Chapter XLI: Appendix: I (2)

It follows also, from what has been stated, that even under direct sunshine the removal of the earth’s atmosphere would tend to lower the temperature of the earth’s surface to a great extent. This conclusion also follows as an immediate inference from the fact that the earth’s atmosphere, as it exists at present charged with aqueous vapour, affects terrestrial radiation more than it does radiation from the sun; for the removal of the atmosphere would increase the rate at which the earth throws off its heat into space more than it would increase the rate at which it receives heat from the sun; therefore its temperature would necessarily fall until the rate of radiation _from_ the earth’s surface exactly equalled the rate of radiation _to_ the surface. Let the atmosphere again envelope the earth, and terrestrial radiation would instantly be diminished; the temperature of the earth’s surface would therefore necessarily begin to rise, and would continue to do so till the rate of radiation from the surface would equal the rate of radiation received by the surface. Equilibrium being thus restored, the temperature would remain stationary. It is perfectly obvious that if we envelope the earth with a substance such as our atmosphere, that offers more resistance to terrestrial radiation than to solar, the temperature of the earth’s surface must necessarily rise until the heat which is being radiated off equals that which is being received from the sun. Remove the air and thus get quit of the resistance, and the temperature of the surface would fall, because in this case a lower temperature would maintain equilibrium.

It follows, therefore, that the moon, which has no atmosphere, must be much colder than our earth, even on the side exposed to the sun. Were our earth with its atmosphere as it exists at present removed to the orbit of Venus or Mars, for example, it certainly would not be habitable, owing to the great change of temperature that would result. But a change in the physical constitution of the atmospheric envelope is really all that would be necessary to retain the earth’s surface at its present temperature in either position.

IV.

REMARKS ON MR. J. Y. BUCHANAN’S THEORY OF THE VERTICAL
DISTRIBUTION OF TEMPERATURE OF THE OCEAN.[328]

Since the foregoing was in type, a paper on the “Vertical Distribution of Temperature of the Ocean,” by Mr. J. Y. Buchanan, chemist on board the _Challenger_, has been read before the Royal Society.[329] In that paper Mr. Buchanan endeavours to account for the great depth of warm water in the middle of the North Atlantic compared with that at the equator, without referring it to horizontal circulation of any kind.

The following is the theory as stated by Mr. Buchanan:—

“Let us assume the winter temperature of the surface-water to be 60° F. and the summer temperature to be 70° F. If we start from midwinter, we find that, as summer approaches, the surface-water must get gradually warmer, and that the temperature of the layers below the surface must decrease at a very rapid rate, until the stratum of winter temperature, or 60° F., is reached; in the language of the isothermal charts, the isothermal line for degrees between 70° F. (if we suppose that we have arrived at midsummer) and 60° F. open out or increase their distance from each other as the depth increases. Let us now consider the conditions after the summer heat has begun to waver. During the whole period of heating, the water, from its increasing temperature, has been always becoming lighter, so that heat communication by convection with the water below has been entirely suspended during the whole period. The heating of the surface-water has, however, had another effect, besides increasing its volume; it has, by evaporation, rendered it denser than it was before, at the same temperature. Keeping in view this double effect of the summer heat upon the surface-water, let us consider the effect of the winter cold upon it. The superficial water having assumed the atmospheric temperature of, say 60° F., will sink through the warmer water below it, until it reaches the stratum of water having the same temperature as itself. Arrived here, however, although it has the same temperature as the surrounding water, the two are no longer in equilibrium, for the water which has come from the surface, has a greater density than that below at the same temperature. It will therefore not be arrested at the stratum of the same temperature, as would have been the case with fresh water; but it will continue to sink, carrying of course its higher temperature with it, and distributing it among the lower layers of colder water. At the end of the winter, therefore, and just before the summer heating recommences, we shall have at the surface a more or less thick stratum of water having a nearly uniform temperature of 60° F., and below this the temperature decreasing at a considerable but less rapid rate than at the termination of the summer heating. If we distinguish between _surface-water_, the temperature of which rises with the atmospheric temperature (following thus, in direction at least, the variation of the seasons), and _subsurface_-water, or the stratum immediately below it, we have for the latter the, at first sight, paradoxical effect of summer cooling and winter heating. The effect of this agency is to diffuse the same heat to a greater depth in the ocean, the greater the yearly range of atmospheric temperature at the surface. This effect is well shown in the chart of isothermals, on a vertical section, between Madeira and a position in lat. 3° 8′ N., long. 14° 49′ W. The isothermal line for 45° F. rises from a depth of 740 fathoms at Madeira to 240 fathoms at the above-mentioned position. In equatorial regions there is hardly any variation in the surface-temperature of the sea; consequently we find cold water very close to the surface all along the line. On referring to the temperature section between the position lat. 3° 8′ N., long. 14° 49′ W., and St. Paul’s Rocks, it will be seen that, with a surface-temperature of from 75° F. to 79° F., water at 55° F. is reached at distances of less than 100 fathoms from the surface. Midway between the Azores and Bermuda, with a surface-temperature of 70° F., it is only at a depth of 400 fathoms that we reach water of 55° F.”

What Mr. Buchanan states will explain why the mean annual temperature of the water at the surface extends to a greater depth in the middle of the North Atlantic than at the equator. It also explains why the temperature from the surface downwards decreases more rapidly at the equator than in the middle of the North Atlantic; but, if I rightly understand the theory, it does not explain (and this is the point at issue) why at a given depth the temperature of the water in the North Atlantic should be higher than the temperature at a corresponding depth at the equator. Were there no horizontal circulation the greatest thickness of warm water would certainly be found at the equator and the least at the poles. The isothermals would in such a case gradually slope downwards from the poles to the equator. The slope might not be uniform, but still it would be a continuous downward slope.

V.

ON THE CAUSE OF THE COOLING EFFECT PRODUCED ON SOLIDS BY
TENSION.[330]

From the _Philosophical Magazine_ for May, 1864.

From a series of experiments made by Dr. Joule with his usual accuracy, he found that when bodies are subjected to tension, a cooling effect takes place. “The quantity of cold,” he says, “produced by the application of tension was sensibly equal to the heat evolved by its removal; and further, that the thermal effects were proportional to the weight employed.”[331] He found that when a weight was applied to compress a body, a certain amount of heat was evolved; but the same weight, if applied to stretch the body, produced a corresponding amount of cold.

