after fatigue, and it is then that cold is most apt to be prejudicial. We have an easy criterion as to the propriety of cold bathing, in the feelings of the person afterwards,-if the bath is followed by a glow of warmth, &c., it will do good, but if the bather feels cold and chilly, &c., it should be discontinued as being useless and hazardous. In the former case cold bathing becomes a tonic, stimulating and invigorating both to mind and body. The time for bathing requires to be modified according to the health of the bather; if the powers are too languid to admit of the necessary reaction, much benefit is derived from mid-day bathing. Apologising for thus writing,-but the interest which I take in your valuable paper, and also on the subject of bathing, which I consider a necessary of life, will I trust be a sufficient excuseI am, &c., MEDICUS. ANSWERS TO CORRESPONDENTS. K. PINETAC: at is pronounced nearly like the English letter i in fine, though a little broader, like the English word age. It is a compound of the sounds ah and ee blended together. av is pronounced like the English a in water, e like the letter i in wine, or like oy in boy, v like wi in wise, and ne nearly like the word you, but with more stress upon the ce sound. There is a French expression, il y avait, for there was. Aos: Your plan of study is excellent, and appears from your letter to answer well. Thanks for the hint you throw out. It shall not be lost sight of. JAMES ROBINSON (Burnopfield): We have already stated, in answer to other correspondents, that the capital Greek upsilon, though like the English Y in form, has no resemblance to it in sound. In writing Greek, it is only necessary to imitate the printed characters as nearly as possible, giving them a slope for the sake of convenience. Mavlavo The Greek upsilon, when a capital letter, takes pretty nearly the form, but not the pronunciation, of the English Y. P has the same sound whether with a straight or a curly tail. BLANDUS: EUTUXia means good fortune, prosperity; and ought to have been given in the vocabulary. iNews is a misprint for New We are obliged to discontinue the etymological vocabularies for want of room. Any good Greek lexicon will supply nearly the same information. A CRIPPLE will find the pronunciation of the German word man, and the others he mentions, fully explained in the interlinear pronunciation of the lesson and the preceding directions. He has only to notice the figure placed over the a, and look in the directions to see what sound it indicates. He will also find it stated that an apostrophe after a vowel has the effect of lengthening it. The accent at the end of a syllable merely denotes that the stress is to be laid upon that syllable. A POWER-LOOM WEAVER'S parcel is forwarded to the Royal Society.A GOVERNESS (Camden-town): The P. E. is published in New York.-W. LEWIS (Manchester): Chemistry in full vigour in vol. iv.-MUSIC is postponed for the present.-T. H. (Cork): The best way to learn to express your ideas is to join a Debating Society.-FABER LIGNARIUS (Turriff): Mr. Cassell's Classical Library, together with Dr. Beard's Latin Dictionary, will contain the books best adapted for making progress in the Latin tongue.--SOCIUS: In learning Bookkeeping there is no need to go to the expense of separate books; separate portions of one book may be carefully and neatly adapted to the purpose, by the student himself.-J. S. CHAPMAN (Manchester): The Leasons in Latin in the P. E. are the best we know.-J. T. BODNIS (Greenwich) is wrong as to the FACT of the letters inserted in the P. E., but right as to the IMPRESSION; a change will be made for the better.-A WEAVER (Clackmannan): ONES in the plural form, referring to a plural noun in a preceding sentence, is an adjective pronoun; see p. 211, vol. iii. P. E.-OPTICUS (London): The subject of Optics is announced for next volume. MRS. SLIPSLOP (Perthshire) must put on her spectacles, and she will then find NAHOR in a line with ABRAHAM, p. 3, vol. I. P. E., Genesis xi. 26. It is not a mistake with Luke, for Moses has been misrepresented; see the Septuagint.-S. J. R. (London): All right; the maps will be continued.-J. E. D. (Edinburgh): It will be done.-W. ROBERTS: The memory is improved by exercising it. Say Chobham like Chatham, not like Kobham. MARK MATHETES (Farnworth) and Q. E. D.: See vol. ii. P. E., p. 215, col. 2, line 34, for the Classical Subjects; the rest are never announced, the student being required to prepare himself to answer any questions that may be proposed on the other subjects; sec page 137, vol. ii. P. E.-T. JENKINS (Cardiff): See Literary Notices.-BOOKKEEPING STUDENT will have his difficulties solved in the course of the lessons.