when high-pressure steam is permitted to escape from its surface, is, therefore, the result of an equally sudden enlargement of volume. We have here an instance of the transition of heat from a sensible to a latent state; the extra 88° (300°-212°) being still combined with the water, and the steam in the vessel; but so changed in its character, as to be no longer appreciable by the thermometer.

To the elastic force of steam, and the facility with which its elasticity is destroyed, by a slight change of temperature, we are indebted for its application as a moving power in the STEAM-ENGINE,-one of the most valuable gifts ever presented by philosophy to the human race. The invention and improvement of this mighty product of human genius, is peculiarly associated with our own age and country. Seventy years have scarcely passed away since Mr. WATT commenced those experiments on steam, which, step by step, have led to results so stupendous, that they are without parallel in the history of the world. It is impossible to contemplate, in all their vastness, the blessings already conferred by the steam-engine upon mankind. Boundless in their extent, and universal in their application, we may yet conclude that they are only preparing the way for more illustrious benefits. What has been done may well excite our admiration, as it ought to awaken our gratitude, to the AUTHOR of all our mercies. Much, however, remains to be accomplished. The discoveries and improvements which are daily unfolding themselves to our view, may attest that human knowledge is at present limited and imperfect; but they are equally calculated to inspire in us new hopes, and enlarged expectations, as respects the future.

The most simple form of the steam-engine is that denominated the high-pressure engine, which occupies but very little space; and may, therefore, be employed in situations where one of a different kind would be unsuitable. In this engine, steam is generally used at a density equal to three or four atmospheres; that is, its expansive force within the boiler is about 50 or 60 lbs. upon every square inch of the metal. Supposing it to be 60 lbs., there are 15 lbs. to be deducted for the ordinary pressure of the air, on the outside of the boiler, so that the real force of the steam, in this case, will be 45 lbs. to the inch. Motion is obtained by permitting steam to pass from the boiler, first to one end, and then to the other, of a metallic, cylindrical vessel; to which is fitted, steamtight, a piston, made of similar materials. The following figures are intended to represent a section of the cylinder, with the piston at its opposite extremities,

admitted through the pipe A", to its upper side, the piston will be forced downwards to B'. On allowing the steam above the piston to escape from the cylinder, at the same time admitting a fresh supply from the boiler, through the pipe B", to the under side of the piston, it will be returned to its former situation at A'. These alternate motions may be continued as long as the necessary quantity of steam is generated within the boiler.

From the danger attending the employment of highpressure steam, it is never applied, in this country, to the purposes of navigation. It is admirably adapted for small engines, where great power is required in a limited space; and especially for loco motive carriages. Notwithstanding the many curious contrivances that have lately been adopted, with a view to security, the risk of using large quantities of water, at a temperature of 250°, or 300°, is still too great to warrant its general introduction.

The low-pressure, or condensing engine, is more complex in its arrangements, and, of course, more costly in its construction, than that already described. In this engine, steam is usually employed whose expansive force is from twenty to twenty-five pounds on the inch; which is only five to ten pounds beyond what is necessary to counteract the pressure of the air on the exterior of the boiler, and from which no serious consequences would result, were the boiler to burst. The elasticity of the steam is not the only source of motion in the condensing engine, for, whilst steam is exerting its force on one side of the piston, a vacuum is produced on the opposite side by the sudden condensation of the steam previously introduced there. In this respect, it differs essentially from the high-pressure engine, whose piston is always opposed by a force equivalent to that of the atmosphere, namely, fifteen pounds to the inch. In the cylinder of the condensing engine, the whole force of the steam, whatever it may be, is brought into effective operation. In that of the high-pressure engine, one atmosphere of steam is entirely wasted.

The condensation of the steam, which formerly took place in the working cylinder, by forcing into it a jet of cold water, is now effected in a separate vessel, so that the temperature of the cylinder is constantly maintained. For this, as well as many other equally important improvements, we are indebted to Mr. Watt.

The safety-valve of a steam-engine consists of a metallic stopper, nicely adapted to a circular orifice, yet moving freely in it, at the top of the boiler. This stopper, or valve, is kept in its place by a lever, moving by a joint at one end, whilst a weight is suspended at the other. By adjusting the weight on the longer arm of the lever, the valve is made to press upon the orifice in the boiler with any required degree of force. When the elasticity of the steam within the boiler increases beyond what is necessary for working the engine, or for the security of the boiler, the valve is forced open, and some of the steam escapes. This is frequently seen to be the case on board steam-packets just before they start, or when the engine is stopped for a few minutes after they have commenced their voyage.

We must now conclude this part of our subject. On a future occasion, we hope to present our readers with a more detailed account of the steam-engine; in which its various parts will be explained by direct reference to suitable illustrations. R. R.

