  “There is a great charm in the well-balanced union of cultivated powers of observation and analytical method, with considerable imagination and much poetical feeling, which runs through the pages of this volume.... We have indicated but imperfectly the philosophical spirit which marks every step of inquiry into the wonders of this ‘Great Ice Age,’ and we strongly recommend the volume to all who are prepared to read thoughtfully, and weigh the evidences of truth carefully, in the assurance of finding that there are indeed, ‘Sermons in Stones.’”—AthenÆum. “Every step in the process is traced with admirable perspicuity and fullness by Mr. Geikie.... This book will mark an epoch in the scientific study of the Ice Age.”—Saturday Review. “The book shows everywhere the marks of acute observation, wide research, and sound reasoning. It presents in a readable form the chief features of the great Ice Age, and illustrates them very amply from those great tracts of Scotland in which glaciation has left its most distinct and most enduring marks.”—Spectator. “No one can peruse this most interesting book without feeling grateful to Mr. Geikie for his masterly summing-up of the evidence, and appreciating the spirit of scientific candour with which he states his conclusions. At once in respect of its matter and its tone, the work forms a valuable contribution to our scientific literature.”—Scotsman. “By far the most important contribution to the chapter of Geological inquiry that has yet appeared. We can assure our readers that they will find in Mr. Geikie’s book an admirable and satisfactory summary of the present condition of opinion on some of the most interesting of geological questions which are here discussed in an agreeable and readable manner.”—Westminster Review. “This work, without any sacrifice of scientific accuracy and completeness, is so clear, and so free from technicalities, as to be intelligible to any reader of ordinary education. For knowledge and command of his subject, for skill in the arrangement of his facts, and for the clearness with which he reasons out his conclusions, Mr. Geikie occupies a high place as a scientific writer.”—Academy. “The most comprehensive and lucid interpretation that has been given of the Great Ice Age.”—Edinburgh Courant. “It offers to the student of geology by far the completest account of the period yet published, and is characterized throughout by refreshing vigour of diction and originality of thought.”—Glasgow Herald. “Can be cordially recommended both to the geologist and the general reader. The explanations are so full, and the method of handling so free from technicality, that with a moderate amount of attention the book may be understood, and its reasoning followed, by those who had previously little or no geological knowledge.”—Nature. DALDY, ISBISTER, & CO., 56, LUDGATE HILL, LONDON. WORKS OF TRAVEL, SCIENCE, AND PHILOSOPHY. Letters from Abroad.
The Reign of Law.
Primeval Man.
Iona.
Walks about the City and Environs of Jerusalem.
The Science of Gems, Jewels, Coins, and Medals, Ancient and Modern.
Holiday Letters.
Sundays Abroad.
Walks in Rome.
BY THE SAME AUTHOR. DAYS NEAR ROME.
WANDERINGS IN SPAIN.
A Year at the Shore.
Walks in Florence.
The Regular Swiss Round.
Popular Lectures on Scientific Subjects.
Town Geology.
God’s Glory in the Heavens.
The Egyptian Sketchbook.
Eastward:
Peeps at the Far East.
Through Normandy.
The Philosophy of the Conditioned:
The Human Intellect.
Westward by Rail.
A Summer in Skye.
Lewsiana;
Our Inheritance in the Great Pyramid.
Man and Beast, Here and Hereafter.