This, although it does not appear to have been remarked, is a most singular result. If we employ a force to compress a body, and then ask what has become of the force applied, it is quite a satisfactory answer to be told that the force is converted into heat, and reappears in the molecules of the body as such; but if the same force be employed to stretch the body, it will be no answer to be told that the force is converted into cold. Cold cannot be the force under another form, for cold is a privation of force. If a body, for example, is compressed by a weight, the _vis viva_ of the descending weight is transmitted to the molecules of the body and reappears under that form of force called heat; but if the same weight is applied so as to stretch or expand the body, not only does the force of the weight disappear without producing heat, but the molecules which receive the force lose part of that which they already possessed. Not only does the force of the weight disappear, but along with it a portion of the force previously existing in the molecules under the form of heat. We have therefore to inquire, not merely into what becomes of the force imparted by the weight, but also what becomes of the force in the form of heat which disappears from the molecules of the body itself. That the _vis viva_ of the descending weight should disappear without increasing the heat of the molecules is not so surprising, because it may be transformed into some other form of force different from that of heat. For it is by no means evident _à priori_ that heat should be the only form under which it may exist. But it is somewhat strange that it should cause the force previously existing in the molecules in the form of heat also to change into some other form.

When a weight, for example, is employed to stretch a solid body, it is evident that the force exerted by the weight is consumed in work against the cohesion of the particles, for the entire force is exerted so as to pull them separate from each other. But the cooling effect which takes place shows that more force disappears than simply what is exerted by the weight; for the cooling effect is caused by the disappearance of force in the shape of heat from the body itself. The force exerted by the weight disappears in performing work against the cohesion of the particles of the body stretched. But what becomes of the energy in the form of heat which disappears from the body at the same time? It must be consumed in performing work of some kind or other. The force exerted by the weight cannot be the cause of the cooling effect. The transferrence of force from the weight to the body may be the cause of a heating effect—an increase of force in the body; but this transferrence of force to the body cannot be the cause of a decrease of force in the body. If a decrease of force actually follows the application of tension, the weight can only be the occasion, not the cause of the decrease.

In what manner, then, does the stretching of the body by the weight become the occasion of its losing energy in the shape of heat? Or, in other words, what is the cause of the cooling effects which result from tension? The probable explanation of the phenomenon seems to be this: if the molecules of a body are held together by any force, of whatever nature it may be, which prevents any further separation taking place, then the entire heat applied to such a body will appear as temperature; but if this binding force becomes lessened so as to allow further expansion, then a portion of the heat applied will be lost in producing expansion. All solids at any given temperature expand until the expansive force of their heat exactly balances the cohesive force of their molecules, after which no further expansion at the same temperature can possibly take place while the cohesive force of the molecules remains unchanged. But if, by some means or other, the cohesive force of the molecules become reduced, then instantly the body will expand under the heat which it possesses, and of course a portion of the heat will be consumed in expansion, and a cooling effect will result. Now tension, although it does not actually lessen the cohesive force of the molecules of the stretched body, yet produces, by counteracting this force, the same effect; for it allows the molecules an opportunity of performing work of expansion, and a cooling effect is the consequence. If the piston of a steam-engine, for example, be loaded to such an extent that the steam is unable to move it, the steam in the interior of the cylinder will not lose any of its heat; but if the piston be raised by some external force, the molecules of the steam will assist this force, and consequently will suffer loss of heat in proportion to the amount of work which they perform. The very same occurs when tension is applied to a solid. Previous to the application of tension, the heat existing in the molecules is unable to produce any expansion against the force of cohesion. But when the influence of cohesion is partly counteracted by the tension applied, the heat then becomes enabled to perform work of expansion, and a cooling effect is the result.

VI.

THE CAUSE OF REGELATION.[332]

There are two theories which have been advanced to explain Regelation, the one by Professor Faraday, and the other by Professor James Thomson.

According to Professor James Thomson, pressure is the cause of regelation. Pressure applied to ice tends to lower the melting-point, and thus to produce liquefaction; but the water which results is colder than the ice, and refreezes the moment it is relieved from pressure. When two pieces of ice are pressed together, a melting takes place at the points in contact, resulting from the lowering of the melting-point; the water formed, re-freezing, joins the two pieces together.

The objection which has been urged against this theory is that regelation will take place under circumstances where it is difficult to conceive how pressure can be regarded as the cause. Two pieces of ice, for example, suspended by silken threads in an atmosphere above the melting-point, if but simply allowed to touch each other, will freeze together. Professor J. Thomson, however, attributes the freezing to the pressure resulting from the capillary attraction of the two moist surfaces in contact. But when we reflect that it requires the pressure of a mile of ice—135 tons on the square foot—to lower the melting-point one degree, it must be obvious that the lowering effect resulting from capillary attraction in the case under consideration must be infinitesimal indeed.

The following clear and concise account of Faraday’s theory, I quote from Professor Tyndall’s “Forms of Water:”—

“Faraday concluded that _in the interior_ of any body, whether solid or liquid, where every particle is grasped, so to speak, by the surrounding particles, and grasps them in turn, the bond of cohesion is so strong as to require a higher temperature to change the state of aggregation than is necessary _at the surface_. At the surface of a piece of ice, for example, the molecules are free on one side from the control of other molecules; and they therefore yield to heat more readily than in the interior. The bubble of air or steam in overheated water also frees the molecules on one side; hence the ebullition consequent upon its introduction. Practically speaking, then, the point of liquefaction of the interior ice is higher than that of the superficial ice....

“When the surfaces of two pieces of ice, covered with a film of the water of liquefaction, are brought together, the covering film is transferred from the surface to the centre of the ice, where the point of liquefaction, as before shown, is higher than at the surface. The special solidifying power of ice upon water is now brought into play _on both sides of the film_. Under these circumstances, Faraday held that the film would congeal, and freeze the two surfaces together.”—_The Forms of Water_, p. 173.

The following appears to be a more simple explanation of the phenomena than either of the preceding:—

The freezing-point of water, and the melting-point of ice, as Professor Tyndall remarks, touch each other as it were at this temperature. At a hair’s-breadth lower water freezes; at a hair’s-breadth higher ice melts. Now if we wish, for example, to freeze water, already just about the freezing-point, or to melt a piece of ice already just about the melting-point, we can do this either by a change of temperature or by a change of the melting-point. But it will be always much easier to effect this by the former than by the latter means. Take the case already referred to, of the two pieces of ice suspended in an atmosphere above the melting-point. The pieces at their surfaces are in a melting condition, and are surrounded by a thin film of water just an infinitesimal degree above the freezing-point. The film has on the one side solid ice at the freezing-point, and on the other a warm atmosphere considerably above the freezing-point. The tendency of the ice is to lower the temperature of the film, while that of the air is to raise its temperature. When the two pieces are brought into contact the two films unite and form one film separating the two pieces of ice. This film is not like the former in contact with ice on the one side and warm air on the other. It is surrounded on both sides by solid ice. The tendency of the ice, of course, is to lower the film to the same temperature as the ice itself, and thus to produce solidification. It is evident that the film must either melt the ice or the ice must freeze the film, if the two are to assume the same temperature. But the power of the ice to produce solidification, owing to its greater mass, is enormously greater than the power of the film to produce fluidity, consequently regelation is the result.

