Orkney Islands, glaciated by land-ice, 444
Osborne, Captain, remarks on recent forest trees in arctic
regions, 262, 263
Oudemans, Dr., on planet Mars, 80
Overton Quarry, inter-glacial bed in, 247
Pacific Ocean, depth of, 147
Packard, Mr., on glacial phenomena of Labrador, 282
Page, Professor, on temperate climate of Coal period, 422
〃 on character of coal plants, 421
〃 on old watercourse at Hailes quarry, 490
Palæontological objections against influence of ocean-currents, 53
Palæontological evidence of last glacial period, 285
Parry, Captain, discovery of recent trees in Melville Island by, 262
Peach, Mr. C. W., on inter-glacial bed at Leith Walk, 246
〃 on boulder clay of Caithness, 436
〃 on striated rock surfaces in Cornwall, 464
Peach, Mr. B. N., on striation of Caithness, 453
Pengelly, Mr. W., on raised beaches, 407
Perigee, nearness of sun in, cause of snow and ice, 74
Perihelion, warm conditions at maximum when winter solstice is at, 77
Permian period, evidence of ice-action in, 298−303
Perthshire hills, ice-worn surfaces at elevations of 2,200 feet on
the, 440
Petermann, Dr. A., on Dr. Carpenter’s theory, 138
〃 on thermal condition of the sea, 138
〃 chart of Gulf-stream and Polar current, 219
〃 _Geogr. Mittheilungen_ of, list of papers in relation to arctic
regions, 556
Phillips, Professor, on influence of eccentricity on climate, 539
Poisson’s theory of hot and cold parts of space, 7
Polar regions, effect of removal of ice from, 64
〃 influence of ice on climate, 64
〃 low summer temperature of, 66
Polar cold considered by Dr. Carpenter the _primum mobile_ of
ocean-currents, 173
〃 confusion of ideas regarding its influence, 180
〃 influence of, according to Dr. Carpenter, 180
Polar ice-cap, displacement of the earth’s centre of gravity by, 368
Port Bowen, mean temperature of, 63
Portobello, striated pavements near, 255, 256
Post-tertiary formations, hypothetical thickness of, 366
Pouillet, M., on the amount of the sun’s heat, 26
〃 on amount of sun’s rays cut off by the atmosphere, 26
Pratt, Archdeacon, on glacial submergence, 387
Prestwich, Professor, on Hoxne inter-glacial bed, 241
Pressure as a cause of circulation, 187
Principles of geology, nature of, 4
Prince Patrick’s Island, discovery of recent tree in, 261
Radiation, rate of, increases with increase of temperature, 37
〃 of gases, 38
〃 the way by which the earth loses heat, 39
〃 how affected by snow covering the ground, 58
〃 how affected by humid air, 59
〃 accelerated by increased formation of snow and ice, 75
Raised beaches, date of, 407
〃 Mr. Pengelly on, 407
Ramsay, Professor, on glacial origin of Old Red Sandstone of North
of England, 294
〃 on Old Red Sandstone, 367
〃 on geological time, 343
〃 on ice-action during Permian period, 298
〃 on boulders of Permian age in Natal, 301
〃 on thickness of stratified rocks of Britain, 267, 361
Redhall Quarry, inter-glacial bed in, 247
Red Sea, why almost rainless, 30
Regelation, _rationale_ of, 520, 554
〃 Professor James Thomson on cause of, 554
〃 Professor Faraday on cause of, 554
Regnault, M., on specific heat of sandstone, 86
Reynaud, Jean, on influence of eccentricity on climate, 541
Rhine, ancient, bed in German Ocean, 480
Ridge between Capes Trafalgar and Spartel, influence of, 167
Rink, Dr., on inland ice of Greenland, 380
River-ice, effect of, 279
River-ice does not produce striations, 279
River systems, carrying-power measure of denudation, 336
River valleys, how striated across, 525
Robertson, Mr. David, on Crofthead and Hillhead inter-glacial
beds, 247, 248
〃 on foraminifera in red clay, 485
Rock-basins, how excavated by ice, 525
Rocks removed by denudation, 361
Ross, Capt. Sir James, on South Shetland, 61
〃 on temperature of antarctic regions in summer, 63
Sandwich Land, description by Capt. Cook, 60
〃 cold summers of, not due to latitude, 64
Salter, Mr., on carboniferous fossils of arctic regions, 298
〃 on warm climate of North Greenland during Oolitic period, 302
Saltness of the ocean, difference of, as a cause of motion, 103
〃 in direct opposition to temperature in producing
ocean-currents, 104
Scandinavian ice, track of, 447
Scandinavian ice-sheet in the North Sea, 444
Scoresby, Dr., on condition of arctic regions in summer, 58, 62
