balgie Burn (184), 173. 
 Balken structure, 73. 
 Ballachulish granitic rocks, 298. 
 
 pyrites in slate of, 80. 
 
 Balleineanoch (141), alluvium, 264, 269, 
 
 270, 271. 
 
 (141), moraines, 243, 256, 258,270. 
 
 (141), watershed between Loch 
 
 Fine and the Clyde near, 284. 
 Balliemore (173), 89, 111, 127, 137, 145, 
 
 161, 185, 214. 
 
 (173), boulder clay at, 236. 
 
 Ballimore (141), 46, 161, 224, 284. 
 
 (141), alluvium, 269, 270, 271. 
 
 (141), arable land near, 293. 
 
 (141), limekilns, 290. 
 
 (141), moraines, 270. 
 
 (171), cultivated land near, 294. 
 
 (171), old forts near, 278. 
 
 Ballochandrain (172), 49, 155, 200. 
 
 (172), alluvium, 269. 
 
 (172), stride near, 250. 
 
 Ballochyle (173), 106. 
 
 (173), boulder clay near, 236. 
 
 (173), glacial sands and gravels 
 
 near, 239. 
 
 (173), moraines near, 241. 
 
 (173), superficial deposits near, 
 
 264. 
 
 Hill, landslip on, 276. 
 
 Balnakailly Bay (Bute), glacial fossils of. 
 
 1, 304-307. 
 BARBOUR, 2. 
 Bargehouse Point (194), boulder clay at, 
 
 236. 
 
 Barnacabber (164), 206. 
 Barnacle (balanus) in glacial shell beds, 
 
 246, 247, 306, 307. 
 Barnacarry (151), 71, 115, 199. 
 
 (151), superficial deposits at, 251. 
 
 Burn, 155, 199, 120. 
 
 Barons Point, 83. 
 
 oarr an Longairt (151), 68, 71. 
 
 Ban- lola (171), old fort on, 278. 
 
 lolaich (192), 194. 
 
 Liath (193), 193, 195. 
 
 (193), reservoir near. 
 
 Ban- nan Damh (151), 67, 68, 69, 70, 
 
 199. 
 
 (191), 193. 
 
 BARROW, G., 18, 36. 49. 
 
 Barytes, 105, 125, 157, 234, 287, 289. 
 
 Basalt, bedded, of Mull, 140. 
 
 boulders, 242, 243. 
 
 quarries, 136, 137, 190, 194, 195, 
 
 290-291, 292. 
 
 Basaltic dykes, general description of, 
 
 126-150. 
 
 incidental references to, 6, 70, 
 
 .74, 75, 80, 89, 90, 94, 95, 96, 107, 
 
 108, 111, 113, 172, 173, 174, 175, 178, 
 
 179, 181, 182, 183, 184, 185, 186, 187, 
 
 237, 255, 265, 276, 282-283, 284, 290- 
 
 291, 292. 
 characters of east and west, 
 
 139-140, 142, 147, 156. 
 
 different ages of, 139-141, 147. 
 
 in Kilfman District, 152-151, 
 
 200. 
 in Strachur District, 155-162, 
 
 205, 207, 210, 211, 212. 213, 214, 215, 
 
 216, 222, 230. 
 in Tighnabruaich District, 
 
 150-151, 190, 191, 193, 194, 195. 
 influence of earlier faults on, 
 
 141, 142-145. 
 segregation veins in the east 
 
 and west, 139-140, 147, 155, 157. 
 
 sills, 146, 151, 155. 
 
 Bathaich ban Cottage (133), 50, 52, 116, 
 
 117, 159, 231. 
 
 (133), boulder clay near, 255. 
 
 Bealach an t-Saic (163), 215, 216. 
 
 na Sreine (183), 172, 174. 
 
 Belonites, 134. 
 
 Beinn an Lochain(134), 2, 110, 159, 231, 
 
 233, 280. 
 
 (134), landslips on, 276. 
 
 (134), strife near top of, 252. 
 
 Beinn an t-Seilich (131), 78, 104, 111, 
 
 124, 159, 233, 234, 254. 
 
 (131), landslip on, 276. 
 
 Beinn Bheag (152), 216. 
 
 Bheula(152), 2, 41, 205, 224, 281. 
 
 (152), striae near top of, 252. 
 
 Bhreac (152 and 153), 121, 201, 203, 
 
 204, 205, 206, 288. 
 (152 and 153), ruined shielings 
 
 near, 294. 
 
 (182), 2. 
 
 (183), 186. 
 
 (183), peat near, 273. 
 
 Bhuidhe (1-inch Map 45), 254. 
 
 Capuill (182), 2, 188. 193, 194, 195. 
 
 (182), boulder clay on, 249. 
 
 (182), peat near, 273. 
 
 Dubhain (152), 202, 282. 
 
 Lochain (141), 44, 82, 280. 
 
 (141), strife near top of, 252. 
 
 Mhor (163), 2, 108, 140, 148, 156. 
 
 (163), landslips on, 276, 277. 
 
 (163), moraines near, 258. 
 
 District, structure of, 208-216. 
 
 Reirhe (142), 113, 120, 121, 229. 
 
 (142), striae near top of, 252. 
 
 Ruadh (164), 161. 
 
 (194), 178. 
 
 (194), glacial contortions near, 
 
 245. 
 
 Tharsuinn (142), 40, 43, 149, 158. 
 
 (142), boulders near, 254. 
 
 Ben Arthur, 101. 
 
 landslips of, 286. 
 
 Cruachan (1-inch Slap 45), 3, 252. 
 
 Damhain, boulders possibly from, 
 
 253. 
 
314 
 
 GEOLOGY OF COWAL. 
 
 Ben Donich (142), 2, 45, 78, 90, 106, 
 115, 119, 206, 227, 228, 233, 283. 
 
 (142), boulder on slope of, 259. 
 
 (142), strire near top of, 252. 
 
 Ime, 101. 
 
 Suardal, Skye, 100. 
 
 Bending of epidote prisms, 62, 6-">. 
 
 of ilmenite plates, 79. 
 
 of mica flakes, 76. 
 
 of quartz-tourmaline veins, 78. 
 
 of tourmaline prisms, 77, 78. 
 
 BENNIE, J., 1, 245, 246, 247, 304, 307. 
 
 Bernice (163), moraines near, 258. 
 
 Glen, 216, 283. 
 
 Bibliography, 6, 308. 
 
 Biotite gneiss, 295-297. See also Anti- 
 cline Schists. 
 
 idiomorphism of, in gneissose grit, 
 
 296. 
 
 in hyperite, 105. 
 
 in the albite schists of Massachu- 
 setts, 297. 
 
 in trachyte, 170. 
 
 or black mica, in granite, 96, 97. 
 
 in porphyrite andfelsite, 102, 
 
 103, 104, 299. 
 
 or black or brown mica, in the 
 
 schists, 8, 22, 23, 34, 36, 37, 38, 39, 
 44, 45, 50, 52, 56, 63, 65, 68, 73, 74, 
 76, 86, 88, 98, 99, 100, 101, 149, 190, 
 279, 295, 296, 297. 
 
 or brown mica, in dolerites, 156. 
 
 Binnein an Fhidleir (134), 2, 44, 48, 78, 
 79, 103, 160, 230, 231, 233, 234. 
 
 (134), granite boulders near 
 
 top of, 253, 254. 
 
 (134), landslips on, 276, 286. 
 
 (134), striae near top of, 252. 
 
 Ban (192), 193, 194. 
 
 Mor (182), 195. 
 
 Birch in hill peat, 273. 
 
 Bishop's Seat (183), 3, 61, 127, 128, 138, 
 146, 149, 174, 182, 281. 
 (183), moraines near, 241. 
 
 (183), strise near, 244. 
 
 Black calcite, in Loch Tay limestone, 46. 
 
 carbonate, near basaltic dykes, 149. 
 
 Harbour (192), 191. 
 
 (192), peat near, 270. 
 
 (192), raised beach near, 267. 
 
 (192), strife near, 274. 
 
 mica lying across foliation planes, 
 
 77. 
 
 nests near the granite, 98, 99, 
 
 101, 100. 
 
 or biotite. in granite, 96, 97. 
 
 . or biotite, in porphyrite and 
 
 felsite, 102, 103, 104, 299. 
 
 or brown mica, in the schists. 
 
 See Biotite. 
 
 or chlorite, supposed formation 
 
 of, from hornblende, 61, 66, 70, 72, 
 124. 
 
 shale of south-east margin of the 
 
 Highlands, 89. 
 
 Blairbeg (174), 180. 
 
 Blairmore, 4, 62, 84, 127, 281, 282. 
 
 boulders on shore of, 248. 
 
 drift near, 243. 
 
 glacial contortions near, 245. 
 
 | Blairmore, water supply of, 293. 
 
 | Burn, 81, 180, 181, 287. 
 
 District, structure of, 179-181. 
 
 Farm, 138, 145. 
 
 sand and gravel pits near, 293. 
 
 Hill, 145, 178, 180. 
 
 glacial deposits near, 238. 
 
 moraines near, 241. 
 
 Blair's Ferry (203), raised beaches north 
 
 of, 267. 
 Blar Buidhe (183), 3, 84, 128, 129, 173, 
 
 176. 
 
 (183), moraines near, 241. 
 
 i Blende, 57, 58, 288. 
 | Blindman's Bay (203), 197. 
 j Bloomeries, 81, 289. 
 ! Blown sand, 5, 277. 
 Blue or opalescent quartz in boulders in 
 
 Glencroe, 101. 
 
 in epidiorites, 15, 61, 65, 67, 68. 
 
 in granite and pegmatite, 97, 98, 
 
 99. 
 
 in Lewisian gneiss, 15. 
 
 in pebbles in Loch Tay limestone, 
 
 47. 
 in schistose grits, etc., 15, 16, 
 
 27, 34, 36, 56, 295, 296. 
 
 in strings in tachylite, 135. 
 
 Blue quartz in conglomerate of the 
 
 Hoosac Mountains, 297. 
 Bodach Bochd (183), 127, 131, 132, 133, 
 
 139, 140, 143, 172, 174, 179. 
 BOECE, HECTOR, 2. 
 Bogany Point (Bute), 150. 
 BOHM, A., 297. 
 Boulder clay, general description of, 235- 
 
 239. 
 incidental references to, 5, 178, 179, 
 
 185, 240, 243, 244, 245, 246, 247, 248, 
 
 264, 265, 268, 271, 285, 286, 293. 
 
 in Kilfinan District, 250, 251, 252. 
 
 in Strachur District, 255-256, 257, 
 
 258, 260, 261. 
 in Tighnabruaich District, 249, 267, 
 
 293. 
 Boulders or erratic blocks, 13, 22, 98, 
 
 101, 236-237, 241, 242, 248, 250, 251, 
 
 252-255, 258, 259, 260, 261, 262, 264, 
 
 268, 286. 
 
 Brack, The (142), landslips on, 286. 
 Brackleymore (183), 131, 132, 141, 176, 
 
 176. 
 
 (183), raised beaches near, 263. 
 
 (183), sands at, 242. 
 
 Braingortan (183), 111, 114, 119, 146. 
 
 (183), boulder clay near, 236. 
 
 Brannie, The, (126), 280. 
 
 Breccias and conglomerates of Upper Old 
 
 Red Sandstone, 5, 92, 93, 94, 95, 96, 175. 
 Brecciation near hyperite, 106. 
 
 of Upper Old Red limestones, 93. 
 
 Bridgend(141), 207, 287. 
 
 (141), arable land near, 293. 
 
 boulder clay and moraines near, 258. 
 
 BRODIE, Mr (of Ardkinglas), 288. 
 Brown mica lying across foliation planes. 
 
 44, 52, 77. 
 
 or biotite, in dolerite, 156, 158. 
 
 or black mica in the schists. 
 
 See Biotite, 
 
INDEX. 
 
 315 
 
 BRYCE, Dr JAMES, 6. 
 
 Buachailean (194), old fort, 278. 
 
 Bull Rock (184), 14, 17, 18, 31,^128, 
 
 288, 292. 
 
 (184), striae on, 244. 
 
 greywacke, general descriptions of, 
 
 15-18, 31. 
 incidental references to, 8, 9, 
 
 29, 31, 84, 172, 173, 175, 177, 178, 
 
 288, 292. 
 
 Bull Wood (184), 33. 
 Burnt Islands, 23, 81. 
 
 contours under water near, 284. 
 
 striae on, 244. 
 
 vitrified fort on, 278. 
 
 Bute, 6, 83, 89, 93, 147, 150, 163. 
 
 glacial shell clay of, 1, 304-307. 
 
 Kyles of, 3, 39, 41, 43, 45, 81, 93, 
 
 139, 151, 187, 287. 
 
 boulder clay on shores of, 235. 
 
 contours under water in, 284. 
 
 description of section in schists 
 
 in, 23-27, 90-91. 
 
 peat near, 273. 
 
 raised beaches of, 262, 267. 
 
 Buthkollidar (184), raised beach, 263, 
 
 266. 
 
 Butterbridge (134), 3, 42, 102, 111, 114, 
 233. 
 
 (134), drift near, 256, 259. 
 
 Bytownite, 154. 
 
 C. 
 
 CAB, river, (141), 33, 48, 78, 104. 
 
 (141), moraines near, 258. 
 
 CADELL, H. M., 285. 
 Cairn Ban (171), old fort, 278. 
 Cairndow (134), 3, 33, 82, 110, 281. 
 (134), moraines near, 286. 
 
 (134), old river channels near, 272. 
 
 District, structure of, 230-234. 
 
 Caisteal Aoidhe (192), vitrified fort, 
 
 278. 
 Calcareous lenticles, etc., in schists, 18, 
 
 30, 38, 45, 49, 54, 77, 84, 187, 208. 
 
 phyllites, 54, 55, 85, 280. 
 
 quartzite schist, 46, 48, 52, 53, 85, 
 
 211, 212, 221, 230. 
 
 schist of Inveryne Barr, 189. 
 
 sericite schist, 54. See also Ardris- 
 
 haig Phyllites. 
 Calcite in igneous rocks, 107, 129-130, 
 
 140, 156, 163, 170. 
 
 in schists, 37, 47, 56, 63, 76, 280. 
 
 in veins, 65, 106,138, 139, 145, 151, 
 
 157, 168, 169, 194, 287, 288. 
 
 or carbonate, black, 46, 149. 
 
 Callander, 83, 85, 89. 
 Callow (182), 151, 196. 
 
 raised beaches, 267. 
 
 Upper, 151, 291. 
 
 raised beaches at, 267. 
 
 sand and gravel pits near, 293. 
 
 Cambrian albite-phyllites of Saxony, 297, 
 
 298. 
 or Durness Rocks of North- West of 
 
 Scotland, 13, 100, 122. 
 or Silurian albite schists of Massa- 
 chusetts, 297, 298. 
 
 CAMPBELLS of Ardkinglas, 1. 
 Camp Cottage (203), 150. 
 
 (203), old fort at, 279. 
 
 Camptonite, or diorite of lamphrophyre 
 group, general description of, 115-118. 
 
 incidental references to, 6, 107, 
 
 158, 210, 298. 
 
 foliated, 121, 122, 125. 
 
 Caol Ghleann, 3, 214, 215. 
 
 deltas at head of, 270. 
 
 drift in or near, 252, 256. 
 
 granite boulders in, 253. 
 
 landslips in, 275, 276. 
 
 moraines in, 252, 257. 
 
 striae near, 250. 
 
 watershed between Stralachlan Glen 
 
 and, 284. 
 
 Caol-ghleann (House), 144, 161, 213 
 214, 215, 292. 
 
 peat used at, 292. 
 
 Capull Cloch (182), 192. 
 
