^{page 25 note *} See biographical notice of L. A. Necker, by Principal Forbes, J. D., Proc. Roy. Soc. Edin., v. (1862) p. 53 Google Scholar.

^{page 26 note *} Karsten's, Archiv (1829), vol. i. p. 56 Google Scholar.

^{page 26 note †} Trans. Nat. Hist. Soc. Northumberland, i. (1831) p. 9 Google Scholar.

^{page 26 note ‡} Op. cit., i. p. 44.

^{page 26 note §} Op. cit., i. pp. 305, 306, 308, 309.

^{page 26 note ∥} Op. cit., ii. (1838) p. 343 Google Scholar.

^{page 26 note ¶} Trans. Northumberland and Durham, ii. (1868) p. 30 Google Scholar.

^{page 26 note **} Proc. Roy. Soc., xxiii. (1875) p. 543 Google Scholar.

^{page 26 note ††} Quart. Jour. Geol. Soc., xl. (1884) p. 209 Google Scholar.

^{page 26 note ‡‡} Brit. Assoc Report, 1850, sections, p. 70, and Quart. Jour. Geol. Soc., vii. (1851) p. 87 Google Scholar.

^{page 27 note *} Quart. Jour. Geol. Soc., vol. vii. (1851) p. 104 Google Scholar.

^{page 27 note †} Trans. Roy. Soc. Edin., xxii. (1861) p. 649 Google Scholar.

^{page 27 note ‡} Proc. Roy. Soc. Edin., vi. (1867) p. 71 Google Scholar.

^{page 28 note *} Brit. Assoc. Report (Dundee), 1867, sects, p. 49 Google Scholar.

^{page 28 note †} Quart. Jour. Geol. Soc., xxvii. (1871) p. 279 Google Scholar.

^{page 28 note ‡} Quart. Jour. Geol. Soc., xxx. (1874) p. 220 Google Scholar.

^{page 28 note §} Geological Essays at Home and Abroad, pp. 271, 274Google Scholar; Nature, November 1880.

^{page 29 note *} Trans. Cambridge Phil. Soc. (1822), vol. ii. p. 23;Google Scholar Winch, , Geol. Trans., iv. (1814) p. 25 Google Scholar.

^{page 34 note *} Trans. Roy. Soc. Edin., xiv. (1840) p. 677 Google Scholar.

^{page 34 note †} Trans. Geol. Soc., iii. (1815) p. 79 Google Scholar.

^{page 36 note *} See Proc. Roy. Phys. Soc. Edin., v. (1880) p. 241 Google Scholar.

^{page 39 note *} See Teall, J. J. H., Quart. Jour, Geol. Soc., xl. (1884) p. 214 Google Scholar.

^{page 42 note *} Quart. Jour. Geol. Soc., vol. xl. (1884)Google Scholar.

^{page 42 note †} Op. cit., vol. xxxix. (1883) p. 444 Google Scholar (basalt-glass); xlii. (1886) p. 49, where Professor Judd discusses the gabbros, dolerites, and basalts as a whole. See postea, p. 77, note.

^{page 42 note ‡} Santorin et ses Éruptions, 1879 p. 203.

^{page 42 note §} See Mr Teall's excellent description of the Cleveland dyke, in the paper above cited.

^{page 43 note *} Proc. Roy. Phys. Soc. Edin., v. (1880) p. 255 Google Scholar.

^{page 44 note *} Mikroskopische Physiographie, 2nd edition, 504 et seq.

^{page 44 note †} For analyses of dykes, see Bell, I. L., Proc. Roy. Soc., xxiii. p. 546;Google Scholar Wilson, J. S. Grant, Proc. Roy. Phys. Soc. Edin., v. p. 253;Google Scholar Teall, , Quart. Jour. Geol. Soc., xl. p. 209;Google Scholar Judd, and Cole, , Quart. Jour. Geol. Soc., xxxix. p. 444 Google Scholar.

^{page 44 note ‡} On this subject see a paper by Dr A. Lagorio, “Über die Natur der Glasbasis sowie der Krystallisationsvorgänge im eruptiven Magma,” Tschermak's, Mineralog. Mittheil., viii. (1887) p. 421 Google Scholar.