VII.

LIST OF PAPERS WHICH HAVE APPEARED IN DR. A. PETERMANN’S
_GEOGRAPHISCHE MITTHEILUNGEN_ RELATING TO THE GULF-STREAM AND
THERMAL CONDITION OF THE ARCTIC REGIONS.

The most important memoir which we have on the Gulf-stream and its influence on the climate of the arctic regions is the one by Dr. A. Petermann, entitled “Der Golfstrom und Standpunkt der thermometrischen Kenntniss des nord-atlantischen Oceans und Landgebiets im Jahre 1870.” _Geographische Mittheilungen_, Band XVI. 1870.

Dr. Petermann has, in this memoir, by a different line of argument from that which I have pursued in this volume, shown in the most clear and convincing manner that the abnormally high temperature of the north-western shores of Europe and the seas around Spitzbergen is owing entirely to the Gulf-stream, and not to any general circulation such as that advocated by Dr. Carpenter. From a series of no fewer than 100,000 observations of temperature in the North Atlantic and in the arctic seas, he has been enabled to trace with accuracy on his charts the very footsteps of the heat in its passage from the Gulf of Mexico up to the shores of Spitzbergen.

The following is a list of the more important papers bearing on the subject which have recently appeared in Dr. Petermann’s _Geogr. Mittheilungen_:—

An English translation of Dr. Petermann’s Memoir, and of a few more in the subjoined list, has been published in a volume, with supplements, by the Hydrographic Department of the United States, under the superintendence of Commodore R. H. Wyman.

The papers whose titles are in English have appeared in the American volume. In that volume the principal English papers on the subject, in as far as they relate to the north-eastern extension of the Gulf-stream, have also been reprinted.

The System of Oceanic Currents in the Circumpolar Basin of the Northern Hemisphere. By Dr. A. Mühry. Vol. XIII., Part II. 1867.

The Scientific Results of the first German North Polar Expedition. By Dr. W. von Freeden. Vol. XV., Part VI. 1869.

The Gulf-stream, and the Knowledge of the Thermal Properties of the North Atlantic Ocean and its Continental Borders, up to 1870. By Dr. A. Petermann. _Geographische Mittheilungen_, Vol. XVI., Part VI. 1870.

The Temperature of the North Atlantic Ocean and the Gulf-stream. By Rear-Admiral C. Irminger. Vol. XVI., Part VI. 1870.

Meteorological Observations during a Winter Stay on Bear Island, 1865−1866. By Sievert Tobilson. Vol. XVI., Part VII. 1870.

Die Temperatur-verhältnisse in den arktischen Regionen. Von Dr. Petermann. Band XVI., Heft VII. 1870.

Preliminary Reports of the Second German North Polar Expedition, and of minor Expeditions, in 1870. Vol. XVII.

Preliminary Report of the Expedition for the Exploration of the Nova-Zembla Sea (the sea between Spitzbergen and Nova Zembla), by Lieutenants Weyprecht and Payer, June to September, 1871. By Dr. A. Petermann. Vol. XVII. 1871.

Der Golfstrom ostwärts vom Nordkap. Von A. Middendorff. Band XVII., Heft I. 1871.

Kapitän E. H. Johannesen’s Umfahrung von Nowaja Semlä im Sommer 1870, und norwegischer Finwalfang östlich vom Nordkap. Von Th. v. Heuglin. Band XVII., Heft I. 1871.

Die Nordpol-Expeditionen, das sagenhafte Gillis-land und der Golfstrom im Polarmeere. Von Dr. A. Petermann. 5 Nov. 1870.

Th. v. Heuglin’s Aufnahmen in Ost-Spitzbergen. Begleitworte zur neuen Karte dieses Gebiets. Tafel 9. 1870. Band XVII., Heft V. 1871.

Die zweite deutsche Nordpolar-Expedition, 1869−70. Schlittenreise an der Küste Grönlands nach Norden, 8 März−27 April, 1870. Von Ober-Lieutenant Julius Payer. Band XVII., Heft V. 1871.

Die Entdeckung des Kaiser Franz Josef-Fjordes in Ost-Grönland, August, 1870. Von Ober-Lieutenant Julius Payer. Band XVII., Heft V. 1871.

Die Erschliessung eines Theiles des nördlichen Eismeeres durch die Fahrten und Beobachtungen der norwegischen Seefahrer Torkildsen, Ulve, Mack Qvale, und Nedrevaag im karischen Meere, 1870. Von Dr. A. Petermann. Band XVII., Heft III. 1871.

Die zweite deutsche Nordpolar-Expedition, 1869−70. Schlittenreise nach Ardencaple Inlet, 8−29 Mai, 1870. Von Ober-Lieutenant Julius Payer. Band XVII., Heft XI. 1871.

Ein Winter unter dem Polarkreise. Von Ober-Lieutenant Julius Payer. Band XVII., Heft XI. 1871.

Die Entdeckung eines offenen Polarmeeres durch Payer und Weyprecht im September, 1871. Von Dr. A. Petermann. Band XVII., Heft XI. 1871.

James Lamont’s Nordfahrt, Mai-August, 1871. Die Entdeckungen von Weyprecht, Payer, Tobiesen, Mack, Carlsen, Ulve, und Smyth im Sommer, 1871.

Stand der Nordpolarfrage zu Ende des Jahres 1871. Von Dr. A. Petermann. Band XVII., Heft XII. 1871.

Das Innere von Grönland. Von Dr. Robert Brown. Band XVII., Heft X. 1871.

Captain T. Torkildsen’s Cruise from Tromsö to Spitzbergen, July 26 to September 26, 1871. Vol. XVIII. 1872.

The Sea north of Spitzbergen, and the most northern Meteorological Observations. Vol. XVIII. 1872.

Results of the Observations of the Deep-sea Temperature in the Sea between Greenland, Northern Europe, and Spitzbergen. By Professor H. Möhn. Vol. XVIII. 1872.

The Norwegian Cruises to Nova Zembla and the Kara Sea in 1871. Vol. XVIII. 1872.

The Cruises in the Polar Sea in 1872. Vol. XVIII. 1872.

The Cruise of Smyth and Ulve, June 19 to September 27, 1871. Vol. XVIII. 1872.

Die fünfmonatliche Schiffbarkeit des sibirischen Eismeeres um Nowaja Semlja, erwiesen durch die norwegischen Seefahrer in 1869 und 1870, ganz besonders aber in 1871. Von Dr. A. Petermann. Band XVIII., Heft X. 1872.

Die neuen norwegischen Aufnahmen des nordöstlichen Theiles von Nowaja Semlja durch Mack, Dörma, Carlsen, u. A., 1871. Von Dr. Petermann. Band XVIII., Heft X. 1872.