 Carbonaceous matter in schists, 9, 30, 
 
 54. 
 ! Carbonate of copper, 81. 
 
 ferriferous, in amygdules, 105. 
 
 in specks in schists, 20, 23, 
 
 24, 28, 30, 61, 76, 171, 180, 183. 
 Carbonates in microscopic slides of 
 schists, 66, 69, 70, 73, 74, 296. 
 
 in veins, 35, 55, 62, 65, 66, 74, 76, 
 
 78, 81, 106, 125, 144, 149, 150, 151, 
 159, 161, 177, 178, 193-194. See 
 also Calcite and Ferriferous Carbonate. 
 
 replacing garnet, 51. 
 
 or calcite, black, 46, 149. 
 
 in lamprophyres, 106, 114, 
 
 115, 116, 118, 119, 120. 
 Carboniferous age, possible, of the east 
 and west basaltic dykes, 147. 
 
 albite-phyllites of Saxony, 298. 
 
 Cam al Tilgidh (161), old cairn near 
 278. 
 
 Ban (163), 82. 
 
 Bhuilg (192), 192. 
 
 Evanechan (171), old cairn at 
 
 278. 
 Carnach Mor (141), 82. 
 
 (141), glacial mound near, 258. 
 
 (141), landslips, 275, 276. 
 
 (141), striae near top of, 252. 
 
 Carrick Castle, 4, 82, 87, 139, 140, 149, 
 155, 160, 285. 
 
 drift near, 259, 264. 
 
 old loch near, 260, 275. 
 
 raised beach at, 264, 267. 
 
 District, structure of, 200-208. 
 
 east and west . dyke, general de- 
 scription of, 155-157. 
 
 incidental references to, 111, 
 
 131, 138, 140, 149, 204. 
 CAKSWELL, Bishop of Argyll, 2. 
 Carry (203), 197. 
 
 Point, raised beaches near, 267. 
 
 Carraig nam Ban (192). 190. 
 
 nan Ron (153), 225, 229, 288. 
 
 Castle Crag (164), 205. 
 
 Crawford (184), 292, 
 
 Lachlan (151), 61, 71. 
 
 Caves, 275. 
 
 Celtic tra<litions, 2, 4. 
 
116 
 
 GEOLOGY OF COWAL, 
 
 Central Highlands, epidiorites of, 15. 
 forces (dynamic) at margins 
 
 of, 29. 
 Chalcopyrite or copper pyrites, 76, 81, 
 
 173, 177, 173, 287, 288," 289. 
 Chalk from Ireland, 290. 
 Chalybite, 178. See also Ferriferous Car- 
 bonate. 
 Chapel Hall (194), 72, 94, 95, 129, 130, 
 
 292. 
 
 Chapelton (194), 30, 31, 92, 95, 178. 
 Cherts, Arenig, 89. 
 
 Upper Old Red, 92, 93. 
 
 Cheviot hypersthene-andesites, 155. 
 
 Chlorite, analysis of, 64. 
 
 edging or replacing garnet, 49, 50, 
 
 51, 52, 57, 73, 77, 79. 
 
 in albite-phyllite of Saxony, 297. 
 
 in albite schists of Massachusetts. 
 
 297. 
 in lamprophyres, 116, 117, 120, 
 
 124. 
 in porphyrites and felsites, 102, 
 
 103, 105. 
 in the sedimentary schists, 14, 15, 
 
 17, 34, 35, 38, 39, 40, 44, 52, 56, 57, 
 
 61, 76, 80, 86, 88, 122, 149, 190, 225, 
 
 243, 297, 299, 300. 
 
 "in the schists related to epidio- 
 rites, 61, 64, 65, 66, 67, 69, 70, 76. 
 or black mica, supposed formation 
 
 of, from hornblende, 61, 66, 70. 72, 
 
 124. 
 pseudomorphs after actinolite, 50, 
 
 51, 77. 
 rim round pyrites and magnetite. 
 
 57, 80. 
 schists of sedimentary origin, 5, 
 
 23, 34. See also Green Beds and 
 
 Albite Schists. 
 
 schists related to epidiorites, gen- 
 eral description of, 60-72. 
 incidental references to, 5, 36, 
 
 218, 280. 
 
 quarries in, 64. 
 
 . slate, 6. 
 
 Chloritic grit, 30. 
 
 rock, pebbles of, 15, 30. 
 
 Chlorophseite, 130, 161, 170, 288. 
 Olach a' Bhreatunnaich (142), 259. 
 
 Beinn (163), 2, 108, 162, 208, 216. 
 
 (163), caves on, 275. 
 
 (163), landslips on, 276, 286. 
 
 Bheinn (153), 225. 
 
 (153), landslip on, 276. 
 
 Dubh na Criche (141), 260, 261, 
 
 268. 
 Clachaig (173), 146, 182. 
 
 (173), landslips near, 276. 
 
 Hill, 183. 
 
 boulder clay near, 236. 
 
 Clachan Hill (126), 280. 
 
 Clasheoin, Upper, 33, 159, 230, 281. 
 
 landslip near, 276, 286. 
 
 Clay Burn (141), 109. 
 
 Clay shell beds, 5, 55, 235, 240, 
 
 245-248, 260-261, 268, 292, 304-309. 
 Clays and marls, Upper Old Red, 94, 95. 
 C LOUGH, C. T., 7. 
 Clunie Wood (164), 45, 207. 
 
 I Oluniter (195), 127, 131, 132, 146, 291. 
 
 I (195), boulder clay near, 237. 
 
 ! Clyde, The, 2, 6, 9, 30, 128, 177, 247, 
 
 254, 278, 282, 283, 285. 
 watershed between Loch Fine and 
 
 the, 257, 270, 274, 284. 
 
 sea area, basins of, 244-245. 
 
 shell beds, 246, 247. See also Clay 
 
 Shell Beds. 
 
 View (184), 9, 173. 
 
 (184), superficial deposits near, 238. 
 
 Onoc a Chasteil (192), 193. 
 
 a Mhadaidh (174), 145, 181. 
 
 (174), drift near, 237. 
 
 Breamanach (182), 114, 185, 186, 
 
 187. 
 
 (182), deltas near, 270. 
 
 Cnoc Coinnich (142), 225, 229. 
 
 (142), landslips on, 276, 286. 
 
 (142), stride near top of, 252. 
 
 Dubh (182), peat near, 273. 
 
 Fraorach (153), 203. 
 
 Madaidh (173), 108, 117. 
 
 (173), boulder clay near, 23. 
 
 Mor (202), 197. 
 
 na Cailliche (193), 197. 
 
 na Carraige (193), 197. 
 
 (193), peat near, 273. 
 
 na Carraigh (193), 197. 
 
 na Eoghainn (171), old fort at, 
 
 278. 
 
 na Tricriche (153), 87, 201, 202, 
 
 203, 204, 205. 
 
 nam Fiantain (174), old fort at, 
 
 278. 
 
 Uaine (182), 193. 
 
 Coal, trials for, 94. 
 
 Cobbler, The, or Ben Arthur, 101. 
 
 landslips of, 286. 
 
 COEL, 2. 
 Coeliu, 2. 
 Coilessan (143), 227. 
 
 Burn, 285. 
 
 Glen, 1, 119. 
 
 raised beach near, 267. 
 
 Coille Mheadhonach (164), 205, 206. 
 
 na Sithe (193), 197. 
 
 Coirantee(163), 208. 
 
 Coire an T Burn (163), landslip near, 
 
 276. 
 Athaich (173), 3, 62, 181, 182. 
 
 183, 289. 
 (173), drift near. 236, 239, 
 
 241. 
 Burn, 182, 282. 
 
 Ban (182), 193. 
 
 Ealt(152), 113, 202. 
 
 (152), drift near, 256. 
 
 (152), erosion terrace near foot 
 
 of, 272. 
 No (133), 104, 160, 208, 216, 222, 
 
 223, 229, 233, 284, 285, 286. 
 
 (133), drift near, 255, 256. 
 
 Burn, 221. 
 
 Odhair (142), drift in, 255. 
 
 Colachra (193), 197. 
 Colintraive, 23, 41. 
 
 boulders on shore of, 248. 
 
 drift near, 235. 
 
 glacial shell bed near, 246, 304-307. 
 
INDEX. 
 
 317 
 
 Colintraive, raised beaches near, 262. 265, 
 
 567. 
 
 District, structure of, 183-187^ 
 
 Colour change near crushes and faults, 9, 
 
 32, 177, 233. 
 near igneous rocks, 9, 35, 36, 
 
 98, 99, 100, 101, 148-150, 159, 166, 
 
 185. 
 
 near pyrites crystals, 80. 
 
 within igneous rocks, 102, 
 
 113. 
 Complex, igneous, of Garabal Hill, etc., 
 
 96, 101, 230. See also Granite. 
 
 -boulders from Garabal Hill, 237, 
 
 253-254. 
 
 Conchra (162), 161. 
 Concretions in green beds, 36, 37. 
 
 in Upper Old Red sandstones, 93. 
 
 with manganese, 243, 259. 
 
 Conglomerate, Loch Fad, 89. 
 
 upper old red, 5, 89, 92, 94, 95, 
 
 96. 
 
 boulders of, 248. 
 
 Contortions in drift, 239-240, 247, 248. 
 
 259, 260, 268. 
 
 superficial, of schist, 245. 
 
 Copper carbonate, 81, 173. 
 
 oxides, 81. 
 
 pyrites or chalcopyrite, 76, 81, 173, 
 
 177, 178, 287, 288, 289. 
 Cor Mheall (181), 189. 190. 
 Coraddie (182), 127, 186. 
 
 (Ii2), drift near, 236, 242. 
 
 Cordierite, 91, 98. 
 
 Corlarach (194), 3, 81, 131, 146, 176, 
 
 177. 
 
 (194), drift near, 237, 241. 
 
 (194), superficial contortions near, 
 
 245. 
 
 Hill, 32, 128, 131, 146, 172, 177. 
 
 Cornstones, 5, 94. 
 Corra (203), 292. 
 
 (203), boulder clay near, 249. 
 
 Corrachaive (173), 2, 3. 
 
 (173), superficial deposits near, 241 , 
 
 269. 
 
 Corran Lochan (153), 81, 229, 283. 
 Corrarsk (173), 282. 
 
 (173). superficial deposits near, 269. 
 
 Corriesyke (142), 206, 288. 
 
 (142), laminated clay near, 261. 
 
 Corroded quartz, 103, 299. 
 Corrow (142) ; drift near, 255. 
 
 (142), raised beaches at, 263. 
 
 Couston (183), 38. 
 
 (183), raised beaches at, 265. 
 
 Cove, 6, 7, 83. 
 
 Cowal, boundaries of, 1. 
 
 derivation of name, 2. 
 
 Coylet (lt>3), 24, 205, 208. 
 
 Cracking or fracturing of garnets, 50, 79. 
 
 of pebbles in schist, 12, 16-17, 185, 
 
 295, 296. 
 
 of pegmatites, 16, 76. 
 
 of tourmaline, 77, 78. 
 
 Craig (183), 117, 118, 130, 171. 
 
 (183), boulder clay near. 
 
 Cottage (203), 292. 
 
 Craigbrac House (152), stone implement 
 
 fuund near, 277. 
 
 Craigendaive (172), 40, 127, 131, 135, 
 
 141, 167, 168, 170, 185, 186. 
 
 (172), sand and gravel near, 842. 
 
 Craignafeich (193), 193, 194, 195, 291. 
 (193), alluvium near, 269. 
 
 (193), boulder clay near, 249. 
 
 (193), raised beach near, 267. 
 
 Crannogs, 279. 
 
 Crarae, 291. 
 
 Creachan Beag (163), landslip on, 276. 
 
 Mor (163), 195, 205, 208. 
 
 Creag a' Chasteil (192), 194. 
 
 (192), old fort at, 279. 
 
 a' Phuill (133), 54, 55, 56, 59, 217, 
 
 280. 
 (133), granite boulders near, 
 
 268. 
 
 (133), raised beach near, 267. 
 
 an Fhasgaidh (192), 192. 
 
 an Fhithich (193), 193, 194, 282. 
 
 an fhithich Burn, 193, 194. 
 
 alluvium of, 269. 
 
 reservoirs on, 293. 
 
 Bhaoigh (152), 62, 214, 284. 
 
 Bhreac (151), 69. 
 
 Capull (173), 113, 182. 
 
 Dhubh (141), 37, 45, 47, 48, 50, 
 
 51, 52, 53, 54, 62, 221, 222. 
 
 (J41), drift near, 255. 
 
 Liath (163), 181. 
 
 Mholach (152), 216. 
 
 Mhor (174), 127. 
 
 (192), 191, 192. 
 
 (192), peat near, 273. 
 
 ua Cailliche (194), 32. 
 
 (194), raised beach at, 263. 
 
 nam Faoileann (141), 66, 209. 
 
 (141), glacial shell bed near, 
 
 260. 
 Tharsuinu (163), 3, 161, 162, 216, 
 
 281. 
 Creagau an Eich (141), 51, 66. 219, 220, 
 
 221. 
 
 CREDNER, Dr, 299. 
 Creggan's (141), 54, 58, 66, 211, 220, 
 
 261, 289, 292. 
 
 (141), bloomeries near, 289. 
 
 (141), erosion terrace at. 265. 
 
 CrilFel granite, 298. 
 Criogan (141), 288. 
 
 (141), boulders near, 254. 
 
 Crofters, 294. 
 
 CROSSKKY, Dr H. W., 245, 304. 
 
 Cruach a' Bhuic (153), 41, 42, 87, 112, 
 
 114, 201, 202, 203, 204, 205, 206. 
 
 (153), landslip near, 276. 
 
 a Chaise (164), 205. 
 
 a Kames (193), 197. 
 
 an Draghair (153), 156, 206. 
 
 an Lochain (151), 2, 45, 281. 
 
 Bhuidhe (152). 160, 161, 216. 
 
 Camuillt (172), 193. 
 
 Chuilceachan (162), 2, 154. 
 
 Conchra (162), 183. 
 
 Eighrach (153), 205. 
 
 Fas^ach (151), 200. 
 
 Mhor (162), 82, 134, 135, 167, 169, 
 
 170, 183, 184. 
 
 peat near, 273. 
 
 Mor (151), 200. 
 
318 
 
 GEOLOGY OF COWAL. 
 
 Cruach na Broighleag (182), 200. 
 
 na Caorach (173), 128, 130, 131. 
 
 na Cioba (141), 76, 223. 
 
 nam Miseag (153), 206. 
 
 (153), boulders near, 252-253. 
 
 (153), drift near, 259. 
 
 (153), peat near, 260, 275. 
 
 (153), raised beach near, 267. 
 
 Mult (134), 36, 62, 114. 115, 223. 
 
 (172), 184. 
 
 (172), boulder clay near, 238. 
 
 nan Capull (133), 45, 46, 49, 50, 
 
 51, 52, 53, 63, 79, 82, 160, 218, 221, 
 222, 223, 254, 281. 
 
 (133), granite boulders on, 254. 
 
 (133), nodules in drift near, 
 
 259. 
 
 (152), 45, 46, 49. 
 
 (183), 2, 3, 128, 131, 141, 288. 
 
 (183), striae near, 244. 
 
 nan Cnilean (172), 76, 185. 
 
 nan Gearran (172), peat near, 273. 
 
 Neuran (173), 2. 
 
 Tuirc (126), 1, 3, 96, 67, 100, 102, 
 
 103, 124, 125, 280. 
 Crush in Clay Burn (141), 109, 
 Crushed grit, 30-81. 
 Cmshed serpentine and crush along 
 
 schist boundary, 72, 73, 74, 89, 95-96. 
 
 boulders of, 284. 
 
 Crushes and faults with ore, 287-289. 
 
 earlier than Upper Old Red Sand- 
 stone, 89. 
 
 horizontal, 89, 145, 146. 
 
 physical features due to, 126, 283. 
 
 running with the graphite schists, 
 
 53, 109, 210, 218, 220. 
 Crushing near hyperite, 106. 
 Cuilmuich (153), 206. 
 Cumberland haematite, 289. 
 Cumbrae, Great, contours under water 
 
 near, 244. 
 CUMHAL, 2. 
 
 CUNEDDA, 2. 
 