^{page 44 note §} Wilson, J. S. Grant, Proc. Roy. Soc. Phys. Edin., v. (1880) p. 253 Google Scholar.

^{page 44 note ∥} Unpublished analyses made by Prof. Dittmar of Glasgow, and communicated to me by Mr Clough.

^{page 45 note *} Cambridge Phil. Trans., ii. p. 28.

^{page 45 note †} Trans. Roy. Soc. Edin., xiv. p. 677.

^{page 45 note ‡} Trans. Geol. Soc., iii. p. 227.

^{page 46 note *} Trans. Geol. Soc., iii. p. 80.

^{page 46 note †} Trans. Roy. Soc. Edin., xiv. p. 690 et seq.

^{page 46 note ‡} Trans. Geol. Soc., iii. p. 226. He believed that dykes in Secondary rocks reach a much greater thickness than in other formations. My own observations do not confirm this generalisation.

^{page 46 note §} At Cockfield, where it has long been quarried, it varies from 15 to 66 feet; at Armathwaite, in the vale of the Eden, it is about 54 feet ( Teall, J. J. H., Quart. Jour. Geol. Soc., xl. p. 211)Google Scholar.

^{page 47 note *} This point did not escape the attention of that excellent observer, Bekger, in his examination of the dykes in the north of Ireland. We find him expressing himself thus:—“The depth to which the dykes descend is unknown; and after having observed the sections of a great many along the coast in cliffs from 50 to 400 feet in height, I have not been able to ascertain (except in one or two cases) that their sides converge or have a wedgeform tendency” (Trans. Geol. Soc., iii. p. 227).

^{page 50 note *} See the careful examination of this dyke by Mr Teall, , Quart. Jour. Geol. Soc., xl. p. 209 Google Scholar.

^{page 51 note *} Trans. Roy. Soc. Edin., xx. p. 650.

^{page 51 note †} Trans. Geol. Soc., iii. p. 225.

^{page 52 note *} This is expressed in the Geological Survey map, Sheet 93, N.E.

^{page 54 note *} Quart. Jour. Geol. Soc., xl. p. 210.

^{page 56 note *} Drawn up for me by Mr Barrow.

^{page 57 note *} This locality was well described by Sedgwick, in his early paper on Trap-Dykes in Yorkshire, and Durham, , Trans. Cambridge Phil. Soc., ii. p. 27 Google Scholar.

^{page 57 note †} Western Islands, plate xvii.

^{page 58 note *} Op. cit., plate xxxiii. fig. 1.

^{page 59 note *} Op. cit., pl. xiv. fig. 4.

^{page 59 note †} Vol. i. pp. 384, 385.

^{page 61 note *} Macculloch figured an example from Strathaird, Western Islands, pl. xviii. fig. 1. Mr Clough has found some good instances in south-eastern Argyleshire.

^{page 62 note *} Explanation of Sheet 22, Geol. Survey Scotland, p. 26.

^{page 63 note *} Proc. Roy. Soc., xxiii. (1875) p. 543 Google Scholar.

^{page 63 note †} Tschermak's, Mineralogische Mittheilungen, ix. (1887) p. 145;Google Scholar Proc. Roy. Soc. Edin., 1888. Dr Stecher's investigation is based upon a series of specimens from the intrusive (Carboniferous) rocks of the basin of the Firth of Forth, and has reference both to the phenomena of contact-metamorphism and the alteration of the eruptive rock; but these changes belong to the Carboniferous period.

^{page 68 note *} Trans. Geol. Soc., iii, p. 75 Google Scholar.

^{page 69 note *} Quart. Jour. Geol. Soc., xiv. p. 1 Google Scholar.

^{page 70 note *} Essai Geologique sur l'Ecosse, p. 272.

^{page 71 note *} The only other known example of such a dyke-structure is that of the Pre-Cambrian series of dykes in the Archæan gneiss of Sutherland.

^{page 71 note †} Cambridge Phil. Trans., vi. (1835) p. 1 Google Scholar.