-GEORGE THE YOUNGER (Pimlico): Buy the large edition of Webster.-A. Z.: Foyer de désordres, means a focus or centre of disorders.-A. SCOTT (Liverpool): Thanks for his note on the comet. CARRICK (Ayr): We cannot tell ourselves.-W. HYMERS (Barnard Castle) The Boy's Own Book, Tegg, London.-R. V. GIBSON (Glasgow): If going into the water does you harm, the best precaution is to give it up. W. F. STONEHENGE (Whitehaven) should get the "Annales de Chimie." ARMACHANUS: Very well; go on and prosper.-S. T. M. (Brighton): French.-D. T. L. (Carmarthen): You are right. (Belherbet): 1. We think not. 2. We can't tell. 3. Yes. 4. Read Saxonly written books, such as "Gulliver's Travels," " Pilgrim's Progress," and Rowland Hill's Village Dialogues."-ANGLAIS (Preston): Yes.HEADBAND (Darlington): English.-os (London): Write to Henry Moore, Esq., Secretary of the University of London.-ECOLIER FRANÇAIS: See our Literary Notices.-J. WORLEY (Reading) recommends to French students the French New Testament, published by the Bible Society at 6d., in roan gilt, good type; and a French Weekly Newspaper, called Chronique de Jersey, published at 14d. The Key to the French Lessons is published separately; see our Literary Notices.-T. C. (Barking): Your suggestions are good.-VIOLINO (Bridport): Received, and under consideration.-J. CORBY (Woodford): Yes, if in good condition, by paying the difference. A PUPIL TEACHER'S lines are very good, and do credit to his head and heart; but we cannot insert them in the P. E.-E. J. (Shelton) and A DROGHEDA SUBSCRIBER will, by writing to Mr. Dunn, Secretary of the Training-School of the British and Foreign School Society, at Boroughroad, London, obtain at once all the information he requires.-H. DUNKLEY (Plumstead): The Lizard Point, Cornwall, is the most southerly point of England.-ZETA: Yes; r is not pronounced at the end of French, except under certain conditions; see the lessons again. Bills of Exchange will be more fully explained.-W. J.: See Lessons in Geography, pp. 30, 61, 144, and 162, vol. iii.-E. H. COOKE (Kidderminster): Under consideration. T. G. B. (Ilchester): We fear that we cannot advise him; he should write to the Secretary of the Apothecaries' Company for information.-A. M. GARDNER (Peasenhall): The French Lessons, reprinted from the P. E., parts I. and II., will completely answer your purpose.-THOMAS CHOPE (Hartland): We fear that his suggestion, though good, is not practicable.CHARLES W. (Islington): Read the papers on the University of London in vol. iii.-PHILOANTE (Bowling): If he has a special call, let him go on; if not, we would advise him to pause. SEVERAL WHO WISH TO BE ARTISTS: We are desirous supply the wants of all our subscribers; but they will see from our advertisements and notices that their wishes cannot consistently with these be immediately gratified; the subject, however, will not be overlooked. AN ORPHAN (London): Apply to the London Orphan Asylum, Clapton.R. J. L. (Littleport) should take C. W. H.'s advice, and write to the Secretary of the Committee of the Council on Education, Downing-street, London.YORKSHIRE PLOUGHBOY can get No. 42, which is the one omitted, to buy in Sheffield; but he should return his copy of Part X. to the bookseller who supplied him with it as incomplete, and get a complete one instead of it.N. B. (Portsea): Not directly, but by the introduction of two or three Lemmas.-WRITING CLERK (Tralee): Under consideration.-R.,B. N. Ross (Camberwell): Right; yes.-PHILO: Many thanks; you are perfectly right in everything; the mistakes have arisen from careless printing; for instance, the multiplier 128 should be 126, and the multiplier 196 should be 96; try these numbers, and you will find that the answers correspond.-AN UNDERGRADUATE OF THE UNIVERSITY OF LONDON: Thanks for his note.C. C. (Halifax): D'Aubuisson, Traite Hydraulique, 98.-A BRICKLAYER (Manchester): Nicholson's works: Principles of Architecture; Architectural Dictionary; Student's Instructor in the Five Orders; Practical Builder, &c. VIVA L'ITALIA: Hutton's Course of Mathematics improved by Davies, or Christie's Course for the Cadets at Woolwich.-W. A. (Aberdeen) should study Writing, Arithmetic, and Bookkeeping, in order to fit himself for a clerkship.-A SUBSCRIBER (Bradford) and his friends had better not meet on Sunday morning for the studies they propose; any other morning will do better. God and his word, religion and a future state, are surely WORTH one day's consideration out of the seven.-A LABOURER IN THE VINEYARD should not trouble himself with what might have happened had not things been as they are. Sin has come into the world, and God has appointed an easy way of escape from it; this is enough. Greek and Latin may assist each other, but study Latin first.