 Cur River, 33, 41, 48, 104, 111, 158, 
 
 222, 223, 
 
 alluvium near, 269, 271. 
 
 drift near, 242, 256, 257, 258, 259. 
 
 old fort near, 277. 
 
 watershed between Loch Fine and, 
 
 270, 274, 284. 
 Curra Lochain (141), 201. 
 
 (141), drift near, 256, 259. 
 
 (141), peat at head of, 275. 
 
 Curve-bedding, 88. 
 Cyprina, 246, 247, 306, 307. 
 
 D. 
 
 DAIL (142), 227. 
 
 DAKYNS, J. R., 96, 237, 253, 254. 
 
 DALE, T. NELSON, 40, 297. 
 
 Dalleik (172), 16, 82, 84. 
 
 Dalmally Parish, 1. 
 
 DALMEK, K., 297. 
 
 Dalriada, 2. 
 
 Damourite, 297. 
 
 Decomposition of boulders in drift, 242- 
 
 243. 
 Deer, red, 293. 
 
 Deformation of epidiorites, 66, 67, 68, 
 
 71, 72. 
 
 of epidote, 63, 65. 
 
 of garnets, 49, 50, 51, 52, 79, 280. 
 
 of ilmenite plates, 79. 
 
 of iron pyrites, 57, 58, 81. 
 
 of magnetite, 57, 59. 
 
 of pebbles in schists, 12, 15, 16, 22, 
 
 27, 30, 31, 45, 185, 186, 192, 196, 
 
 296, 297. 
 
 of pegmatites and veins, 17, 77, 78. 
 
 of pseudomorphs after actinolite, 
 
 54, 280. 
 
 of serpentine, 73, 74. 
 
 of tourmaline, 77, 78. 
 
 Deltas, 267, 270, 274. 
 Depressions crossing valleys and water- 
 sheds, 285. 
 Derybruich (192), 193, 194. 
 
 (192), raised beach at, 266. 
 
 Devon, dolerites of, 156. 
 
 Diabase, Mica-, 298. 
 
 Diorite boulders, 236, 237, 253. 
 
 east of Glen Falloch, 254. 
 
 near the granite, 96, 97, 99, 100. 
 
 101, 103. 
 
 of Ben Arthur, 101. 
 
 of epidiorite group, 67, 71. 
 
 of lamprophyre group, 117, 118, 
 
 298. See also Camptonite. 
 (or epidiorite) of Dunoon Castle 
 
 dyke, 140. 
 
 Dioritic grauitite, 97. 
 Diorite, Quartz-, 298. 
 DITTMAR, Prof., 117, 139. 
 Dolerite, 6, 298. See also Basaltic Dykes. 
 altered into epidiorite, 65. 
 
 Mica-, 105, 298. 
 
 of Midland Valley of Scotland, 147, 
 
 157, 166. 
 
 of Sith an t-Sluaiu, 106, 163, 166. 
 
 boulders of, 254. 
 
 Dolomite, ferriferous, 73, 74. 
 Dolomitic limestones, Upper Old Red, 5, 
 
 92, 93, 94, 95, 96, 289. 
 Donich Burn (142), 106, 160, 229, 237. 
 
 (142), boulders in, 254. 
 
 (142), drift near, 256. 
 
 Lodge, 105, 157. 
 
 boulders near, 254. 
 
 DOUGLAS, GAWIX, 2. 
 
 Douglas Pier, laminated clay near, 261. 
 
 Water (1-inch Map 38), 285. 
 
 Drachenfels trachyte, 299. 
 
 Draighen, 4. 
 
 Drinsynie (142), 149, 158, 224, 225, 285. 
 
 Burn, 224, 225. 
 
 Drimsyniebeg (142), 41, 42, 224, 225. 
 
 (142), boulders near, 254, 259. 
 
 Drum (181), 151, 189, 190, 191, 291. 
 
 (181), old limekilns near, 290. 
 
 Point, 188, 189. 
 
 erosion terrace near, 266. 
 
 Duillater (162), 135, 154. 
 
 (162), moraines near, 241. 
 
 Dun an Oir (162), 278. 
 
 Dun Mor (172), 106, 111, 113, 119, 120, 
 
 127, 131, 132, 167, 169, 170, 185, 186. 
 
 (172), boulder clay near, 236. 
 
 (172), peat near, 275. 
 
INDEX. 
 
 319 
 
 Dunaus(162), 162, 167, 168, 170. 
 
 (162), moraines near, 252, 257. 
 
 Burn, 213, 288, 292. 
 
 peat, near, 273. 
 
 Castle, stone used in building, 292. 
 
 DUNBAR, 2. 
 
 DUNCAN, Mr, lately of Benmore, 287. 
 
 Dunderave Castle (133), 1, 44. 
 
 Dunkeld, 7. 
 
 Dunloskin (184), 6, 177. 
 
 raised beach at, 263. 
 
 Duuoon, 3, 4, 6, 30, 31, 33, 40, 59, 60, 
 
 76, 80, 81, 82, 128, 136, 140, 146, 148, 
 
 282, 287, 294. 
 
 bloomeries near, 289. 
 
 boulders near, 237, 248. 
 
 drift near, 236, 238, 241, 243. 
 
 raised beaches at, 263, 265, 266, 267. 
 
 sand and gravel of, 293. 
 
 section in schists south of, 9-18, 34, 
 
 84, 88, 90, 91, 225. 
 
 stone used at, 291, 292. 
 
 water supply of, 293. 
 
 basin of the Clyde, 244. 
 
 Castle dyke, general description of, 
 
 139-140. 
 incidental references to, 6, 
 
 127, 128, 142-143, 144, 147, 148, 151, 
 
 155, 156, 157, 179, 186, 193, 194, 293. 
 
 District, structure of, 171-179. 
 
 phyllite, pieces of, in Upper Old 
 
 Red breccias, 92. 
 series, general descriptions of, 
 
 9-18, 31-33. 
 incidental references to, 5, 7, 
 
 8, 19, 20, 22, 29, 30, 56, 76, 80, 83, 
 
 84, 86, 89, 173, 174, 175, 176, 177, 
 
 280, 292. 
 Durness or Cambrian Rocks, thrusts in, 
 
 13, 100, 122. 
 metamorphism of, in Skye, 
 
 100. 
 
 EAGLES FALL (126), 51, 100, 102, 124, 
 
 125, 234, 287, 288. 
 
 (126) ruined shielings near, 294. 
 
 Eas Davain (163), peat to west of, 273. 
 Dubh (141), 49, 51, 53, 54, 66, 109, 
 
 209, 210, 218, 220. 
 
 (141), drift near, 256. 
 
 (141), peat at head of, 273. 
 
 (141), watershed between the 
 
 Cur and, 257. 
 
 (151), 153. 
 
 Mor (173), 182. 
 
 Riachain (126), 48, 51, 103, 123, 
 
 159, 233. 
 (126), superficial deposits near, 
 
 256, 259, 270. 
 Easan Donn (Tighnabruaich Burn), 151, 
 
 195. 
 
 Echaig River, 2. 
 superficial deposits near, 241, 266, 
 
 272. 
 
 arable land near, 293. 
 
 Little, 2. 
 
 superficial deposits at sides of, 
 
 264. 
 
 Echinus or sea urchin, 246, 305, 307. 
 
 Economic resources, 287-294. 
 
 Eilean Aoidhe (202), 195, 196. 
 
 (202), in times of raised 
 
 beaches, 267, 
 
 (202), old cairn near, 278. 
 
 (202) vitrified fort on, 267. 
 
 Buic (192), 192. 
 
 (192), in time of 50-foot beach. 
 
 Buidhe (192), 192. 
 
 Dearg (182), 111, 119. 
 
 (182), bloomeries near, 289. 
 
 (182), striae near, 250. 
 
 Dubh (193), 196. 
 
 (193), in time of 50-foot beach, 
 
 267. 
 
 Elongation or stretching, general descrip- 
 tion of directions of, 81-82. 
 
 of garnets, 49, 50. 
 
 of pebbles and particles, 9, 11, 15, 
 
 16, 20, 21, 22, 27, 30, 34, 35, 37, 39, 
 40, 41, 42, 45, 46, 49, 51, 56, 57, 58, 
 
 62, 65, 66, 68, 69, 71, 73, 76, 78, 79 
 80, 81, 100, 185, 186, 192, 196. 
 
 Enacher Burn (162), 152. 
 
 Ennsthal, albite-gneiss of the, 297. 
 
 Epidiorite, boulders of, 236, 242, 261. 
 262, 268. 
 
 glaciation of, 250, 251. 
 
 standing stones of, 277. 
 
 or related schists, quarries in, 64, 
 
 291-292. 
 
 Epidiorites, hornblende schists and re- 
 lated chlorite schists, general descrip- 
 tion of, 60-72. 
 
 incidental references to, 5, 7, 8, 
 
 15, 36, 75, 79, 81, 148, 151, 153, 281, 
 291-292, 298. 
 
 in Beinn Mhor District, 208, 209, 
 
 210, 212. 
 
 in St Catherine's District, 217, 218, 
 
 219. 
 
 in Tighnabruaich District, 188, 189- 
 
 190, 199. 
 
 Epidosite, 67, 69, 72. 
 
 Epidote, 5, 8, 33, 34, 36, 37, 44, 48, 61, 
 
 63, 65, 67, 68, 69, 71, 76, 79, 99, 101, 
 114, 120, 190, 297. 
 
 Epidotised epidiorite, 67. 
 
 pebbles in green beds, 34. 
 
 surfaces in Lewisian gneiss, 36. 
 
 Erratic blocks. See Boulders. 
 
 Erins, 5. 
 
 Erosion terraces, 262, 265, 266, 268, 
 
 272. 
 Erzgebirge, albite-phyllites of the, 297, 
 
 298. 
 
 Eskdale pitchstone, 133. 
 Ettrick Bay (Bute), 150. 
 Eucalyptus, 3. 
 Eye (augen) structure, 34, 36, 62, 65 
 
 66, 68, 69, 70, 71, 72, 73, 74. 
 
 FALSE-BEDDING, apparent, in schists, 19, 
 25. 
 
 in Torridoniau rocks, 88. 
 
 in Upper Old Red Sandstone, 92, 95. 
 
320 
 
 GEOLOGY OF COWAL. 
 
 Faults, general description of chief, 89, 
 90. 
 
 affecting Upper Old Red Sandstone, 
 
 8, 29, 73, 74, 89, 90, 94-96, 146, 283. 
 
 in Blairmore District, 179-180. 
 
 in Beinn Mhor District, 157, 209- 
 
 216. 
 
 in Cairndow District, 99, 103, 110, 
 
 123-125, 230-234, 276. 
 
 in Carrick District, 201-207, 276. 
 
 in Colin traive District, 167, 183- 
 
 187. 
 
 in Dunoon District, 12, 31, 171- 
 
 179. 
 in Glen Massan District, 182-183. 
 
 in Kilfinau District, 70, 75, 199-200. 
 
 in Lochgoilhead District, 226-229, 
 
 276. 
 
 in Si Catherine's District, 58, 104, 
 
 105, 217-224, 254, 291. 
 
 Tighnabruaich District, 150, 189- 
 
 197. 
 
 influence of, on later intrusions, 
 
 109-110, 141, 142-145, 146, 148, 155, 
 156, 157, 158, 159, 160, 161, 167, 
 168, 179, 181, 182, 186, 234. 
 
 on scenery, general descrip- 
 tion of, 282-285. 
 
 interstitial, in Upper Old Red lime- 
 stones, 93. 
 
 majority of, later than lampro- 
 
 phyres, 108, 111. 
 
 repeated movements along, 73, 89, 
 
 90, 95-96, 
 
 with ore, 287-289. 
 
 which are earlier than felsite, 104. 
 
 which are earlier than some of the 
 
 lamprophyres 1C8--110, 218, 220. 
 
 which are of known age in relation 
 
 to basaltic dykes near them, 145-146, 
 152, 157, 158, 160, 161, 167, 168, 181, 
 183, 200, 205, 222. 
 
 Fearna Bagh (182), 23, 24, 25, 27, 8:-, 
 113, 114, 185, 186, 29(5. 
 
 (182), boulder clay near, 235. 
 
 (182), boulders on shore at, 248. 
 
 (182), glacial shell bed near, 245, 
 
 304-307. 
 
 Fearn'ach (182), 127, 131. 
 
 (182), boulder clay near, 235. 
 
 ( 182), glacial shell bed near, 245-246, 
 
 307. 
 
 Felsite and hornblende-porphyrite, gen- 
 eral descriptions of, 102, 105, 298-299. 
 
 Felsite, incidental references to, 6, 125, 
 192, 219, 220, 230, 231, 233, 287, 291, 
 299. 
 
 boulders of, 254. 
 
 Ortho-, 299. 
 
 Felstone-like pebbles in Loch Fad con- 
 glomerate, 89. 
 
 Feoileann (153), 229. 
 
 (153), raised beaches near, 267. 
 
 Feorlean (182), 145. 
 
 FERGUS Mon, 2. 
 
 Ferriferous carbonate in amygdules, 105. 
 
 or chalybite, in veins, 17, 35, 
 
 66, 76, 81, 125, 144, 151, 159, 161, 
 177, 178, 191, 194, 206, 210, 224, 229, 
 234, 243, 287, 288. 
 
 Ferriferous carbonate specks in schists, 
 
 20, 23, 24, 28, 30, 35, 61, 62, 76, 
 171, 180, 183. 
 
 dolomite, 73, 74. 
 
 Ferrite, 118, 157. 
 Ferruginous cement, 58, 271. 
 Finbracken Hill (174), 173. 
 
 (174), reservoir near, 293. 
 
 Fine river, 96, 97, 98, 99, 101, 103, 123, 
 125. 
 
 superficial deposits near, 258, 270. 
 
 Fingal Well, 2. 
 FIN AN, Saint, 188. 
 Finart Bay (164), 207, 208. 
 Finnart (183), 38. 
 
 (183), laminated clay near, 240. 
 
 Finnartbeg (174), 181. 
 Finnartmore (174), 181. 
 
 FIONN, 2, 188. 
 Fionn's Well, 2. 
 Flaser diabase, 62. 
 
 structure, 16, 149, 297, 300. 
 
 Flints from Ireland, 290. 
 
 Fluxion structure, doubtful, in diorite, 
 
 100. 
 in basaltic dykes, 129, 137-138, 
 
 156. 
 
 in boulders, 101. 
 
 in granite, 97. 
 
 in lamprophyres, 107, 118, 119, 
 
 120-121. 
 
 in porphyrite, 105 
 
 in trachytic dykes, 168, 169, 170, 
 
 171. 
 Folding, differences in yielding to, 15, 
 
 21, 24, 33. 
 
 law of chief "anticline," 26. 
 
 near Dunoon, 13. 
 
 of strain slips, etc., 14, 20, 23, 24, 
 
 28, 225. 
 
 on shore of Loch Fine, 58-60. 
 
 Folds, metamorphism, or thinning, or 
 
 deformation, in different parts of, 13, 
 
 17, 19, 22, 26, 27, 29, 45, 58, 59, 60, 
 
 88, 180. 
 squeezing from between limbs of, 
 
 59. 
 
 Foliated lamprophyres, 121-125. 
 Foliation at sides and centres of igneous 
 
 masses, 63, 66, 67, 70, 71, 72, 73, 75. 
 dip, differences in, in beds of the 
 
 same section, 12, 208. 
 Folding of, 12, 14, 19, 21, 25, 27, 
 
 28, 41, 42, 51, 52, 60, 83, 187, LOS, 
 
 300. 
 prominence of, in different beds or 
 
 parts of beds, 12, 15, 16, 19, 20, 21, 
 
 31, 36, 60. 
 Foliations of different ages, 9, 11, 14, 21, 
 
 25, 121-122, 123. 
 Foraminifera, 246, 304, 305. 
 Forfarshire, hornblendic pebbly green 
 
 beds of, 36. 
 