Nachrichten über die sieben zurückgekehrten Expeditionen unter Graf Wiltschek, Altmann, Johnsen, Nilsen, Smith, Gray, Whymper; die drei Überwinterungs-Expeditionen; die Amerikanische, Schwedische, Österreichisch-Ungarische; und die zwei neuen: die norwegische Winter-Expedition und diejenige unter Kapitän Mack. Von Dr. A. Petermann. Band XVIII., Heft XII. 1872.

Konig Karl-Land im Osten von Spitzbergen und seine Erreichung und Aufnahme durch norwegische Schiffer im Sommer 1872. Von Professor H. Möhn. Band XIX., Heft IV. 1873.

Resultate der Beobachtungen angestellt auf der Fahrt des Dampfers “Albert” nach Spitzbergen im November und Dezember, 1872. Von Professor Möhn. Band XIX., Heft VII. 1873.

Die amerikanische Nordpolar-Expedition unter C. F. Hall, 1871−3. Von Dr. A. Petermann. Band XIX., Heft VIII. 1873.

Die Trift der Hall’schen Nordpolar-Expedition, 16 August bis 15 Oktober, 1872, und die Schollenfahrt der 20 bis zum 30 April, 1873. Von Dr. A. Petermann. Band XIX., Heft X. 1873.

Das offene Polarmeer bestätigt durch das Treibholz an der Nordwestküste von Grönland. Von Dr. A. Petermann. Band XX., Heft V. 1874.

Das arktische Festland und Polarmeer. Von Dr. Joseph Chavanne. Band XX., Heft VII. 1874.

Die Umkehr der Hall’schen Polar-Expedition nach den Aussagen der Offiziere. Von Dr. A. Petermann. Band XX., Heft VII. 1874.

Die zweite österreichisch-ungarische Nordpolar-Expedition unter Weyprecht und Payer, 1872−4. Von Dr. A. Petermann. Band XX., Heft X. 1874.

Beiträge zur Klimatologie und Meteorologie des Ost-polar-Meeres. Von Professor Möhn. Band XX., Heft V. 1874.

Kapitän David Gray’s Reise und Beobachtungen im ost-grönländischen Meere, 1874, und seine Ansichten über den besten Weg zum Nordpol. Original-Mittheilungen an A. Petermann, d.D., Peterhead, Dezember, 1874. Band XXI., Heft III. 1875.

VIII.

LIST OF PAPERS BY THE AUTHOR TO WHICH REFERENCE IS MADE
IN THIS VOLUME.

On the Influence of the Tidal Wave on the Earth’s Rotation and on the Acceleration of the Moon’s Mean Motion.—_Phil. Mag._, April, 1864.

On the Nature of Heat-vibrations.—_Phil. Mag._, May, 1864.

On the Cause of the Cooling Effect produced on Solids by Tension.—_Phil. Mag._, May, 1864.

On the Physical Cause of the Change of Climate during Geological Epochs.—_Phil. Mag._, August, 1864.

On the Physical Cause of the Submergence of the Land during the Glacial Epoch.—The _Reader_, September 2nd and October 14th, 1865.

On Glacial Submergence.—The _Reader_, December 2nd and 9th, 1865.

On the Eccentricity of the Earth’s Orbit.—_Phil. Mag._, January, 1866.

Glacial Submergence on the Supposition that the Interior of the Globe is in a Fluid Condition.—The _Reader_, January 13th, 1866.

On the Physical Cause of the Submergence and Emergence of the Land during the Glacial Epoch, with a Note by Professor Sir William Thomson.—_Phil. Mag._, April, 1866.

On the Influence of the Tidal Wave on the Motion of the Moon.—_Phil. Mag._, August and November, 1866.

On the Reason why the Change of Climate in Canada since the Glacial Epoch has been less complete than in Scotland.—_Trans. Geol. Soc. of Glasgow_, 1866.

On the Eccentricity of the Earth’s Orbit, and its Physical Relations to the Glacial Epoch.—_Phil. Mag._, February, 1867.

On the Reason why the Difference of Reading between a Thermometer exposed to direct Sunshine and one shaded diminishes as we ascend in the Atmosphere.—_Phil. Mag._, March, 1867.

On the Change in the Obliquity of the Ecliptic; its Influence on the Climate of the Polar Regions and Level of the Sea.—_Trans. Geol. Soc. of Glasgow_, vol. ii., p. 177. _Phil. Mag._, June, 1867.

Remarks on the Change in the Obliquity of the Ecliptic, and its Influence on Climate.—_Phil. Mag._, August, 1867.

On certain Hypothetical Elements in the Theory of Gravitation and generally received Conceptions regarding the Constitution of Matter.—_Phil. Mag._, December, 1867.

On Geological Time, and the probable Date of the Glacial and the Upper Miocene Period.—_Phil. Mag._, May, August, and November, 1868.

On the Physical Cause of the Motions of Glaciers.—_Phil. Mag._, March, 1869. _Scientific Opinion_, April 14th, 1869.

On the Influence of the Gulf-stream.—_Geol. Mag._, April, 1869. _Scientific Opinion_, April 21st and 28th, 1869.

On Mr. Murphy’s Theory of the Cause of the Glacial Climate.—_Geol. Mag._, August, 1869. _Scientific Opinion_, September 1st, 1869.

On the Opinion that the Southern Hemisphere loses by Radiation more Heat than the Northern, and the supposed Influence that this has on Climate.—_Phil. Mag._, September, 1869. _Scientific Opinion_, September 29th and October 6th, 1869.

On Two River Channels buried under Drift belonging to a Period when the Land stood several hundred feet higher than at present.—_Trans. Geol. Soc. of Edinburgh_, vol. i., p. 330.

On Ocean-currents: Ocean-currents in Relation to the Distribution of Heat over the Globe.—_Phil. Mag._, February, 1870.

On Ocean-currents: Ocean-currents in Relation to the Physical Theory of Secular Changes of Climate.—_Phil. Mag._, March, 1870.

The Boulder Clay of Caithness a Product of Land-ice.—_Geol. Mag._, May and June, 1870.

On the Cause of the Motion of Glaciers.—_Phil. Mag._, September, 1870.

On Ocean-currents: On the Physical Cause of Ocean-currents. Examination of Lieutenant Maury’s Theory.—_Phil. Mag._, October, 1870.

On the Transport of the Wastdale Granite Boulders.—_Geol. Mag._, January, 1871.

On a Method of determining the Mean Thickness of the Sedimentary Rocks of the Globe.—_Geol. Mag._, March, 1871.

Mean Thickness of the Sedimentary Rocks.—_Geol. Mag._, June, 1871.

On the Age of the Earth as determined from Tidal Retardation.—_Nature_, August 24th, 1871.

