Part 3 (1/2)

Again, older than the true carboniferous age, are the Silurian anthracites of Co Cavan, and certain Norwegian coals, whilst in New South Wales we are confronted with an asse strata which extend apparently froe we have considered ht to the title, coal appearing there not merely as an occasional bed, but as a marked characteristic of the formation

The types of animal life which are found in this forh they do not excel in number, there are yet sufficient varieties to show probabilities of the existence of hest forms yet found, show an advance as compared with those from earlier formations, and exhibit areat classes of fishes and reptiles Numerous specimens proper to the extinct order of _labyrinthodontia_ have been arranged into at least a score of genera, these having been drawn froh, Kilkenny, Saarbruck, Bavaria, Pennsylvania, and elsewhere The _Archegosaurus,_ which we have figured, and the _Anthracosaurus,_ are forreat nue The fish of the period belong alanoids and placoids Of the ganoids, the great _hout the whole of the system

Wonderful accumulations of fish remains are found at the base of the system, in the bone-bed of the Bristol coal-field, as well as in a sih Many fishes were armed with powerful conical teeth, but thePort Jackson shark, were possessed of , and in others for cutting

[Illustration: FIG 24--_Archegosaurus minor_ Coal-measures]

[Illustration: FIG 25--_Psa palate of a fish]

[Illustration: FIG 26--_Orthoceras_ Mountain limestone]

In the mountain limestone we see, of course, the predoreater proportion of the mass

There are occasional plant re drifted for some distance from the shore But next to the _encrinites_, the corals are the most important and persistent Corals ofpolished marble-like sections, are in abundance _Polyzoa_ are well represented, of which the lace-coral (_fenestella_) and screw-coral (_archimedopora_) are instances

_Cephalopoda_ are represented by the _orthoceras_, sooniatites_, the forerunner of the familiar _ammonite_

Many species of brachiopods and lahout all geological time, is abundant in the coal-shales, but not in the limestones _Aviculopecten_ is there abundant also In the mountain limestone the last of the trilobites (_Phillipsia_) is found

[Illustration: FIG 27--_Fenestella retipora_ Mountain limestone]

[Illustration: FIG 28--_Goniatites_ Mountain limestone]

We have evidence of the existence in the forests of a variety of _centipede_, speci been found in the erect stuh the fossil is an extremely rare one The same may be said of the only two species of land-snail which have been found connected with the coal forests, viz, _pupa vetusta_ and _zonites priscus_, both discovered in the cliffs of Nova Scotia These are sufficient to demonstrate that the fauna of the period had already reached a high stage of development In the estuaries of the day, masses of a species of freshwater mussel (_anthracosia_) were in existence, and these have left their remains in the shape of extensive beds of shells They are familiar to the miner as _o period, as are the aggregations of mussels on every coast at the present day

[Illustration: FIG 29--_Aviculopecten papyraceus_ Coal-shale]

CHAPTER III

VARIOUS FORMS OF COAL AND CARBON

In considering the various forms and combinations into which coal enters, it is necessary that we should obtain a clear conception of what the substance called ”carbon” is, and its nature and properties generally, since this it is which fore of all kinds of coal, and which indeed forms the actual basis of it In the shape of coke, of course, we have a fairly pure for produced, as we shall see presently, by the driving off of the volatile or vaporous constituents of coal, we are able to perceive by the residue how great a proportion of coal consists of carbon In fact, the two have al in the popular reat masses of strata, in which are contained our principal and most valuable seams of coal, are termed ”carboniferous,” from the Latin _carbo_, coal, and _fero_, I bear, tends to perpetuate the existence of the idea

There is always a certain, though slight, quantity of carbon in the air, and this reh it may be in proportion to the quantity of pure air in which it is found, it is yet sufficient to provide the carbon which is necessary to the growth of vegetable life Just as some of the animals known popularly as the _zoophytes_, which are attached during life to rocks beneath the sea, are fed bytheir food to the the day through their under-surfaces, are provided with it byaround the taken in beneath, the heat and light are being received froestion

It is assuin of the various seams and beds of coaly combinations which exist in the earth's crust, we o so far back in the world's history as the period when our incandescent orb had only just severed connection with a gradually-di sun, we should probably find the carbon there, but locked up in the bonds of che therewith in a gaseous condition But, as the solidifying process went on, and as the vegetable world afterwards made its appearance, the carbon beca absorbed by trees and plants, finally becaetable world, and is now presented to us in the fores through which the pasty etation passed, in consequence of the fact that we have this es of carbonisation, in the strata beneath our feet These we propose to deal with individually, in as unscientific and untechnical a etable matter commences to decay, it soon loses its colour There is no more noticeable proof of this, than that when vitality is withdrawn from the leaves of autumn, they at once commence to assume a rusty or an ashen colour Let the leaves but fall to the ground, and be exposed to the early frosts of October, the dae of colour is at once apparent Trodden under foot, they soon assume a dirty blackish hue, and even when removed they leave a carbonaceous trace of themselves behind them, where they had rested Another proof of the rapid acquisition of their coaly hue is noticeable in the spring of the year When the trees have burst forth and the buds are rapidly opening, the cases in which the buds of such trees as the horse-chestnut have been enclosed will be found cast off, and strewing the path beneath Moistened by the rains and the daht-mists, and trodden under foot, these cases assume a jet black hue, and are to all appearance like coal in the very first stages of formation

But of course coal is not s of all sizes, and someti in their upright position, and piercing the strata which have been formed above them At other ti been thron previously to the formation of the shale or sandstone, which now rests upon them They are often petrified into solid sandstone the a rind of coal where forh the trunk of a tree looks so very different to the leaves which it bears upon its branches, it is only naturally to be supposed that, as they are both built up after the same manner from the juices of the earth and the nourishment in the atmosphere, they would have a similar chemical composition One very palpable proof of the carbonaceous character of tree-trunks suggests itself Take in your hand a few dead twigs or sticks fro since dropped; pull away the dead parts of the ivy which has been creeping over the sunarled old monster of the forest in your arms, and you will quickly find your hand covered with a black se which the living plant has ress towards its condition as dead coal But an easy, though rough, chemical proof of the constituents of wood, can bea few pieces of wood in ait over a flame In a short time a certain quantity of steaaseous constituents of wood, and finally nothing will be left but a few pieces of black brittle charcoal The process is of course the sarate, only that hereto its being intimately exposed to the action of the flames If we adopt the same experiment with some pieces of coal, the action is siiven off is not so great, coal containing a greater proportion of carbon than wood, owing to the fact that, during its long burial in the bowels of the earth, it has been acted upon in such a way as to lose a great part of its volatile constituents

Fro on around us, it is easily possible to satisfy ourselves that vegetation will in the long run undergo such changes as will result in the formation of coal

There are certain parts in most countries, and particularly in Ireland, where e in s Ireland is _par excellence_ the land of bogs, so said to be covered by them, and they yield an als near the Shannon is between two and three th, whilst its depth varies fros have in no way ceased to be forrows afresh every year; and rushes, horse-tails, and reeds of all descriptions grow and thrive each year upon the ruins of their ancestors The foretation would only be possible where the physical conditions of the country allowed of an abundant rainfall, and depressions in the surface of the land to retain theoperations have taken place, peat-bogs have often been formed, and many of those in existence in Europe undoubtedly owe their formation to that destruction of forests which went on under the sway of the Roe would soon be obstructed by fallen trees, and the forrowth of marsh-plants and their successive annual decay, a peaty row in thickness without let or hindrance