A system of Physical Geography ... To which is added a treatise on the Physical Geography of the United States ... The whole embellished by numerous engravings and ... maps ... by J. H. Young

Front matter

5> A SYSTEM OF PHYSICAL GEOGRAPHY CONTAINING A DESCRIPTION OF THE NATURAL FEATURES OF THE LAND AND WATER, THE PHENOMENA OF THE ATMOSPHERE, AND THE DISTRIBUTION OF VEGETABLE AND ANIMAL LIFE. TO WHICH IS ADDED, A TREATISE ON THE PHYSICAL GEOGRAPHY OF THE UNITED STATES BY D. M. WARREN. SJte fojprf* SmMK4& 6g i»rmi5 fugmiriup, AND ILLUSTRATED BY SEVERAL COPPER-PLATE AND ELECTROTYPED MAPS AND CHARTS, DRAWN EXPRESSLY FOR THE WORK BY JAMES H. YOUNG. LONDON: SAMPSON LOW, SON & CO., 47 LUDGATE HILL, PHILADELPHIA: H. COWPERTHWAIT & CO. 18 57.

Preface

. The admirable works of such writers as Humboldt, Maury, Guyot, and Mrs. SomerviUe, have obtained, in late years, a very wide circulation ; and the attention of the public, especially of teachers, seems to have been directed thereby to the science of Physical Geography. The brief allusions to this subject found in the ordinary text-books on Geography appear to have been considered far from satisfactory ; and the desire has been very generally manifested, that a work, exclusively devoted to this subject, should be prepared, adapted to the use of schools. The frequent expression of this desire by many teachers induced Mr. D. M. Warren, one of the publishers, to undertake the preparation of the present volume. He has derived much valuable assistance in this labor from Mr. Arthur Sumner, of the Rhode Island State Normal School, at Providence ; and from Mr. P. W. Bartlett, Principal of the Chapman School, Boston.

The maps, which are specially designed to illustrate the text, were drawn by Mr. James H. Young, and hare been engraved under his direct supervision. Mr. Young originally prepared all the matter, and drew all the maps illustrating Mitchell's Series of School Geographies ; and to his critical accuracy and extensive geographical knowledge, the Compiler is indebted for many suggestions, which have materially increased the value of this book. Most of the engravings, which are also especially intended to illustrate the text, are from original designs by Mr. George G. White. The principal authorities relied upon in the preparation of the present work, in addition to those already enumerated, have been the magnificent Folio Edition of Johnston's Physical Atlas, Ansted's Physical Geography, and the works of Petermann and Milner.

The arrangement of the latter authors has been generally adopted in this volume, and in some cases their language has been used. The articles on the Ocean, especially on the Currents and Navigation, would have been very imperfect without the aid obtained from the investigations of Lieut. Maury, furnished to the world in his " Sailing Directions." Interesting deductions on the Winds of the Northern Hemisphere have been drawn from the work of Professor Coffin, published by the Smithsonian Institution. Dr. Kane has kindly furnished the information by which we are enabled to designate on the map the location of his winter quarters, and the nearest point to the North Pole attained by his recent Expedition. The treatise on the Physical Geography of the United States is new, and entirely original in its arrangement.

Much of the information on which it is based was obtained from the "Army Meteorological Register," and the "Report of the Explorations and Surveys for the Pacific Railroad." It is believed that no subject of instruction will be more attractive to the young, or better fitted to elevate and expand the mind, than that of Physical Geography. It treats of the natural adaptation of the earth for the abode of man ; — it describes the diversities of the surface of the globe its divisions of land and water, its mountains and plains ; — it draws our attention to the atmosphere, and explains that wonderful process, invisible to us, by which the water of the ocean is lifted into the air, thence to be distributed over the land to form lakes and rivers, and to give life to vegetation, which in its turn sustains animal life.