Ocean-currents: On the Physical Cause of Ocean-currents. Examination of Dr. Carpenter’s Theory.—_Phil. Mag._, October, 1871.

Ocean-currents: Further Examination of the Gravitation Theory.—_Phil. Mag._, February, 1874.

Ocean-currents: The Wind Theory of Oceanic Circulation.—_Phil. Mag._, March, 1874.

Ocean-currents.—_Nature_, May 21st, 1874.

The Physical Cause of Ocean-currents.—_Phil. Mag._, June, 1874. _American Journal of Science and Art_, September, 1874.

On the Physical Cause of the Submergence and Emergence of the Land during the Glacial Epoch.—_Geol. Mag._, July and August, 1874.

INDEX.

Absolute heating-power of ocean-currents, 23
〃 amount of heat received from the sun per day, 26

Adhémar, M., theory founded upon a mistake in regard to
radiation, 81, 85
〃 on submergence, 368
〃 on influence of eccentricity on climate, 542

Aërial currents increased in action by formation of snow and ice, 76
〃 function of, stated, 51
〃 heat conveyed by, 27

Africa, South, glacial and inter-glacial periods of, 242
〃 boulder clay of Permian age, 300

Age and origin of the sun, 346

Air, on absorption of rays by, 59
〃 when humid, absorbs rays which agree with it in period, 59
〃 when perfectly dry incapable of absorbing radiant heat, 59

Airy, Professor, earth’s axis of rotation permanent, 7

Aitken’s, Mr., experiment on density of polar water, 129

Aland islands, striation of, 447

Alternate cold and warm periods, 236

Allermuir, striations on summit of, 441

America, low temperature in January, 72
〃 thickness of ice-sheet of North, 381

Anderson, Captain Sir James, never observed a stone on an iceberg, 282

Antarctic regions, mean summer temperature of, below
freezing-point, 63

Antarctic ice-cap, probable thickness of, 375
〃 diagram representing thickness of, 377
〃 thickness of, estimated from icebergs, 384

Antarctic snowfall, estimates of, 382

Aphelion, glacial conditions at maximum when winter solstice is at, 77

Arago, M., on influence of eccentricity on climate, 536

Arctic climate, influence of ocean-currents on, during glacial
period, 260

Arctic regions, influence of Gulf-stream on climate of, 45
〃 mean summer temperature of, 63

Arctic regions, amount of heat received by, per unit surface, 195
〃 warm periods best marked in, 258
〃 warm inter-glacial periods in, 258−265
〃 state of, during glacial period, 260
〃 evidence of warm periods in, 261
〃 occurrence of recent trees in, 261, 265
〃 evidence of warm inter-glacial periods, 293
〃 warm climate during Old Red Sandstone period in, 295
〃 glacial period during Carboniferous age in, 297
〃 warm climate during Permian period in, 301
〃 list of papers relating to, 556

Arctic Ocean, area of, 195
〃 according to gravitation theory ought to be warmer than Atlantic
in torrid zone, 195
〃 heat conveyed into, by currents, compared with that received by it
from the sun, 195
〃 blocked up with polar ice, 444

Armagh, boulder beds of, 299

Arran, Island of, glacial conglomerate of Permian age in, 299

Astronomical causes of change of climate, 10

Astronomy and geology, supposed analogy between, 355

Atlantic, atmospheric pressure on middle of, 33
〃 inability of, to heat the south-west winds without the
Gulf-stream, 34
〃 mean annual temperature of, 36
〃 mean temperature of, raised by Gulf-stream, 36, 40
〃 isothermal lines of, compared with those of the Pacific, 46
〃 area of, from equator to Tropic of Cancer, 194
〃 inquiry whether the area of, is sufficient to supply heat
according to Dr. Carpenter’s theory, 194

Atlantic, North, heat received by, from torrid zone by currents, 194
〃 according to Dr. Carpenter’s theory ought to be warmer in
temperate regions than in the torrid zone, 195
〃 great depth of warm water in, 198
〃 North, an immense whirlpool, 216
〃 above the level of equator, 221
〃 probable antiquity of, 367
〃 from Scandinavia to Greenland probably filled with ice, 451

Atmosphere-pressure in Atlantic a cause of south-west winds, 33

Atmosphere, on difference between black-bulbed and shaded thermometer
in upper strata of, 547

Australia, evidence of ice-action in conglomerate of, 295

Ayrshire, ice-action during Silurian period in, 293

Bakewell, Mr. R., on influence of eccentricity on climate, 540

Banks’s Land, discovery of ancient forest in, 261
〃 Professor Heer, on fossilized wood of, 309

Ball, Mr., objection to Canon Moseley’s results, 501

Baltic current, 171

Baltic, glaciation of islands in, 448

Baltic glacier, passage of, over Denmark, 449

Bath, grooved rock surfaces of, 464

Bay-ice grinds but does not striate rocks, 277

Belcher, Sir E., tree dug up by, in latitude 75° N., 263
〃 carboniferous fossils found in arctic regions by, 298

Belle-Isle, Strait of, observations on action of icebergs in, 276

Bell, Mr. A., on Mediterranean forms in glacial bed at Greenock, 254

Belt, Mr. Thomas, theory of the cause of glacial epochs, 415

Bennie, Mr. James, on surface geology, 468
〃 on deposits filling buried channel, 486

Blanford, Mr., on ice-action during Carboniferous age in India, 297

Borings, evidence of inter-glacial beds from, 254
〃 examination of drift by, 467
〃 journals of, 483, 484

Boulder clays of former glacial epochs, why so rare, 269
〃 a product of land-ice, 284
〃 if formed from icebergs must be stratified, 284
〃 scarcity of fossils in, 285
〃 formed chiefly from rock on which it lies, 285
〃 of Caithness a product of land-ice, 435
〃 on summit of Allermuir, 441

Boulders, how carried from a lower to a higher level, 527

Boussingault on absorption of carbon by vegetation, 428

Britain, climate of, affected most by south-eastern portion of
Gulf-stream, 33

Brown, Dr. R., cited on Greenland ice-sheet, 378, 380
〃 on inland ice of Greenland, 284
〃 on cretaceous formation of Greenland, 305
〃 on Miocene beds of the Disco district, 310

Brown, Mr. Robert, on growth of coal plants, 421

Brown and Dickeson, on sediment of Mississippi, 330

Buchan, Mr., on atmosphere-pressure in the Atlantic, 33
〃 on force of the wind, 220

Buchanan, Mr. J. Y., on vertical distribution of heat of the
ocean, 550

Buckland, Dr., observations by, on occurrence of red chalk on
Cotteswold hills, 459

Buff, Professor, on oceanic circulation, 145

Buried river channels, 466
〃 channel from Kilsyth to Grangemouth, 468
〃 section at Grangemouth, 474
〃 from Kilsyth to Clyde, 481
〃 not excavated by sea nor by ice, 469
〃 other examples of, 488−494