[116] Trans. of Geol. Soc. of Glasgow, vol. iv., p. 146. [117] Geol. Mag., vi., p. 391. [118] See “Memoirs of Geological Survey of Scotland,” Explanation of sheet 22, p. 29. See also Trans. Glasgow Geol. Soc., iv., p. 150. [119] “Great Ice Age,” p. 374. [120] “Great Ice Age,” p. 384. [121] “Geological Survey of Ohio, 1869,” p. 165. See also “Great Ice Age,” chap. xxviii. [122] Quart. Journ. Geol. Soc., xxviii., p. 435. [123] Brit. Assoc. Report, 1863. [124] Trans. Glasgow Nat. Hist. Soc., vol. i., p. 115. [125] Trans. of the Geol. Soc. of Glasgow, vol. iii., p. 133. See also “Great Ice Age,” chaps. xii. and xiii. [126] Chap. XXIX. [127] Edin. New Phil. Journ., vol. liv., p. 272. [128] “Newer Pliocene Geology,” p. 129. John Gray & Co., Glasgow. [129] “Glacial Drift of Scotland,” p. 67. [130] “Glacial Drift of Scotland,” p. 12. [131] See Chapter IV. [132] “Discovery of the North-West Passage,” p. 213. [133] “Voyage of the Resolute,” p. 294. [134] Quart. Journ. Geol. Soc., vol. xi., p. 540. [135] “McClure’s North-West Passage,” p. 214. Second Edition. [136] “British Association Report for 1855,” p. 381. “The Last of the Arctic Voyages,” vol. i., p. 381. [137] Mr. James Geikie informs me that the great accumulations of gravel which occur so abundantly in the low grounds of Switzerland, and which are, undoubtedly, merely the re-arranged materials originally brought down from the Alps as till and as moraines by the glaciers during the glacial epoch, rarely or never yield a single scratched or glaciated stone. The action of the rivers escaping from the melting ice has succeeded in obliterating all trace of striÆ. It is the same, he says, with the heaps of gravel and sand in the lower grounds of Sweden and Norway, Scotland and Ireland. These deposits are evidently in the first place merely the materials carried down by the swollen rivers that issued from the gradually melting ice-fields and glaciers. The stones of the gravel derived from the demolition of moraines and till, have lost all their striÆ and become in most cases well water-worn and rounded. [138] Report on Icebergs, read before the Association of American Geologists, Silliman’s Journal, vol. xliii., p. 163 (1842). [139] “Manual of Geology,” p. 677. [140] Quart. Journ. Geol. Soc., vol. ix., p. 306. [141] Dana’s “Manual of Geology,” p. 677. [142] Quart. Journ. Geol. Soc., vol. ix., p. 306. [143] “Journal,” vol. i., p. 38. [144] “Short American Tramp,” pp. 168, 174. [145] “Short American Tramp,” pp. 239?241. [146] “Travels in North America,” vol. ii., p. 137. [147] Ibid., vol. ii., p. 174. [148] Proceedings of the Royal Society of Edinburgh, Session 1865?66, p. 537. [149] “Short American Tramp,” Eccentricity in (t) years after January 1, 1800 = vh2 + l2 where h = 0·000526 Sin (gt + ß) + 0·016611 Sin (g1t + ß1) + 0·002366 Sin (g2t + ß2) and l = 0·000526 Cos (gt + ß) + 0·016611 Cos (g1t + ß1) + 0·002366 Cos (g2t + ß2)
[195] See Professor C. V. Zenger’s paper “On the Periodic Change cf Climate caused by the Moon,” Phil. Mag. for June, 1868. [196] Phil. Mag. for February, 1867. [197] Phil. Mag. for May, 1868. [198] Student’s “Elements of Geology,” p. 91. Second Edition. [199] In an interesting memoir, published in the Phil. Mag. for 1850, Mr. Alfred Tylor estimated that the basin of the Mississippi is being lowered at the rate of one foot in 10,000 years by the removal of the sediment; and he proceeds further, and reasons that one foot removed off the general surface of the land during that period would raise the sea-level three inches. Had it not been that Mr. Tylor’s attention was directed to the effects produced by the removal of sediment in raising the level of the ocean rather than in lowering the level of the land, he could not have failed to perceive that he was in possession of a key to unfold the mystery of geological time. [200] Proc. Roy. Soc., No. 152, 1874. [201] I have taken for the volume and mass of the sun the values given in Professor Sir William Thomson’s memoir, Phil. Mag., vol. viii. (1854). [202] Phil. Mag., § 4, vol. xi., p. 516 (1856). [203] Phil. Mag. for July, 1872, p. 1. [204] “Principles,” p. 210. Eleventh Edition. [205] “Principles,” vol. i., p. 107. Tenth Edition. [206] The conception of submergence resulting from displacement of the earth’s centre of gravity, caused by