Climate and Time in Their Geological Relations: A Theory of Secular Changes ... - James Croll - Google Libros

Libros

Imágenes de páginas

FORMER GLACIAL EPOCHS; GEOLOGICAL EVIDENCE OF.

Cambrian Conglomerate of Islay and North-west of Scotland.-Ice-action

in Ayrshire and Wigtownshire during Silurian Period.—Silurian

Limestones in Arctic Regions.-Professor Ramsay on Ice-action during

Old Red Sandstone Period.-Warm Climate in Arctic Regions during

Old Red Sandstone Period.-Professor Geikie and Mr. James Geikie

on a Glacial Conglomerate of Lower Carboniferous Age.-Professor

Haughton and Professor Dawson on Evidence of Ice-action during

Coal Period.-Mr. W. T. Blanford on Glaciation in India during

Carboniferous Period.-Carboniferous Formations of Arctic Regions.

-Professor Ramsay on Permian Glaciers.-Permian Conglomerate in

Arran.--Professor Hull on Boulder Clay of Permian Age.-Permian

Boulder Clay of Natal.-Oolitic Boulder Conglomerate in Sutherland-

shire. Warm Climate in North Greenland during Oolitic Period.-

Mr. Godwin-Austen on Ice-action during Cretaceous Period.-Glacial

Conglomerates of Eocene Age in the Alps.-M. Gastaldi on the Ice-

transported Limestone Blocks of the Superga.--Professor Heer on the

Climate of North Greenland during Miocene Period

GEOLOGICAL TIME.-PROBABLE DATE OF THE GLACIAL EPOCH.

Geological Time measurable from Astronomical Data.-M. Leverrier's For-

mulæ. Tables of Eccentricity for 3,000,000 Years in the Past and

1,000,000 Years in the Future.-How the Tables have been computed.

-Why the Glacial Epoch is more recent than had been supposed.—

Figures convey a very inadequate Conception of immense Duration.—

Mode of representing a Million of Years.-Probable Date of the

GEOLOGICAL TIME.-METHOD OF MEASURING THE RATE OF SUBAËRIAL

Rate of Subaërial Denudation a Measure of Time.-Rate determined from

Sediment of the Mississippi.-Amount of Sediment carried down by

the Mississippi; by the Ganges.-Professor Geikie on Modern Denu-

dation.-Professor Geikie on the Amount of Sediment conveyed by

European Rivers.-Rate at which the Surface of the Globe is being

denuded. Alfred Tylor on the Sediment of the Mississippi.-The

Law which determines the Rate of Denudation.-The Globe becoming

less oblate.-Carrying Power of our River Systems the true Measure

of Denudation.-Marine Denudation trifling in comparison to Sub-

aërial.-Previous Methods of measuring Geological Time.--Circum-

stances which show the recent Date of the Glacial Epoch.-Professor

Ramsay on Geological Time.

THE PROBABLE AGE AND ORIGIN OF THE SUN.

Gravitation Theory.-Amount of Heat emitted by the Sun.-Meteoric

Theory.-Helmholtz's Condensation Theory.-Confusion of Ideas.—

Gravitation not the chief Source of the Sun's Heat.-Original Heat.-

Source of Original Heat.-Original Heat derived from Motion in Space.

-Conclusion as to Date of Glacial Epoch.-False Analogy.-Probable

Date of Eocene and Miocene Periods

A METHOD OF DETERMINING THE MEAN THICKNESS OF THE

SEDIMENTARY ROCKS OF THE GLOBE.

Prevailing Methods defective.-Maximum Thickness of British Rocks.—

Three Elements in the Question.-Professor Huxley on the Rate of

Deposition. Thickness of Sedimentary Rocks enormously over-

estimated.-Observed Thickness no Measure of mean Thickness.-

Deposition of Sediment principally along Sea-margin.—Mistaken In-

ference regarding the Absence of a Formation.-Immense Antiquity

of existing Oceans

THE PHYSICAL CAUSE OF THE SUBMERGENCE AND EMERGENCE

OF THE LAND DURING THE GLACIAL EPOCH.

Displacement of the Earth's Centre of Gravity by Polar Ice-cap.-Simple

Method of estimating Amount of Displacement.-Note by Sir W.

Thomson on foregoing Method.-Difference between Continental Ice

and a Glacier.-Probable Thickness of the Antarctic Ice-cap.-

Probable Thickness of Greenland Ice-sheet.-The Icebergs of the

Southern Ocean.-Inadequate Conceptions regarding the Magnitude

of Continental Ice

THE PHYSICAL CAUSE OF THE SUBMERGENCE AND EMERGENCE OF

THE LAND DURING THE GLACIAL EPOCH.-(Continued.)

Extent of Submergence from Displacement of Earth's Centre of Gravity.—

Circumstances which show that the Glacial Submergence resulted from

Displacement of the Earth's Centre of Gravity.-Agreement between

Theory and Observed Facts.-Sir Charles Lyell on submerged Areas

during Tertiary Period.-Oscillations of Sea-Level in Relation to Dis-

tribution.-Extent of Submergence on the Hypothesis that the Earth

is fluid in the Interior .

THE INFLUENCE OF THE OBLIQUITY OF THE ECLIPTIC ON CLIMATE

AND ON THE LEVEL OF THE SEA.

The direct Effect of Change of Obliquity on Climate.-Mr. Stockwell on

the maximum Change of Obliquity.-How Obliquity affects the Dis-

tribution of Heat over the Globe.-Increase of Obliquity diminishes

the Heat at the Equator and increases that at the Poles.-Influence of

Change of Obliquity on the Level of the Sea.-When the Obliquity

was last at its superior Limit.-Probable Date of the 25-foot raised

Beach.-Probable Extent of Rise of Sea-level resulting from Increase

of Obliquity.-Lieutenant-Colonel Drayson's and Mr. Belt's Theories.