Caithness, difficulty of accounting for
the origin of the boulder clay of, 435

Caithness, boulder clay of, a product of land-ice, 435
〃 boulder clay not formed by icebergs, 437
〃 theories regarding the origin of the boulder clay of, 437
〃 why the ice was forced over it, 444
〃 Professor Geikie and B. N. Peach on path of ice over, 453

Cambrian conglomerate of Islay, 292

Campbell, Mr., observations of, on icebergs, 276
〃 on supposed striation of rocks by large icebergs, 278
〃 evidence that river-ice does not striate rocks, 279

Canada, change of climate less complete than in Scotland, 71

Carboniferous period of arctic regions, 298
〃 evidence of glacial epoch during, 296−298
〃 temperate climate of, 422

Carboniferous limestone, mode of formation, 433

Carpenter’s, Dr., objections examined, 141
〃 theory, mechanics of, 145
〃 idea of a 〃vertical circulation〃 stated, 153

Carpenter’s, Dr., radical error in theory of, 155
〃 on difference of density between waters of Atlantic and
Mediterranean, 168
〃 theory, inadequacy of, 191
〃 estimate of thermal work of Gulf-stream, 199

Charpentier’s, M., theory of glacier-motion, 513

Carse clays, date of, 405

Cattegat, ice-markings on shore of, 446

Cave and river deposits, 251

Chalk, erratic blocks found in, 304
〃 _débris_, conclusion of Mr. Searles Wood, 460

_Challenger’s_ temperature-soundings at equator, 119
〃 crucial test of the wind and gravitation theories, 220

Chambers, Dr. Robert, on striated pavements, 255
〃 observations on glaciation of Gothland, 446

Champlain Lake, inter-glacial bed of, 241

Chapelhall, ancient buried channel at, 491
〃 inter-glacial sand-bed, 244

Chart showing the agreement between system of currents and system
of winds, 212

Christianstadt, crossed by Baltic glacier, 450

Circulation without difference of level, 176

Climate, Secular changes of, intensified by reaction of physical
causes, 75, 76
〃 affected most by temperature of the surface of ground, 88
〃 ocean-currents in relation to, 226
〃 cold conditions of, inferred from absence of fossils, 288
〃 cold condition of, difficulty of determining, from fossil
remains, 289
〃 warm, of arctic regions during Old Red Sandstone period, 295
〃 rough sketch of the history of, during the last 60,000 years, 409
〃 of Coal period inter-glacial in character, 420
〃 alternate changes of, during Coal period, 426

Climates, Mr. J. Geikie on difficulty of detecting evidence of ancient
glacial conditions, 289
〃 evidence of, from ancient sea-bottoms, 289

Coal an inter-glacial formation, 420

Coal beds, alternate submergence and emergence during formation
of, 424
〃 preservation of, by submergence, 426

Coal period, flatness of the land during, 430

Coal plants, conditions necessary for, preservation of, 423

Coal seams, thickness of, indicative of length of inter-glacial
periods, 428

Coal seams, time occupied in formation of, 429

Coal strata, on absence of ice-action in, 429

Coal measures, oscillations of sea-level during formation of, 425

Cold periods best marked in temperate regions, 258

Colding, Dr., oceanic circulation, 95

Confusion of ideas in reference to the agency of polar cold, 179

Continental ice, inadequate conceptions of, 385
〃 absence of, during glacial epochs of Coal period, 432

Contorted drift near Musselburgh, 465

Cook, Captain, description of Sandwich Land by, 60
〃 on South Georgia, 60

Cornwall, striated rocks of, 464

Cotteswold hills, red chalk from Yorkshire found on, 459

Couthony, Mr., on action of icebergs, 275

Coutts, Mr. J., on buried channel, 493

Craig, Mr. Robert, on inter-glacial beds at Overton Hillhead and
Crofthead, 247

Craiglockhart hill, inter-glacial bed of, 245

“Crawling” theory considered, 507

“Crevasses,” origin of, according to molecular theory, 521

Cretaceous period, evidence of ice-action during, 303−305

Cretaceous age, evidence of warm periods during, 304

Cretaceous formation of Greenland, 305

Crofthead, inter-glacial bed at, 248

Cromer forest bed, 250

Crosskey, Rev. Mr., comparison of Clyde and Canada shell beds, 71
〃 on southern shells in Clyde beds, 253

Croydon, block of granite found in chalk at, 303

Crucial test of the wind and gravitation theories, 220

Crystallization, force of, a cause of glacier-motion, 523

Currents, effects of their stoppage on temperatures of equator and
poles, 42
〃 produced by saltness neutralize those produced by temperature, 106

Dalager, excursion in Greenland by, 378

Dana, Professor, on action of icebergs, 275
〃 on striations by icebergs, 275
〃 on thickness of ice-sheet of North America, 381

Darwin, Mr., on alternate cold and warm periods, 231
〃 on migration of plants and animals during glacial epoch, 395
〃 on peat of Falkland Islands, 422

Date of the 40-foot beach, 409

Date when conditions were favourable to formations of the Carse
clay, 409

Davis’ Straits, current of, 132

Dawkins, Mr. Boyd, on the animals of cave and river deposits, 251

Dawson, Principal, on esker of Carboniferous age, 296

〃 on habitats of coal plants, 424

Deflection of ocean-currents chief cause of change of climate, 68

De la Beche, Sir H. T., on influence of eccentricity on climate, 539

De Mairan, on influence of eccentricity on climate, 528

Denmark, crossed by Baltic glacier, 449−452

Denudation, method of measuring rate of, 329
〃 as a measure of geological time, 329
〃 measured by sediment of Mississippi, 330
〃 subaërial rate of, 331
〃 law which determines rate of, 333
〃 marine, trifling, 337

Deposition, rates of, generally adopted, quite arbitrary, 360
〃 rate of, determined by rate of denudation, 362
〃 range of, restricted to a narrow fringe surrounding the
continents, 364
〃 area of, 365
〃 during glacial epoch probably less than present, 366

Deposits from icebergs cannot be wholly unstratified, 437

Despretz, tables by, of temperature of maximum density of
sea-water, 117

Desor, M., on tropical fauna of the Eocene formation in
Switzerland, 306

Derbyshire, breaks in limestone of, marks of cold periods, 434

Derbyshire limestone a product of inter-glacial periods, 434

Devonshire, boulder clay discovered in, 463

Diagram illustrating descent of water from equator to poles, 155
〃 showing variations of eccentricity, 313
〃 illustrative of fluidity of interior of the earth, 396
〃 showing formation of coal beds, 426

Dick, Mr., chalk flints in boulder clay, 454

Dick, Mr. R., on buried channel, 491

Difference of level essential to gravitation theory, 176

Dilatation of sea-water by increase of temperature calculated by Sir
John Herschel, 116

