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forging, and converting iron: almost, if not all, the processes through which iron passed in the arts were then effected by the use of this vegetable coal, and the ancient forests which abounded in this and in almost every country where iron ores were found, afforded a plenteous supply of refuse timber for all these purposes, and many others in the arts. But the ancient forests are cut down and consumed; and the difficulty of procuring this species of fuel became, within the last twenty years, so great in these islands, that many of the owners of forges were compelled to have recourse to processes which admitted of the use of mineral coal in their refineries; wherein they convert pig or cast iron into bar, plate, or hoop iron. And such is the reaction upon charcoal, that, since these methods have been almost universally adopted in the mineral districts, instead of its being difficult to procure a sufficient supply of charcoal for the uses of the arts, the refuse timber or cord-wood which every wood affords, whenever a fall of timber is made therein, is become a drug in the market. But such are the immense quantities of iron which now pass through the refineries, that if the ancient mode were re-adopted, in a single year charcoal could not be found to supply a tithe of the demand, if even, instead of charring the refuse only, the whole of the falls of timber throughout the mineral districts, however valuable for other purposes, were not charred also; and even these would not supply any thing like a permanent demand for charcoal.

There are foreign nations, even in Europe, where the forest timber amply suffices for all the purposes in the manufactories of iron, to which we apply mineralcoal; and some of these, for instance Sweden, Norway, and other districts bordering upon the Baltic sea, produce annually great quantities of iron, as well as other metals. How long, even these countries may derive supplies of vegetable coal from their forests sufficient for the manufacture of iron therein, especially if their manufactories were to increase in any thing like the rapid progression of those in Great Britain, is a question difficult to answer. But whenever a period arrives when the manufacture of iron outruns the supply of vegetable fuel, then, like Britain, these countries must immediately resort to the use of mineral coal, or otherwise they must, of necessity, contract their manufactories.

In addition to the immense consumption of coal in the smelting furnaces and

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refineries for iron, the modern art of war has made heavy demands upon that article. In order to produce cannon, bombs, muskets, pistols, bayonets, swords, cannon balls, grape shot, and all the munitions of modern warfare, what an enormous demand must be made upon the article of mineral coal! Chain-cables for ships and other vessels, as well as chain rigging, both fixed and running, are modern additions to the consumption of coals and iron. And the increase of ships has increased the demand for anchors, bolts, braces, strops for blocks, stanchions and irons therein and thereon, exceedingly. Iron railways for carriages, iron corses and waggons, iron cranes and chains thereto, and iron axles, bushes, and tira for wheels, have also increased with the increase of carriages; and anvils, vices, hammers, and other iron tools, with the increase of workmen. Machinery has grown up amidst the manufactories of these islands into a vast colossus-huge in the extreme; and, notwithstanding its enormous growth during the last thirty years, from the vigour of its increase from year to year, it yet seems only a boy, compared with the manhood it is aspiring after. Those immense limbs of this giant, which are in use for forging, slitting, rolling, and drawing iron, for throwing silk, for spinning cotton, flax, and wool, for weaving, shearing, and dressing calicoes and cloth, for grinding corn, and dressing flour, yea, for thrashing corn from the ear and winnowing away the chaff, and for almost every purpose of life, all of which are adding in size and multiplying in number daily, astonish the thinking mind while it contemplates them, and leads it to exclaim, "Where will these additions end?"

Last, but by no means least, is the steam engine: a machine which, like a mushroom, or rather a fungus, has grown up in a night, to a size wonderful to behold. Had we nothing else, the alarming consumption of coal in the use of these machines, which has grown up within the last half century, and is growing to the present hour with a vigour which threatens to ingulf the whole coal strata of these islands; had we nothing else, I repeat, steam engines alone are sufficient to deal alarm, as to the future comforts of mankind, by their prodigal consumption of this necessary of life, coal, therein, throughout Great Britain: for Great Britain is a land wherein domestic comfort cannot be secured without the use of mineral coal, during three-fourths of the year, in every habitation of man. For blowing furnaces

and refineries, for working forge hammers, rollers and slitters of iron, for drawing wire, for grinding, polishing, and burning iron and steel into mercantile articles, for turning those immense masses of machinery which throw silk, spin flax, wool, and cotton, and weave webs of sundry kinds, for pumping water out of mines and low grounds, and pumping water into canals, docks, or reservoirs, for drawing waggons upon rail roads, for grinding and dressing corn, and a thousand other purposes, steam engines are growing up, until the smoke whieh issues from their towering chimneys covers the land. But this is not enough; their smoke already covers our navigable rivers, and it aspires after the dominion of the sea; for, if we may predict from the past what the future will achieve, their smoke will cover the oceans also. And as though all the means already enumerated, and full as many more which might be added, were not enough, we have another novelty, whereby the consumption of coal is insured daily; viz. that of extracting gas from coal, in order to give light within our houses, churches, public buildings, shops, and manufactories; and even without, along our streets and highways; for, in order to procure this gas, we consume coal in heating the retorts which produce it.