In short, to use the language of another, (Alexander Keith Johnston,) " Physical Geography is the history of Nature presented in its most attractive form, the exponent of the wonders which the Almighty Creator has scattered so profusely around us." It would be presumptuous to state, that, in a work like this, embracing so great a variety of subjects, and comprising such a multiplicity of facts, gathered from numerous and often conflicting authorities, no error will be found. Much care has been taken to test the accuracy of every statement ; but should any errors be discovered, the author will gratefully acknowledge the kindness of his friends who may furnish him the information by which they may be corrected. TABLE OE CONTENTS. Chapter Pa8« IL— TEMPERATURE -. 40 Chapter Page INTRODUCTORY— DEFINITIONS 5 III.— THE WINDS 42 IV.— MOISTURE OF THE ATMOSPHERE — DEW, FOGS, RAIN, SNOW, AND HAIL 48

Part I. Geology

V.— CLIMATE 5* VI.— ELECTRICAL AND OPTICAL PHENOMENA 57 I.— GENERAL STRUCTURE OF THE LAND 8 II.— CONTINENTS 10 III.— ISLANDS 11

PART IV. IV.

— MOUNTAINS AND VALLEYS 13 V.— PLATEAUS, OR TABLE-LANDS 16 ORGANIC LIFE VI.— PLAINS 18 VII.— VOLCANOES AND EARTHQUAKES 21 I.— BOTANICAL GEOGRAPHY 60 II.— ZOOLOGICAL GEOGRAPHY 66 III.— ETHNOGRAPHY 73

Part II. Hydrography

I.— SPRINGS 27 PHYSICAL GEOGRAPHY OF THE UNITED STATES. II.— RIVERS 28 III.— LAKES 31 IV.— THE OCEAN 32 V.— OCEANIC MOVEMENTS — WAVES, TIDES, AND CURRENTS 33 I.— GEOGRAPHICAL POSITION AND EXTENT — PENINSULAS, CAPES, AND ISLANDS 78

Part III

IL— MOUNTAINS - 79 III.— GENERAL SURFACE OF THE COUNTRY 80 METEOROLOGY. IV.— RIVERS AND LAKES 82 V.— CLIMATE, RAINFALL, AND PRODUCTIONS 84 I.— THE ATMOSPHERE 39 VI.— MINERALOGY 86 INDEX TO THE MAPS AND CHARTS. Page Pago GEOLOGY 11. Chart op the Distribution of Rain and Snow over the Surface of the Earth 53 1. Map exhibiting the Mountain Chains of Central Europe, Western Asia, and Northern Africa 15 12. Rain Chart of India 53 13. Sketch of a Part of the Glacier of Chamouni 53 2. Chart exhibiting the Continents, Islands, Chief Mountain Ranges, and other diversities of the land surface of the earth 21 14. Climatic Chart, showing, by Isothermal Lines, the Mean Annual Temperature op the Different Parts of the Earth's Surface 56 3. Chart op the Mountains, Plains, &c, op India '. 21 4. Chart of the Principal Mountains, Plains, _c, of South America 21 5.

Chart showing the Distribution of the Principal Active Volcanoes, and the Regions visited by Earthquakes 26 ORGANIC LIFE. 15. Chart showing the Distribution of the Most Important Trees, Grains and Fruits, according to Zones of Climate and Moisture 64 HYDROGRAPHY. 16. Distribution op Plants in a Vertical Direction g,j 17. Chart showing the Geographical Distribution of the Principal Mammalia gg 6. Tidal Chart of the World, showing the Progress of the Wave of High Water from East to West 35 18. Chart showing the Geographical Distribution of the Principal Birds and Reptiles 7. Hydrographic Chart of the World, exhibiting the Principal River Basins, the Ocean, and Oceanic Currents 38 19. Ethnographic Chart of the World, showing the Distribution and Varieties of the Human Race y» 8. The Connection of the Orinoco and Amazon by the River Cassiquiare, 38 9.

Chart exhibiting the Depth of the Atlantic Ocean, on the Coast of the United States and the West Indies 38 PHYSICAL GEOGRAPHY OF THE UNITED STATES. METEOROLOGY 10. Chart showing the Distribution of the Winds over the Surface of the Earth; also the Regions subject to Storms 47 20. Physical Map of ™e United States, showing its Mountains, Plains Rivers, Isothermal Lines, &c ' g» INTRODUCTORY. — DEFINITIONS. I. GEOGRAPHY is a description of the Earth. starting from a given port, and sailing constantly in the same direction, have at length arrived at the place from which they started ; and 3. The shadow cast by the earth on the moon is always circular. The term is derived from two Greek words, signifying " the earth," and "to describe," and the great variety of subjects comprehended in this general definition may be considered under the three divisions of Mathematical, Physical, and Political Geography.