Disco district, Dr. R. Brown cited on Miocene beds of, 310

Disco Island, Upper Miocene period of, 307−308

Distribution, how effected by ocean-currents, 231

Dove, Professor, method of constructing normal temperature tables
by, 40
〃 on mean annual temperature, 401

Dover, mass of coal imbedded in chalk found at, 303

Drayson, Lieutenant-Colonel, on obliquity of ecliptic, 410

Drayson, Lieutenant-Colonel, theory of the cause of the glacial
epoch, 410

Drift, examination by borings, 467

Drumry, deep surface deposits at, 482

Dubuat’s, M., experiments, 182
〃 experiments by, on water flowing down an incline, 120

Duncan, Captain, on under current in Davis’ Strait, 134

Dürnten lignite beds, 240

Dürnten beds an example of inter-glacial coal formation, 433

Durham, buried river channel at, 488

Earth’s axis of rotation permanent, 7

Earth, mean temperature of, increased by water at equator, 30
〃 not habitable without ocean-currents, 54
〃 mean temperature of, greatest in aphelion, 77, 78
〃 centre of gravity of, effects of ice-cap on, 370, 371

Eccentricity of the earth’s orbit, Mr. Stockwell’s researches
regarding, 54
〃 primary cause of change of climate, 54
〃 primary cause of glacial epochs, 77
〃 how it affects the winds, 228
〃 tables of, 314−321
〃 its influence on temperature, 323
〃 explanation of tables of, 324
〃 De Marian, on influence of, on climate, 528
〃 Sir J. F. Herschel, on influence of, on climate, 529
〃 Œpinus, on influence of, on climate, 529
〃 R. Kirwan, on influence of, on climate, 529
〃 of planetary orbits, superior limits as determined by Lagrange,
Leverrier, and Mr. Stockwell, 531
〃 Sir Charles Lyell, on influence of, on climate, 529, 535
〃 M. Arago, on influence of, on climate, 536
〃 Baron Humboldt, on influence of, on climate, 538
〃 Sir H. T. de la Beche, on influence of, on climate, 539
〃 Professor Phillips, on influence of, on climate, 539
〃 Mrs. Somerville, on influence of, on climate, 540
〃 L. W. Meech, on influence of, on climate, 540
〃 Mr. R. Bakewell, on influence of, on climate, 540
〃 M. Jean Reynaud, on influence of, on climate, 541
〃 M. Adhémar, on influence of, on climate, 542

Equator, reduction of level by denudation, 336

Ecliptic, supposed effect of a change of obliquity of, 8
〃 changes of, effects on climate, 398−417
〃 obliquity of, Lieutenant-Colonel Drayson on, 410

Emergence, physical cause of, 368

England, inter-glacial beds of, 249
〃 glacial origin of Old Red Sandstone of, 294
〃 ice-action during Permian period in, 298
〃 North of, ice-sheet of, 456
〃 ice-sheet of South of, 463

Eocene period, total absence of fossils in flysch, 286
〃 glacial epoch of, 305

Eocene and Miocene periods, date of, 357

Equator, heat received per square mile at, 26
〃 temperature of earth increased by water at, 30
〃 and poles, effects of stoppage of currents on temperature of, 42
〃 surface-currents warmer than the under currents, 92
〃 heat transferred by currents from southern hemisphere compared
with that received by land at, 93
〃 temperature soundings at, 119
〃 temperature of sea at, decreases most rapidly at the surface, 119
〃 heat received by the three zones compared with that received by
the, 194
〃 migration across, 234
〃 glaciation of, 234

Equatorial current, displacement of, 229

Erratic blocks in stratified rocks, evidence of former land-ice, 269
〃 in chalk, 304
〃 why not found in coal strata, 432

Erratics extend further south in America than in Europe, 72

Etheridge, R., jun., on glacial conglomerate in Australia of Old Red
Sandstone age, 295

Europe, influence of Gulf-stream on climate of, 31
〃 effect of deflection of Gulf-stream on condition of, 68
〃 glacial condition of, if Gulf-stream was stopped, 71
〃 river systems of, unaltered since glacial period, 393

Faraday, Professor, on cause of regelation, 554

Faroe Islands glaciated by land-ice from Scandinavia, 450

Ferrel, Mr., on Dr. Carpenter’s theory, 126
〃 argument from the tides, 184

Findlay, Mr. A. G., objection by, considered, 31, 203
〃 estimate of heat conveyed by Gulf-stream, 206

Fisher, Rev. O., on the 〃trail〃 of Norwich, 251
〃 on glacial submergence, 387

Fitzroy, Admiral, on temperature of Atlantic, 36

Fluid molecules crystallize in interstices, 523

Fluvio-marine beds of Norwich, 250

“Flysch” of Eocene period, absence of fossils in, 286
〃 of Switzerland of glacial origin, 306

Fogs prevent the sun’s heat from melting ice and snow in arctic
regions, 60

Forbes, Professor J. D., method adopted by, of ascertaining
temperatures, 48
〃 on temperature of equator and poles, 48
〃 on the conductivity of different kinds of rock, 86
〃 on underground temperature, 86
〃 experiments by, on the power of different rocks to store up
heat, 86

Forest bed of Cromer, 250

Former glacial periods, 266−310
〃 why so little known of, 266
〃 geological evidence of, 292

France, evidence of ice-action during Carboniferous period in, 296

Fraserburgh, glaciation of, 450
〃 crossed by North Sea ice, 454

Fundamental problem of geology, 1

Ganges, amount of sediment conveyed by, 331

Gases, radiation of, 38

Gastaldi, M., on the Miocene glacial epoch of Italy, 306

Geikie, Professor, on geological agencies, 1
〃 on inter-glacial beds of Scotland, 243
〃 remarks on inter-glacial beds, 245
〃 on striated pavements, 256
〃 on ice-markings on Scandinavian coast, 281
〃 striated stones found in carboniferous conglomerate by, 296
〃 on sediment of European rivers, 332
〃 on modern denudation, 332
〃 suggestion regarding the loess, 452
〃 on striation of Caithness, 453
〃 on buried channel at Chapelhall, 491
〃 and Mr. James, on glacial conglomerate of Lower Carboniferous
age, 296

Geikie, Mr. James, on Crofthead inter-glacial bed, 248
〃 on the gravels of Switzerland, 268
〃 on difficulty of recognising former glacial periods, 289
〃 on Cambrian conglomerate of north-west of Scotland, 293
〃 on ice-action in Ayrshire during Silurian period, 293
〃 on boulder conglomerate of Sutherland, 301
〃 on buried channels, 492