I have been led into this digression, if digression it may be deemed, because it is the geometrical progression of our coal mines, which rings the alarm-bell incessantly in our ears; seeing, to these mines may be referred almost all the reasonings which constitute the article that precedes this, and almost all the dangers to which miners are exposed in these islands. As one means, therefore, of averting the evils to which so large a proportion of our fellow-men are exposed as miners now are, and ere long will be, it is not too much to attempt, at least to hang a drag upon the rapid progression of coal consumption, by calling the attention of the public at large to this enormous and yet growing evil. It is a question well worth a thousand experiments, if even these issued in a solution thereof, Is there no other mode of producing artificial heat, but by means of the fuel which inflammable substances yield? Could our able chemists be better employed than in attempting such a discovery? In this age of discoveries, when chemistry has attained such vantageground, is it too much to suppose some such discovery may be made by them? Such a discovery would certainly save from danger, and even death, multitudes, all of 115.-VOL. X.

whom, like ourselves, are men; and, therefore, must be a work of humanity worthy of the most exalted mind.

In general, immediately upon the termination of the bold escarpments of the chalk strata in the eastern counties of England, a level stratum is found, and to this succeeds a limestone stratum, the planes of which are considerably inclined to the eastward. Wherever this limestone strata exists, I am persuaded coal strata exists also, although at great depths beneath it; and I have no doubt succeeding ages will find means to extract the coal from this strata, deep as they are. What a subject for the contemplation of a mind formed in the mould of humanity! Our fellow-men must descend into an abyss of matter, to the depth of a thousand, if not twelve hundred yards from the light of the sun and the salubrious atmosphere, to sweat in darkness amidst sulphureous emanations and pestilent gases, from day to day, for their daily bread, to send up mineral coal for smoke and vapour! (To be continued.)

ESSAYS ON PHYSIOLOGY, OR THE LAWS OF ORGANIC LIFE.

(Continued from col. 553.) ESSAY IX.-On Animal Temperature, Instinct.

IN our last essay, we noticed the influence which the cutaneous system exerts upon the body, as to the regulation of its temperature, allowing at the same time that the muscular, nervous, and digestive organs concur also by their action, in this object; their operations tending to enable the body to resist to a certain point, the great natural depressions which take place in the temperature of the atmosphere around us.

With regard to the muscular system, it must be sufficiently evident to all, that its influence is very considerable, for we know from common experience, how necessary, under exposure to a cold temperature, vigorous muscular action, as running, walking, &c. becomes, to maintain the body at its natural standard,-while, on the contrary, if the body be suffered to remain inactive, even for a short period, the natural temperature begins to decline, and sensations of pain (preceding numbness and loss of vitality) proclaim the necessity of exertion to which they arouse us. During a state of profound rest, as in sleep, there is naturally a slight decrease of temperature, hence animals instinctively retire to a warm retreat, or assume such

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positions, in sleep, as are best calculated for protection against the cooling influence of the surrounding atmosphere.-Man too, refining on the dictates of instinct, seeks even here, not merely to satisfy nature, but to gratify his luxury, he robs the swan and the eider-duck of their down, to pamper his enervating indolence. The nervous system also exercises great control over the animal temperature, inasmuch as it influences respiration, and through this again, the action of the heart and arteries;—hence all the organs of secretion, diversified and numerous as they are, participate in the impulse. In this view we may regard the actions of the digestive organs, first as affording a supply by means of which the vital energy is recruited; and secondly, as by the operations themselves by which the extraneous matter is so converted as to become part and parcel of the living body, they affect its temperature.

The changes which take place in the temperature, in morbid states of the body, certainly merit attention. There are several instances on record, in which individuals labouring under madness, have lain exposed to so severe a cold, as to freeze the water or milk provided for them, into a mass of ice, without suffering in any apparent degree the consequences which might have been anticipated.

It would however, be foreign to the nature of our plan to follow up this branch of the subject ;- -we shall therefore proceed to notice the theory of animal temperature. Whence, or how does the temperature of animal bodies originate?

An ingenious hypothesis on this subject was devised by Dr. Black, which, however, has met with formidable objections, totally subversive of its truth.-These objections Dr. Crawford subsequently attempted to obviate; and his theory, which may be accounted an improvement upon that of Dr. Black, is still not without its supporters.