^{page 71 note ‡} Op. cit., p. 10.

^{page 72 note *} Op. cit., p. 69.

^{page 73 note *} Scenery of Scotland, 2d edit. (1887), p. 149. But see the remarks already made (p. 55) on the curious coincidence sometimes observable between the upper limit of a dyke and the overlying inequalities of surface.

^{page 74 note *} Quart. Jour. Geol. Soc., xxv. (1869) p. 163 Google Scholar.

^{page 74 note †} It is interesting to note that in the great paper on Physical Geology already cited, Hopkins considered the question of the outflow of lava from the fissures which he discussed. “If the quantity of fluid matter forced into these fissures,” he says, “be more than they can contain, it will, of course, be ejected over the surface; and if this ejection take place from a considerable number of fissures, and over a tolerably even surface, it is easy to conceive the formation of a bed of the ejected matter of moderate and tolerably uniform thickness, and of any extent” (op. cit., p. 71).

^{page 77 note *} In the course of my investigations I have had many hundreds of thin slices cut from the Tertiary volcanic rocks for microscopic determination. These I have myself studied in so far as their microscopic structure appeared likely to aid in the investigation of those larger questions of geological structure in which I was more specially interested. But for their detailed examination I have placed them with Dr Hatch, in whose hands, together with the large series of specimens accumulated by the Geological Survey, they will form the subject of a future memoir on the microscopic petrography of this most interesting group of rocks. He has submitted to me the results of his preliminary examination, and where these offered points of geological import I have availed myself of them by citations in the course of this memoir. Professor Judd, in a series of valuable papers, has discussed the general petrography of the Tertiary volcanic rocks; Quart. Jour. Geog. Soc., vols. xxxix., xli., xliiGoogle Scholar.

^{page 79 note *} See Explanation of Sheet 20, Geol. Survey, Ireland, p. 11.

^{page 83 note *} This is noticed by Mr Gardner, Starkie, Quart. Jour. Geol. Soc., xliii. (1887) p. 283,Google Scholar note.

^{page 84 note *} Mr Gardner is now describing and illustrating the flora fully for the Palæontographical Society; see vols. xxxviii., xxxix. et seq.

^{page 84 note †} The basalts of Antrim are the subject of an abundant literature. I may refer particularly to the papers of Berger and Conybeare (Trans. Geol. Soc., iii.), the Geological Report of Portlock, and the Explanations of the Sheets of the Geological Survey of Ireland.

^{page 86 note *} Explanatory Memoir of Sheets 7 and 8, Geological Survey, Ireland, by Messrs Symes, Egan, and M'Henry (1888), p. 37.

^{page 86 note †} Portlock:, Report on Geology of Londonderry, &c. (Geological Survey), p. 117.

^{page 86 note ‡} See Portlock, op. cit., p. 116.

^{page 87 note *} See Explanation of Sheets 7 and 8 of the Geological Survey of Ireland (1888), p. 23.

^{page 91 note *} There are no fewer than three faults in the basalt-capping on the summit of Ben Iadain. By bringing the basalts and schists into juxtaposition, they have given rise to topographical features that can be seen even from a distance. See fig. 20.

^{page 92 note *} Quart. Jour. Geol. Soc., xliii. (1887) p. 277 Google Scholar.

^{page 93 note *} For fuller local details regarding the Ardtun leaf-beds, I may refer to the original paper by the Duke of Argyll (Quart. Jour. Geol. Soc., vii. p. 89), and to the recent memoir by Mr Starkie-Gardner ( op. cit., xliii., 1887, p. 270)Google Scholar.

^{page 93 note †} Western Islands, vol. i. p. 568, and plate xxi. fig. 1.

^{page 93 note ‡} Quart. Jour. Geol. Soc., xliii. p. 283 Google Scholar.

^{page 95 note *} That the lava-fields did not completely bury this nucleus of older rock has been supposed to be shown by the fragments of red sandstone found in the ancient river-bed of Eigg, which was scooped out of the basalt-plateau and sealed up under pitchstone. But I am disposed to think that these fragments, together with those of Jurassic sandstone, came, not from Rum, but from some district more to the north and east, as will be adverted to in a later part of this paper.