a heaping up of ice at one of the poles, was first advanced by M. AdhÉmar, in his work “RÉvolutions de la Mer,” 1842. When the views stated in this chapter appeared in the Reader, I was not aware that M. AdhÉmar had written on the subject. An account of his mode of viewing the question is given in the Appendix. [207] Petermann’s Geog. Mittheilungen, 1871, Heft. x., p. 377. [208] Geol. Mag., 1872, vol. ix., p. 360. [209] “Open Polar Sea,” p. 134. [210] Journal of the Royal Geographical Society, 1853, vol. xxiii. [211] “Physics of Arctic Ice,” Quart. Journ. Geol. Soc. for February, 1871. [212] Some writers have objected to the conclusion that the antarctic ice-cap is thickest at the pole, on the ground that the snowfall there is probably less than at lower latitudes. The fact is, however, overlooked, that the greater thickness of an ice-cap at its centre is a physical necessity not depending on the rate of snowfall. Supposing the snowfall to be greater at, say, lat. 70° than at 80°, and greater at 80° than at the pole; nevertheless, the ice will continue to accumulate till it is thicker at 80° than at 70°, and at the pole than it is at 80°. [213] It is a pity that at present no record is kept, either by the Board of Trade or by the Admiralty, of remarkable icebergs which may from time to time be met with. Such a record might be of little importance to navigation, but it would certainly be of great service to science. [214] See Chapter XXVII., and also Geol. Mag. for May and June, 1870, and January, 1871. [215] Phil. Mag. for April, 1866, p. 323. [216] Ibid., for March, 1866, p. 172. [217] Reader, February 10, 1866. [218] In a former paper I considered the effects of another cause, viz., the melting of polar ice resulting from an increase of the Obliquity of the Earth’s Orbit.—Trans. Glasgow Geol. Soc., vol. ii., p. 177. Phil. Mag., June, 1867. See also Chapter XXV. [219] Phil. Mag. for November, 1868, p. 376. [220] Phil. Mag., November, 1868. [221] “Origin of Species,” chap. xi. Fifth Edition. [222] Lieutenant-Colonel Drayson (“Last Glacial Epoch of Geology”) and also Mr. Belt (Quart. Journ. of Science, October, 1874) state that Leverrier has lately investigated the question as to the extent of the variation of the plane of the ecliptic, and has arrived at results differing considerably from those of Laplace; viz., that the variation may amount to 4° 52', whereas, according to Laplace, it amounts to only 1° 21'. I fear they are comparing things that are totally different; viz., the variation of the plane of the ecliptic in relation to its mean position with its variation in relation to the equator. Laplace estimated that the plane of the ecliptic would oscillate to the extent of 4° 53' 33 on each side of its mean position, a result almost identical with that of Leverrier, who makes it 4° 51' 42. But neither of these geometricians ever imagined that the ecliptic could change in relation to the equator to even one-third of that amount. Laplace demonstrated that the change in the plane of the ecliptic affected the position of the equator, causing it to vary along with it, so that the equator could never possibly recede further than 1° 22' 34 from its mean position in relation to the ecliptic (“MÉcanique CÉleste,” vol. ii., p. 856, Bowditch’s Translation; see also Laplace’s memoir, “Sur les Variations de l’ObliquitÉ de l’Écliptique,” Connaissance des Temps for 1827, p. 234), and I am not aware that Leverrier has arrived at a different conclusion. [223] Memoir on the Secular Variations of the Elements of the Orbits of the Planets, “Smithsonian Contributions to Knowledge,” vol. xvii. [224] “Smithsonian Contributions to Knowledge,” vol. ix. [225] “Distribution of Heat on the Surface of the Globe,” p. 14. [227] Quart. Journ. Geol. Soc., June, 1866, p. 564. [228] Quart. Journ. Geol. Soc., vol. xxi., p. 186. [229] “Geological Observer,” p. 446. See also Mr. James Geikie’s valuable Memoir, “On the Buried Forests and Peat Mosses of Scotland.” Trans. of the Royal Society of Edinburgh, vol. xxiv., and Chambers’ “Ancient Sea-Margins.” [230] See Lyell’s “Antiquity of Man,” Second Edition, p. 282; “Elements,” Sixth Edition, p. 162. [231] In order to determine the position of the solstice-point in relation to the aphelion, it will not do to assume, as is commonly