To explain it as briefly and clearly as possible, it must be observed in the first place, that different substances have different capacities for caloric, that is, if two different substances be placed for a given length of time, in a medium of a higher or lower temperature than their own, they will be found at the end of that period not of the same, but of different degrees of temperature; and that which is of the higher is said to have a less, that which is of the lower temperature, a greater capacity for caloric, for it is evident that to be raised to a given degree, the former will require less than the latter.-Solids have

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a less capacity for caloric than fluids, and fluids than aëriform bodies;-if therefore, a solid become fluid, or a fluid aëriform, it absorbs a great portion of caloric, as requisite for its change to such a state, while its temperature remains precisely the same :-And on the contrary, if a liquid become solid, or an aëriform liquid, the caloric which it before contained being more than sufficient to preserve it merely in its former temperature, raises it consequently to a higher degree, which of course is quickly reduced by the contact of surrounding bodies.

Now, Dr. Crawford endeavours to shew by experiments, that arterial has a larger capacity for caloric, than venous blood, and common air than carbonic acid;when, therefore, the carbon of the venous blood unites (in its passage through the lungs) with the oxygen of the atmosphere, to form carbonic acid, it must follow that the temperature of the carbonic acid so formed, must be increased, its capacity for caloric being less than that of the atmospheric air, but the blood also having as. sumed during this operation its arterial character, has acquired a greater capacity than when venous, and consequently it absorbs the caloric disengaged from the carbonic acid.-The arterial blood is not now sensibly warmer than it was, because the addition of caloric is only sufficient to preserve it of its previous temperature. The arterial blood now circulates through the system, and becoming venous, its capacity for caloric becomes at the same time diminished,-and the caloric, before latent, is consequently evolved, and so keeps up the natural temperature of the body, supplying the continual abstraction occasioned by the colder medium that surrounds us;-while the blood, returning to the heart and thence to the lungs, acquires a fresh store, to be again exhausted and again renewed till life ceases.

Besides this, there is also another source from which a portion of caloric is derived, and which depends upon the principle we have before stated,-viz. that fluids, when becoming solid, impart to bodies in contact, their superabundant caloric, before latent.-Now this conversion of fluids into solids is perpetually going on in the animal frame, hence, as perpetually will latent caloric become disengaged, and so become sensible in the system.

This theory, which we have endeavoured to state as clearly as possible, is, on a superficial view, very plausible; but upon a closer examination our credence will not be so readily yielded;-for setting

aside the difficulty of ascertaining the respective capacities for caloric, of arterial and venous blood concerning which the statements of eminent men are at utter variance, we obtain no satisfaction as to the differences of temperature which exist between the warm and cold blooded animals, whose blood equally undergoes a change by means of the action of atmospheric air,-besides which there are numberless phenomena, utterly irreconcileable with it, so much so, that its supporters seem blinded by its ingenuity, or perhaps have neglected to examine it in all its

relations.

The present state of physiological knowledge is yet too imperfect to allow a complete and satisfactory theory to be given. To ourselves it appears that the temperature of animal bodies depends neither on chemical nor mechanical principles, but that it is associated in some mysterious manner with the vital principle, as exhibited in the innumerable operations continually taking place in the organic frame, -those endless combinations and decompositions involving perpetual electrical changes, that strange energetic influence of the nerves, whose true nature and mode of action is yet veiled in obscurity.

Having thus far explained the leading phenomena of life, in organic sentient beings, resulting from those inherent properties or laws which we have termed sensibility and contractility, or, according to others, irritability, it remains for us to notice another law, which we stated to be associated also with organic existence. This law is Instinct.

But in the first place, it will be requisite that we should clearly explain what we mean by this term, a term very vaguely used, and often confounded with reason. Instinct, then, we consider to be a property of vitality, possessed by the brute and man;-its actions being not the result of judgment, or reflection, not dependent upon mind, but arising from a principle imparted, with certain modifications, by the divine Author of all things, to the whole series of organic beings, and consequently, as far as it goes, it is a principle unerring in its operations.

If we examine the constitution of our own minds, we shall find that the powers, by which, through the medium of our senses, we gain an acquaintance with the nature of things around us, may be resolved into three-viz. Attention, Memory, and Imagination;-but from the operations of these powers,--their complicated processes, and especially the

unceasing combinations and decompositions of imagination, arise from what may be termed secondary ideas, or ideas of reflection;-these, though depending upon the powers above named, are connected inseparably with the constitution of the mind, and are necessarily formed in the course of its operations.-Without expatiating upon them, (as the line of our plan merely touches upon the subject,) we shall state what we 'consider them to include ;1st, Ideas of Personality or Distinction,

2nd, of Time,-3rd, of Power,-4th, of Truth,-5th, of Duty,-6th, of Deity.— Though this is an inviting field, we shall not enter its precincts, but return to our main subject.