FLY him, who, from mere curiosity, asks three questions running, about a thing which cannot interest him.

THE HUMAN HAND. IN that portion of the works of Galen which bears this title, "On the use of the various parts of the Body;" after having defined what is to be understood by the term part or member, as applied to an animal body, he proceeds in the following manner :

But all these parts of the body were made for the use of the soul, that sentient and intelligent principle which animates the body, and of which the body is merely the organ; and on this account, the component parts of animals differ according to the nature of this principle: for some animals are bold and fierce; others are timid and gentle; some are gregarious, and co-operate for their mutual sustenance and defence; others are solitary, and avoid the society of their fellows; but all have a form or body accommodated to their natural dispositions and habits. Thus, the lion has powerful fangs and claws; the hare has swiftness of foot, but in other points is defenceless. But to man, the only animal that partakes of Divine intelligence, the Creator has given, in lieu of every other nocturnal weapon, or organ of defence, that instrument, the hand; an instrument applicable to every act and occasion, as well of peace as of war. Man, therefore, wants not a hoof, or horn, or any other natural weapon; inasmuch as he is able with his hand to grasp a much more effective weapon, the sword, or spear. Besides which, natural weapons can be employed only in close conflict; while some of the weapons employed by man, as javelins or arrows, are even more effectual at a distance. And, again, though man may be inferior to the lion in swiftness, yet by his dexterity and skill, he breaks into his use a still swifter animal,-the horse; mounted on whose back, he can escape from, or pursue the lion, or attack him at every advantage. He is enabled, moreover, by means of this instrument, to clothe himself with armour of various kinds, or to intrench himself within camps or fenced cities. Whereas, were his hands encumbered with any natural armour, he would be unable to employ them for the fabrication of those instruments and means which give him such a decided advantage over all the other animals of Nor have we yet enumerated the most important of those privileges which the hand imparts to man. With this he weaves the garment that protects him from the Summer's heat or Winter's cold; with this he forms the various furniture of nets and snares, which give him a dominion over the inhabitants as well of the water as of the air and earth; with his hand he constructs the lyre and lute, and the numerous instruments employed in the several arts of life; with his hand he erects altars and shrines to immortal gods; and lastly, by means of the same instrument, he bequeaths to posterity, in writings, the intellectual treasures of his own divine imagination.

creation.

Thus then the hand is framed in the manner the most convenient for laying a firm hold on objects both greater and less than itself. And in order to enable it to apply itself to objects of various shapes, it is evidently most convenient that it should be divided into many parts, as it is, and seems to be better constituted for this purpose than any similar instrument; for it not only can apply itself to substances of a spherical form, so as to touch them with every part of itself, but it also can securely hold substances of a plane or of a concave surface; and, consequently, it can hold substances of any form.

And, because many bodies are of too great a size to be held by one hand alone, Nature has, therefore, made each hand an assistant to its fellow; so that the two, when together laying hold of bodies of unusual bulk, on opposite sides, are fully equivalent to a single hand of the very largest dimensions; and, on this account, the hands are inclined towards, and in every point are made equal to, each other, which is at least desirable, if not necessary, in instruments intended to have a combined action.

Take then any one of those unwieldy bodies which a man can only lay hold of by means of both his hands, as a mill-stone or a rafter; or take one of the smallest objects, as a millet-seed or a hair, or a minute thorn; or, lastly, reflect on that vast multitude of objects of every possible size, intermediate, to the greatest and the least of those above-mentioned, and you will find the hands so exactly capable of grasping each particular one, as if they had been expressly made for grasping that alone. Thus the smallest things of all we take up with the tips of the fingers; those which are a little larger, we take up with the same fingers, but not with the tips of them; substances still larger, we take up with three fingers, and so on with four, or with all the five fingers, or even with the whole hand; all which we could not do, were not the hand divided, and divided precisely as it is. For, suppose the thumb were not placed as it is, in opposition to the other four fingers, but that all the five were ranged in the same line,—is it not evident that in this case their number would be useless? For, in order to have a firm hold of any thing, it is necessary either to grasp it all round, or at least to grasp it in two opposite points; neither of which would have been possible, if all the five fingers had been placed in the same plane: but the end is now fully attainable, simply in consequence of the position of the thumb, which is so placed, and has exactly such a degree of motion, as, by a slight in

In the first place, it possesses, in an eminent degree, a leading quality of an organ of grasp, since it readily applies itself to, and securely holds, bodies of every form and size, that are capable of being moved by human strength. Nor need we inquire whether it be better for this purpose that it should be divided into several parts, or that it should be altogether undivided; for is it not apparent, without further reasoning, that, had it been undivided, it could have grasped only just such a portion of every object presented to it as was equal to itself? but that, being divided into many parts, it can both easily grasp bodies much larger than itself, and can accurately search out, and lay hold of, the smallest particles of matter; for to the former, it is capable of applying itself so as to encompass them by the separation of the fingers, while, in laying hold of very minute objects, the entire hand is not employed, but only the tips of two of the fingers, because from the grasp of the whole hand minute objects would easily escape.