done, that the point makes a revolution from aphelion to aphelion in any regular given period, such as 21,000 years; for it is perfectly evident that owing to the great irregularity in the motion of the aphelion, no two revolutions will probably be performed in the same length of period. For example, the winter solstice was in the aphelion about the following dates: 11,700, 33,300, and 61,300 years ago. Here are two consecutive revolutions, the one performed in 21,600 years and the other in 28,000 years; the difference in the length of the two periods amounting to no fewer than 6,400 years. [232] Quart. Journ. Geol. Soc., vol. xxvii., p. 232. See also “The Last Glacial Epoch of Geology,” by the same author. [233] Quart. Journ. of Science, October, 1874. [234] The longer diameter passes from long. 14° 23' E. to long. 165° 37' W. [235] “Principles,” vol. i., p. 294. Eleventh Edition. [236] Phil. Mag. for August, 1864. [237] “Elementary Geology,” p. 399. [238] “The Past and Present Life of the Globe,” p. 102. [239] “Memoirs of the Geological Survey,” vol. ii., Part 2, p. 404. [240] “Coal Fields of Great Britain,” p. 45. Third Edition. [241] “Journal of Researches,” chap. xiii. [242] “Coal Fields of Great Britain,” p. 67. [243] See “Smithsonian Report for 1857,” p. 138. [244] Quart. Journ. Geol. Soc., May, 1865, p. civ. [245] “Geology of Fife and the Lothians,” p. 116. [246] “Life on the Earth,” p. 133. [247] Quart. Journ. Geol. Soc., vol. xi., p. 535. [248] Ibid., vol. xii., p. 39. [249] Miller’s “Sketch Book of Practical Geology,” p. 192. [250] From Geological Magazine, May and June, 1870; with a few verbal corrections, and a slight re-arrangement of the paragraphs. [251] See Phil. Mag. for November, 1868, p. 374. [252] See Phil. Mag. for November, 1868, pp. 366-374. [253] Journ. Geol. Soc., vol. xxi., p. 165. [254] Specimens of the striated summit and boulder clay stones are to be seen in the Edinburgh Museum of Science and Art. [255] Phil. Mag. for April, 1866. [256] “Tracings of the North of Europe,” 1850, pp. 48-51. [257] Quart. Journ. Geol. Soc., vol. ii., p. 364. [258] “Tracings of the North of Europe,” by Robert Chambers, pp. 259, 285. “Observations sur les PhÉnomÈnes d’Erosion en NorvÈge,” by M. HÖrbye, 1857. See also Professor Erdmann’s “Formations Quaternaires de la SuÈde.” [259] “Glacial Drift of Scotland,” p. 29. [260] Geological Magazine, vol. ii., p. 343. Brit. Assoc. Rep., 1864 (sections), p. 59. [261] Trans. Roy. Soc. Edin., vol. vii., p. 265. [262] “Tracings of Iceland and the Faroe Islands,” p. 49. [263] See Chap. XXIII. [264] Mr. Thomas Belt has subsequently advanced (Quart. Jour. Geol. Soc., vol. xxx., p. 490), a similar explanation of the steppes of Siberia. He supposes that an overflow of ice from the polar basin dammed back all the rivers flowing northward, and formed an immense lake which extended over the lowlands of Siberia, and deposited the great beds of sand and silt with occasional freshwater shells and elephant remains, of which the steppes consist. [265] Proc. Roy. Phys. Soc., Edin., vols. ii. and iii. [266] From Geol. Mag. for January, 1871. [267] Quart. Journ. Geol. Soc., xxvi., p. 517. [268] British Assoc. Report for 1864 (sections), p. 65. [269] Quart. Journ. Geol. Soc., xxvi., p. 90. [270] Geol. Mag., vii., p. 349. [271] Trans. Edin. Geol. Soc., vol. i., p. 136. [272] Geol. Mag. for June, 1870. See Chap. XXVII. [273] This was done by Mr. R. H. Tiddeman of the Geological Survey of England (Quart. Journ. Geol. Soc. for November, 1872), and the result established the correctness of the above opinion as to the existence of a North of England ice-sheet. Additional confirmation has been derived from the important observations of Mr. D. Mackintosh, and also of Mr. Goodchild, of the Geological Survey of England. [274] Trans. Geol. Soc., vol. v., p. 516 (first series). [275] Quart. Journ. Geol. Soc., vol. xi., p. 492. “Memoir of the Country around Cheltenham,” 1857. “Geology of the Country around Woodstock,” 1859. [276] Geol. Mag., vol. vii., p. 497. [277] Quart. Journ. Geol. Soc., vol. xxvi., p. 90. [278] My colleague, Mr. R. L. Jack. [279] The greater portion of this chapter is from the Trans. of Geol. Soc. of Edinburgh, for 1869. [280] Chapter XV., p. 253. [281] Trans. of the Geol. Soc. of Glasgow, vol. iii., part