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Now the actions of instinct are evidently unconnected with these intellectual operations,-they result from no intellectual process, nor require mind for their performance; for we witness the effects of this power in the zoophyte, and worm destitute of brain, as well as in the higher orders, arising even to man. We may observe also; that instinct presents a feature the reverse of what is exhibited by any intellectual process leading to action, inasmuch as such action is not of necessity, -in other words, the impressions made upon us by external objects, or the ideas of reflection suggested by memory, when they are the subjects of our intellectual powers, do not necessarily lead to any control over the body, in consequence of an act of volition.-Between the impression and action, there is always a process of thinking, of course varying greatly in its nature and duration, according to the subject, but still absolutely required to connect the action with the impression, or idea.

Now, as it respects instinct, the case is very different,-here the action is immediate, there is no process of thinking, no deliberation, no train of reasoning, influencing volition.-There is required, as it were, an effort to carry into effect the action which depends on an intellectual process, while, on the contrary, the actions of instinct require no such efforts, they are spontaneous; they follow the impressions with immediate consent; and indeed the impulse cannot be successfully resisted without a considerable struggle.Hence the discipline our domestic animals. require, to render them serviceable to our wants;-while in ourselves, obedience to the voice of reason and religion, rather than to the impulse of instinct, creates a perpetual warfare.

We trust that our ideas of instinct are understood,-there has been much confu

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sion on the subject, which renders a clear explanation the more desirable. Reason then we would call the exercise of the mental powers, comprehending all their movements;-Instinct, those active powers associated with vitality, which impel to the performance of actions (often intricate and curious,) unconnected with any process of reasoning, and independent of habit. Thus it is the work of mind, in man, to construct the simplest habitation,-but instinct impels the bee to build the "sightly hexagon," the bird, to frame the nest.

In our application of the principles thus laid down, we would not be understood as denying that the brute orders, throughout the whole series, are in any degree gifted with powers of a higher order than instinct ;-On the contrary, however many, who have not duly considered the subject, may ridicule the idea, we cannot doubt that numbers evince the possession of thinking powers, and we are sure that those who have paid attention to the habits of animals, will agree with our opinion. They are certainly endowed with the powers of attention, and memory, and perhaps also imagination, they display a knowledge of time, of power, and of cause and effect, the results, strictly speaking, of mental operations, and called forth and modified accordingly, by different circumstances;-but in the impulse of instinct, no mental operation participates. -The brute creation, however, possesses these higher powers in a very limited and inferior degree;-hence, though the dog or horse may discover, to a certain extent, a knowledge of time, or power, and cause and effect, we cannot suppose either of them to possess even the most imperfect ideas of truth, (abstractedly considered,) of duty, or Deity.-Man, therefore, stands pre-eminent and alone, a being destined for immortality; his mind, in grasp gigantic, confines its views not alone upon the present, but with anxiety looks onward to the future, and believes, where it cannot comprehend; limits its speculations not only to this fair world, with all its changes, all its objects, all its varied beauties, but mounts to other spheres, tracks the shining planets in their mazy path, measures their distance, calculates their rapidity, and weighs them, as it were, in a balance, then passing onward from these glorious works to the Power who made them, bows humbly and adores. These high endowments are wisely denied to the brutes; though, as we have said, we may often discern the operations of reason, low indeed and limited, influencing their actions.

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The nearest of the inferior animals, to man, although it must be confessed at an immense distance and inferiority, is the elephant, and now descending down the chain of beings, and decreasing in every link, reason becomes more and more confined, till in a few removes from man, or far at least before it has attained the limits of the succession of animals, it has died imperceptibly away. W. MARTIN.

Hammersmith.

(To be continued.)

ON THE SECURITY OF ROOFS IN LARGE BUILDINGS.

MR. EDITOR, SIR,-Half a century, at least, has elapsed since it became fashionable to crown very spacious and lofty rooms with flat ceilings, without the intervention of columns or side arches, as collateral supports, in order to divide the bearings of the principal beams. Thus the whole weight of the roof, notwithstanding the trusses which the principals form aloft, rests upon the ends of these beams, and presses entirely upon the walls of the edifice; and, should one of these ends fail, it might bring down the roof.

In large public buildings, such as churches, chapels, halls, &c. this is considered to be a great modern improvement; because the eye of the spectator can in such rooms rove over a very spacious area without interruption; and the whole congregation or company are thus at once introduced to each other and to the preacher or speaker, and he is at once introduced to them. The voice, also, in these rooms is supposed to range more freely throughout a large area, and to be more distinctly heard than in rooms of equal dimensions, where columns or side arches are reared from the floor to the ceiling.

Modern invention has, however, in the cast iron column, introduced to the architect a strong and durable support, which, from the smallness of its dimensions, neither interrupts the eye nor confuses the finest tuned voice: and these columns might, during the erection of an edifice, be carried up to the underside of each principal beam, upon the head of each gallery column, by merely adapting the places of the columns which support the galleries to the places of the principal beams. Thus every principal beam of the roof would have four supports, instead of two; and the bearings of these beams would