-E. BLURTON (Stourbridge): We regret that we cannot give the required information. LITERARY NOTICES. FRENCH. Now ready, price 48. in stiff Wrapper, or 5s. strongly bound in eloth, the First Part complete, consisting of the French and English, of CASSELL'S FRENCH DICTIONARY: the entire work will be completed in Twenty-six Threepenny Numbers, and will form one handsome Volume of eight hundred and thirty-two pages. Price 8s. 6d. bound in cloth, or the Two Divisions may be had separate. A COMPLETE MANUAL OF THE FRENCH LANGUAGE, by Professor De Lolme, just published, price 3s. neatly bound. This forms one of the most simple, practical, and complete Guides to a thorough knowledge of the French Language which has hitherto been published. The plan upon which it is conducted is admirally calculated to accomplish the proposed object. In the first place, the Grammatical Principles of the Language are clearly laid down, and, secondly, these Principles are copiously illustrated by suitable Exercises of English to be turned into French. CASSELL'S LESSONS IN FRENCH, in a neat volume, price 2s. in stiff covers, or 23. 6d. neatly bound in cloth. A KEY TO CASSELL'S LESSONS IN FRENCH, Containing Translations of all the Exercises, with numerous references to the Grammatical Rules, price 18. paper covers, or ls. 6d. cloth. GERMAN. CASSELL'S GERMAN DICTIONARY is now issuing in Numbers, at 3d. eacL; Monthly Parts, 1s. each. CASSELL'S LESSONS IN GERMAN, price 28. in stiff covers, or 2s. 6d: cloth. LATIN. CASSELL'S LESSONS IN LATIN, price 2s. in stiff covers, or 2s. 6d. cloth. CASSELL'S KEY TO THE LATIN EXERCISES, now ready, price ls. GREEK. The Third Volume of CASSELL'S CLASSICAL LIBRARY will contain Acts of the Apostles in the original Greek, according to the text of Augus Hahn; with grammatical, historical, and expository Notes; followed by a Lexicon, explaining the meaning of every word-the whole carefully revised and corrected. This work is well adapted for the use of Schools, Colleges, and Theological Seminaries, and will supply our Greek studer to with excellent materials for practice in translation. LESSONS IN GEOLOGY.-No. XLIII. BY THOS. W. JENKYN, D.D., F.R.G.S., F.G.S., &c. CHAPTER IV. your attention. Ask yourself, what comes, then, of all the vegetable masses, and of all the animal matter, that rot in forests and woodlands, every year, over the extent of the globe? The answer of science is, that a portion of this vegetable and animal mass is volatilized into the air, and that the rest is carried away by ON THE INFLUENCE OF ORGANIC AGENTS UPON THE running water, in which it either sinks into the earth, or flows EARTH'S CRUST. SECTION I. ON BOTANIC AGENTS. IN the course of our lessons, the first three chapters have taught you the operations of fire, of water, and of the atmosphere, upon the earth's crust. This fourth chapter, which is also the last, is intended to illustrate the effects of vitality, in the forms of vegetation and animal life, in the changes which have been produced on the surface of the earth. The business of this lesson is with the agency of plants, and with the effects which their growth and decay produce on the earth's crust. In this inquiry, we are not to limit our observation to the surface of the dry land, but to extend our survey to the towards the sea. By this process, the same ingredients enter again and again into the composition of a variety and a succession of organic beings in vegetable and animal life. It is well known that thousands of carcasses of terrestrial animals, and immense forests of drift timber, are every century floated into the sea, where both are imbedded in subaqueous deposits. Nevertheless, the vegetable mould on the earth's surface is kept in equilibrium. The principal elements tha chemists have found in plants are the three gases, hydrogen, carbon, and oxygen. Vegetables and animals derive them from water and from the atmosphere. But whence do water and the atmosphere derive them, in order to supply plants with them? They derive them from the putrefaction of vegetable substances and animal matter, from the decay of rocks as the result of weathering and abrasion, and also from the agency of mineral larger portions of the globe which are under water, and which springs, which bring constant supplies from the interior of the are extensively covered by aquatic plants. earth. I. PLANTS AND TREES. The quantity of plants, shrubs, bushes, and timber that grows on most lands, and especially in tropical forests, in the course of one century, must