That the earth is slightly flattened at the opposite sides has been demonstrated by eminent French and English astronomers, from measure ments of an arc of a meridian at different stations on the globe. The length of a degree was found to increase as they approached the poles. Any part of the circumference of a circle is called an arc. II. Mathematical Geography treats of the form, size, and motions of the earth ; of its position among the other bodies of the universe, its divisions by circles, and the representations of the whole or portions of its surface on globes or maps. 2. The circumference of the earth is about 25,000 miles ; its diameter is about 8000 miles. In exact numbers, the equatorial circumference of the earth is 24,899 miles. The equatorial diameter, carefully computed, is 41,849,548 feet, equal to about 7926 miles.

The polar diameter is 41,709,642 feet, equal to about 7899J miles. It will thus be seen that the distance through the earth from East to West, owing to the flattening at the poles, is 26} miles greater than the distance through it from North to South. III. Physical Geography treats of the natural divisions of land and water, the phenomena of the atmosphere, and the distribution and arrangement of organic life. IV. Political Geography treats of the extent and popula tion of different countries, and the civil and social condition of their inhabitants. 3. The earth has two motions — the daily and the yearly, — both of which are from West to East. The daily motion of the earth is its revolution on its axis, causing day and night ; the yearly motion is its revolution round the sun, causing the succession of seasons.

The axis of the earth is an imaginary line passing through its centre from North to South, and is the diameter on which the earth is supposed to turn. The northern extremity of the axis is the North Pole — the southern extremity the South Pole. MATHEMATICAL GEOGRAPHY. I. The Earth is that planet which we inhabit. Until the beginning of the sixteenth century, it was generally supposed that the earth was stationary, and that the heavenly bodies revolved about it once in 24 hours. That the earth, on the contrary, revolves, is demon strable by astronomy; that this is highly probable, apart from scientific proof, appears from the following consideration : 1st. No other supposition accounts for the bulging of the earth at the equator; the centrifugal motion, its revolutions upon its own axis, would produce this effect. 2d. A stone, dropped from the top of a high perpendicular tower, will always fall a short distance to the east of the base ; the stone has the motion of the top of the tower, which moves more rapidly than the base. 3d. This supposition alone will account for the equatorial current and the trade winds.

At the equator, the rotary velocity of the earth is about 1000 miles an hour. 1. It is variously denominated terrestrial ball, sphere, and globe, the terms having reference to its form. The form of the earth, in popular language, is expressed as round. More correctly speaking, however, its shape is that of an oblate spheroid — a ball bulging out in the middle, and flattened at the two opposite sides. The annual motion of the earth round the sun is conclusively proved by astronomical observations of the phenomena known as aberration of light. The succession of the seasons is the result of the annual revolution of the earth round the sun, and of the inclination of the earth's axis to the plane of the ecliptic. The angle of inclination is about 23} degrees. It thus follows that the axis of the earth, though it always points in the same direction, is at every period of its progress around the ecliptic, assuming a different position towards the sun.

Twice in the year, on the 21st of March and 23d of September, the axis is perpendicular to the direction of the sun's rays ; these are the equinoxes, (equal nights). On the 21st of June, the North Pole leans towards the sun, bringing the Northern Hemisphere the most under the influence of his rays. On the 21st of December the South Pole leans towards the sun, brin»inc the Southern Hemisphere the most under this influence; these points in the ecliptic are called the solstices, (sun stands). Illustration of one of the proofs that the earth is nearly round. The proofs that the earth is nearly round are: 1. The tops of the masts of a ship coming into harbor are always seen before the hull. 2. Navigators Questions. — What is Geography ? — Under what three divisions may the subject be considered? — Of what does Mathematical Geography treat? — Physical Geography? — Political Geography ?

Questions. — State the evidence of the earth's being flattened at the poles. What is the extent of the circumference of the earth ? — Of the diameter of the earth? How manv motions has the earth, and what are they? — What is the axis of the earth 9 What is the earth ? — State some of the names by which it is called. — What is its correct form ? — Give some of the proofs of the rotundity of the earth. State some of the reasons which render it probable the earth revolves? What con clusively proves the annual revolution of the earth ?— Explain the succession of seasons. INTRODUCTORY. called great circles. The tropics, polar circles, and parallels divide the earth into unequal parts, and are called small circles. Every circle is divided into 360 equal parts, called degrees. The length of a degree, on a great circle, is about 69 miles ; on small circles, the length of a degree varies with the size of the circle.