^{page 95 note †} For further details regarding this plateau in Eigg, see my paper, Quart. Jour. Geol. Soc., xxvii. (1871) p. 290 Google Scholar.

^{page 97 note *} These features are more fully described in my Scenery of Scotland, 2d edit. (1887), pp. 74, 145, 216.

^{page 98 note *} A striking and illustrative contrast between the relative thickness of the beds of the two kinds of rock is supplied by the fine sections of this district. The amygdaloids range from perhaps 6 or 8 to 25 or 30 feet; but the prismatic basalts, while never so thin as the others, sometimes enormously exceed them in bulk. In the island of Wiay, for example, a bed of compact black basalt, with the confused starch-like grouping of columns, reaches a thickness of no less than 170 feet. Its bottom rests upon a red parting on the top of a dull greenish earthy amygdaloid.

^{page 100 note *} The instance of Carrict-a-raide, to be immediately referred to, is as near such a positive demonstration as could be looked for.

^{page 102 note *} This neck was recognised by Du Noyer in 1868 as “one of the great pipes or feeders of the basaltic flows.” See Prof. Hull, Explanation of Sheets 21, 28, and 29, Geol. Survey of Ireland (1876), p. 30 Google Scholar.

^{page 103 note *} Quart. Jour. Geol. Soc., xxx. (1874) p. 264 Google Scholar.

^{page 105 note *} See Explanation of Sheets 7 and 8, Geol. Survey of Ireland (1888), p. 31.

^{page 106 note *} One of these felsites when viewed under a high magnifying power is seen to present an abundant development of exceedingly minute micropegmatite arranged in patches and streaks parallel with the lines of fluxion structure in the general cryptocrystalline ground mass. The close relationship between the felsites, quartz-porphyries, and granophyres will be afterwards pointed out in the description of the acid rocks. It is remarkable that, though these rooks occur abundantly in fragments in the volcanic necks and agglomerates of the plateaux, not a single instance has been observed of their intercalation as contemporaneous sheets among the basic lavas. An analogous case of the interstratification of felsitic tuffs among basic lavas occurs in the volcanic series of the Old Red Sandstone of central Scotland.

^{page 107 note *} This extensive mass was not separated from the “syenite” of the Red Hills by Macculloch. Von Oeynhausen and Von Dechen noticed it as a conglomerate with quartz pebbles, but did not realise its volcanic nature (Karsten's Archiv, i. p. 90). In my map of Strath (Quart. Jour. Geol. Soc., xiv. plate i.) I distinguished it from the rock of the Red Hills, but no name for it appears in the legend of the map, nor is it referred to in the text. Its character as a true volcanic agglomerate was recognised by Professor Judd, Op. cit., p. 255. See Plate II. of the present memoir.

^{page 110 note *} In this connection I may again refer to Hopkins's Researches in Physical Geology, where the conditions of the problem here discussed have been distinctly realised. Speaking of the ejection of lava from a number of fissures, he remarks that the imperfect fluidity of the melted material “would seem to require a number of points or lines of ejection as a necessary condition.” “If there were only a single centre of eruption, a bed of such matter approximating to uniformity of thickness, could only be produced on a surface of a conical form.” “Where no such tendency to this conical structure can be traced, it would probably be in vain to look for any single centre of eruption. On the supposition, too, of ejection through continued fissures, or from a number of points, that minor unevenness of surface which must probably have existed under all circumstances during the formation of the earth's crust, would not necessarily destroy the continuity of a comparatively thin extensive bed of the ejected matter, in the same degree in which it would inevitably produce that effect in the case of central ejection” ( Cambridge P'il. Trans., vi. (1835), p. 71)Google Scholar.

^{page 111 note *} Dutton, C. B., “Tertiary History of the Grand Canon District,” U.S. Geol. Survey (1882), p. 104 Google Scholar.

^{page 111 note †} Dutton, C. E., “Geology of the High Plateaux of Utah,” U.S. Geol. Survey of the Rocky Mountain Region (1880), pp. 198, 200Google Scholar. See also pp. 232, 234, 276 of the same Monograph for additional examples.