be enormous. Were these masses of vegetation deposited in a sea, they would pile up into a hill of considerable size; but though timber grows and decays for thousands of years, yet no such wood mountains are found to pile on the sites of forests, even within the tropics. It might have been expected that the masses of solid matter which are every day derived from the decay of terrestrial plants and animals would contribute to augment the amount of soil on the earth's surface. It must, therefore, awaken your surprise, when you learn that the vegetable mould which clothes the globe does not grow in thickness. This statement ought to awaken not only your surprise, but VOL. IV. In our chapter on Aqueous Agency, we considered the tendency of running water to scoop out gullies in the soil, and to carry the detritus towards the sea. This operation of streams and rivulets is counteracted by the power of vegetation. Vegetation counteracts the operations of running water in two ways. 1. It is in some degree antagonistic to the transporting power of rivers, and may be considered as reconstructive. The agency of vegetable life, by absorbing various gases from the atmosphere, causes a large mass of solid matter to accumulate on the surface of the land. Such a mass must, alone, constitute a great counterpoise to all the earthy detritus transported by the aqueous agents of decay. 2. The influence of vegetation is conservative, and tending to retard the waste of land. You constantly witness in a field, where a rivulet flows from a well, that the green sward through which the water runs prevents the soil from being carried away. Upon sloping ground, also, it is seen that a covering of herbage protects the mould from being transported by rains, or being washed away by running water. As a further illustration of the conservative influence of vegetable life, it may be remarked that it also prevents loose sand from being blown away, by the wind. In this case, the roots bind the separate particles of the soil together into a firm mass, and the leaves intercept the rain-water so as to make it dry up gradually, instead of rushing in a mass, and with velocity, upon the soil below. That vegetation tends to preserve the mould that covers the earth, is evident from the observations which antiquarians and travellers have made on the increased removal of land that always takes place, after the clearing away of the woods that covered them. This is especially the case on the removal of woods that clothed the steep declivities of a mountain. In every such instance, the quantity of sand and soil washed down into the nearest river has increased enormously. The reason is, that as soon as the bushes and the trees are removed, the rain-water rushes with unbroken force upon the ground, flows off more rapidly, and sweeps away the soil and gravel. II. PEAT AND MOSS. Peat has not only a conservative influence to protect the underlying soil, but it has a reconstructive power, by which it augments the mass of vegetation on the earth. Peat is not the product of any one species of plant, but consists of any herb or moss that is capable of growing in moist and cold situations, and that has also the property of throwing up new shoots at its upper part, while its lower portions are decaying. Peat, as the remains of dead plants, is a product intermediate between vegetable matter and lignite. It is first a plant, and it is turned into a lignite by a gradual and prolonged action of the water that covers it. Beds of peat are seldom, perhaps never, found within the tropics. Even in Spain and in the south of France they very rarely occur. In proportion as you advance from the tropics towards the north, beds of peat become more frequent, and its substance becomes more inflammable. This is also true in latitudes between the tropics and the south pole. The depth of peat soil and the number of peat bogs depend on the physical condition of the district. On the declivities of mountains, the depth of a peat bed rarely exceeds four feet. But in low and hollow grounds, into which peaty matter is constantly carried down by running water, the depth of a peat bog becomes forty feet and more. The extent of some of these bogs in the north of Europe is enormous. On the Shannon in Ireland there is a bog, or moss, that is fifty miles long and two or three miles wide. In France, between the city of Nantes and the sea, there is, about the mouth of the Loire, a bog that is one hundred and fifty miles in circumference. Many of the peat mosses are known to occupy the sites of ancient forests of pines and oaks, some of which have disappeared even thin periods of history. Such