The explanation given on the preceding page will he more clearly under stood by an examination of the annexed diagram. _1.L Mnreh. Geographers have adopted the measure of a degree, because the length of a mile varies in different countries. A German mile, for example, is equal to more than four English miles. The equator encircles the earth from east to west, at equal distances from the poles. The tropics, polar circles, and parallels are small circles extending round the earth, parallel with the equator. There are two tropics and two polar circles; the number of parallels is unlimited. The Tropic of Cancer is 23 J degrees north of the equator; the Tropic of Capricorn 23=. degrees south of it. The Arctic circle is 23$ degrees south of the North pole ; the Antarctic circle 23$ degrees north of the South Pole.

The Meridians are great circles extending round the earth north and south, through the poles; their number is unlimited. 23rd. -.piember. On the 21st of March, one half of both the Northern and Southern Hemispheres is turned towards the sun, and the days and nights are of equal length throughout the entire globe. As the earth continues its revolution round the sun, from March 21st to June 21st, the North Pole is more and more turned towards the sun, and the South Pole is in consequence farther turned from it. The longest day in the Northern Hemisphere, and shortest day in the Southern, is the 21st of June. It is then mid-summer in the Northern Hemisphere, while it is mid-winter in the Southern. As the earth still continues its course, the length of a day in the Northern Hemisphere decreases, and in the Southern it increases, until on the 23d of September the days and nights are again of equal length.

It is then autumn in the Northern Hemisphere, and spring in the Southern. Zones. 5. Zones are divisions of the earth's surface, formed by the tropics and polar circles. They are five in number — two Frigid, two Temperate, and one Torrid. The North Frigid Zone is north of the Arctic Circle ; the As the earth still further continues its course, from the 23d of September to the 21st of December, the South Pole is more turned towards the sun, and in consequence the North Pole is turned from it. The longest day in the Southern Hemisphere, and shortest in the Northern, is the 21st of December. It is then mid-summer south of the equator, and mid-winter north of it. South Frigid, south of the Antarctic Circle ; the North Temperate Zone is between the Arctic Circle and Tropic of Cancer ; the South Temperate between the Tropic of Capricorn and Antarctic Circle ; the Torrid Zone is between the Tropics. 6.

The Latitude and Longitude of a place being known, it is easy to determine its relative position and distance from other places. Latitude is distance from the equator, north or south. Longitude is distance from any given meridian, east or west. From the 21st of December to the 21st of March, the days increase in length in the Northern Hemisphere, and decrease in the Southern, until on March 21st they are again equal. It is then spring in the Northern Hemi sphere, and autumn in the Southern. Places north of the equator are in North Latitude ; those south of it in South Latitude. The distance from the equator to the poles is 90 degrees ; Latitude, therefore, can never exceed 90 degrees. Latitude is measured on great circles (meridians), therefore the length of a degree must be about 69 miles.

If a place is said to be in 10 degrees North Latitude, it is under stood to be 10 degrees north of the equator, or about 690 miles from it ; and a line encircling the earth from east to west, passing through this place, is the 10th parallel of Latitude. The ecliptic is the orbit in which the earth revolves round the sun. It is so called because it is the circle in which eclipses occur. It is the path in which the sun appears to move round the earth. The velocity of the earth, in its revolution round the sun, exceeds 1000 miles a minute. Different nations usually reckon Longitude from the meridians of the capitals of their own countries. Thus, on French maps, Longitude is reckoned from the meridian of Paris. On the maps in this book, Longitude is computed from the meridian of Greenwich, in England.

A line passing round the earth, through Greenwich and the North and South poles, is the meridian of Greenwich. All places east of this line are in East Longitude • all west of it, in West Longitude. A degree of Longitude may be measured on any circle extending east and west. On the equator, its length is the same as a degree of Latitude, or 69 miles ; proceeding from the equator towards the poles, it diminishes with the size of the circles. On the 30th parallel, it is 60 miles ; on the 60th parallel, 34$ miles. Longitude is com puted 180 degrees in each direction. Equator, Tropics, and Polar Circles. Parallels. 4. For purposes of geographical description, imaginary lines are em ployed, which divide the earth into different sections. These are the equator, the meridians, the parallels, and the polar circles.