 Forth, drainage area of the, 285. 
 Forts, old, 258, 278-279. 
 Fracturing or cracking of garnets, 50, 7f. 
 of pebbles in the schists, 12, 16-17, 
 
 185, 295, 296. 
 
 of pegmatites, 16, 76. 
 
 of tourmaline, 77, 78, 
 
INDEX. 
 
 321 
 
 Freestone boulders, 248. 
 French chalk, 74. 
 Fuchsia, 3. 
 
 Furnace, origin of name, 289. 
 quarries at, 291. 
 
 G. 
 
 GABBRO, altered, of epidiorite group, 6, 8. 
 
 connected with serpentine, 74, 75. 
 
 Olivine, 165. 
 
 Gairletter (174), 15. 
 
 Gairletter Point, 18, 19, 20, 21, 38, 59, 
 
 181. 
 
 erosion terrace near, 265. 
 superficial deposits near, 243, 263, 
 
 304-307. 
 
 Galena, 57, 58, 181, 288, 289. 
 Galloway, igneous rocks of, 298. 
 Galls, 15, 30, 31. 
 Gantcocks (184), 31. 
 
 (184), striae on, 244. 
 
 Garabal Hill, 6, 96, 101, 230. 
 
 boulders from complex of, 237, 253. 
 
 Garbh Allt (163), 127. 
 
 Mor (126), 43, 78, 159, 288. 
 
 Garbhallt Lochain (151), peat near, 273. 
 Gareloch (Dumbartonshire), 285. 
 Garnets, 37, 48, 49, 51, 52, 57, 63, 73, 
 
 79, 190. 
 deformation of, 49, 50, 51, 52, 79, 
 
 280. 
 edged or replaced by chlorite, 49, 
 
 50, 51, 52, 57, 73, 77, 79. 
 Garnetiferous mica schist, general de- 
 scription of, 48-53. 
 incidental references to, 5, 8, 37, 
 
 41, 44, 46, 53, 54, 55, 79, 85, 91, 99, 
 
 209, 218, 219, 230, 231, 280. 
 
 boulders of, 252-253, 254-255. 
 
 horizon in Tighnabruaich District, 
 
 188-189. 
 
 Garrachoran (173), 288. 
 Garrachra (163), 216. 
 
 (163), alluvium near, 272. 
 
 Burn, 115. 
 
 Glen, 3, 156, 157, 202, 215, 216, 
 
 228, 284. 
 
 landslip in, 276. 
 
 old cairn in, 277. 
 
 ruined shielings in, 294. 
 
 Garroch Head (Bute), 147. 
 Garrowchoran Hill (184), 127, 128, 132, 
 
 178. 
 
 (184), reservoir near, 293. 
 
 Garvie (162), moraines near, 257. 
 
 Burn, 37, 38, 213, 214. 
 
 moraines near, 257. 
 
 GEIKIE, Sir A., 7, 133, 139, 147, 243, 
 
 247. 
 
 Giant's Knowe (183), 32, 172, 174. 
 Glacial deposits and glaciation, general 
 
 description of, 235-248. 
 
 in Kilfinan District, 250-252. 
 
 in Strachur District, 252-262. 
 
 in Tighnabruaich District, 
 
 249-250. 
 -_ influence of, in scenery, 282, 
 
 285-286. 
 
 Glacial sands and gravels, 5, 235, 237, 
 
 238, 239-240, 242, 243, 249, 251, 255, 
 
 257, 258, 259, 262, 264, 269, 272. 
 shell beds, 5, 55, 235, 240, 245- 
 
 248, 260-261, 268, 269, 304-307. 
 stri*, 243, 244, 249-250, 251, 
 
 252, 253, 254, 261, 268. 
 Glaic (194), 187. 
 
 Glass, Basalt-, (tachylite), general de- 
 scription of, 132-136. 
 incidental references to, 6, 
 
 126, 128, 140, 141, 142, 143, 
 Gleann Beag (134). See Hell's Glen. 
 Gleann Canachadan (142), 3, 223, 224. 
 
 (142), boulders in, 253. 
 
 Gleann Dubh (152), 110, 131, 211, 
 
 214. 
 (152), sm-erficial deposits near, 257, 
 
 273. 
 Gleann Laoigh (163), 3, 131, 182, 183, 
 
 285. 
 
 (163), old bloomeriesin, 289. 
 
 (163), superficial deposits in or near, 
 
 236, 237, 238, 240, 273, 275. 
 
 Burn, 130. 
 
 GLEN, D. C., 80. 
 
 Glen Branter (152), 214. 
 
 (152), mined dwellings in, 294. 
 
 (152), superficial deposits in or 
 
 near, 256, 272,273,275. 
 Glen Falloih, 254, 285. 
 Glen Finart (164), 42, 149, 202, 206, 
 
 284, 285. 
 
 (164), old bloomeries in, 289. 
 
 (164), superficial deposits in, 255, 
 
 263, 269, 293. 
 Glen Fine, 1, 3, 43, 48, 51, 55, 90, 91, 
 
 106, 121, 230, 280, 285. 
 boulders from, 252, 260, 262, 268. 
 
 See also Granite Boulders. 
 
 superficial deposits of, 264, 270. 
 
 Glen Fyne (183 and 194), 32, 175. 
 
 (183 and 194), superficial deposits 
 
 of, 243, 269. 
 
 Glen Kin (173 and 183), 171, 172, 285. 
 (173 and 183), superficial de- 
 posits in, 236, 237, 239, 241, 243, 
 
 269. 
 
 Burn, 172. 
 
 Glen Kinglas (134), 41, 111, 125,. 160.. 
 
 161, 224, 231, 233. 
 
 (134), landslips in, 276, 286. 
 
 (134), superficial deposits in, 256, 
 
 270. 
 Glen Lean (173), 16, 118, 127, 128, 145, 
 
 171, 183, 284. 
 
 (173), old limekiln in, 290. 
 
 (173), striae in, 243. 
 
 (173), superficial deposits in, 236, 
 
 269, 270, 271, 273, 274. 
 Glenlean (house), 182. 
 
 boulder clay near, 236. 
 
 pieces of basalt on hilltop near, 
 
 243. 
 Glen Hassan (163 and 173), 4, 79, 118, 
 
 283, 284. 
 
 (163 and 173), alluvium in, 269. 
 
 (163 and 173), landslip in, 276. 
 
 , (163 and 173), strife in, 243, 244, 
 District, structure of, 181-183. 
 
322 
 
 GEOLOGY OF COWAL. 
 
 Glenmassan (house), 21, 25, 88, 108, 111, 
 
 113, 114, 120, 127, 137, 141, 145, 150, 
 
 182, 183. 
 superficial deposits near, 241, 
 
 272. 
 Gleu Morag(184), 9, 12, 17, 127, 128, 
 
 132, 146, 149, 150, 178. 
 Glen Shellish (152), 216, 284. 
 
 (152), drift in, 256, 259. 
 
 (152), ruined dwellings in, 294. 
 
 Glenshellish (house), 216, 258. 
 
 Glen Tarsan(173), 87, 114, 127, 128, 
 
 130, 182, 283, 284. 
 
 (173), ruined dwellings in, 294. 
 
 (173), striations in, 244. 
 
 (173), superficial deposits in, 236, 
 
 269, 273, 292. 
 Glenacre (195), 29, 30. 
 
 (195), glacial contortions near, 245. 
 
 Glenan (192), 192, 294. 
 
 (192), Bay, 192. 
 
 (192), East Burn, 192. 
 
 (192), West Burn, 192. 
 
 Glencroe, 3, 101. 
 
 High, 3. 
 
 Glendaruel, 2, 3, 4, 46, 63, 75, 78, 79, 
 
 84, 86, 87, 89, 126, 127, 133, 136, 
 
 153, 154, 197, 198, 199, 200, 281, 283, 
 
 284, 288, 294. 
 
 glaciation of, 243, 250. 
 
 granite boulders in, 237. 
 
 old limekilns in, 290. 
 
 superficial deposits of, 241, 263, 
 
 269, 271, 272, 273, 293, 294. 
 
 clachan of, 81, 128, 133, 137. 
 
 House, 46, 153, 154, 198. 
 
 old cairn near, 278. 
 
 superficial deposits near, 240, 
 
 272. 
 Glensluan (hamlet), 46, 47, 48, 62, 77, 
 
 210, 211, 291. 
 
 limekilns at, 290. 
 
 superficial deposits near, 242, 
 
 257. 
 
 Glenstriven (house), 137, 146. 
 Glomero-porphyritic felspar, 131. 
 Gneiss, Albite, of the Alps, 297, 298. 
 Biotite, 295-297. See also Antic- 
 line Schists. 
 
 Lewisian, 15, 36, 103. 
 
 Sericite, 16. 
 
 Gneissose grit, 295-297. See also Antic- 
 line Schists. 
 Goil, river, 2, 228. 
 Gold, 58, 288. 
 Gortanansaig (194), sand and gravel pit 
 
 near, 293. 
 
 Gortnamhuinn (173), 20. 
 Gourock whinstone, 290-291. 
 Granite or granitite, general descriptions 
 
 of, 96-101, 298. 
 incidental references to, 6, 90, 91, 
 
 102, 103, 106, 121, 122, 125, 230, 280, 
 
 287, 289, 291. 
 boulders of, 236, 237, 242, 243, 
 
 250, 252, 253-254, 255, 260, 262, 268. 
 Granophyres of Skye, metamorphism 
 
 near, 100. 
 Granulite, Quartz-, 5. See also Quartzite 
 
 Schist. 
 
 Granulitic biotite gneiss, 295-297. See 
 
 also Anticline Schists. 
 or mosaic texture, 5, 15, 18, 28, 
 
 34, 50, 54, 68, 185, 279, 295-297, 
 
 299, 300. 
 Granulitisation, comparative freedom 
 
 from, of felspar pebbles, 16, 27, 296. 
 Graphitic limestone, 8, 53, 85, 210. 
 
 schists, general description of, 53, 54. 
 
 incidental references to, 5, 
 
 8, 37, 48, 52, 54, 62, 63, 85, 90, 108, 
 
 161, 284. 
 in Beinn Mh6r District, 209, 
 
 210. 
 in St Catherine's District, 218, 
 
 219, 220. 
 Green beds, general descriptions of, 33- 
 
 39, 297. 
 incidental references to, 5, 8, 31, 
 
 32, 61, 62, 66, 80, 84, 85, 89, 149, 
 
 254, 280, 281, 288, 292. 
 
 boulders of, 242, 243, 253. 
 
 in Beinn Mhor District, 209, 210, 
 
 211, 212, 213, 214-216. 
 
 in Cairndow District, 230-232, 234. 
 
 in Colintraive District, 183-185, 187. 
 
 in Dunoon District, 171, 172-177. 
 
 in Kilfinan District, 197-198, 199. 
 
 in St Catherine's District, 205, 219, 
 
 221, 222, 223-224. 
 in Tignabruaich District, 188, 189- 
 
 190. 
 in zone of Ardrishaig phyllites, 37, 
 
 41. 
 of garnetiferous mica schist, 
 
 37, 44, 57. 
 on the two sides of "anticline" 
 
 contrasted, 33, 34, 35, 86. 
 pieces of, in Upper Old Red breccias, 
 
 92. 
 
 with albites, 41, 44. 
 
 with garnets, 37, 48, 49, 52. 
 
 with hornblende in Forfarshire, etc., 
 
 36. 
 Green earth, 129, 130. 
 
 mica, 34, 296. 
 
 crossing foliation, 76. 
 
 Mountains, Massachusetts, albite 
 
 schists of, 40, 297, 298. 
 Greenstone, slaty, 6. 
 Greyloch Mountains, Massachusetts, 
 
 albite schists of, 40, 297, 298. 
 Greywacke, Bull Rock schistose, general 
 
 descriptions of, 15-18, 31. 
 incidental references to, 8, 9, 
 
 32, 172, 173, 176, 177, 178, 288, 292. 
 Grit, crushed, 30-31. 
 pebbles in Loch Fad conglomerate, 
 
 89. 
 Grits, schistose, south-east of the Bull 
 
 Rock greywacke, 29-31. 
 Gritty, phyllite, 30-31, 178. 
 GUMBEL, C. W., 107, 298. 
 
 HEMATITE and haematite staining, 80, 
 146, 156, 167, 178, 186, 236, 289. 
 See also Specular Iron Ore. 
 
INDEX 
 
 323 
 
 Hafton (174), glacial contortions near, 
 245. 
 
 (174), superficial deposits near, 174, 
 
 263. 
 
 HABKER, A., 80. 
 
 Hartz, quartz-albite veins of the, 18. 
 HATCH, Dr F. H., 34, 62, 70, 73, 92, 
 117, 118, 119, 130, 132, 133, 135, 
 136, 140, 142, 156, 163, 169. 
 Hearthstones, clay for whitening, 261, 
 
 292. 
 
 HEDDLE, M. F., 130. 
 Hell's Glen, or Gleann Beag, 125, 222, 
 223, 224, 226, 228, 229, 230, 231, 234, 
 283. 
 
 boulders in, 253. 
 
 landslips in, 275, 276, 277, 286. 
 
 road metal used in, 291. 
 
 superficial deposits in or near, 256, 
 
 270. 
 
 Highlands, Central, dynamic forces at 
 sides of, 29. 
 
 epidiorites of, 15. 
 
 North-West, dynamic forces in the, 
 
 13, 29. 
 
 pebbles in Torridonian rocks 
 
 of the, 15. 
 
 HILL, J. B., 43, 46, 254, 263. 
 Hills, list of chief, in Cowal, 2. 
 HINXMAN, L. W., 241. 
 Holy Loch, 1, 38, 108, 181. 
 
 old fort overlooking, 278. 
 
 superficial deposits in or near, 243, 
 
 263, 293. 
 Hoosac Mountains, Massachusetts, albite 
 
 schists of, 40, 297, 298. 
 Horizontal crushes, 89, 145, 146. 
 Hornblende in granite or granitite, 96, 
 97, 98. 
 
 in green beds of Forf arshire, etc., 36. 
 
 in " greenstone," 6. 
 
 in lamprophyres, 104, 110, 112, 
 
 113, 115, 116, 117, 118, 119, 125, 
 298. 
 
 in foliated lamprophyres, 123, 124. 
 
 in porphyrites and felsites, 102, 
 
 103, 104, 299. 
 
 in porphyritic forms in epidiorite, 
 
 67. 
 
 in schist near the granite, 100. 
 
 in segregation veins in the Dunoon 
 
 Castle dyke, 140. 
 
 in strings in andalusite-hornfels, 98. 
 
 schists, epidiorites and related 
 
 chlorite schists, general description 
 of, 60-72. 
 
 incidental references to, 5, 
 
 32, 36, 46, 47, 52, 84, 281, 291, 298. 
 
 boulders of, 236, 241, 262. 
 
 in Blairmore District, 179, 
 
 180-181. 
 
 in Beinn Mhor District, 208, 
 
 210, 211-212, 213, 214, 215. 
 
 in Cairndow District, 230, 
 
 231. 
 
 in Colintraive District, 183. 
 
 in Dunooii District, 171, 173, 
 
 174, 175, 176, 177, 244. 
 
 in Glen Massan District, 182, 
 
 183. 
 
 Hornblende schists in Kilfinan District, 
 
 198, 199. 
 in St Catherine's District, 217, 
 
 221, 222, 223. 
 in Tighnabruaich District, 
 
 188, 189-190, 191. 
 
 with garnets, 48, 49, 52, 63. 
 
 supposed formation of black mica or 
 
 chlorite from, 61, 66, 70, 72, 124. 
 porphyrite and felsite, general 
 
 descriptions of, 102-105, 298-299. 
 incidental references to, 6, 99, 
 
 107, 124, 125, 218, 219, 220. 
 Hornfels, 98. 
 
 Hornstone-like pebbles, 15. 
 Horse Seat (183), 132, 175, 176. 
 
 (183), peat near, 273. 
 