〃 on density of Gulf-stream water, 129
Scotland, inter-glacial beds of, 243−249
〃 evidence of ice-action in carboniferous conglomerate of, 296
〃 buried under ice, 439
〃 ice-sheet of, in North Sea, 442
〃 why ice-sheet was so thick, 452
Sea, height of, at equator above poles, 119
〃 rise of, due to combined effect of eccentricity and obliquity, 403
〃 bottoms not striated by icebergs, 272
Sea and land, present arrangement indispensable to life, 52
Sea-level, oscillations of, in relation to distribution, 394
〃 oscillations of, during formation of coal measures, 424
〃 raised, by melting of antarctic ice-cap, 388
〃 influence of obliquity of ecliptic on, 403
Section of Mid-Atlantic, 222
Section across antarctic ice-cap, 377
Sedimentary rocks existing fragmentary, 361
〃 of the globe, mean thickness of, hitherto unknown, 361
〃 how mean thickness might be determined, 362
〃 mean thickness of, over-estimated, 364
Shearing-force of ice, 496
〃 momentary loss of, 518
Shetland islands glaciated by land-ice from Scandinavia, 450
Shetland, South, glacial condition of, 61
Shell-beds, evidence of warm inter-glacial periods from, 252
Shells of the boulder clay of Caithness, 450
Shore-ice, striations produced by, in Bay of Fundy, 280
Silurian period, ice-action in Ayrshire during, 293
〃 evidence in Wigtownshire of ice-action during, 293
Slitrig, inter-glacial bed of, 243
Slope of surface of maximum density has no power to produce
motion, 120
〃 from equator to pole, erroneous view regarding, 120
Smith, Mr. Leigh, temperature soundings, 129
Smith, Mr., of Jordanhill, on striated pavements, 256
Snow, how radiation is affected by, 58
〃 common in summer in arctic regions, 62
〃 rate of accumulation of, increased by sun’s rays being cut off by
fogs, 75
〃 formation increased by radiation, 75
Somerset, West, glaciation of, 463
Somerville, Mrs., on influence of eccentricity on climate, 540
South Africa, glaciation of, 242
〃 boulder clay of Permian age in, 300
South of England ice-sheet, 463
South Shetland, glacial condition of, at mid summer, 61
South-west winds, heat conveyed by, not derived from equatorial
regions, 28
〃 heat conveyed by, derived from Gulf-stream, 28
Southern hemisphere, present extension of ice on, due partly to
eccentricity, 78
〃 why colder than northern, 81−92
〃 absorbs more heat than the northern, 90
〃 lower temperature of, due to ocean-currents, 92
〃 surface currents from, warmer than under currents to, 92
〃 glacial and inter-glacial periods of, 242
Southern Ocean, thermal condition of, 225
Specific gravity can act only by causing water to descend a slope, 99
〃 mode of action in causing ocean-currents, 100
〃 inadequacy of, to produce ocean-currents demonstrated by Sir John
Herschel, 116
Spitzbergen, Gulf-stream and under current at, 134
〃 Miocene flora of, 309
Stellar space, temperature of, 35
〃 received temperature of, probably too high, 39
Stewart, Professor Balfour, experiment on radiation, 37
〃 on cause of glacial cold, 79
Stirling, Mr., on old watercourse near Grangemouth, 481
St. John’s River, action of ice on banks of, 279
St. Lawrence, action of ice on bank of river, 279
Stockwell, Mr., on eccentricity of earth’s orbit, 54
〃 on obliquity of ecliptic, 399
〃 table of superior limits of eccentricity, 531
Stone, Mr., on eccentricity of the earth’s orbit, 322
Stow, G. W., on glacial beds of South Africa, 242
〃 on Karoo beds, 301
Striæ, direction of, show the clay of Caithness came from the sea, 436
Striations obliterated rather than produced by icebergs, 274
Striated pavements why so seldom observed, 256
〃 evidence of inter-glacial periods from, 255
Striated stones found in conglomerate of Lower Carboniferous age by
Professor Geikie, 296
〃 in Permian breccias, 299
〃 in the glacial conglomerate of the Superga, Turin, 306
Stratified rocks may be formed at all possible rates, 360
〃 rate of formation of, as estimated by Professor Huxley, 363
Struve, M., formula of obliquity of ecliptic, 404
Subaërial denudation, rate of, 331
Submarine forests, 409
〃 (ancient), coal seams the remains of, 428
Submergence, physical causes of, 368
〃 coincident with glaciation, 389
〃 of land resulting from melting of antarctic ice-cap, 389
〃 how affected by fluidity of interior of the earth, 395