Note. — As many of the principles in this treatise have reference to the foregoing definitions, it is recommended that they be carefully perused before commencing the chapters which follow. The equator and meridians divide the earth into equal parts, and are Explain the diagram. — What is the ecliptic? — How great is the velooity of the earth in its revolution round the sun ? Why have geographers adopted the measure of a degree?— What is the Equator? — Wha*-,are the Tropics, Polar Circles, and Parallels?— What are the Meridians? I What are Zones? — How many are there?— What is Latitude? — Longitude? For what purpose are imaginary lines employed ? — Name these lines. The matter of which the Earth is composed is collected into a mass of the form of an orange, or an oblate spheroid. Its outside part, or surface, is composed of land and water.

Surrounding the earth, and extending to the height of about 45 miles, is the atmosphere. Physical Geography treats of the natural features and laws of the land, the water, the atmosphere, and of the plants and animals which belong to the globe. These subjects will be examined in this work under the general divisions of: — 1st. Geology, or a description of the land ; 2d. Hydrography, or a description of the water ; 3d. Meteorology, or a description of the atmosphere and its phenomena; 4th. Organic Life, or the arrangement and distribution of vegetable and animal life.

Part I. Geology

Geology is that department of Physical Geography which treats of the natural features of tbe land of the Earth. The subject will be considered under the several divisions of: — 1. General Structure of the Land ; 2. Continents ; 3. Islands ; 4. Mountains and Valleys ; 5. Plateaus, or Table-lands ; 6. Plains ; and 7. Volcanoes and Earthquakes. The science of Creology proper treats of the formation and general structure of the Earth beneath the surface, and of the changes the globe has undergone ; but as a department of Physical Geography, the signification of the term is limited to a description of the more immediate land-surface of the globe, as the form of the land and the diversities of its surface. State the subjects of which Physical Geography treats? — Under what general divisions will these subjects be examined ?

Of what does Geology treat ? — Under what general divisions will the subject be considered ? — Of what does the science of Geology proper treat ? that are seen on the sea-shore, and in the beds of rivers. At first, these fragments are rough, but when subjected to the rolling of waves on the beach, or to the action of running water in rivers, by rubbing and grinding against each other, they become smooth and rounded.

Chapter I General Structure Of The Land

I. The subject of which this chapter treats, strictly speaking, belongs to the science of Geology, and not to Physical Geogra phy ; but before proceeding to the consideration of the form of the land and the diversities of its surface, some knowledge of its general structure will be found useful. VI. After digging through the different earths which lie at the surface, we come to hard or consolidated materials, which are called rocks. These rocks form what is called the " crust of the earth," and, generally speaking, they are of the same materials as the earths we have just described : the only difference being, that in the earths the materials are loose, or unconsolidated ; and in the rocks, hard, or consolidated. II. The various substances which constitute the Earth may be divided into simple and compound.

A simple substance, or ele ment, is one which cannot be separated into other component parts. A compound substance is formed by the combination of two or more simple substances or elements. Popularly, the term "rock" is applied only to the more compact and solid portions of the globe, but geologically it extends to every formation ; to the loose sands, gravels, and clays, as well as to the limestones and granites. Our positive knowledge of the formations constituting the interior of the earth is very limited, the labors of the miner having extended to but com paratively a short distance below the surface of the earth, and scarcely 2000 feet below the level of the sea. The entire number of elements yet discovered is sixty-one, of which only fourteen are found in nature in a pure state, and these occur rarely, and in very limited quantities.

Gold, silver, and copper are elements, generally found combined with other substances, but frequently discovered in a pure, unmixed state. Granite and limestone are compound substances. The greatest depth below the level of the sea yet reached by man is probably the bore of the new salt works, at Minden, Prussia; which, in June, 1844, reached the depth of 1993 feet, or, from the mouth of the mine, 2231 feet. Probabl/ the deepest mine in the world, though not now worked, is that of Kuttenberg, in Bohemia, which has an absolute depth of 3778 feet. It does not, however, extend so far below the level of the sea as that of Minden. The deepest mine in America is the silver-mine of Valenciana, near Guanaxuato, in Mexico, which has a depth of 1887 feet ; yet the bottom of this mine is more than 5000 feet above the level of the sea.