^{page 111 note ‡} Tertiary History of the Grand Cañon, &c, p. 95 Google Scholar.

^{page 111 note §} Nature, xxxi. (1884) p. 89 Google Scholar.

^{page 111 note ∥} Quart. Jour. Geol. Soc., xxvii. (1871) p. 296 Google Scholar.

^{page 112 note *} For an excellent summary of it and an epitome of the descriptions of the Portrush section, see the Report on the Geology of Londonderry, &c., by J. E. Portlock (1843), p. 37.

^{page 112 note †} Dr F. Hatch, Explanation of Sheets 7 and 8, Geol. Survey of Ireland, p. 40 Google Scholar.

^{page 112 note ‡} “Address to Geological Society of Dublin, 1835,” p. 13, Jour. Geol. Soc. Dublin, vol. i. The varieties of the Portrush rock were described by the late Dr Oldham, in Portlock's Report on the Geology of Londonderry, p. 150; see also the same work for Portlock's own remarks, p. 97.

^{page 112 note §} For a list of the minerals in this rock, see Oldham, op. cit., p. 151.

^{page 114 note *} Professor Judd has described what he calls a “glomero-porphyritic structure” in this rock ( Quart. Jour. Geol. Soc., xlii. (1886) p. 71)Google Scholar.

^{page 118 note *} This locality has been described by Professor Judd, who believed the dolerites to be streams proceeding from a volcanic vent ( Quart. Jour. Geol. Soc., xxx. (1874) p. 261)Google Scholar.

^{page 120 note *} Quart. Jour. Geol. Soc., xxvii. (1871) p. 297 Google Scholar.

^{page 122 note *} This was my own first impression, when I began, as a boy, to ramble among them. Macculloch had correctly grouped them with the other overlying rocks, and this conclusion was afterwards confirmed by Zirkel.

^{page 122 note †} Western Islands of Scotland, vol. i. pp. 385, 484.

^{page 122 note ‡} Zeitschrift. Deutsch. Geol. Gesellsch., xxiii. (1871) p. 1 Google Scholar.

^{page 122 note §} Quart. Jour. Geol. Soc., xli. (1885) p. 354,Google Scholar xlii. (1886) p. 49.

^{page 123 note *} Zeitschr. Deutsch. Geol. Gesellsch., xxiii. (1871), p. 59 Google Scholar.

^{page 123 note †} Professor Judd, (Quart. Jour. Geol. Soc., xlii. p. 62)Google Scholar believes that originally all the gabbros contained olivine, and that where it is now absent, it has been altered into magnetite or serpentine.

^{page 123 note ‡} Op. cit., xli. In a later paper he insists on the gradation of the coarse granitoid varieties (gabbros) into holocrystalline compounds, where the felspar appears in lath-shapes with crystals or rounded grains of augite and olivine (dolerites), and thence into true basalts, magma-basalts, and tachylytes (op. cit., xlii. p. 62).

^{page 124 note *} MS. of Dr Hatch.

^{page 124 note †} Mineralogical Travels (1813), vol. ii. p. 72 Google Scholar.

^{page 125 note *} See his Western Islands, vol. i. pp. 368, 374, 385, 386. With much admiration for the insight and zeal, amounting almost to genius, which Macculloch displayed in his work among the Western Islands, at a time when, with poor maps and inadequate means of locomotion, geological surveying was a more difficult task than it is now, I have found it impossible to follow in his footsteps with his descriptions in hand, and not to wish that for his own fame he had been content to claim credit only for what he had seen. His actual achievements were enough to make the reputation of half-a-dozen good geologists. It was unfortunate that he did not realise how inexhaustible nature is, how impossible it is for one man to see and understand every fact even in the little corner of nature which he may claim to have explored. He seems to have had a morbid fear lest any one should afterwards discover something he had missed; he writes as if with the object of dissuading men from travelling over his ground, and he indeed tacitly lays claim to any thing they may ascertain by averring that those who may follow him “will find a great deal that is not here described, although little that has not been examined” (p. 373). Principal Forbes long ago exposed this weak side of Macculloch and his work ( Edin. New Phil. Jour., xl. (1846) p. 82)Google Scholar.