bogs are formed by the fall of trees, and by the stagnation of water. Had these trees fallen in warm climates, the woody matter would be removed either by insects or by putrefaction; but, in Europe, having fallen in low or moist situations, they are preserved by water. The agency of peat mosses is not always conservative of the surface soil. In some districts where the climate is cold and moist, bgs occasionally grow to be agents of destruction. A peat bog acts like a sponge. It absorbs water in large quantities, and swells to the height of many yards above the surrounding soil. The capillary action of the turf fibres enables it to retain the fluid for some length of time, but not for ever. It frequently bursts, and then a violent inundation follows, and the muddy torrent, as instanced more than once in Ireland, scoops out ravines in the slopes of hills, bears away blocks and timber, and scatters them over the plains, or deposits them in the nearest lake or sea. III. SEA-WEEDS AND FUCOIDS. The "unfathomed caves of ocean" bear not only "full many a gem," but also full many a plant. Beneath the surface of the latitudes and longitudes, wherever a ray of light can penetrate mighty sea, a magnificent vegetable world extends through all This world of vegetation is more wide-spread than the verdant covering of the dry land. Marine plants are exceedingly numerous, but they are divided into two great classes, or groups. First, the jointed kind, which consist of simple tubes-some of them even microscopic. Secondly, embrace the species called CONFERVE, very small plants which the disjointed group, consisting of such sea-weeds as dulse, laver, wrack, and all the gigantic species which either luxuriate in submarine forests, or float like green meadows or boundless prairies, in the ocean. The sea-weeds that grow in comparatively small depths near the shore, are both the most limited in number, and the least extensive in distribution. The fuci that grow at the greatest depth of the ocean are both the greater in number, and the wider in extent of range. This circumstance suggests a correspondence of latitude, in the amount of vegetation, between height on land and depth in the ocean. On land, the lower the height or the latitude is, the more luxuriant is the growth of trees. And, in the ocean, the greater the depth, the more abundant is the growth of marine plants. The seeds of marine plants are produced in their native element; they can therefore remain immersed in it for an indefinite period without any injury to their power of fructification. This fact enables us to account easily for their wide-spread diffusion in every zone where uncongenial climates or contrary currents do not interfere with their distribution. Sea-weeds have well-contrived facilities for sowing themselves over the body of the ocean. First, they generally have hollow pod-like receptacles in which their seeds are lodged. These pods give them buoyancy for floating. Other seed vessels have this power of floating in consequence of filaments which are attached to them. Secondly, a very large number of species are enveloped with mucous or adhesive matter, like that which surrounds the eggs of fish. This mucus not only prevents them from injury, but serves to attach them to rocks or to floating bodies. These sea-weeds fix their roots to anything and everything, to stones, to wood, or to other sea-weeds. This circumstance shows that they must derive all their nutriment from the water of the sea, and from the air contained in the water. Thirdly, naturalists have shown that these thalassophytes, or seaplants, are what is technically called proliferous; that is, they are so full of power to propagate their kind, that the smallest fragment of a branch of them can develop itself into a perfect plant. Some of the gigantic sea-weeds grow up to the surface of the ocean, and appear like green meadows of immeasurable extent. These occur on each side of the equator in the Atlantic, Pacific, and Indian Oceans. The most extensive bank in the Atlantic is a little to the west of the meridian of Fayal, one of the Azores, between 35° and 36° of north latitude. When COLUMBUS came to it, he compared it to a vast inundated field of grass, and he states that the weeds were so thick as to retard the progress of the vessel. This part of the Atlantic is called Mar de Sargasso, or the Gulph-weed sea. It includes two banks of Fucus connected by a transverse band of Fucus natans, or floating sea-weed, and occupies a space larger than the whole surface of France. From the time of Columbus till now, that is, for three centuries, the situation of this great accumulation of