Nearly all the matter of the globe is composed of different combinations of eighteen of these elements ; and no matter pertaining to the earth, no part of the land or water, no particle of air, no plant or animal, has yet been discovered, which, on being submitted to the analysis of the chemist, is not found to be composed of one, or some combination of two or more of the sixty-one elements first mentioned. III. On and immediately below the surface of the land will be found, generally speaking, loose or unconsolidated materials, which are called earths. The first in order, usually occupying the immediate surface, is composed principally of decayed vege table and animal substances, and is called vegetable mould. VII. All rocks may be classified — 1. As Stratified, or Unstratified ; 2. As Fossiliferous, or Non-fossiliferous ; 3.

As Igneous, Metamorphic, or Aqueous. IV. The other earths are composed principally of particles which have been worn off by the atmosphere, the winds, and the rain, from the solid rocks which form the crust of the earth. These are called mineral earths, and bear the names respectively of the minerals which enter most largely into their composition. VIII. Stratified rocks are found in the regular form of beds or layers, varying in depth from the thickness of a sheet of paper to many feet. These beds are sometimes arranged horizontally, but oftener inclined at various angles to the horizon. This class of rocks is estimated to occupy about nine-tenths of the land surface of the earth, and to have an average depth of eight or ten miles. Thus, when earths are composed principally of silex, or flint, they are called silicious earths (sand is an example) ; when of calx, or lime, calcareous earths ; and when of argilla, or clay, argillaceous earths.

If there were only silicious earth there could be no vegetation, for it is too porous to retain the moisture. Sandy deserts are examples of tracts of land composed almost wholly of silicious earth. Calcareous earth is too dry and hot for vegetation, and argillaceous earth is too wet and cold. When these earths, however, are mixed together in due proportions, they correct and improve each other, and form the fertile soil of our gardens and fields. Sand corrects the stiffness of clayey land, and lime adds to its warmth. Without sand, no glass could be made ; nor could houses of brick or stone be built, for sand is a necessary ingredient in mortar. Without clay, we should have no springs ; for beds of clay, or clayey rocks, alone arrest the downward progress of the water which falls in rain, thus forming the reser voirs from which springs flow.

Stratified and Unstratified Rocks. V. The wearing away of solid rocks, by the influences already enumerated, is not confined exclusively to the particles which form mineral earths. Large fragments are frequently broken off, from which are formed the gravel, pebbles, and rounded stones IX. Unstratified rocks are irregular masses, the lowest of all rocks, forming the basis or bed on which the others rest. But while they thus form this basis or bed, they are frequently pressed up through the stratified rocks, constituting in many places the What is a simple substance ? — What is a compound substance ? — What Dame is given to the soil which occupies the immediate surface ? — What are mineral earths ? — Describe silicious earths. — Calcareous earths. — Argillaceous earths. — Could there be any vegeta tion if there were only silicious earth? — Why? — Of what should we be deprived if What difference do you observe between the substances at the surface of the earth and those below it?— What is tho difference between the popular and geological signi fication of the term "rock?"- How far below the surface does our knowledge of the formations extend? — How may all rocks be classified ? — What are stratified rocks?— there were no silicious earth ?

What are unstratified rocks ? GENERAL STRUCTURE OF THE LAND. 9 summits of lofty mountains. They do not probably occupy more than one-tenth part of the earth's surface, but we have reason to suppose they constitute the internal parts of the globe to a great depth. IX. Metamorphic rocks are supposed to have been formed in regular beds or layers, of the sediment of water, but having been deposited near the place where plutonic rocks were generated, their character has been changed by the immense heat, and they have become as highly crystallized as granite itself, without losing their regular form. They are stratified, and non-fossiliferous. VII. Fossiliferous rocks contain, in a petrified state, the re mains of plants and animals, sometimes in small, but often in enormous quantities. The fossiliferous rocks are stratified.

A part of the non-fossiliferous rocks are stratified — a part are unstratified. 1. Gneiss, a very common rock in some parts of the United States, especially in New England, and often so nearly resembling granite, as hardly to be distinguished from it even by a practised eye, is a metamorphic rock. X. Aqueous rocks appear to have been formed by the gradual deposit of sedimentary matter in water, which has become more or less hardened into solid rocks. They are stratified and fossiliferous. 1. Prof. Hitchcock infers that two-thirds of the Burface of the existing continents are composed of fossiliferous rocks, and they are often several thousand feet in thickness. The quantity of microscopic shells discovered by the great Prussian naturalist, M. Ehrenberg, in rocks of this formation, is most wonderful.