^{page 125 note †} Karsten's, Archiv, i. p. 99 Google Scholar. They frankly admit that “the relation of the hypersthene-rock to the other trap rocks was not ascertained.”

^{page 125 note ‡} Edin. New Phil. Jour., xl. (1846) pp. 85, 86 Google Scholar.

^{page 125 note §} Quart. Jour. Geol. Soc., xxx. (1874) p. 249 Google Scholar.

^{page 125 note ∥} Zeitschrift, Deutsch. Geol. Gesellsch., xxiii. (1871) pp. 58, 92 Google Scholar.

^{page 125 note ¶} In two of my excursions in Mull, and once in Skye, I was accompanied by my colleague Mr H. M. Cadbll, and I gladly acknowledge the great assistance he rendered me in mapping those regions.

^{page 126 note *} Though this and the other bosses are here spoken of as consisting of gabbro, it will be understood that this rock only constitutes the larger portion of their mass, which includes also dolerites, basalts, and other basic compounds.

^{page 129 note *} This limestone was noticed by Von Oeynhausen and Von Dechen, but they believed it to be a portion of the Lias torn off and carried upward by the eruptive rocks ( Karsten's, Archiv, i. p. 79)Google Scholar.

^{page 129 note †} This rock was first recognised by Mr H. M. Cadell, who accompanied me in one of my excursions over the ground.

^{page 132 note *} Western Islands, i. p. 486.

^{page 132 note †} Quart. Jour. Geol. Soc., xxx. p. 253 Google Scholar.

^{page 132 note ‡} Op. cit., xli. (1885) p. 354 Google Scholar. See also his paper in vol. xlii. of the same Journal.

^{page 137 note *} Mineralogy of the Scottish Isles, i. p. 205.

^{page 137 note †} Zeitsch. Deutsch. Geol. Gesellsch., xxiii. (1871) p. 58 Google Scholar.

^{page 138 note *} Quart. Jour. Geol. Soc., xxx. (1874)Google Scholar.

^{page 140 note *} On this subject, see the papers by Professor Judd already cited.

^{page 142 note *} Many years ago I was much struck with the evidence of alteration in the igneous rocks of Mull, and referred to it in several papers, Proc. Roy. Soc. Edin. (1866–1867), vol. vi. p. 73;Google Scholar Quart. Jour. Geol. Soc., xxvii. (1871) p. 282,Google Scholar note.

^{page 143 note *} “Geology of the Henry Mountains,” by G. K. Gilbert, U. S. Geographical and Geological Survey of the Rocky Mountain Region, 1877.

^{page 144 note *} Mineralogical Travels, ii. 90.

^{page 144 note †} Western Isles, see the descriptions of Skye, Mull, and Rum.

^{page 144 note ‡} Berger, , Trans. Geol. Soc., iii. (1816) p. 190 Google Scholar.

^{page 144 note §} Zeitsch. Deutsch. Geol. Gesellsch., xxiii. (1871) pp. 54, 77, 84, 88 Google Scholar.

^{page 144 note ∥} Tschermak's Min. und Petrog. Mittheilungen, 1878, p. 412.

^{page 146 note *} Tschermak's Min. und Pet. Mittheil., 1878, p. 412.

^{page 149 note *} Karsten's, Archiv, i. p. 89 Google Scholar.

^{page 150 note *} Trans. Edin. Geol. Soc., vol. ii. part 3.

^{page 150 note †} See Mr Teall's British Petrography (1888), p. 328.

^{page 150 note ‡} Explanation to Sheets 60, 61, and 71, Geol. Survey, Ireland, pp. 16, 30.

^{page 150 note §} Western Islands, i. p. 368; see also pp. 188; 575, 578.

^{page 150 note ∥} Op. cit., p. 370.

^{page 151 note *} Essai Géologique sur l'Écosse, pp. 291, 322, 327.

^{page 151 note †} Karsten's, Archiv, i. p. 82 Google Scholar.

^{page 151 note ‡} Edin. New Phil. Jour., xl. (1846) p. 84 Google Scholar.