〃 necessary for preservation of coal plants, 423
〃 frequent during formation of coal beds, 426
Subsidence insufficient to account for general submergence, 390
〃 necessary to accumulation of coal seams, 427
Sun supposed by some to be a variable star, 8
〃 maximum and minimum distance of, 55
〃 rays of, cut off by fogs in ice-covered regions, 60
〃 nearness in perigee a cause of snow and ice, 74
〃 total amount of heat radiated from, 346
〃 age and origin of, 346
〃 source of its energy, 347
〃 heat of, origin and chief source of, 349
〃 originally an incandescent mass, 350
〃 energy of, may have originally been derived from motion in
space, 355
Surface currents which cross the equator warmer than the compensatory
under currents, 92
Surface currents from poles to equator, according to Maury, produced
by saltness, 108
Sutherland, Dr., observations by, on stranding of icebergs, 275
〃 testimony, that icebergs do not striate rocks, 278
〃 on the boulder clay of Natal, 300
Sutherland, boulder conglomerate of Oolitic period of, 302
Sweden, Southern, shells in glacial shell beds of, 253
Switzerland, inter-glacial period of, 239
〃 M. Morlat on inter-glacial periods of, 240
〃 gravels of, by Mr. James Geikie, 268
〃 Eocene glacial epoch in, 305
Table of June temperatures in different latitudes, 65
〃 soundings in temperate regions, 222
Tables of eccentricity, 314−321
〃 of eccentricity, explanation of, 322
Tay, valley of, striated across, 526
〃 ancient buried channel of, 490
Temperate regions, cold periods best marked in, 258
Temperature of space, 532
〃 reasons why it should be reconsidered, 39
Temperature (mean) of equator and poles compared, 41
〃 why so low in polar regions during summer, 66
〃 how difference of specific gravity is caused by, 102
〃 higher, of the waters of Gulf-stream considered by Lieutenant
Maury as the real causes of its motion, 111
〃 of sea at equator decreases most rapidly at the surface, 119
〃 of Greenland in Miocene period, 310
〃 of poles when obliquity was at its superior limit, 402
Tension, effect of, on ice, 522
〃 the cause of the cooling effect produced by, 552
Tertiary period, climate of, error in regard to, 288
Thermal condition of Southern Ocean, 225
Thibet, table-land of, 418
Thomson, Professor James, on cause of regelation, 554
〃 theory of glacier-motion, 512
Thomson, Mr. James, on glacial conglomerate in Arran, 299
〃 on ice-action in Cambrian conglomerate of Islay, 292
Thomson, Professor Wyville, on Dr. Carpenter’s theory, 129
〃 cited, 130
〃 thermal condition of the sea, 138
Thomson, Sir W., amount of internal heat passing through earth’s
crust, 142
〃 on limit to age of the globe, 343
〃 on influence of ice-cap on sea-level, 372
〃 climate not affected by internal heat, 6
〃 earth’s axis of rotation permanent, 7
〃 on volume and mass of the sun, 347
Tidal wave, effect of friction, 336
Tides, supposed argument from, 184
Time, geological, 311−359
〃 as represented by geological phenomena, 326
〃 represented by existing rocks, 361
Torrid zone, annual quantity of heat received by, per unit of
surface, 194
Towncroft farm, section of channel at, 474
Towson, Mr., on icebergs of Southern Ocean, 383
Trade-winds (anti), heat conveyed by, over-estimated, 28
〃 (anti) derive their heat from the Gulf-stream, 32
〃 of warm hemisphere overborne by those of cold hemisphere, 70
〃 causes which determine the strength of, 70
〃 strongest on glaciated hemisphere, 70
〃 reaction upon trade-winds by formation of snow and ice, 76
〃 influence of, in turning ocean-currents on warm hemisphere, 97
〃 do not explain the antarctic current, 211
Tiddeman on North of England ice-sheet, 458
〃 displacement of, 230
Transport of boulders and rubbish the proper function of icebergs, 281
Trafalgar, effect of ridge between Capes Spartel and on Gibraltar
current, 167
Turner, Professor, on arctic seal found at Grangemouth, 485
Tylor, Alfred, on denudation of Mississippi basin, 333
Tyndall, Professor, on heat in aqueous vapour, 29
〃 on sifted rays, 47
〃 on diathermancy of air, 59
〃 on glacial epoch, 78
Udevalla, Mediterranean shell in glacial shells, bed of, 253
Under currents to southern hemisphere colder than surface currents
from, 92
〃 produced by saltness, flow from equator to poles, 106