 Hunter's Quay, 6, 32, 38 62, 84, 175, 
 
 177. 
 
 boulder clay at, 235. 
 
 HUTCHINGS, W. M., 18. 
 Hypersthene, 64, 155. 
 
 in hyperite, 105, 106. 
 
 andesites of the Cheviots, 155. 
 
 Hyperite, general description of, 105- 
 
 106. 
 incidental references to, 6, 237, 298. 
 
 I 
 
 ICE scratches, 243-244, 249-250, 251, 
 
 252, 253, 261, 268. 
 Idocrase, 47, 48. 
 
 62, 76, 79, 
 
 Igneous rocks, list of, 5-7. 
 Ilmenite in schists, 44, 52, 
 
 99. 
 in basaltic dykes, 80, 140, 158. 
 
 in lamprophyre, 117. 
 
 or magnetite, 34. 
 
 Inchnadampf, basic sills of, 116. 
 Inclusions in albite, 34, 35, 40, 43, 44, 
 
 101, 297, 298, 300. 
 
 in augite of lamprophyres, 116. 
 
 in basaltic dykes, 138, 142, 151. 
 
 in biotite of the granite, 97. 
 
 in biotite of lamprophyres, 115, 
 
 116. 
 in calcite or carbonate, 35, 46. 
 
 in felspar of Sith an t-Sluaiu 
 dolerite, 165. 
 
 (porphyritic) of basaltic dykes, 
 
 138, 142, 151. 
 
 (porphyritic) of granite, 97. 
 
 in garnets, 52. 
 
 in granite, 97, 298. 
 
 in lamprophyres, 106-107, 111- 
 
 112, 113, 114, 125, 193. 
 
 in foliated lamprophyres, 123. 
 
 in vein quartz, 17. 
 
 "Injection" of schists by granite, 97- 
 
 98 99. 
 Inellan, 4, 6, 29, 72, 73, 74, 79, 92, 94, 
 
 95, 96, 131, 132, 176, 282, 292. 
 
 boulder clay near, 236. 
 
 water supply of, 293. 
 
 Hill, 15. 
 
 Perch, 93, 94, 95, 96, 163, 175. 
 
 Tom, 30, 178. 
 
324 
 
 GEOLOGY OF COWAL. 
 
 Inveraray, 56, 285. 
 
 contours under water near, 245. 
 
 Castle, 64, 291. 
 
 Inverchaolain (183), 32, 38, 79, 132. 
 
 136, 141, 173, 175. 
 
 (183), drift near, 236, 238, 239. 
 
 Burn, 38, 172, 174, 179. 
 
 landslip near, 276. 
 
 Glen, 32, 171, 172. 
 
 drift in, 239, 243. 
 
 Inverchapel(163), flood gravel near, 272. 
 
 Burn, 76, 130, 132. 
 
 drift near, 239, 244. 
 
 flood gravel of, 272.' 
 
 Invcrlounin (142), 227, 229. 
 
 (142), raised beach at, 268. 
 
 Inverraasan, 4. 
 Inverneil Burn (183), 82. 
 Invernoaden (152), drift near, 255, 257. 
 Inveronich (142), 226, 292. 
 
 (142), boulder near, 259. 
 
 Invervegain (183), raised beaches, 265. 
 
 Burn, 117. 
 
 superficial deposits near, 236, 
 
 242. 
 
 Glen, boulder clay in, 236. 
 
 Inveryne(181), 189. 
 
 (181), ruined farm buildings at, 
 
 294. 
 
 Barr, 188, 189. 
 
 lona, old crosses of, 292. 
 
 Ireland, early immigration from, 2, 4. 
 
 importations from, 290, 292. 
 
 Iron glance, or specular iron ore, 55, 80, 
 
 178, 288-289. 
 ores in microscope slides of schist 
 
 or epidiorite, 16, 30, 34, 36, 37, 296. 
 
 See also Magnetite and Ilmenite. 
 in microscope slides of ba- 
 saltic dykes, 134, 135, 158. See also 
 
 Ilmeuite and Magnetite. 
 in microscope slides of dolerite 
 
 of Sithan t-Sluain, 165. 
 in microscope slides of granite, 
 
 97. 
 in microscope slides of hy- 
 
 perite, 105. 
 in microscope slides of lampro- 
 
 phyres, 114, 116, 118, 119, 120, 124. 
 
 See also Magnetite. 
 
 in river gravel, 271. 
 
 oxides, segregation of, in Upper Old 
 
 Red Sandstone, 93. 
 pyrites, 9, 48, 57, 58, 63, 76, 80, 
 
 81, 98, 99, 106, 114, 148, 157, 158, 
 
 170, 288. 
 
 sulphate, 58. 
 
 IRVINE, ROBERT, 271. 
 Islands in times of raised beaches, 267. 
 Isle Ornsay, epidotic grits near, 36. 
 Islay, Old Crosses of, 292. 
 
 JAMIESON, T. F., 7. 
 
 Jasper-like pebbles in Upper Old Red 
 
 sandstone, 92. 
 
 strings in Dunoon Castle dyke, 139. 
 Joints in andesite, 163. 
 
 Joints in basaltic dykes, 113, 126, 127- 
 128, 133, 136, 137, 138, 140, 141, 154- 
 155, 157, 158, 159, 161, 168. 
 
 in dolerite of Sith an t-Sluain, 163, 
 
 164, 165. 
 
 in felsite, 104. 
 
 in granite, 280. 
 
 in lamprophyres, 110, 111, 113, 
 
 125. 
 
 in porphyrite, 105. 
 
 in schists, 56, 108, 189, 192, 193, 
 
 194, 216, 231, 282, 283. 
 
 in trachytic dykes, 167, 168. 
 
 Jura, Paps of, 3. 
 
 K 
 
 KAMES, 188, 195, 197. 
 
 boulder clay near, 249. 
 
 standing stones near, 278. 
 
 striae near, 249. 
 
 farm, reservoirs near, 293. 
 
 Powder Work, reservoirs for, 293. 
 
 Kersantite, 114, 115, 298. 
 Kilbride (193), 292. 
 
 (193), old fort near, 279. 
 
 (193), raised beach at, 266. 
 
 Bay, 188, 196, 294. 
 
 islands near, in time of 50-foot 
 
 beach, 267. 
 superficial deposits near, 266, 
 
 277. 
 Church (193), peat and moorland 
 
 near, 274, 294. 
 
 Chapel (151), 69. 
 
 Hill (183), 133, 179. 
 
 (183), superficial deposits near, 
 
 238, 273. 
 Kilbridemore Burn (162), 46, 199. 
 
 (162), old limekilns near, 290. 
 
 Glen (162), moraines in, 252. 
 
 Kilchoman (Islay), old crosses of, 292. 
 Kilfinan, 6, 49, 104, 188, 189, 191, 198, 
 
 290, 292. 
 
 antiquities near, 278. 
 
 cultivated land near, 294. 
 
 superficial deposits near, 249, 265, 
 
 293. 
 
 Burn, 2, 198, 200. 
 
 raised beaches at foot of, 265. 
 
 District, basaltic dykes, description 
 
 of, 151-155. 
 glacial deposits, description of, 
 
 250-252. 
 
 structure in, 197-200. 
 
 Killellan (194), superficial deposits near, 
 
 238, 247. 
 
 (194), stones used in building, 278. 
 
 Kilmarnock Hill (194), 176, 177. 
 
 (194), landslip near, 268, 276. 
 
 (194), superficial deposits near, 238, 
 
 275. 
 
 Kilmorich Parish, 1. 
 Kilmun, 4, 6, 81. 
 
 glacial contortions near, 245. 
 
 Cottage, raised beach near, 266. 
 
 Hill, 181. 
 
 glaciation of, 243. 
 
INDEX. 
 
 325 
 
 Kinglas, river or water, 3, 33, 42, 43, 
 
 78, 88, 103, 110, 114, 160, 230, 231, 
 
 234. 
 old river channels at foot of, 
 
 272. 
 
 red deer to north of, 293. 
 
 superficial deposits near, 259, 
 
 270. 
 
 Kin tyre, 2, 295. 
 Kirn, 4, 32, 80, 177. 
 
 water supply of, 293. 
 
 Knap Burn (164), 43, 206. 
 
 (164), raised beach at foot of, 267. 
 
 Knapdale, 2. 
 
 Knockdow (194), 32, 144. 
 
 (194), arable land near, 293. 
 
 Knox's Liturgy, 2. 
 
 Knotted schist, 51. 
 
 Kyle, (Ayrshire), 2. 
 
 Kyles of Bute, 3, 23, 39, 41, 43, 44, 81, 
 
 139, 151, 187, 188, 288. 
 coast line of, at time of 100- foot 
 
 beach, 267. 
 
 contours under water in, 284. 
 
 section of schists in, 23-27, 90-91. 
 
 superficial deposits in, 235, 263, 
 
 273. 
 
 striae in, 244. 
 
 vitrified fort in, 278. 
 
 Kylerhea (Skye), green grits of, 36. 
 
 LABRADORITE, 142, 155, 156. 
 Lachlan Bay (151), 2, 67, 71, 148. 
 Laglingarten (133), 50, 53, 114, 219, 220. 
 
 (133), boulder clay near, 255. 
 
 (133), boulders near, 254. 
 
 Lake dwellings, 279. 
 
 Lamprophyres and mica traps, general 
 
 descriptions of, 106-126, 298. 
 incidental references to, 6, 90, 
 
 102, 147, 237, 277, 282. 
 in Beinn Mhor District, 157, 
 
 161, 209, 210, 211, 212, 213, 216. 
 
 in Blairmore District, 181. 
 
 iii Cairndow District, 101, 
 
 103-104, 159. 
 in Carrick District, 43, 201, 
 
 202, 204, 205, 207. 
 
 in Colintraive District, 186. 
 
 in Glen Massan District, 182, 
 
 183. 
 in Lochgoilhead District, 79, 
 
 226, 229, 230, 231, 233, 234. 
 in Tighnabraaich District, 
 
 191, 192, 193, 194, 195, 1P6, 197. 
 
 iu boulder clay, 236. 
 
 Landslips, general description of, 275- 
 
 277. 
 incidental references to, 123, 132, 
 
 159, 160, 171, 268, 286. 
 Larach Hill (164), 111, 131, 138, 156, 
 
 208. 
 
 (164), drift on, 255. 
 
 Largiemore (171), 198, 199. 
 
 (171), cultivated land at, 294. 
 
 . (171), old cairns near, 278. 
 (171), raised beach at, 264. . 
 
 Leacaun nan Gall (173), 128, 141, 145, 
 
 147. 
 
 (173), moraines near, 241. 
 
 Lead ore, 57, 58, 181, 287, 288. 
 
 Leak (151), 59, 60, 66, 84, 115, 161, 208, 
 
 209, 210. 
 
 (151), old bloomery near, 289. 
 
 (151), raised beaches near, 265, 267. 
 
 Leamhanin (141), 48, 104, 207, 224, 284. 
 (141), drift in or near, 255, 256, 
 
 258. 
 Leanach (151), 49, 53, 54, 161, 210, 212, 
 
 218, 291. 
 
 (151), deltas near, 271. 
 
 Lephinchapel (162), 66, 154, 155. 
 
 Burn, 155. 
 
 Lephinkill (172), 16, 27, 35, 49, 80, 81, 
 
 89, 184, 185. 
 
 Lephinmore (162), 154, 199. 
 (162), contortions in boulder clay 
 
 near, 251. 
 
 Burn, 154, 199, 200. 
 
 Lettermay Burn (142), 284. 
 
 (142), drift near, 256. 
 
 Leucoxene, 16, 37, 62, 63, 66, 67, 70, 
 
 79, 116. 
 
 Lewisian gneiss, 15, 36, 103. 
 Liebenerite porphyry, 93. 
 Limekilns, 54, 290. 
 Limestone, schistose, accompanying 
 
 graphite schists, 8, 53, 54, 85, 210. 
 Loch Tay, general description 
 
 of, 45-48. 
 Loch Tay, incidental references 
 
 to, 5, 8, 37, 41, 48, 49, 53, 61, 85, 86, 
 
 253, 281, 290. 
 Loch Tay, in Beinn Mhor 
 
 District, 210-212. 
 Loch Tay, in Cairndow 
 
 District, 52, 63, 104, 230, 231. 
 Loch Tay, in Kilfinan District, 
 
 63, 75, 197, 198, 199. 
 Loch Tay, in St Catherine's 
 
 District, 62, 219/220, 221-223. 
 Ix)ch Tay, in Tighnabruaich 
 
 District, 151, 188, 189, 190. 
 in the Ardrishaig phyllite 
 
 series, 5, 8, 54, 85. 
 in the Dunoon phyllite series, 
 
 5, 6, 8, 9, 14, 19, 31, 32, 84, 85, 86, 
 
 150, 281, 290, 298. 
 in the garnetiferous mica 
 
 schist, 8, 52, 85, 188, 209, 219-221. 
 
 in the green beds, 35. 
 
 south-east of the Bull Rock 
 
 greywacke, 8, 29, 30, 84. 
 pebbles of, in Loch Fad con- 
 glomerate. 
 Upper Old Red, general description 
 
 of, 93-94. 
 incidental references to, 5, 6, 
 
 92, 95, 96, 163, 289. 
 Lindsaig (181), raised beach near, 265. 
 LINDSAY, Sir D. , 2. 
 Limonite, 80, 134. 
 Liogau (141), 158, 288. 
 
 (141), drift in and near, 256, 258.-- 
 
 (141 ), landslip near, 276. 
 
 Lismore, Book of the Dean of, 4. 
 Literature, 6-7, 308-309. 
 
326 
 
 GEOLOGY OF COWAL. 
 
 Littorina, 245, 246, 248, 307. 
 
 Llandeilo Rocks, 89. 
 
 Loch Ascog (192), 188, 193, 194. 
 
 (192), peat near, 274. 
 
 Awe, 152, 252. 
 
 Earn, 7. 
 
 . Eck, 2, 3, 24, 107, 113, 127, 179, 
 
 181, 202, 205, 208, 216, 257, 270, 274, 
 
 282, 285, 291. 
 
 erosion terrace at side of, 272. 
 
 granite boulders on sides of, 
 
 237, 253. 
 superficial deposits near, 244, 
 
 255, 258, 264, 269, 270, 271, 286, 293, 
 294. 
 
 Fad conglomerate, 89. 
 
 Fine, 1, 6, 8, 37, 49, 54, 55, 56, 58, 
 
 60, 61, 64, 66, 67, 80, 84, 89, 91, 101, 
 102, 115, 117, 121, 129, 130, 140, 149, 
 152, 153, 158, 159, 188, 193, 194, 198, 
 199, 217, 237, 252, 253, 254, 280, 281, 
 
 283, 284, 285, 288, 291, 299. 
 
 boulders on shore of, 253. 
 
 contours under water of, 245. 
 
 erosion terraces on, 265. 
 
 islands of, in times of raised 
 
 beaches, 267. 
 old forts and cairns near, 
 
 278. 
 striae and glaciation near, 249, 
 
 250, 251. 
 superficial deposits near, 255, 
 
 256, 260, 263, 264, 267, 270, 292. 
 
 water of, character of, 261. 
 
 watershed between Clyde and, 
 
 near Strachur, 257, 270, 274, 284. 
 Goil, 1, 41, 42, 43, 82, 87, 119, 
 
 156, 202, 225, 229, 282, 283, 285. 
 
 boulders on shore of, 253. 
 
 contours under water of, 244, 
 
 245. 
 
 erosion terraces on, 265. 
 
 superficial deposits near, 263, 
 
 269, 270, 272. 
 
 Holy. See Holy Loch. 
 
 Lomond, 89, 237, 285. 
 
 Long, 1, 6, 18. 38, 41, 87, 119, 
 
 136, 156, 181, 206, 207, 208, 225, 229, 
 282, 283, 285, 288. 
 
 boulders on shore of, 237, 253, 
 
 254. 
 
 contours under water of, 244. 
 
 landslips at side of, 276, 286. 
 
 old fort at entrance of, 278. 
 
 superficial deposits near, 243, 
 
 246, 247, 261, 267. 
 Loskin (184), 61, 84, 146, 174, 175, 
 
 281, 291. 
 