-Sir Charles Lyell on Influence of Obliquity

398

COAL AN INTER-GLACIAL FORMATION.

Climate of Coal Period Inter-glacial in Character.-Coal Plants indicate

an Equable, not a Tropical Climate.-Conditions necessary for Preser-

vation of Coal Plants.-Oscillations of Sea-level necessarily implied.-

Why our Coal-fields contain more than One Coal-seam.-Time re-

quired to form a Bed of Coal.-Why Coal Strata contain so little

evidence of Ice-action.-Land Flat during Coal Period.-Leading Idea

of the Theory.-Carboniferous Limestones

PATH OF THE ICE-SHEET IN NORTH-WESTERN EUROPE AND ITS

RELATIONS TO THE BOULDER CLAY OF CAITHNESS.

Character of Caithness Boulder Clay.-Theories of the Origin of the Caith-

ness Clay.-Mr. Jamieson's Theory.-Mr. C. W. Peach's Theory.-

The proposed Theory.-Thickness of Scottish Ice-sheet.-Pentlands

striated on their Summits.-Scandinavian Ice-sheet.-North Sea filled

with Land-ice.-Great Baltic Glacier.-Jutland and Denmark crossed

by Ice.-Sir R. Murchison's Observations.-Orkney, Shetland, and

Faroe Islands striated across.-Loess accounted for.-Professor Geikie's

Suggestion.-Professor Geikie and B. N. Peach's Observations on East

Coast of Caithness.-Evidence from Chalk Flints and Oolitic Fossils in

CHAPTER XXVIII.

NORTH OF ENGLAND ICE-SHEET, AND TRANSPORT OF WASTDALE

Transport of Blocks; Theories of.-Evidence of Continental Ice.-Pennine

Range probably striated on Summit.-Glacial Drift in Centre of Eng-

land. Mr. Lacy on Drift of Cotteswold Hills.-England probably

crossed by Land-ice.-Mr. Jack's Suggestion.-Shedding of Ice North

and South.-South of England Ice-sheet.-Glaciation of West Somer-

set.-Why Ice-markings are so rare in South of England.-Form of

Contortion produced by Land-ice.

EVIDENCE FROM BURIED RIVER CHANNELS OF A CONTINENTAL PERIOD

Remarks on the Drift Deposits.-Examination of Drift by Borings.-

Buried River Channel from Kilsyth to Grangemouth.-Channels not

excavated by Sea nor by Ice.-Section of buried Channel at Grange-

mouth. Mr. Milne Home's Theory.-German Ocean dry Land.—

Buried River Channel from Kilsyth to the Clyde.-Journal of Borings.

-Marine Origin of the Drift Deposits.-Evidence of Inter-glacial

Periods.-Oscillations of Sea-Level.-Other buried River Channels

THE PHYSICAL CAUSE OF THE MOTION OF GLACIERS.-THEORIES

OF GLACIER-MOTION.

Why the Question of Glacier motion has been found to be so difficult.-

The Regelation Theory.-It accounts for the Continuity of a Glacier,

but not for its Motion.-Gravitation proved by Canon Moseley insuf-

ficient to shear the Ice of a Glacier.-Mr. Matthew's Experiment.-

No Parallel between the bending of an Ice Plank and the shearing of

a Glacier.-Mr. Ball's Objection to Canon Moseley's Experiment.-

Canon Moseley's Method of determining the Unit of Shear.-Defect of

Method.-Motion of a Glacier in some Way dependent on Heat.-

Canon Moseley's Theory.-Objections to his Theory.-Professor James

Thomson's Theory.-This Theory fails to explain Glacier-motion.-De

Saussure and Hopkins's "Sliding" Theories.-M. Charpentier's "Dila-

tation" Theory.-Important Element in the Theory

THE PHYSICAL CAUSE OF THE MOTION OF GLACIERS.-THE

MOLECULAR THEORY.

Present State of the Question.-Heat necessary to the Motion of a Glacier.

-Ice does not shear in the Solid State.-Motion of a Glacier molecular.

-How Heat is transmitted through Ice.-Momentary Loss of Shear-

ing Force.-The Rationale of Regelation.-The Origin of "Cre-

."-Effects of Tension.-Modification of Theory.-Fluid Mole-

cules crystallize in Interstices.-Expansive Force of crystallizing

Molecules a Cause of Motion.-Internal molecular Pressure the chief

Moving Power.-How Ice can excavate a Rock Basin.-How Ice can

ascend a Slope.-How deep River Valleys are striated across.-A

remarkable Example in the Valley of the Tay.-How Boulders can be

carried from a lower to a higher Level

514

I. Opinions expressed previous to 1864 regarding the Influence of the

Eccentricity of the Earth's Orbit on Climate

II. On the Nature of Heat-Vibrations

III. On the Reason why the Difference of Reading between a Thermo-

meter exposed to direct Sunshine and One Shaded diminishes as we

ascend in the Atmosphere

IV. Remarks on Mr. J. Y. Buchanan's Theory of the Vertical Distribu-

tion of Temperature of the Ocean.

V. On the Cause of the Cooling Effect produced on Solids by Tension. 554

VI. The Cause of Regelation

556

VII. List of Papers which have appeared in Dr. A. Petermann's Geo-

graphische Mittheilungen relating to the Gulf-stream and Thermal

Condition of the Arctic Regions

VIII. List of Papers by the Author to which Reference is made in this

« Anterior Continuar »