〃 account for cold water at equator, 124, 142
〃 in Davis’ Strait, 134
〃 take path of least resistance, 130
〃 why considered improbable, 135
〃 difficulty regarding, obviated, 217
〃 theory of, 217
Underground temperature, Professor J. D. Forbes on, 86
Underground temperature exerts no influence on the climate, 88
〃 absolute amount of heat derived from, 142
〃 supposed influence of, 176
Uniformity, modern doctrine of, 325
United States’ coast survey of Gulf-stream, 24
〃 hydrographic department, papers published by, 556
Unstratified boulder clay must be the product of land-ice, 437
Upsala and Stockholm striated by Baltic glacier, 447
Vertical circulation, Lieutenant Maury’s theory of, 108
〃 according to Dr. Carpenter, 153
Vertical descent of polar column caused by extra pressure of water
upon it, 154
〃 effects of, and slope, the same, whether performed simultaneously
or alternately, 159
〃 of polar column illustrated by diagram, 160
Vertical distribution of heat in the ocean, Mr. Buchanan’s theory, 550
Vogt, Professor, on Dürnten lignite bed, 241
Warm hemisphere made warmer by increased reaction of physical
causes, 76
Warm periods best marked in arctic regions, 258
〃 in arctic regions, evidence of, 261
〃 better represented by fossils than cold periods, 288
〃 evidence of, during Cretaceous age, 304
Warm inter-glacial periods in arctic regions, 258−265
Water at equator the best means of distributing heat derived from the
sun, 30
Water, a worse radiator than land, 91
Wastdale granite boulders, difficulty of accounting for transport
of, 456
Wastdale Crag glaciated by continental ice, 457
Weibye, M., striation observed by, 280
Wilkes, Lieutenant, on cold experienced in antarctic regions in
summer, 63
Wellington Sound, ancient trees found at, 265
Winter-drift of ice on coast of Labrador, 276
West winds, moisture of, derived from Gulf-stream, 29
Wind, work in impelling currents, 219
Winds, ocean-currents produced by, 212
〃 system of, agrees with the system of ocean-currents, 213
Wind theory of oceanic circulation, 210
〃 crucial test of, 220
Wigtownshire, ice-action during Silurian age, 293
Work performed by descent of polar column, 157
Wood, Mr. Nicholas, on buried channel, 488
Wood, Jun., Mr. Searles, middle drift, 250
〃 on occurrence of chalk _débris_ in south-west of England, 460
Woodward, Mr. H. B., on boulder clay in Devonshire, 463
Wunsch, Mr. E. A., on glacial conglomerate in Arran, 299
Yare, ancient buried channel of, 489
Young, Mr. J., objection considered, 482
Yorkshire drift common in south of England, 460
Zenger, Professor, on the moon’s influence on climate, 324
THE END.
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+----------------------------------------------------------------------+
| FOOTNOTES: |
| |
| [1] Trans. of Edin. Geol. Soc., vol. ii. p. 252. |
| |
| [2] Phil. Mag., January, 1863. |
| |
| [3] _Athenæum_, September 22, 1860. |
| |
| [4] Trans. Glasgow Geol. Soc., vol. iv., p. 313. |
| |
| [5] See Mr. Hopkin’s remarks on this theory, Quart. Journ. Geol. |
| Soc., vol. viii. |
| |
| [6] See Chap. xxv. |
| |
| [7] See Chap. iv. |
| |
| [8] “Treatise on Astronomy,” § 315; “Outlines,” § 368. |
| |
| [9] _Annuaire_ for 1834, p. 199. Edin. New Phil. Journ., April, |
| 1834, p. 224. |
| |
| [10] “Cosmos,” vol. iv. p. 459 (Bohn’s Edition). “Physical |
| Description of the Heavens,” p. 336. |
| |
| [11] Phil. Mag. for February, 1867, p. 127. |
| |
| [12] The Gulf-stream at the narrowest place examined by the Coast |
| Survey, and where also its velocity was greatest, was found to be |
| over 30 statute miles broad and 1,950 feet deep. But we must not |
| suppose that this represents all the warm water which is received |
| by the Atlantic from the equator; a great mass flows into the |
| Atlantic without passing through the Straits of Florida. |
| |
| [13] It is probable that a large proportion of the water |
| constituting the south-eastern branch of the Gulf-stream is never |
| cooled down to 40°; but, on the other hand, the north-eastern |
| branch, which passes into the arctic regions, will be cooled far |
| below 40°, probably below 30°. Hence I cannot be over-estimating |
| the extent to which the water of the Gulf-stream is cooled down in |