 - (184), barrier of, 244. 
 
 (184), peat and alluvium at 
 
 head of, 275. 
 na Melldalloch (181), 105, 188, 191, 
 
 192. . 
 
 (181), boulder near, 250. 
 
 (181), superficial deposits near, 
 
 249, 269, 273. 
 
 Kestil (134), 2, 3, 106, 111, 116, 
 
 117, 140, 227. 
 
 (134), granite boulders near. 
 
 253. 
 
 Loch Restil (134), superficial deposits 
 
 near, 256, 275. 
 east and west dyke, general 
 
 description of, 158-159. 
 east and west dyke, incidental 
 
 references to, 140, 231, 234. 
 Striven, 1, 32, 38, 40, 82, 83, 87, 
 
 89, 106, 108, 111, 114, 119, 130, 131, 
 
 132, 138, 140, 141, 142, 171, 172, 186, 
 
 187, 283. 
 
 boulders on shore of, 237. 
 
 erosion terraces on, 265. 
 
 strise near, 247. 
 
 superficial deposits near, 236, 
 
 242, 247, 263. 
 
 Tay limestone. See Limestone. 
 
 Lochain Garbhallt (151), peat near, 273. 
 Lochan Chuilceachan (162), peat near, 
 
 273. 
 
 na Leirg (182), 186, 187, 244. 
 
 Lochgilphead, 70. 
 
 Lochgoilhead, 3, 4, 41, 42, 80, 87, 117, 
 
 140, 155, 160, 218, 219, 231, 283. 
 
 landslips near, 275, 276, 286. 
 
 superficial deposits near, 286, 293, 
 
 294. 
 District, basaltic dykes, description 
 
 of, 155-162. 
 glacial deposits, description of, 
 
 252-262. 
 
 structure in, 225-229. 
 
 east and west dyke, description of, 
 
 157-158. 
 incidental references to, 140, 
 
 149, 223, 224, 226, 255. 
 Lochs, freshwater, barriers of, 244. 
 
 now filled up, 244, 260, 269, 275. 
 
 sea, origin of, 238, 284. 
 
 Lome andesites, 252, 253, 
 
 Firth of, 252. 
 
 LOSSEN, K. A., 18. 
 
 Lower Old Red Sandstone, 74, 89, 100. 
 Lub Faochaige (192), 193, 194. 
 Lustre-mottling, 116. 
 
 M 
 
 MACADAM, W. IVISON, 46, 55, 130, 260, 
 
 289, 290. 
 
 MACCULLOCH, Dr J., 6, 7, 130, 170. 
 MACKINTOSH, CHARLES, 289. 
 MACLAREN, CHARLES, 241, 257, 258. 
 MACNAUGHTON, Mr, of Craigbrac, 277. 
 MACNAUGHTONS of Duuderave, 1. 
 MThuu's Cairn (141), 57, 58, 129, 131, 
 
 161, 288. 
 Magnesian limestones, Upper Old Red, 
 
 5, 6, 92, 93, 94, 95, 96, 289. 
 
 boulders of, 248. 
 
 Magnetic sand, 80. 
 Magnetite in andesite, 163. 
 
 in basaltic dykes, 80, 115, 118, 119. 
 
 in dolerite of Sith an t-Sluain, 165. 
 
 in lamprophyres, 115, 118, 119. 
 
 in porphyrite, 103. 
 
 in trachytic dykes, 169, 170. 
 
 in schists, 35, 40, 57, 63, 70, 76, 
 
 79, 80, 81, 101, 149, 171, 297, 299, 
 
 300. 
 
INDEX. 
 
 327 
 
 Magnetite in veins in schist, 288. 
 
 or ilmenite, in schists. 34, 76 
 
 101. 
 
 MAIN, R., 93, 290. 
 Malacolite, or augite in the lampro- 
 
 phyres, 111, 112, 113, 115, 116, 118. 
 Maol Odhar (162), 62, 160, 214. 
 
 (162), landslip near, 276. 
 
 (162), superficial deposits near, 256. 
 
 273. 
 Manganese, 64, 271. 
 
 black oxide of, 242, 258, 259, 271. 
 
 Marcasite, 80, 81. 
 
 Mark (153), 18, 41, 119, 225, 229, 288. 
 
 (153), boulders near, 254. 
 Marls and clays, Upper Old Red, 94, 
 
 95. 
 
 Massan, river, 2, 111, 114, 182. 
 superficial deposits near, 240, 
 
 269, 270. 
 Massachusetts, albite schists of, 297. 
 
 See also Green Mountains. 
 Meal Breac (152), 112, 216. 
 Meall an-T (163), 160, 216. 
 
 (163), drift near, 255. 
 
 an Fharaidh (173), 289. 
 
 -, (173), drift near, 236, 239. 
 
 Beag (126), 1, 99, 160. 
 
 (126), drift near, 256, 259. 
 
 Breac (1-inch map 38), 6, 96, 101, 
 
 230. 
 
 (1-inch map 38), boulders from 
 
 near, 237, 253, 254. 
 
 Buidhe (173), 146, 289. 
 
 Daraich (153), 229. 
 
 Dubh (163), 157, 161. 
 
 (163), boulders near, 254. 
 
 Reamhar (141), 44, 50, 51, 210. 
 
 (152), 131. 
 
 (171), cairn near, 278. 
 
 Meallan Glaic (194), 138. 
 
 (194), raised beach near, 268. 
 
 Biabhach (183), superficial deposits 
 near, 236, 237, 273. 
 
 Sithean (183), landslip on, 276. 
 
 (183), peat near, 273. 
 
 Metamorphisin near basaltic dykes, 
 general description of, 148-150. 
 
 near basaltic dykes, incidental 
 
 references to, 6, 9, 75, 101, 111, 145, 
 146, 151, 153, 157, 158, 160, 161, 162, 
 185, 186, 197, 205, 237. 
 
 near dolerite of Sith an t-Sluain, 
 
 106, 166. 
 
 near epidiorites, etc., 61, 70, 72, 
 
 190. 
 
 near granite, 91, 98, 99, 100-101, 
 
 106, 121, 125, 230, 237, 280. 
 
 near hyperite, 106, 237. 
 
 near lamprophyres, 113, 114, 237. 
 schist producing, general remarks 
 
 on, 90-91, 295. 
 deformation and thinning in 
 
 the different parts of folds, 13, 17, 22, 
 
 26, 27, 29, 225, 296. 
 in relation to movement, 22, 
 
 23, 26, 27, 28, 91. 
 in the garnetiferous mica 
 
 schist, 52, 91. 
 in the Hartz, 18. 
 
 Metamorphisin schist, increase of, near 
 
 the "anticline," 7, 8, 22, 26, 27, 28, 
 
 39, 42, 43, 60, 78, 90-91, 193, 295. 
 
 ; Nicol's theory of, 7. 
 
 Mica, biotite or brown, in dolerites, 156. 
 in schists, biotite or black, or 
 
 brown, 8, 22, 23, 34, 37, 38, 39, 44, 
 
 45, 50, 56, 63, 65, 68, 73, 74, 76, 86, 
 
 88, 99, 100, 101, 149, 190, 279, 295, 
 
 296, 297. 
 brown, or black, lying across 
 
 foliation, 52, 77. 
 
 green, 34, 296. 
 
 green, lying across foliation, 76. 
 
 white, and sericite, 10, 1 1, 14, 
 
 15, 16, 17, 18, 22, 34, 35, 36, 40, 43, 
 
 52, 54, 56, 57, 66, 76, 149, 189, 295, 
 
 296, 297, 299, 300. 
 white,lying across foliation, 43, 
 
 44, 77, 297, 300. 
 
 yellow, 62, 66. 
 
 development along strain slips, 
 
 20, 22, 27. 
 development in limbs of folds, 
 
 22, 26, 203. 
 
 dolerite, 105, 114, 115. 
 
 " Mica slate," 6, 7, 55. 
 
 trap. See Lamprophyres. 
 
 of Assynt, 122. 
 
 Microlites in albite, 40, 300. 
 
 in basaltic dykes, 75, 132, 134, 136, 
 
 140, 142, 155, 156. 
 
 in lamprophyre, 120. 
 
 in porphyrite, 105, 299. 
 
 Micropegmatitic structure, 65, 158. 
 Microscope slides, list of, 300-303. 
 Mid Hill (173), 81, 171. 
 Letter (141), 37, 41, 52, 54, 111, 
 
 130, 160, 209, 210, 212. 
 Middle Inens (193), reservoir near, 293. 
 Middle Old Red Sandstone, 74. 
 Midland valley of Scotland, basaltic 
 
 sheets of, 147, 166; 
 MILCH, L., 295. 
 MILL, Dr H. R., 238, 244. 
 Millhouse (193), superficial deposits near, 
 
 249, 266, 293. 
 
 (193), tillage ground near, 294. 
 
 Milton Burn (184), 186. 
 
 Minard, contours under Loch Fine near, 
 
 245. 
 
 Monovechadan (134), 117, 119, 120, 124. 
 Montherme, phyllade aimantifere of, 80. 
 Moorland once cultivated, 294. 
 Moraines, 5, 235, 238, 239, 240-242, 244, 
 
 252, 256-259, 264, 269, 270, 274, 275, 
 
 286, 293. 
 
 Moses' Well (134), 286. 
 Mottled bands in Loch Tay limestone, 
 
 46, 85, 212. 
 Mountain-making movements, direction 
 
 of, in the Highlands, 13, 29. 
 Moymore (172), 198. 
 Mull, island of, 2. 
 
 basaltic dykes of, 147. 
 
 Mullach a' Chuirn (142), 206, 208. 
 
 Choire a' Chuir (142), 44, 219. 
 
 (142), granite boulders near, 254. 
 
 . (142), landslips on and near, 
 
 276. 
 
GEOLOGY OF COWAL. 
 
 MUNRO, Dr ROBERT, 279. 
 MURCHISON, Sir R., 7. 
 MURRAY, Dr JOHN, 271. 
 Muscovite in albite schist of Massa- 
 chusetts, 297. 
 
 Mussels (mytilus), 248, 306. 
 Mya, 246, 247, 307. 
 
 N 
 
 NATROLITE, 130. 
 
 Nepheline iu pebble of Upper Old Red 
 
 conglomerate, 92, 93. 
 Nests of black mica near granite, 98, 99, 
 
 100, 101. 
 
 partly of black mica near serpent- 
 ine, 73. 
 
 Newton (151), 49, 57, 61, 66, 97. 
 (151), glacial shell bed near, 292. 
 
 See also Creag nam Faoileann. 
 
 Bay, 56, 58, 67, 148, 166, 199. 
 
 boulders in, 262. 
 
 raised beaches near, 264. 
 
 (194), boulder clay near, 235. 
 
 Hill (126), 233, 285. 
 
 NICOL, Professor JAMES, 6, 7, 85. 
 North Wales, pyrites in slate of, 80. 
 North- West Highlands, pebbles in Torri- 
 
 donian rocks, 15. 
 pre-Torridonian dykes, 121. 
 relation of moraines to 50- foot beach, 
 
 241. 
 thrusts and dynamic forces, 13, 29, 
 
 88, 90. 
 
 OBSCURING of earlier foliations, 21, '23, 24, 
 
 25, 28, 59, 90, 295. 
 Old Red Sandstone, Lower, 74, 89, 100. 
 
 Middle, 74. 
 
 Upper, general* description of, 92- 
 
 96. 
 incidental references to, 5, 89, 
 
 107, 147, 150, 163, 171, 175, 236, 292. 
 
 boulders of, 248, 262. 
 
 Olenellus quartzite of Massachusetts, 297. 
 Oligoclase, doubtful, in andesite, 163. 
 
 felspar allied to, in porphyrite, 103. 
 
 pebbles of, in Torridonian rocks of 
 
 Skye, 15. 
 Olivine in basaltic dykes, 131-132, 136, 
 
 142, 154, 156, 159. 
 indolerite of Sith an t-Sluain, 164, 
 
 165. 
 
 in lamprophyres, 115, 116, 119. 
 
 no indications of, in the Toward 
 
 serpentine, 74. 
 pseudomorphs after, in hyperite, 
 
 106. 
 
 Oliviiie (rabbro, 165. 
 Opalescent or blue quartz. See Blue or 
 
 Opalescent Quartz. 
 Ophitic augite, 115, 130, 142, 154, 158, 
 
 164, 165. 
 
 Ormidale (172), 3. 
 (172), glacial shell bed near, 246, 
 
 247, 304-307. 
 Ornsay, Isle, green grits of, 36. 
 
 Orthoclase in felsite, 105, 299. 
 
 in granite, 97. 
 
 in kersantite, 115. 
 
 in lamprophyres, 298. 
 
 in segregation veins in Loch<;oil- 
 
 head east and west dyke, 140, 157. 
 in Stralachlan deformed igneous 
 
 rock, 68. 
 
 in trachytic dykes, 170. 
 
 Orthofelsite, 299. 
 
 Otter, 2, 6, 7, 47, 148, 198. 
 
 contours under water near, 245. 
 
 Ferry, 3, 284, 292. 
 
 old cairns near, 278. 
 
 raised beaches at, 265. 
 
 House, raised beaches at, 265. 
 
 Over Inens (193), raised beaches at, 267. 
 
 PAPS of Jura, 3. 
 
 Paragonite, 35. 
 
 Paul's Cave (162), 275. 
 
 PEACH, B. N., 133. 
 
 Peat, general description of, 273-275. 
 
 Peat, mosses, and bogs, incidental refer- 
 ences to, 5, 183, 188, 189, 190, 191, 
 192, 197, 200, 210, 213, 215, 228, 244, 
 251, 256, 257, 259, 260, 266, 267, 269, 
 270, 271, 284. 
 
 Pebbles and pieces in the Upper Old Red 
 rocks, 89, 92, 93, 94, 95, 96. 
 
 iu the Loch Fad conglomerate, 89. 
 
 in the schists, lithological char- 
 acters, 9, 12, 15, 16, 20, 26, 29, 30, 31, 
 33, 34, 52, 54, 56, 57, 84, 178, 179, 
 185, 192, 196, 295, 296. 
 
 elongation or deformation of, 
 
 15, 16, 21, 22, 30, 34, 45. 
 
 in a limestone in garnetiferous 
 
 schist, 52. 
 
 in Loch Tay limestone, 47. 
 
 Pecten islandicus, 245, 246, 247, 306, 307. 
 
 Pegmatitic structure, 65, 164. 
 
 Pegmatites, Albite, 10, 17, 18, 34, 40, 43, 
 76, 80, 149, 225. 
 
 basic, of the Sith an t-Sluain 
 
 dolerite, 164, 165, 166. 
 
 connected with the granite, 98. 
 
 of the Lewisian gneiss, 103. 
 
 pebbles of, in the schists, 15. 
 
 Pennine (chlorite), 300. 
 
 Peridotite, 75. 
 
 Perlitic structures, 132-136, 154. 
 
 Phyllade aimantifere of Montherme, 80. 
 
 Phyllite, Albite, of Saxony, 297. 
 
 analyses of, 39, 55. 
 
 and phyllitic mica schists, foliation 
 
 in, compared to that in the more 
 massive schists, 12, 14, 19, 20, 21. 
 
 obliteration of early structures 
 
 in, 21, 59. 
 
 calcareous, 54, 55, 85, 280. 
 
 gritty, 30, 178. 
 
 pieces in the Upper Old Red breccias, 
 
 92. 
 
 Phyllite series of Ardrishaig. See Ardris- 
 haig. 
 
 of Dunoon. See Dunoon. 
 
INDEX. 
 