sea-weed, whether resulting from the local character of the sea bottom, or from the direction of the gulph stream, has remained precisely the same. Of this sea-weed, called Sargassum bacciferum, two new species have been lately discovered by navigators in the southern seas. One, called Macrocystis pyrifera, is of gigantic size and covers a vast extent. The other is called Laminaria radiata, and forms vast meadows off the Cape of Good Hope, and in the Atlantic Ocean. Specimens of both of these weeds have been taken up, ported to be 1,000 and even 1,500 feet long. They are found in the open sea, hundreds of miles from land. Around Kerguelen Island, the two weeds form a great part of a band so thick that a boat can scarcely be pulled through them. Near California there are fields of them so dense and so impenetrable, as to have saved many vessels from shipwreck when driven by heavy swells towards that coast. If such a moss bursts near an arm of the sea, that part of the sea becomes the receptacle of drift peat. On many coasts in the Baltic Sea and the German Ocean, we constantly meet with sec-measuring 300 and 400 feet long. Some of them have been retions in which alternations of clay and sand with differ Cayers of peat are of frequent occurrence. At the bottom of many of the mosses in Holland, the remains of ships, of oars, &c., have been found; and in the valley of the Somme in France, there was found, in the lowest tier of the bog, a boat loaded with bricks. These two facts prove that, at one period and that very late, these mosses were navigable lakes or arms of the sea. sixty or seventy feet high. The third kind of vegetation is that of horse-tails, or the Equisetaceae, distinguished in the engraving by having jointed and furrowed trunks and branches. With us, the largest plants of this kind attain but a very few feet in height, but in the coal measures they are found with arborescent or tree-like trunks, ten feet high and five or six inches in diameter. These three families of plants form about three-fourths of the vegetation of the coal period. The remainder consists of cone-bearing trees, and of vast quantities of a kind, apparently, like the cactus. Of the entire number of species discovered in the carboniferous rocks, two-thirds belong to a vegetation like the Fern. These immense fields of marine plants must, like land vegeta- | present themselves as arborescent plants with branched trunks, tion, suffer decay-and their decayed remains, as they subside and sink to the sea bottom, must, in the course of centuries, produce considerable beds of vegetable matter. In Holland, a submarine peat was dug up that was formed by the decay of sea-weeds. You have now been introduced to the agency which vegetation exerts in the formation and in the conservation of the soil that forms the green surface of the earth. The principles and the facts which have been thus briefly intimated, you must now apply not only to the superficial covering of the globe, but also to the structure of the crust of the earth, as formed at different geological periods. As you walk or ride over plains or mountains, an entire vegetable world may be lying in ruins under your feet. Geology has demonstrated that, at different periods or epochs in our world's history, vegetation has played a distinguished part, both in rank, luxuriance, and in extensive distribution. Different geologists have their respective systems for dividing the epochs of ancient vegetation. M. ADOLPHE BRONGNIART divides them into four. The first begins with the earliest traces of vegetable life, and terminates with the coal formation. The second concludes with the .triassic. The third comprises the oolite and chalk. The fourth ends with the tertiary period. COUNT STERN In these coal forests, there were no plants bearing flowers, no trees bearing fleshy, juicy fruits, no kind of grass, and no birds. It used to be thought that it was a forest without a single living thing to move in it; but lately the skeleton of a reptile has been discovered in rocks much older than the coal series. One remarkable characteristic of the vegetation of the coal period is the uniformity or monotony of its plants. In our age we find that different countries, in different climates, produce different plants; but, in the carboniferous era, the same plants grew in Germany, Belgium, France, England, North America, and BERG, by uniting the second and third of these epochs, reduces the periods of ancient vegetation to three. His divisions are1. the vegetation of islands; 2. that of sea coasts; and 3. that of continents. The earliest vegetation of the globe, and that which terminated in the carboniferous