| fixing upon 40° as the average minimum temperature. |
| |
| [14] “Physical Geography of the Sea,” § 24, 6th edition. |
| |
| [15] “Physical Geography,” § 54. |
| |
| [16] Trans. of Roy. Soc. of Edin., vol. xxi., p. 57. Phil. Mag., § |
| 4, vol. ix., p. 36. |
| |
| [17] “Smithsonian Contributions to Knowledge,” vol. ix. |
| |
| [18] “Heat as a Mode of Motion,” art. 240. |
| |
| [19] Trans. Roy. Soc. of Edin., vol. xxv., part 2. |
| |
| [20] See “Smithsonian Contributions to Knowledge,” vol. ix. |
| |
| [21] “Meteorology,” section 36. |
| |
| [22] _Comptes-Rendus_, July 9, 1838. Taylor’s “Scientific Memoirs,” |
| vol. iv., p. 44 (1846). |
| |
| [23] The mean temperature of the Atlantic between the tropics and |
| the arctic circle, according to Admiral Fitzroy’s chart, is about |
| 60°. But he assigns far too high a temperature for latitudes above |
| 50°. It is probable that 56° is not far from the truth. |
| |
| [24] The probable physical cause of this will be considered in the |
| Appendix. |
| |
| [25] The mean temperature of the equator, according to Dove, is |
| 79°·7, and that of the north pole 2°·3. But as there is, of course, |
| some uncertainty regarding the actual mean temperature of the |
| poles, we may take the difference in round numbers at 80°. |
| |
| [26] Trans. of Roy. Soc. Edin., vol. xxii., p. 75. |
| |
| [27] _Connaissance des Temps_ for 1863 (Additions). Lagrange’s |
| determination makes the superior limit 0·07641 (Memoirs of the |
| Berlin Academy for 1782, p. 273). Recently the laborious task of |
| re-investigating the whole subject of the secular variations of the |
| elements of the planetary orbits was undertaken by Mr. Stockwell, |
| of the United States. He has taken into account the disturbing |
| influence of the planet Neptune, the existence of which was not |
| known when Leverrier’s computations were made; and he finds that |
| the eccentricity of the earth’s orbit will always be included |
| within the limits of 0 and 0·0693888. Mr. Stockwell’s elaborate |
| Memoir, extending over no fewer than two hundred pages, will be |
| found in the eighteenth volume of the “Smithsonian Contributions to |
| Knowledge.” |
| |
| [28] When the eccentricity is at its superior limit, the absolute |
| quantity of heat received by the earth during the year is, however, |
| about one three-hundredth part greater than at present. But this |
| does not affect the question at issue. |
| |
| [29] Scoresby’s “Arctic Regions,” vol. ii., p. 379. Daniell’s |
| “Meteorology,” vol. ii., p. 123. |
| |
| [30] Tyndall, “On Heat,” article 364. |
| |
| [31] Tyndall, “On Heat,” article 364. |
| |
| [32] See Phil. Mag., March, 1870, p. |
| |
| [33] Captain Cook’s “Second Voyage,” vol. ii., pp. 232, 235. |
| |
| [34] “Antarctic Regions,” vol. ii., pp. 345−349. |
| |
| [35] Ibid., vol. i., p. 167. |
| |
| [36] Ibid., vol. ii., p. 362. |
| |
| [37] Edinburgh Philosophical Journal, vol. iv., p. 266. |
| |
| [38] Scoresby’s “Arctic Regions,” vol. i., p. 378. |
| |
| [39] Ibid., p. 425. |
| |
| [40] See Meech’s memoir “On the Intensity of the Sun’s Heat and |
| Light,” “Smithsonian Contributions,” vol. ix. |
| |
| [41] “Antarctic Regions,” vol. i., p. 240. |
| |
| [42] _Challenger_ Reports, No. 2, p. 10. |
| |
| [43] See “Smithsonian Contributions,” vol. ix. |
| |
| [44] Quart. Journ. Geol. Soc., vol. xxv., p. 350. |
| |
| [45] Trans. of Glasgow Geol. Soc. for 1866. |
| |
| [46] _Revue des Deux Mondes_ for 1867. |
| |
| [47] Letter to the author, February, 1870. |
| |
| [48] “Révolutions de la Mer,” p. 37 (second edition). |
| |
| [49] Edin. Phil. Journ., vol. iv., p. 262 (1821). |
| |
| [50] Phil. Mag., § 4, vol. xxviii., p. 131. _Reader_, December 2nd, |
| 1865. |
| |
| [51] This point will be found discussed at considerable length in |
| the Phil. Mag. for September, 1869. |
| |
| [52] See Phil. Mag. for October, 1870, p. 259. |
| |
| [53] Proceedings of the Royal Society, No. 138, p. 596, foot-note. |
| |
| [54] The edition from which I quote, unless the contrary is stated, |
| is the one published by Messrs. T. Nelson and Sons, 1870, which is |
| a reprint of the new edition published in 1859 by Messrs. Sampson |
| Low and Co. |
| |