 Pipe rock of Sutherland, 56. 
 Pitch of axes of folds, 59, 87. 
 Pitchstoiie of Eskdale, 133. 
 Plagioclase in segregation veins in Dunoon 
 Castle dyke, 140. 
 
 in basaltic dykes, 136, 140, 142, 
 
 156, 158. 
 
 in diorite of Castle Lachlan, 71. 
 
 in dolerite, etc. of Sith an t-Sluain, 
 
 165. 
 
 in felsite, 105, 299. 
 
 in granite or granitit*-, 96. 
 
 in hy perite, 1 05. 
 
 in lamprophyres, 114, 116, 298. 
 
 in porphyrite, 103, 105, 299. 
 
 PLATER, J. HOKT, 170. 
 Point Farm (203), 197, 292. 
 Polchorkan (142), 226, 227, 228. 
 
 (142), superficial deposits near, 269, 
 
 274, 293. 
 Polphail (192), 194. 
 
 (192), standing stones near, 278. 
 
 Population, 4, 294. 
 
 I'orphyrite and felsite, general descrip- 
 tion* of, 102-105, 298-299. 
 
 incidental references to, 6, 99, 234. 
 
 Quartz-, 299. 
 
 like pebbles in Upper Old Red 
 
 Sandstone, 92. 
 
 Porphyritic crystals (phenocrysts) of 
 felspar in basaltic dykes, 130-131, 
 133, 134, 135,136, 137, 138, 140, 141, 
 142, 150, 152, 153, 154, 156, 161, 162, 
 185. 
 
 in diorite near the granite, 99. 
 
 in epidiorites, 62, 66, 68. 
 
 in granite, 97, 98. 
 
 in porphyrite and felsite, 99, 
 
 102, 103, 104, 105, 299. 
 Porphyry, Liebeneiite, 93. 
 Port a Ghobhlan (203), 150. 
 
 a Mhadaidh (192), 193, 194. 
 (192), islands near, in time of 
 
 50-foot beach, 267. 
 
 an Eilein (182), 23, 27, 28. 
 
 (182), supeificial deposits 
 
 near, 245, 247, 304-307. 
 
 an Lochan, 206. 
 
 raised beach near, 267. 
 
 Driseach (182), 195. 
 
 (182), superficial deposits at, 
 
 249, 267. 
 
 Ghabhar, (192), 194. 
 
 Leathan (202), 189, 194. 
 
 (202), superficial deposits at 
 
 or near, 266, 293. 
 
 na Beiste, 196. 
 
 Portavaidue (192), 282. 
 
 (192). raised beach near, 266. 
 
 (192)1 tillage ground near, 294. 
 
 Post-Cambrian movements in North- 
 West of Scotland, 13, 29. 
 
 Post-tertiary and recent deposits, list of, 
 5. 
 
 Potash felspar pebbles in Torridoniuu 
 rocks, 15. 
 
 Pottery clay, 109, 291, 292. 
 
 Predazzo, Liebeneiite porphyry of, 93. 
 
 Preglacial stream courses, 237, 244. 
 
 Prehistoric remains, 277-279, 
 
 Pre-Torridonian dykes of the North-West 
 
 of Scotland, 121. 
 PROUDFOOT, Mr, of Bernice, 277. 
 PUMPELLY, R., 297. 
 Pyrites, iron, 9, 48, 57, 58, 63, 76, 80, 
 
 81, 98, 99, 106, 114, 148, 157, 158, 
 
 170, 288. 
 copper, 76, 81, 173, 177, 178, 287, 
 
 288, 289. 
 Pyrrhotine, 288. 
 
 Q 
 
 QuAKEiEsin albite schists and anticline 
 
 schists, 195, 292. 
 in basaltic dykes, 136, 137, 190, 
 
 194. 195, 290-291, 292. 
 in epidiorite and related roek, 64, 
 
 291-292. 
 
 in felsite, 104, 105, 192, 291. 
 
 in garnetiferous schist horizon, 189. 
 
 in green beds, 292. 
 
 in lamprophyres, 197, 291. 
 
 in magnesian limestone, 93, 289- 
 
 290. 
 in phyllites or slates, 30, 32, 178, 
 
 290. 
 in schistose greywackes or grits, 16, 
 
 31, 32, 178, 288, 292. 
 limestones, 32, 46, 189, 210, 
 
 290. 
 
 in Upper Old Red sandstone, 292. 
 
 Quartz, opalescent or bine. See Blue or 
 
 Opalescent Quartz. 
 granulite, 5. See also Quartzile 
 
 Schist. 
 
 porphyrite, 299. 
 
 lorphyry, blocks of, in Newton 
 
 Bay, 262. 
 
 rims round garnets, 50. 
 
 pyrites and magnetite, 57, 58, 
 
 81. 
 
 rock, 7- 
 
 veins, 9, 10. 13, 17, 22, 27, 28, 37, 
 
 38, 40, 44, 45,' 50, 52, 88, 139, 148, 
 
 149, 151, 161, 166, 177, 178, 188, 190, 
 
 191, 193, 194, 195, 196, 206, 225. 
 
 boulders from, 236, 243. 
 
 pebbles from, in Upper Old 
 
 Red sandstone, 89, 92, 93, 94. 
 pieces of, included in igneous 
 
 rocks, 113, 114, 138. 
 
 striae on, 252. 
 
 with epidote, 33, 61, 79. 99, 
 
 101. 
 
 with ilinenite, 79. 
 
 with tourmaline, 35, 78. 
 
 -albite veins. See Albite Pegma- 
 
 tites. 
 Quartzite, Olenellus, of Massachusetts, 
 
 297. 
 
 pebbles, in Upper Old Red sand- 
 stone, 92, 94. 
 schist or quartz schist, 5, 8, 14, 45, 
 
 52, 54, 55, 56, 57, 58, 59, 60, 61, 66, 
 
 70, 71, 78, 79, 88, 197, 199, 200, 217, 
 
 218, 221, 225, 231. 
 calcareous, 46, 48, 52, 53, 85, 
 
 211, 212, 230. 
 
330 
 
 GEOLOGY OF COWAL. 
 
 R 
 
 RADIOLARIAN cherts of Aberfoil, etc., 89. 
 
 Radstadter Tauern, albite-gneiss of, 297. 
 
 Rainfall, 3. 
 
 liaised beaches, general description of, 
 262-268. 
 
 incidental references to, 31, 58, 
 
 64, 72, 92, 95, 119, 172, 173, 174, 
 175, 178, 180, 186, 187, 194, 207, 217, 
 218, 220, 239, 241, 242, 244, 245, 247, 
 248, 249, 250, 251-252, 260, 261, 269, 
 274, 276, 277, 278, 282, 285, 286, 291, 
 292, 293, 294. 
 
 Rashaeld (173), 288. 
 
 (173), alluvium near, 271. 
 
 (173), glacial shell bed near, 307. 
 
 (173), old bloomeries near, 289. 
 
 Recent and post- tertiary deposits, list of, 
 
 Red Well (183), 172. 
 
 RENARD, Professor, 80. 
 
 Reservoirs, 293. 
 
 RHYND, Mr, of Strachur, 166. 
 
 RHYS, Professor, 1. 
 
 Rivers, list of chief, in Cowal, 2. 
 
 ROBERTSON, Dr DAVID, 245, 246, 304. 
 
 Rock basins, 244. 
 
 Rodding, 10, 27, 40, 42, 45, 46, 49, 50, 
 
 76. 
 
 ROSEN BUSCH, Professor, 298. 
 Rothesay, East Bay, 80. 
 Rudha Ban (182), 195. 
 
 (182), raised beach near, 267. 
 
 Rudhaban (house), boulder clay at, 249. 
 Rudha Bathaich Bhain (133), 37, 49, 50, 
 
 232. 
 
 (133), boulders at, 253. 
 
 Croise (152), moraines near, 258. 
 
 Garbh (152), boulder clay near, 255. 
 
 na Peilige (203), 196. 
 
 (203), granite boulder near, 
 
 250. 
 
 nan Eoin (153) 42, 203. 
 
 (153), erosion terrace near, 
 
 268. 
 
 Preasach (192), 191. 
 
 (192), vitrified fort near, 278. 
 
 Stillaig (202), 194. 
 
 Ruel, river, 2, 185, 198. 
 
 superficial deposits near, 239- 
 
 240, 246. 
 
 estuary, striee at side of, 250. 
 
 Rutile, 14, 34, 35, 76, 297, 300. 
 
 S. 
 
 SADDLE, The, (153), 226, 229, 283, 285, 
 
 288. 
 St Catherine's, 3, 15, 49, 54, 56, 57, 59, 
 
 63, 64, 65, 66, 90, 105, 109, 110, 119, 
 
 139, 160, 231, 280, 281, 291. 
 superficial deposits near, 255, 267, 
 
 286. 
 
 District, structure of, 217-225. 
 
 ST FINAN, 188. 
 Sand, blown, 5, 277. 
 
 for iron castings, 293. 
 
 pits, 266, 267, 293. 
 
 Sandbank, 4, 84, 173. 
 
 sand and gravel pit at, 293. 
 
 water supply of, 293. 
 
 Sandstone boulders, 248. 
 | Sandstones, Upper Old Red, general de- 
 scription of, 92-93. 
 incidental references to, 5, 94, 
 
 95, 107, 150, 292. 
 
 Sanidine of Drachenfels trachyte, 299. 
 Saussurite, 62, 180. 
 Saxony, albite- phyllite of, 297, 298. 
 Scenery, geological aspects of, general 
 
 description of, 278-288. 
 incidental references to, 113, 
 
 126-127, 147, 152-153, 161, 266. 
 
 of Cowal, 3, 4. 
 
 of Tignabruaich District, 188. 
 
 Schists between the south-east green 
 
 beds and the albite schists, general 
 
 descriptions of, 18-22, 38-39. 
 incidental references to, 179- 
 
 181, 183, 188, 196-197. 
 sedimentary, probable order of, 
 
 86. 
 south-east of the Bull Rock grey- 
 
 wacke, general description of, 29, 
 
 31. 
 incidental references to, 84, 
 
 178. 
 
 Sea urchin or echinus, 246, 305, 307. 
 Sea-weed, stony, in glacial shell beds, 
 
 247, 304. 
 
 Segregation veins in east and west 
 
 basaltic dykes, 139-140, 147, 155, 
 
 157. 
 Sericite, 10, 11, 14, 15, 16, 17, 18, 22, 
 
 26, 54, 56, 76, 188, 296, 297. 
 
 gneiss, 16. 
 
 Serpentine, general description of, 72- 
 
 75, 
 incidental references to, 5, 6, 79, 
 
 152, 153, 175, 199, 200. 
 
 boulders, 248, 250. 
 
 pseudomorphs of, in basaltic dykes, 
 
 131, 136, 140, 156. 
 Serpula in glacial shell beds, 246, 305, 
 
 307. 
 
 Seters, 294. 
 Sgarach Mor (173), 2, 108, 114, 129, 
 
 131, 138, 182, 183. 
 
 (173), striations near, 244. 
 
 Sgat Bheag (202), 196. 
 
 Mor (202), 196. 
 
 Sgian Dubh (183), 132. 
 
 landslip on (183), 276. 
 
 Sgor Coinnich (153), 87, 112, 115, 121, 
 
 161, 201, 204. 
 
 (153), striee near top of, 252. 
 
 Shales, black, of Aberfoil, etc., 89. 
 
 Upper Old Red, 92. 
 
 Shap Fell granite, 291. 
 
 SHARPE, DANIEL, 17. 
 
 Shell beds, glacial, 5, 55, 235, 240, 245- 
 
 248, 304-307. 
 Shielings, 294. 
 Sillimannite, 91, 98. 
 
 Sills, basaltic, 146, 151, 155. 
 
 Silurian or Cambrian albite schists of 
 
 Massachusetts, 298. 
 Silver, 58, 288. 
 
INDEX. 
 
 331 
 
 Sith an t-Sluain (152), 41, 46, 52, 77, 
 
 210, 211, 213, 281. 
 
 (152), boulders near, 254. 
 
 dolerite, 106, 163-166. 
 
 boulders of, 254. 
 
 Sitheaii Mor (193), 197. 
 SKENE, Dr W. F., 2, 4. 
 Skye, basaltic dykes of, 131. 
 
 lamprophyres of, 109. 
 
 metamorphism near granophyres, 
 
 of, 100. 
 
 Torridonian rocks of, 15, 36. 
 
 Slate, 6, 7, 12, 19, 54, 55, 178. Sue 
 
 also Dunoon Phyllite Series. 
 Slaty cleavage, 17. See also Foliation. 
 greenstone, 6. See also Epidiorite 
 
 and Hornblende Schists. 
 Sleat, basaltic dykes of, 131. 
 
 lamprophyres of, 109. 
 
 SMITH, ERNEST A., 58. 
 
 SMITH, JAMES, of Jordanhill, 245. 
 
 Socach (141), 87, 104, 109, 148, 149, 
 
 158, 160, 223, 288, 291. 
 
 boulders near, 253, 254. 
 
 drift near, 258, 259. 
 
 Uachdarach, 223, 281. 
 
 Soret's principle, 136. 
 
 South Hall (194), 3. 
 
 (194), boulder clay and glaciation 
 
 near, 235, 236, 243. 
 
 (194), raised beaches near, 265. 
 
 South of Scotland, Arenig and Llaudeilo 
 
 rocks of, 89. 
 Southern Uplands, rocks of, correlated 
 
 with those of the Highlands, 7. 
 Specular irou ore or iron glance, 55, 80, 
 
 178, 288-289. 
 Sphene in schists and epidiorite, 34, 
 
 57, 65, 76, 79. 
 
 in granite, 97, 298. 
 
 Spherulites in lamprophyres, 119-120. 
 
 in trachytic dykes, 168-170, 
 
 Spinelle in glass from vitrified fort, 279. 
 Springfield (182), 107, 144. 
 
 (182), boulders on shore near, 248. 
 
 (182), superficial deposits near, 235, 
 
 304-307. 
 
 Springs, 239, 247, 275. 
 Squeezing from between limbs of folds, 59. 
 Sron Criche (152), 215. 
 
 (152), moraines near, 256. 
 
 Cruaich (151), 198, 212. 
 
 Dubh (181), 191. 
 
 Standing stones, 278. 
 
 Start Point, Devonshire, quartz-albite 
 
 veins near, 18. 
 Steatite, 72, 74. 
 Stillaig Farm (192), 195. 
 (192), moor once enclosed near, 
 
 294. 
 
 (192), stria? near, 250. 
 
 (192), superficial deposits near, 
 
 249, 266, 293. 
 Low (192), islands near, iu time of 
 
 100-foot beach, 267. 
 
 (192), old fort near, 279. 
 
 (192), standing stone near, 
 
 278. 
 (192), superficial deposits near, 
 
 266, 270. 
 
 Stob an Eas (134), 33, 82, 104, 114, 115, 
 
 231, 234, 254, 281. 
 
 (134), moraines near, 256. 
 
 (134), striae near, 252. 
 
 Liath(142), 108, 224. 
 
 (142), landslips on, 276, 286. 
 
 Stonefield (163), 182, 183. 
 (163), superficial deposits near, 269, 
 
 270. 
 Stonehaven, 6, 295. 
 
 quartz-albite veins of, 18. 
 
 Storm banks, 266. 
 
 Stowhall Burn (181), 191. 
 
 Strachur, 4, 52, 53, 56, 59, 79, 90, 102, 
 
 109, 140, 158, 223, 228, 283. 
 old fort and standing stones near, 
 
 277. 
 polished stone implement found 
 
 near, 277. 
 superficial deposits near, 260, 269, 
 
 274, 286, 292. 
 
 Bay, 49, 53, 57, 158, 209, 284. 
 
 boulders on shore of, 268. 
 
 superficial deposits near, 209, 
 
 293. 
 District basaltic dykes, description 
 
 of, 155-162. 
 glacial deposits, description of, 
 
 252-262. 
 Strachurmore (141), 111, 158. 
 
 (141), alluvium near, 270, 271. 
 
 Stralachlan, 6, 7, 69, 71, 152, 153, 155, 
 
 199. 
 
 river terraces of, 294. 
 