period, was simple but very magnificent. An ideal landscape of the earth during the carboniferous age is represented in fig. 97. Look at the forest represented in this engraving. The plants and trees are different from all vegetable products that you now see. There is nothing like it in. the temperate zones, nor within the tropics. The vegetation consists of ferns but ferns not herbaceous as in our cold climate, but ferns which grow in the form of trees of considerable height, with palm-like, unbranched trunks. The next kind of vegetation is that of club mosses, or the Lycopodiaceae. With us, these club mosses are dwarf plants, small in size and few in number, but in the coal formations they Australia. This fact proves a remarkable uniformity of climat at that period. When North America was discovered, there were found in it only two wild plants that agreed with the vegetation of Europe. But of 53 kinds of plants found in the North American coal beds, 35 are common in the European coal fields. However luxuriant this vegetation of the carboniferous era was, all the species of its plants, and almost all their genera, passed away before the second period of vegetation set in. A few ferns entered into the second era, but all the palms and calamites disappeared. The first flora, therefore, which was universally diffused over all the dry land of the ancient globe, was especially distinguished from the second, which is regarded as the flora of the triassic, the oolite, and the wealden, group of plants. This second family passed imperceptibly into the third, which comprises the plants of the tertiary formations. In the trias the characters of vegetation are altered by the complete disappearance of the cactus tribe, by a diminution of the proportion of ferns, and ty the appearance of a few new species. Of this triassic vegetation very little is known, and what is known is generally classed with that of the tertiary. A few coniferous plants grew in the eras of the lias and the oolites, but they were not of the species that existed at the coal period. Immediately after the chalk period, a decided change took place in the features of the vegetation. The fern tribe still continued to diminish, but the cone-bearing wood increased in quantity. With the palms and other tropical trees, there grew willows, elms, poplars, chesnuts, and other similar trees, which increased in number and variety, till the flora of the more recent tertiary period had little to distinguish it from the vegetation of the present day. The contrast between it and the carboniferous flora, and the similarity between it and the present vegetation, are presented in fig. 98. In this landscape the woodland does not appear so strange and foreign to you as the coal forest did. This is very little different from the forest scenes of the present day. Among the trees we find the palm tree lifting up its feathered top, and a beautiful brushwood grows in all directions. The landscape is now varied; its outline is more uneven; and its aspect is more sunny. The forest is enlivened with quadrupeds that live on plants. Among these woods grew that remarkable pine tree, called Pinus succinifer, which produced the fossil resin called amber. This amber LESSONS IN is of immense interest to the geologist, as it often encloses specimens of insects, spiders, flies, small crustaceans, leaves of trees, &c., which are monuments of the flora and the fauna of that period. Upwards of 800 species of insects have been preserved in fossil amber. Amber is chiefly obtained from the brown coals of northern Germany, or the submarine beds of lignite found in Russia, and along the coast of the Baltic. These forests of amber pines grew in the south-eastern part of what is now the bed of the Baltic. As the amber found in the lignite and brown coal contains several fragments of vegetable matter, it has been ascertained that this tertiary forest contained four other species of pines, and several kinds of cypress, yew, juniper, oak, poplar, and beech. The brief hints that have been given to you in this lesson upon submarine vegetation, and upon the formation of peat and drift wood, will prepare you for understanding the fucoid fossils which are found in ancient rocks, and for the vegetable remains found in the coal series. You have only to imagine layers of peat and deposits of drift wood to become bituminised, and the different seams of sand and mud between them to become consolidated by pressure from above and heat from below, to be able to account for their carbonisation, and for the structure of a genuine coal formation. GERMAN.-No. LXIX. Irregular Verbs, continued from p. 19. |