| [55] “Physical Geography,” article 57. |
| |
| [56] Philosophical Magazine, vol. xii. p. 1 (1838). |
| |
| [57] “Mémoires par divers Savans,” tom. i., p. 318, St. |
| Petersburgh, 1831. See also twelfth number of Meteorological |
| Papers, published by the Board of Trade, 1865, p. 16. |
| |
| [58] Dubuat’s “Hydraulique,” tom. i., p. 64 (1816). See also |
| British Association Report for 1834, pp. 422, 451. |
| |
| [59] See Proceedings of the Royal Society for December, 1868, |
| November, 1869. Lecture delivered at the Royal Institute, _Nature_, |
| vol. i., p. 490. Proceedings of the Royal Geographical Society, |
| vol. xv. |
| |
| [60] Trans. of Glasgow Geol. Soc. for April, 1867. Phil. Mag. for |
| February, 1867, and June, 1867 (Supplement). |
| |
| [61] Phil. Mag. for February, 1870. |
| |
| [62] “The Depths of the Sea,” pp. 376 and 377. |
| |
| [63] “The Threshold of the Unknown Region,” p. 95. |
| |
| [64] See “Physical Geography of the Sea,” chap. ix., new edition, |
| and Dr. A. Mühry “On Ocean-currents in the Circumpolar Basin of the |
| North Hemisphere.” |
| |
| [65] “Depths of the Sea,” _Nature_ for July 28, 1870. |
| |
| [66] “Memoir on the Gulf-stream,” _Geographische Mittheilungen_, |
| vol. xvi. (1870). |
| |
| [67] Dr. Carpenter “On the Gulf-stream,” Proceedings of Royal |
| Geographical Society for January 9, 1871, § 29. |
| |
| [68] Dr. Petermann’s _Mittheilungen_ for 1872, p. 315. |
| |
| [69] Proceedings of the Royal Society, vol. xvii., p. 187, xviii., |
| p. 463. |
| |
| [70] The average depth of the Pacific Ocean, as found by the |
| soundings of Captain Belknap, of the U.S. steamer _Tuscarora_, made |
| during January and February, 1874, is about 2,400 fathoms. The |
| depth of the Atlantic is somewhat less. |
| |
| [71] Proceedings of Royal Geographical Society, vol. xv., § 22. |
| |
| [72] It is a well-established fact that in polar regions the |
| temperature of the sea decreases from the surface downwards; |
| and the German Polar Expedition found that the water in very |
| high latitudes is actually less dense at the surface than at |
| considerable depths, thus proving that the surface-water could not |
| sink in consequence of its greater density. |
| |
| [73] Proceedings of the Royal Society, vol. xix., p. 215. |
| |
| [74] _Nature_ for July 6, 1871. |
| |
| [75] Since the above objection to the Gravitation Theory of the |
| Gibraltar Current was advanced three years ago, Dr. Carpenter |
| appears to have abandoned the theory to a great extent. He now |
| admits (Proceedings of Royal Geographical Society, vol. xviii., |
| pp. 319−334, 1874) that the current is almost wholly due not to |
| difference of specific gravity, but to an excess of evaporation in |
| the Mediterranean over the return by rain and rivers. |
| |
| [76] Proceedings of Royal Society, No. 138, § 26. |
| |
| [77] Proceedings of Royal Geographical Society, January 9, 1871. |
| |
| [78] Ibid. |
| |
| [79] See §§ 20, 34; also Brit. Assoc. Report for 1872, p. 49, and |
| other places. |
| |
| [80] See also to the same effect Brit. Assoc. Report, 1872, p. 50. |
| |
| [81] Phil. Mag. for Oct. 1871. |
| |
| [82] The actual slope, however, does not amount to more than 1 in |
| 7,000,000. |
| |
| [83] Proc. of Roy. Geog. Soc., January 9, 1871, § 29. |
| |
| [84] Trans. of Geol. Soc. of Glasgow for April, 1867; Phil. Mag. |
| for June, 1867. |
| |
| [85] _Nature_, vol. i., p. 541. Proc. Roy. Soc., vol. xviii., p. |
| 473. |
| |
| [86] Chapter II. |
| |
| [87] Chapter II. |
| |
| [88] Chapter II. |
| |
| [89] Mr. Findlay considers that the daily discharge does not exceed |
| 333 cubic miles (Brit. Assoc. Rep., 1869, p. 160). My estimate |
| makes it 378 cubic miles. Mr. Laughton’s estimate is 630 cubic |
| miles (Paper “On Ocean-currents,” Journal of Royal United-Service |
| Institution, vol. xv.). |
| |
| [90] Proceedings of the Royal Geographical Society, vol. xviii., p. |
| 393. |
| |
| [91] Phil. Mag. for October, 1871, p. 274. |
| |
| [92] Proceedings of the Royal Geographical Society, vol. xv. |
| |
| [93] Phil. Mag., February, 1870. |
| |
| [94] Brit. Assoc. Report, 1869, Sections, p. 160. |
| |
| [95] Journal of Royal United-Service Institute, vol. xv. |
| |