Geogr. Mittheilungen, list of papers in, relating to arctic
regions, 556

Geological agencies climatic, 2

Geological principle, nature of, 4

Geological climates, theories of, 6

Geological time, 311−359
〃 measurable from astronomical data, 311
〃 why it has been over-estimated, 325
〃 method of measuring, 328, 329
〃 Professor Ramsay on, 343

Geology, fundamental problem of, 1
〃 a dynamical science, 5
〃 and astronomy, supposed analogy between, 355

German Polar Expedition on density of polar water, 151
〃 list of papers relating to, 556

German Ocean once dry land, 479

Germany, Professor Ramsay on Permian breccia of, 300

Gibraltar current, Dr. Carpenter’s theory of, 167
〃 cause of, 215

Glacial conditions increased by reaction of various physical
causes, 75
〃 reach maximum when winter solstice arrives at aphelion, 77

Glacial epoch, date of, 327
〃 circumstances which show recent date of, 341
〃 Mr. Belt’s theory of cause of, 415

Glacial epochs dependent upon deflection of ocean-currents, 68
〃 caused primarily by eccentricity, 77
〃 why so little known of, formerly, 266
〃 boulder clays of former, why so rare, 269
〃 geological evidence of former, 292

Glacial period in America more severe than in Western Europe, 73
〃 mean temperature of the earth greatest at aphelion during, 78
〃 records of, fast disappearing, 270
〃 of the Eocene formation, 305

Glacial periods, indirect evidence of, in Eocene and Miocene
formations, 287
〃 difficulty of determining, from fossil remains, 289

Glacial submergence resulting from displacement of the earth’s centre
of gravity, 389

Glaciation a cause of submergence, 390
〃 remains of, found chiefly on land surfaces, 267
〃 of Scandinavia inexplicable by theory of local glaciers, 448

Glacier des Bois, 497

Glacier-motion, Canon Moseley’s theory of, 507
〃 Professor James Thomson’s theory of, 512
〃 M. Charpentier’s theory of, 513
〃 molecular, 516

Glacier-motion, present state of the question, 514
〃 molecular theory of, 514−527
〃 heat necessary to, 515
〃 due to force of crystallization, 523
〃 due chiefly to internal molecular pressure, 523

Glaciers, pressure exerted by, 274
〃 physical cause of the motion of, 495−527
〃 difficulties in accounting for motion of, 495

Glasgow, actual January temperature of, 28° above normal, 72

Godwin-Austen, Mr., on ice-action during the Carboniferous period in
France, 296
〃 on evidence of ice-action during Cretaceous period, 303
〃 on mass of coal found in chalk at Dover, 304
〃 on the flatness of the land during Coal period, 430

Gothland, glaciation of, 446

Grangemouth, buried river channel at, 468
〃 surface-drift of, 484

Gravitation, the whole work of, performed by descent of water down the
slope, 154
〃 of sun’s mass, 348
〃 insufficient to account for sun’s heat, 349, 350

Gravitation theory, its relation to the theory of Secular changes of
climate, 97
〃 three modes of determining it, 115
〃 mechanics of, 145
〃 of the Gibraltar current, 167
〃 inadequacy of, 191
〃 _crucial_ test of, 220
〃 of the sun’s heat, 346−355

Gravity, force of, impelling water from equator to poles, 119, 120
〃 force of, insensible at a short distance below the surface, 120
〃 work performed by, 150
〃 diagram illustrating the action of, in producing currents, 155
〃 amount of work performed by, due solely to _difference_ of
temperature between equatorial and polar waters, 164
〃 specific difference in, between water of Atlantic and
Mediterranean insufficient to produce currents, 169
〃 centre of, displacement, by polar ice-cap, 368

Greenland, summer warm if free from ice, 59
〃 receives as much heat in summer as England, 66
〃 continental ice free from clay or mud, 284
〃 North, warm climate during Oolitic period in, 302
〃 Cretaceous formation of, 305

Greenland, evidence of warm conditions during Miocene period in, 307
〃 Professor Heer cited on Miocene flora of, 308, 309
〃 state of, during glacial period, 259
〃 effect of removal of ice from, 260

Greenland ice-sheet, probable thickness of, 378
〃 invaded the American continent, 445

Greenland inland ice, 379

Gulf-stream, estimate of its volume, 24
〃 United States’ coast survey of, 24
〃 absolute amount of heat conveyed by, 25, 26
〃 heat conveyed by, compared with that carried by aërial
currents, 27
〃 heat conveyed by, compared with that received by the frigid zone
from the sun, 27
〃 influence on climate of Europe, 31
〃 efficiency of, due to the slowness of its motion, 32
〃 climate of Britain influenced by south-eastern portion of, 33
〃 heat conveyed by, compared with that derived by temperate regions
from the sun, 34
〃 heat of, expressed in foot-pounds of energy, 35
〃 mean temperature of Atlantic increased one-fourth by, 36
〃 the only current that can heat arctic regions, 45
〃 influence of, on climate of arctic regions, 45
〃 the compensating warm current, 46
〃 palæontological objections to influence of, 53
〃 agencies which deflect the, in glacial periods, 69
〃 result, if stopped, 71
〃 large portion of the heat derived from southern hemisphere, 94
〃 Lieut. Maury on propulsion of, by specific gravity, 102
〃 contradictory nature of, the causes supposed by Lieut. Maury for
the, 110
〃 higher temperature of, considered by Lieut. Maury as the real
cause of its motion, 111
〃 amount of heat conveyed by, not over-estimated, 197
〃 amount of heat conveyed by, 192
〃 amount of heat conveyed by, compared with that by general oceanic
circulation, 194
〃 heat conveyed by, compared with that received by torrid zone from
the sun, 194
〃 heat conveyed by, into Arctic Ocean compared with that received by
it from the sun, 195
〃 Capt. Nares’s observations of, 198
〃 Dr. Carpenter’s estimate of the thermal work of, 199

Gulf-stream, volume and temperature of, according to Mr. A. G.
Findlay, 203, 206
〃 erroneous notion regarding depth of, 207
〃 list of papers relating to, 556

Haughton, Professor, on recent trees in arctic regions, 263
〃 on fragments of granite in carboniferous limestone, 296
〃 on coal beds of arctic regions, 298
〃 on _Ammonites_ of Oolitic period in arctic regions, 303

Hayes, Dr., on Greenland ice-sheet, 379

Heat received from the sun per day, 26
〃 received by temperate regions from the sun, 34
〃 radiant, absorbed by ice remains insensible, 60
〃 sun’s, amount of, stored up in ground, 87
〃 transferred from southern to northern hemisphere, 93
〃 internal, supposed influence of, 176
〃 received by the three zones compared with that received by the
equator, 194
〃 amount radiated from the sun, 346
〃 received by polar regions 11,700 years ago, 403
〃 necessary to glacier-motion, 515
〃 how transmitted through ice, 517

Heat-vibrations, nature of, 544