 District, basaltic dykes, description 
 
 of, 151-155. 
 glacial deposits, description of, 
 
 250-252. 
 
 structure in, 197-200. 
 
 epidiorites, 67-72. 
 
 Glen, 115, 119, 199, 281. 
 
 glaciation of, 250, 251. 
 
 superficial deposits of, 250, 
 
 251, 269. 
 
 River or Burn, 153, 199, 211, 212. 
 
 deltas near head of, 270. 
 
 Strain bands, 24, 26, 27, 28, 40. 
 
 lines in crushed serpentine, 73. 
 
 in Stralachlan epidiorite, 68. 
 
 slip or Ausweichung foliation. See 
 
 Ausweichung. 
 Strath Echaig, superficial deposits in, 
 
 236, 238, 269. 
 
 nan Lub (163), 33, 162, 213, 215. 
 
 (163), superficial deposits in 
 
 and near, 255, 256, 257, 259, 273, 275. 
 Stretching. See Elongation. 
 Striae, ice, 243, 214, 249-250, 251, 252, 
 
 253, 254, 261, 268. 
 Stronafian, Upper, (182), 27, 40. 
 StronchuUiu (174), 55, 136, 145, 181. 
 
 (174), boulder clay near, 237. 
 
 Burn, 180, 181, 287. 
 
 Hill, 62, 127, 179, 180, 181. 
 
 superficial deposits near, 270, 
 
 273. 
 
 Strondavain (162), 37, 62, 161, 168, 213. 
 Strone (174), 4. 
 
 (174), water supply of, 293. 
 
 Dearg (183), landslip on, 275, 276. 
 
332 
 
 GEOLOGY OF COWAL. 
 
 Strone Point (174), 81, 180, 181. 
 
 (174), old fort on, 278. 
 
 (194), 32, 33, 38, 81, 187. 
 
 (194), boulders at, 238. 
 
 (194), erosion terrace at, 265. 
 
 (194), superficial deposits near, 
 
 235, 236, 238, 247. 
 
 Saul (173), 171, 172, 281. 
 
 (173), strise near, 244. 
 
 Strone-duich, 294. 
 
 Stronlonag (163), strise near, 244. 
 
 (163), superficial deposits near, 269. 
 
 Stuck (152), 21P. 
 
 Burn, 40, 44, 78, 283. 
 
 Stuckbeg(153), 225, 227, 229, 285. 
 (153), contours under water near, 
 
 245. 
 
 (153), terraces near, 264, 265. 
 
 Stucreach (140), 56, 57, 60, 66, 208, 209, 
 
 210. 
 
 (140), erosion terrace near, 265. 
 
 (140), raised beach near, 267. 
 
 Sugach Aodaiim (152), drift in, 207, 255. 
 
 (152), landslip near, 276. 
 
 Sulphate of iron, 58. 
 
 Sutherland, Lewisian gneiss of, 103. 
 
 pipe rock of, 56. 
 
 Swallow holes in limestone, 45, 281. 
 
 TABULAR view ot the rocks, 5-6. 
 Tachylite, general description of, 132- 
 
 136. 
 incidental references to, 6, 126, 
 
 128, 140, 141, 142, 143, 154. 
 Talc, 66, 72, 73, 117. 
 Tamhnish Burn (172), 77, 108, 111, 114, 
 
 185. 
 (172), superficial deposits in 
 
 or near, 238, 271. 
 Tangy Glen (Campbultowu), glacial shell 
 
 beds of, 215. 
 TEALL, J. J. H., 14, 15, 18, 22, 30, 31, 
 
 34, 39, 40, 43, 44, 47, 54, 57, 64, 65, 
 
 66, 67, 68, 69, 70, 71, 75, 77, 96, ( .7, 
 
 104, 105, 114, 115, 116, 118,120, 122, 
 
 121, 136, 140, 149, 153, l;-5, 157, 165, 
 
 237, 279, 291, 295, 299. 
 Telliua, 245, 307. 
 Tertiary age, supposed, of many basaltic 
 
 dykes, 147. 
 of Sith an t-Sluain dclerite, 
 
 166. 
 granophyrcs of Skye ; metamor- 
 
 phism near, 100 
 Thinning of limbs of folds, 13, 22, 26, 
 
 28, 29, 58, 59, 60, 88, 180, 225, 296. 
 
 of strain bunds, 27, 28. 
 
 Tholeite, 135. 
 
 Thrust lines in North-West of Scotland, 
 
 13, 88, 90, 122. 
 Thrust-like lines, small, in Cowal schists, 
 
 88, 207. 
 
 in glacial deposits, 240. 
 
 Tigh ua Cliche (141), 57, 81, 162, 210. 
 (141), glacial shell bed of, 260, 
 
 261. 
 
 Tighe Claddich (133), 105, 291. 
 
 (133), boulders at, 254. 
 
 Tighnabruaich, 4, 82, 292. 
 
 water supply of, 293. 
 
 Burn (Easan Donn), 151, 195. 
 
 District, basaltic dykes, description 
 
 of, 150-151. 
 glacial deposits, description of, 
 
 249-250. 
 
 structure in, 188-197. 
 
 Titaniferous iron mica (ilmenire), 158. 
 Tighnuillt (183), 32, 34, 79, 172, 173. 
 
 (183), sands and gravels at, 242. 
 
 Tobar an Fhionn, 2. 
 
 TOD, JAMES, 289, 307. 
 
 Toll a' Bhuic (164), 43, 204, 206, 207. 
 
 nam Muc (153), 205. 
 
 Tom a' Bhiorain (152), 214. 
 
 (152), deltas near, 271. 
 
 an lasgaire (152), 296. 
 
 . Conch ra (162), 141. 
 
 Dubh (133), 232, 233. 
 
 Molach (153), 229. 
 
 (153), peat moss near, 260, 
 
 275. 
 
 ua h' lolaire (171), 61. 
 
 nan Con (162), 45, 206. 
 
 (162), boulder clay near, 255. 
 
 (162), strife near, 253. 
 
 nan Gamhna (142), 227. 
 
 Odhar (184), 127, 173, 177. 
 
 Soilleir (162), 154. 
 
 (163), 205, 207. 
 
 (163), drift near, 255. 
 
 Toman Dubh (182), 108, 114. 
 Tombuidhe (141), 211. 
 
 (141), moraines near, 257. 
 
 Torridonian rocks, 15, 36, 88. 
 
 thrusts in, 13, 122. 
 
 Tourmaline, 35, 39, 40, 44, 45, 76, 77, 
 
 78, 297, 299, 300. 
 Toward, 4, 6, 8, 72, 73, 74, 79, 92 ; 9">, 
 
 96, 128, 143, 146, 171, 289. 
 
 boulders near, 237, 248. 
 
 superficial deposits near, 236, 243, 
 
 265. 
 
 Castle, 72, 92. 
 
 old fort near, 278. 
 
 Cottages, 92, 94, 95, 130, 131, 136, 
 
 150, 291. 
 
 Hill, 172, 175, 177, 178. 
 
 Point, 1, 4, 30, 39. 
 
 cultivated land near, 294. 
 
 Quay, 29, 30, 31. 
 
 boulders near, 248, 260, 262. 
 
 glacial shell bed, 247, 304-307. 
 
 Taynuill, 72, 74, 94, 95. 
 
 Trachyte of Drachenfels, 299. 
 Trachytic dykes, general description of, 
 
 166-171. 
 
 incidental references to, 6, 147. 
 
 Traditions affecting Cowal, 2, 4. 
 Transitional period, albite-gueisses of the 
 
 Alps sometimes referred to, 298. 
 Trees in peat, 273, 274. 
 
 of Cowal, 3, 188. 
 
 Tremolite, 63, 64, 65, 66, 70. 
 
 in altered limestones of Skye, 100. 
 
 Trichites, 134, 135, 142. 
 Troetolite, 165. 
 
INDEX. 
 
 333 
 
 Troustan (183), 120, 127, 132, 140, 141, 
 
 145, 187. 
 (183), superficial deposits of, 236, 
 
 242. 
 Troisgeach, boulders possibly from, 
 
 253. 
 Tyndrum, 89, 183, 233, 285, 287. 
 
 D 
 
 UIG (173), 61, 108, 130, 289. 
 (173), boulder clay near, 236. 
 
 Upper Old Red Sandstone, general de- 
 scription of, 92-96. 
 
 incidental references to, 5, 89, 107, 
 
 147, 150, 163, 171, 175, 236, 292. 
 
 boulders of, 248, 262. 
 
 Uralite in deformed igneous rocks, 68. 
 
 in Dunoon Castle dyke, 140. 
 
 VALLEYS, origin of, 284-285. 
 Veins, Quartz. See Quartz. 
 Quartz-albite. See Albite Pegma- 
 tites. 
 
 - with barytes, 105, 125, 157, 234, 
 
 287, 289. 
 with calcite, 65, 106, 138, 139, 
 
 145, 151, 157, 168, 169, 194, 287, 
 
 288. 
 
 with epidote, 33, 61, 79, 99, 101. 
 
 with ferriferous carbonate or chaly- 
 
 bite. See Ferriferous Carbonate. 
 with haematite, iron glance, or 
 
 specular iron ore, 55, 80, 146, 156, 
 
 167, 178, 236, 288-289. 
 
 with ilmenite, 79. 
 
 with magnetite, pyrrhotine, etc., 
 
 288. 
 
 with tourmaline, 35, 78. 
 
 Vesicles in glass from vitrified fort, 
 
 279. 
 
 Vitrified forts, 278-279. 
 Vogesite, 298. 
 VON FOULLON, Baron, 297. 
 
 W 
 
 WATCH HILL, Bute, 150. 
 
 Water supply, 293. 
 
 Watersheds, lowness of some, 257, 270, 
 
 274, 284. 
 
 WATSON, Rev. R. BOOG, 245. 
 Weathering of basaltic dykes, 127, 130, 
 
 133, 139, 154, 282-283. 
 
 of boulder clay, 235, 251. 
 
 of dolerite of Sith an t-Sluain, 164. 
 
 of granite, 105, 280. 
 
 of iron pyrites, 57, 58, 80. 
 
 of lamprophyres, 107, 113, 114, 
 
 115-116, 117, 119, 120, 121, 123, 282. 
 
 of Loch Tay limestone, 45, 47, 281. 
 
 of porphyrite, 102. 
 
 Wechselgebirge, schists of the, 297. 
 
 West Glen (182), raised beach at, 267. 
 
 Westmoreland, granite of Shap Fell, 291. 
 
 Whistlefield (152), 208, 284. 
 
 White mica. See Mica. 
 
 WHYTE, DUNCAN, 1, 2. 
 
 Wiener Neustadt, albite-gneiss south of 
 
 297. 
 
 WOOD, Mr, formerly of Blairmore, 287. 
 Woodlands (142), erosion terrace near, 
 
 265. 
 
 Woodside Lodge (142), 41, 42, 43. 
 WOLFF, J. E., 40, 297. 
 Worm tubes, appearances resembling, 47, 
 
 48, 56, 57. 
 
 Yellow mica in schists, 62, 66. 
 mineral, doubtful, in schists, 35, 
 
 76, 77, 81. 
 
 YOUNG, J. WALLACE, 64. 
 JOHN, M.D., 304. 
 
 ZEOLITE, 130, 165. 
 
 Zinc blende, 57, 58, 288. 
 
 ZIRKEL, Professor, 93. 
 
 Zoisite, 48. 
 
 Zone structure, in augite of lampro- 
 phyres, 115. 
 
 in felspars of granite, 97. 
 
 of lamprophyres, 115, 298. 
 
 of porphyrite, 103. 
 
 in hornblende of lamprophyre, 110-- 
 
 117. 
 
 SKILL AND COMPANY, PRINTERS, EDINBURGH. 
 
DESCRIPTION OF PLATES I.-V. 
 
 These are reproductions of Photographs of Natural Rock Exposures 
 taken by R. Limn. 
 
 PLATE I. 
 
 Schistose limestone with folding of the prominent foliation planes. Half a mile 
 north of the Bull Rock, Dunoon. Observer looking south-west. See p. 14. A 
 basalt dyke is seen in the background and a large erratic block from the "anticline" 
 grits. 
 
 PLATE II. 
 
 Folded phyllite with quartz veins. East Hay of Dunoon. Observer looking west. 
 The axes of the fold shade S.S.E. 
 
 PLATE III. 
 
 Contorted mica schist. North side of Fearna Bagh, Colintraive. Observer looking 
 east. The prominent folds have axes hading north-west at a low angle. They are 
 probably of " anticline " age. 
 
 PLATE IV. 
 
 Schistose greywacke with folded strain slips. North sideot'Fearua Bagh, Colin traive. 
 Observer looking east. The folds which affect the strain slips have axes hading 
 north-west, and are probably of " anticline " age. See p. 26. 
 
 PLATE V. 
 
 Contorted mica schist in cliff by the roadside a little south of Coylet Inn, Loch 
 Eck. Observer looking east. The prominent folds have axes hading north-west, 
 and are probably of " anticline " age. 
 
 To fare I'tattl. 
 
, 
 
GEOLOGY OF COWAL. 
 
 PLATE VI. 
 
 MICROSCOPIC SECTIONS or ROCKS. 
 Reproduced from Photographs taken by J. J. H. Teall. 
 
DESCRIPTION OF PLATE VI. 
 By J. J. H. Teall, F.R.S. 
 
 FIG. 1. x 35. Natural light. Slide 3418. Albite schist i mile 
 E.N.E. of Ard a' Chapuill (182). See p. 40 and Appendix I. 
 
 Section of a large albite crystal containing inclusions. The lines of 
 inclusions are curved near the margins, but the crystal has not been 
 strained. The ground-mass is mainly formed of white mica, chlorite, and 
 iron ores. 
 
 FIG. 2. x 35. Natural light. Slide 4733. Albite schist of Beinn 
 Tharsuinn (142), somewhat altered by basalt dyke. 
 
 Numerous albite-crystals in a matrix similar to the above. The 
 marginal portions of the albite-crystals are almost entirely free from 
 
 inclusions. 
 
 t Plate VI. 
 
DESCRIPTION OF PLATE VII. 
 By J. .1. H. Teall, F.R.S. 
 
 YIG. 3. x 35. Natural light. Albite schist from head of Stuck 
 Burn (152). Similar to the figures on Plate I., but containing also large 
 plates of white mica, two of which are seen in cross-section in the lower 
 half of the figure. 
 
 FIG. 4. x 35. Natural light. " Green bed " with albite and epidote, 
 1 mile slightly south of east of Dimderave Castle (133). See p. 44. 
 
 The minerals in the portion of the slide represented in this figure are 
 chlorite, biotite (scarce), granular epidote, quartz and albite. The biotite 
 cannot be distinguished from the chlorite : nor the albite from the quartz. 
 
 To face Plate VI J. 
 
GEOLOGY OF COWAL. 
 PLATE VII. 
 
 
 MICROSCOPIC SECTIONS OF ROCKS. 
 Reproduced from Photographs taken by J. J. H. Teali. 
 
NOTES ON PLATES VIII. AND IX. 
 
 In the Index of Plate VIII. the tablets for albite schist, schistose 
 limestone, and graphitic schist, have, through a misunderstanding, been 
 placed in close connection. These schists have, however, no closer 
 relationship to one another than to the other schists. 
 
 In Plate IX. the shelves of marine erosion and the blown sand are 
 shown by the same pattern as the alluvia. The width of this pattern is 
 slightly exaggerated along some of the sea margins. 
 
 To face Plate VIII 
 
LJ 
 
X 
 
 LJ 
 

N. W. 
 
 Diagram section to rej>rescut possible structure of the "anticline" between Inellan and (II 
 
 syncline is drawn in an interrupted dark li 
 
X. 
 
 S. E. 
 
 frit*. 
 
 e.ff- 
 
 el. Not drawn to scale, and all faults and minor folds omitted. The axis of the supposed 
 ;is folded bv the action of the "anticline." 
 
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