| [96] Dr. Carpenter (Proc. of Roy. Geog. Soc., vol. xviii., p. |
| 334) misapprehends me in supposing that I attribute the Gibraltar |
| current wholly to the Gulf-stream. In the very page from which he |
| derives or could derive his opinion as to my views on the subject |
| (Phil. Mag. for March, 1874, p. 182), I distinctly state that |
| “the excess of evaporation over that of precipitation within the |
| Mediterranean area would of itself produce a considerable current |
| through the Strait.” That the Gibraltar current is due to two |
| causes, (1) the pressure of the Gulf-stream, and (2) excess of |
| evaporation over precipitation in the Mediterranean, has always |
| appeared to me so perfectly obvious, that I never held nor could |
| have held any other opinion on the subject. |
| |
| [97] Paper read to the Edinburgh Botanical Society on January 8, |
| 1874. |
| |
| [98] Proc. Roy. Geog. Soc., vol. xviii., p. 362. A more |
| advantageous section might have been chosen, but this will suffice. |
| The section referred to is shown in Plate III. The peculiarity of |
| this section, as will be observed, is the thinness of the warm |
| strata at the equator, as compared with that of the heated water in |
| the North Atlantic. |
| |
| [99] The temperature of column C in Dr. Carpenter’s section is |
| somewhat less than that given in the foregoing table; so that, |
| according to that section, the difference of level between column C |
| and columns A and B would be greater than my estimate. |
| |
| [100] Captain Nares’s Report, July 30, 1874. |
| |
| [101] See Chapter IV. |
| |
| [102] Phil. Mag. for August, 1864, February, 1867, March, 1870; see |
| Chap. IV. |
| |
| [103] Quarterly Journal of Science for October, 1874. |
| |
| [104] See a paper by M. Morlot, on “The Post-Tertiary and |
| Quaternary Formations of Switzerland.” Edin. New Phil. Journal, New |
| Series, vol. ii., 1855. |
| |
| [105] Edin. New Phil. Journ., New Series, vol. ii., p. 28. |
| |
| [106] Vogt’s “Lectures on Man,” pp. 318−321. |
| |
| [107] See Mr. Prestwich on Flint Implements, Phil. Trans. for 1860 |
| and 1864. Lyell’s “Antiquity of Man,” Second Edition, p. 168. |
| |
| [108] Edin. New Phil. Journ., New Series, vol. ii., p. 28. |
| Silliman’s Journ., vol. xlvii., p. 259 (1844). |
| |
| [109] Quart. Journ. Geol. Soc., vol. xxvii., p. 534. |
| |
| [110] Ibid., vol. xxviii., p. 17. |
| |
| [111] “Glacial Drift of Scotland,” p. 54. |
| |
| [112] “Glacial Drift of Scotland,” p. 58. |
| |
| [113] Quart. Journ. Geol. Soc., vol. v., p. 22. |
| |
| [114] “Glacial Drift of Scotland,” p. 64. |
| |
| [115] Trans. Edin. Geol. Soc., vol. ii., p. 391. |
| |
| [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,” pp. 77, 81, 111. |
| |
| [150] “Second Visit,” vol. ii., p. 367. |
| |
| [151] “Memoirs of Boston Society of Natural History,” vol. i. |
| (1867), p. 228. |
| |
| [152] “Antiquity of Man,” p. 268. Third Edition. |
| |
| [153] “Great Ice Age,” p. 512. |
| |
| [154] Brit. Assoc., 1870, p. 88. |
| |
| [155] Quart. Journ. Geol. Soc., vol. v., p. 10. Phil. Mag. for |
| April, 1865, p. 289. |
| |
| [156] “Great Ice Age,” p. 512. |
| |
| [157] Jukes’ “Manual of Geology,” p. 421. |
| |
| [158] See also Quarterly Journal Geological Society, vol. xi., p. |
| 510. |
| |
| [159] The _Reader_ for August 12, 1865. |
| |
| [160] “History of the Isle of Man,” p. 86. My colleague, Mr. John |
| Horne, in his “Sketch of the Geology of the Isle of Man,” Trans. of |
| Edin. Geol. Soc., vol. ii., part iii., considers this conglomerate |
| to be of Lower Carboniferous age. |
| |
| [161] See Selwyn, “Phys. Geography and Geology of Victoria.” 1866. |
| pp. 15−16; Taylor and Etheridge, _Geol. Survey Vict., Quarter Sheet |
| 13, N.E._ |
| |
| [162] Report on the Geology of the District of Ballan, Victoria. |
| 1866. p. 11. |
| |
| [163] _Atrypa reticularis._ |
| |
| [164] Quart. Journ. Geol. Soc., vol. xii., p. 58. |
| |
| [165] “Great Ice Age,” p. 513. |
| |
| [166] “Great Ice Age,” p. 513. |
| |
| [167] Brit. Assoc. Report for 1873. |
| |
| [168] Quart. Journ. Geol. Soc., vol. xi., p. 519. |
| |
| [169] _Orthis resupinata._ |
| |
| [170] _Prod. semireticulatus_ var. _Martini_. Sow. |
| |