i., page 133. [282] Mr. Milne Home has advanced, in his “Estuary of the Firth of Forth,” p. 91, the theory that this trough had been scooped out during the glacial epoch by icebergs floating through the Midland valley from west to east when it was submerged. The bottom of the trough, be it observed, at the watershed at Kilsyth, is 300 feet above the level of its bottom at Grangemouth; and this Mr. Milne Home freely admits. But he has not explained how an iceberg, which could float across the shallow water at Kilsyth, say, 100 feet deep, could manage to grind the rocky bottom at Grangemouth, where it was not less than 400 feet deep. “The impetus acquired in the Kyle at Kilsyth,” says Mr. Milne Home, “would keep them moving on, and the prevailing westerly winds would also aid, so that when grating on the subjacent carboniferous rocks they would not have much difficulty in scooping out a channel both wider and deeper than at Kilsyth.” But how could they “grate on the subjacent carboniferous rocks” at Grangemouth, if they managed to float at Kilsyth? Surely an iceberg that could “grate” at Grangemouth would “ground” at Kilsyth. [283] Trans. of the Geol. Soc. of Glasgow, vol. iii., p. 141. [284] Mr. John Young and Mr. Milne Home advanced the objection, that several trap dykes cross the valley of the Clyde near Bowling, and come to so near the present surface of the land, that the Clyde at present flows across them with a depth not exceeding 20 feet. I fear that Mr. Young and Mr. Milne Home have been misinformed in regard to the existence of these dykes. About a mile above Bowling there are one or two dykes which approach to the river-bank, and may probably cross, but these could not possibly cut off a channel entering the Clyde at Bowling. In none of the borings or excavations which have been made by the Clyde Trustees has the rock been reached from Bowling downwards. I may also state that the whole Midland valley, from the Forth of Clyde to the Firth of Forth, has been surveyed by the officers of the Geological Survey, and only a single dyke has been found to cross the buried channels, viz., one (Basalt rock) running eastward from Kilsyth to the canal bridge near Dullatur. But as this is not far from the watershed between the two channels it cannot affect the question at issue. See sheet 31 of Geological Survey Map of Scotland. [285] Trans. Geol. Soc. Glasgow, vol. iv., p. 166. [286] “Great Ice Age,” chap. xiii. [287] See further particulars in Mr. Bennie’s paper on the Surface Geology of the district around Glasgow, Trans. Geol. Soc. of Glasgow, vol. iii. [288] See also Smith’s “Newer Pliocene Geology,” p. 139. [289] British Association Report for 1863, p. 89. Geologist for 1863, p. 384. [290] See Geological Magazine, vol. ii., p. 38. [291] Proc. Geol. Soc., vol. iii., 1840, p. 342. [292] “Antiquity of Man” (Third Edition), p. 249. [293] “Glacial Drift of Scotland,” p. 65. Trans. Geol. Soc. Glas., vol. i., part 2. [294] “Memoir, Geological Survey of Scotland,” Sheet 23, p. 42. [295] Mr. Robert Dick had previously described, in the Trans. Geol. Soc. Edinburgh, vol. i., p. 345, portions of these buried channels. He seems, however, to have thought that they formed part of one and the same channel. [296] A description of this channel was read to the Natural History Society of Glasgow by Mr. James Coutts, the particulars of which will appear in the Transactions of the Society. [297] “Occasional Papers,” pp. 166, 223. [298] Memoir read before the Royal Society, January 7, 1869. [299] “Alpine Journal,” February, 1870. [300] Phil. Mag., January, 1872. [301] Phil. Mag., July, 1870; February, 1871. [302] Philosophical Magazine for January, 1870, p. 8; Proceedings of the Royal Society for January, 1869. [303] Philosophical Magazine for March, 1869. [304] Proceedings of Bristol Naturalists’ Society, p. 37 (1869). [305] Ibid., vol. iv., p. 37 (new series). [306] Phil. Mag., S. 4, vol. x., p. 303. [307] Proceedings of the Bristol Naturalists’ Society, vol. iv., p. 39 (new series). [308] See Philosophical Transactions, December, 1857. [309] There is one circumstance tending slightly to prevent the rupture of the glacier, when under tension, which I do not remember to have seen noticed; that is, the cooling effect which is produced in solids, such as ice, when subjected