^{page 151 note §} Zeitsch. Deutsch. Geol. Gesellsch., xxiii. (1871) pp. 90, 95 Google Scholar. He says that the gabbro seems to be the younger rock, so far as their relations to each other can be seen.

^{page 151 note ∥} Quart. Jour. Geol. Soc., xxx. p. 255 Google Scholar.

^{page 152 note *} This marble was believed to be altered Lias; but I have proved it by lithological, stratigraphical, and palæontological evidence to be Silurian, Lower (Quart. Jour. Geol. Soc., xliv. (1888) p. 62)Google Scholar.

^{page 154 note *} This rock appears to the eye as a Hack finely crystalline-granular felsite. Under the microscope “it presents a markedly granulitic structure, consisting mainly of small rounded grains of dirty brown turbid felspar, with isolated granules of colourless quartz. Scattered through the rock, or accumulated in patches, are small spherical or drop-like granules of a bright green augite (coccolite).”—Dr Hatch.

^{page 159 note *} Quart Jour. Geol. Soc., xxvii. (1871) p. 294 Google Scholar.

^{page 159 note †} Western Islands, vol. i. p. 487.

^{page 160 note *} In a thin slice cut from a specimen showing the junction, there is a minute vein of the porphyry penetrating the basalt which is much altered, while the porphyry becomes much finer in grain than at a distance from the contact.

^{page 161 note *} The best account yet published of these varieties in Skye is that by Prof. Zirkel, , Zeitsch. Deutsch. Geol. Gesellsch., xxiii. (1871) p. 88 Google Scholar.

^{page 162 note *} Edin. New Phil. Jour., xl. p. 78.

^{page 162 note †} Geology and Extinct Volcanoes of Central France, 2d edit, p. 68.

^{page 162 note ‡} The difference of contour and colour between the ordinary reddish smooth-sloped “syenite” and the black craggy “hypersthene rock” and “greenstone” at the Glamaig group of hills caught the eyes of Von Oyenhausen and Von Dechen ( Karsten's, Archiv, i. p. 83)Google Scholar.

^{page 164 note *} Quart. Jour. Geol. Soc., vol. xliv. (1888) p. 62 Google Scholar.

^{page 169 note *} Quart. Jour. Geol. Soc., xiv. p. 16 Google Scholar.

^{page 171 note *} For an early account of the Antrim trachytic rocks, see Berger, , Trans. Geol. Soc., iii. (1816) p. 190 Google Scholar. Professor Hull has described the Tardree rock in the Explanation to Sheets 21, 28, and 29, Geol. Survey of Ireland (1876), p. 17, and has supposed it to be older than the basalts, referring it to the Eocene period. Duffin (quoted by Mr Kinahan) believed that “the trachytes occur at the centres of eruption, and were probably poured out at the end of the outburst.” Du Noyer also (quoted by the same writer) thought them to be newer than the plateau-basalts, and to have lifted up masses of these rocks. Mr Kinahan himself (Geology of Ireland, p. 172) has pointed out the absence of any trachytic fragments between the basalts as an argument against the supposed antiquity of the acid protrusions. A full petrographical account of the Tardree rock is given by Von Lasaulx in the paper already cited, Tschermak's Min. Pet. Mittheil., 1878, p. 412.

^{page 171 note †} [Since this paper was read, and as it is passing through the press, I have received from Mr A. M'Henry, of the Geological Survey, some interesting information recently obtained by him at Templepatrick, co. Antrim. He has there found what he considers to be conclusive evidence that the trachyte is intrusive in the Lower Basalts; but that it is pierced by younger basic dykes. This is precisely the structure which my experience in the Inner Hebrides would have led me to expect.]

^{page 172 note *} Zeitsch. Deutsch. Geol. Gesellsch., xxiii. p. 54.

^{page 178 note *} For an account of the pitchstone veins of Eigg, see Quart. Jour. Geol. Soc., xxvii. p. 299 Google Scholar.

^{page 178 note †} Quart. Jour. Geol. Soc., xxvii. (1871) p. 303 Google Scholar.