| [171] “Belcher’s Voyage,” vol. ii., p. 377. |
| |
| [172] “Journal of a Boat Voyage through Rupert-Land,” vol. ii., p. |
| 208. |
| |
| [173] Quart. Journ. Geol. Soc., vol. xi., p. 197. |
| |
| [174] Explanation Memoir to Sheet 47, “Geological Survey of |
| Ireland.” |
| |
| [175] Phil. Mag., vol. xxix., p. 290. |
| |
| [176] “Memoirs of the Geological Survey of India,” vol. i., part i. |
| |
| [177] Quart. Journ. Geol. Soc., vol. xxvi., p. 514. |
| |
| [178] Ibid., vol. xxvii., p. 544. |
| |
| [179] Phil. Mag., vol. xxix., p. 290. |
| |
| [180] Journal of the Royal Dublin Society for February, 1857. |
| |
| [181] Quart. Journ. Geol. Soc., vol. xi., p. 519. |
| |
| [182] “The Last of the Arctic Voyages,” by Captain Sir E. Belcher, |
| vol. ii., p. 389. Appendix Brit. Assoc. Report for 1855, p. 79. |
| |
| [183] Ibid., vol. ii., p. 379. Appendix. |
| |
| [184] “Manual of Geology,” pp. 395, 493. |
| |
| [185] Appendix to McClintock’s “Arctic Discoveries.” |
| |
| [186] Quart. Journ. Geol. Soc., vol. xiv., p. 262. Brit. Assoc. |
| Report for 1857, p. 62. |
| |
| [187] Quart. Journ. Geol. Soc., vol. xvi., p. 327. _Geologist_, |
| 1860, p. 38. |
| |
| [188] Phil. Mag., vol. xxix., p. 290. |
| |
| [189] Trans. Geol. Soc. of Glasgow, vol. v., p. 64. |
| |
| [190] “Principles,” vol. i., p. 209. Eleventh Edition. |
| |
| [191] “Memoirs of the Royal Academy of Science of Turin,” Second |
| Series, vol. xx. I am indebted for the above particulars to |
| Professor Ramsay, who visited the spot along with M. Gastaldi. |
| |
| [192] “Antiquity of Man,” Second Edition, p. 237. |
| |
| [193] Dr. Robert Brown, in a recent Memoir on the Miocene Beds of |
| the Disco District (Trans. Geol. Soc. Glasg., vol. v., p. 55), |
| has added considerably to our knowledge of these deposits. He |
| describes the strata in detail, and gives lists of the plant and |
| animal remains discovered by himself and others, and described by |
| Professor Heer. Professor Nordenskjöld has likewise increased the |
| data at our command (Transactions of the Swedish Academy, 1873); |
| and still further evidence in favour of a warm climate having |
| prevailed in Greenland during Miocene times has been obtained by |
| the recent second German polar expedition. |
| |
| [194] The following are M. Leverrier’s formulæ for computing the |
| eccentricity of the earth’s orbit, given in his “Memoir” in the |
| _Connaissance des Temps_ for 1843:— |
| |
| Eccentricity in (_t_) years after January 1, 1800 |
| _____________ |
| = √_h_^2 + _l_^2 where |
| |
| _h_ = 0·000526 Sin (_gt_ + _ß_) + 0·016611 Sin (_g_{1}t_ + _ß_{1}_) |
| + 0·002366 Sin (_g_{2}t_ + _ß_{2}_) |
| + 0·010622 Sin (_g_{3}t_ + _ß_{3}_) |
| - 0·018925 Sin (_g_{4}t_ + _ß_{4}_) |
| + 0·011782 Sin (_g_{5}t_ + _ß_{5}_) |
| - 0·016913 Sin (_g_{6}t_ + _ß_{6}_) |
| and |
| |
| _l_ = 0·000526 Cos (_gt_ + _ß_) + 0·016611 Cos (_g_{1}t_ + _ß_{1}_) |
| + 0·002366 Cos (_g_{2}t_ + _ß_{2}_) |
| + 0·010622 Cos (_g_{3}t_ + _ß_{3}_) |
| - 0·018925 Cos (_g_{4}t_ + _ß_{4}_) |
| + 0·011782 Cos (_g_{5}t_ + _ß_{5}_) |
| - 0·016913 Cos (_g_{6}t_ + _ß_{6}_) |
| |
| _g_ = 2″·25842 _ß_ = 126° 43′ 15″ |
| _g_{1}_ = 3″·71364 _ß_{1}_ = 27 21 26 |
| _g_{2}_ = 22″·4273 _ß_{2}_ = 126 44 8 |
| _g_{3}_ = 5″·2989 _ß_{3}_ = 85 47 45 |
| _g_{4}_ = 7″·5747 _ß_{4}_ = 35 38 43 |
| _g_{5}_ = 17″·1527 _ß_{5}_ = −25 11 33 |
| _g_{6}_ = 17″·8633 _ß_{6}_ = −45 28 59 |
| |
| [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. |
| |
| [226] Chapter IV. |
| |
| [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:— |
| |
| By Lagrange. By Leverrier. By Mr. Stockwell. |
| |
| Mercury 0·22208 0·225646 0·2317185 |
| Venus 0·08271 0·086716 0·0706329 |
| Earth 0·07641 0·077747 0·0693888 |
| Mars 0·14726 0·142243 0·139655 |
| Jupiter 0·06036 0·061548 0·0608274 |
| Saturn 0·08408 0·084919 0·0843289 |
| Uranus — 0·064666 0·0779652 |
| Neptune — — 0·0145066 |
| |
| [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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Transcriber’s Notes:
- Text enclosed by underscores is in italics (_italics_).
- Blank pages have been removed.
- Obvious typographical errors have been silently corrected.
- Some spelling and hyphenation variations have been made consistent.