to tension. Tension would tend to lower the temperature of the ice-molecules, and this lowering of temperature would have the tendency of freezing them more firmly together. The cause of this cooling effect will be explained in the Appendix. [310] Phil. Mag., March, 1869; September, 1870. [311] “Forms of Water,” p. 127. [312] See text, p. 10. [313] Mathematical and Physical Series, vol. xxxvi. (1765). [314] “Memoirs of St. Petersburg Academy,” 1761. [315] The calculations here referred to were made by Lagrange nearly half a century previous to the appearance of this paper, and published in the “MÉmoires de l’AcadÉmie de Berlin,” for 1782, p. 273. Lagrange’s results differ but slightly from those afterwards obtained by Leverrier, as will be seen from the following table; but as he had assigned erroneous values to the masses of the smaller planets, particularly that of Venus, the mass of which he estimated at one-half more than its true value, full confidence could not be placed in his results. Superior limits of eccentricity as determined by Lagrange, Leverrier,and Mr. Stockwell:—
[J. C.] [316] “MÉm. de l’Acad. royale des Sciences.” 1827. Tom. vii., p. 598. [317] Absolute zero is now considered to be only 493° Fah. below the freezing-point, and Herschel himself has lately determined 271° below the freezing-point to be the temperature of space. Consequently, a decrease, or an increase of one per cent. in the mean annual amount of radiation would not produce anything like the effect which is here supposed. But the mean annual amount of heat received cannot vary much more than one-tenth part of one per cent. In short, the effect of eccentricity on the mean annual supply of heat received from the sun, in so far as geological climate is concerned, may be practically disregarded.—[J. C.] [318] “Principles of Geology,” p. 110. “Mr. Lyell, however, in stating the actual excess of eight days in the duration of the sun’s presence in the northern hemisphere over that in the southern as productive of an excess of light and heat annually received by the one over the other hemisphere, appears to have misconceived the effect of elliptic motion in the passage here cited, since it is demonstrable that whatever be the ellipticity of the earth’s orbit the two hemispheres must receive equal absolute quantities of light and heat per annum, the proximity of the sun in perigee exactly compensating the effect of its swifter motion. This follows from a very simple theorem, which may be thus stated: ‘The amount of heat received by the earth from the sun while describing any part of its orbit is proportional to the angle described round the sun’s centre,’ so that if the orbit be divided into two portions by a line drawn in any direction through the sun’s centre, the heats received in describing the two unequal segments of the ellipse so produced will be equal.” [319] When the eccentricity of the earth’s orbit is at its superior limit, the absolute quantity of heat received by the globe during one year will be increased by only 1/300th part; an amount which could produce no sensible influence on climate.—[J. C.] [320] Sir Charles has recently, to a certain extent, adopted the views advocated in the present volume, viz., that the cold of the glacial epoch was brought about not by a decrease, but by an increase of eccentricity. (See vol. i. of “Principles,” tenth and eleventh editions.) The decrease in the mean annual quantity of heat received from the sun, resulting from the decrease in the eccentricity of the earth’s orbit—the astronomical cause to which he here refers—could have produced no sensible effect on climate.—[J. C.] [321] It is singular that both Arago and Humboldt should appear to have been unaware of the researches of Lagrange on this subject. [322] “RÉvolutions de la Mer,” p. 37. Second Edition. [323] See text, p. 37. [324] See Philosophical Magazine for December, 1867, p. 457. [325] Silliman’s American Journal for July, 1864. Philosophical Magazine for September, 1864, pp. 193, 196. [326] Philosophical Magazine for August, 1865, p. 95. [327] See text, p. 80. [328] See text, p. 222. [329] Proc. Roy. Soc., No. 157, 1875. [330] See text, p. 522. [331] Phil. Trans. for 1859, p. 91. [332] See text, p. 527. |
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