of the four fingers. But it is not merely necessary in laying hold of minute objects to employ the extremities of the fingers opposed to each other, but that those extremities should be exactly of the character they are, namely soft and round, and furnished with nails; for, if the tips of the fingers were of bone, and not of flesh, we could not then lay hold of such minute bodies as thorns or hairs; or, if they were a softer and moister substance than flesh, neither then could such small bodies have been secured. For, in order that a body may be firmly held, it is necessary that it be in some degree infolded in the substance holding it; which condition could not have been fulfilled by a hard or bony material; and on the other hand, a material too soft would easily yield to substances of which it attempted to lay hold, and would continually let them escape: whereas the extremities of the fingers are just of that intermediate degree of consistence which is calculated for their intended use.

But, since tangible substances vary much in their

Thus, then, the soft flesh at the tips of the fingers compensating for the unyielding nature of the nails, and the nails giving support to the yielding softness of the flesh, the fingers are hereby rendered capable of holding substances that are both small and hard. And this will be more evident, if you consider the effect of an unusual length of the nails; for where the nails are immoderately long, and consequently come in contact with each other, they cannot lay hold of any minute object, as a small thorn or hair: while, on the other hand, if, from being unusually short, they do not reach to the extremities of the fingers, minute bodies are incapable of being held, through defect of the requisite support: but if they reach exactly to the extremities of the fingers, they then, and then only, fulfil the intention for which they were made. The nails, however, are applicable to many other purposes besides those which have been mentioned, as in polishing and in scraping, and in tearing and peeling off the skin of vegetables or animals: and in short, in almost every act where nicety of execution is required, the nails are called into action.

Whoever admires not the skill and contrivance of nature, must either be deficient in intellect, or must have some private motive, which withholds him from expressing his admiration. He must be deficient in intellect, if he do not perceive that the human hand possesses all those qualifications which it is desirable it should possess, or if he think that it might have had a form and construction preferable to that which it has; or he must be prejudiced, by having imbibed some wretched opinions, consistently with which he could not allow that contrivance is observable in the works of nature.

[KIDD's Bridgewater Treatise.j

LOVE FOR THE DEAD. THE grave is the ordeal of true affection. It is there that the divine passion of the soul manifests its superiority to the instinctive impulse of mere animal attachment. The latter must be continually refreshed and kept alive by the presence of its object; but the love that is seated in the soul can live on long remembrance. The mere inclinations of sense languish and decline with the charms which excited them, and turn with disgust from the dismal precincts of the tomb; but it is thence that truly spiritual affection rises purified from every sensual desire, and returns, like a holy flame, to illumine and sanctify the heart of the survivor.

The sorrow for the dead is the only sorrow from which we refuse to be divorced. Every other wound we seek to heal; every other affliction to forget; but this wound we consider it as a duty to keep open,—

Where is the mother who would willingly forget the infant that perished, like a blossom, from her arms, though every recollection is a pang? Where is the child that would forget the most tender of parents, though to remember be but to lament? Who, even in the hour of agony, would forget the friend over whom he mourns? Who, even when the tomb is closing upon the remains of her he most loved,-when he feels his heart, as it were, crushed in the closing of its portals,-would accept of the consolation that must be brought by forgetfulness? No; the love which survives the tomb, is one of the noblest attributes of the soul. If it has its woes, it has likewise its delights; and, when the overwhelming burst of grief is calmed into the gentle tear of recollection,when the sudden anguish, and the convulsive agony over the present ruins of all that we most loved, are softened away into pensive meditation on all that it was in the days of its loveliness, who would root out such a sorrow from the heart? Though it may sometimes throw a passing cloud over the brightest hours of gaiety, or spread deeper sadness over the hour of gloom, yet who would exchange it, even for the song of pleasure, or the burst of revelry? No; there is a voice from the tomb sweeter than song. There is a remembrance of the dead to which we turn, even from the charms of the living. Oh, the grave! the grave! it buries every error; covers every defect; extinguishes every resentment! From its peaceful bosom spring none but fond regrets, and tender recollections. Who can look down upon the grave, even of an enemy, and not feel a compunctious throb, that he should ever have warred with the poor handful of earth that lies mouldering before him?

Ay! go to the grave of buried love, and there meditate; there settle the account with thy conscience, for every past endearment unregarded, of that departed being, who can never, never, never return, to be soothed by thy contrition! If thou art a child,. and hast ever added a sorrow to the soul, or a furrow to the silvered brow of an affectionate parent; if thou art a husband, and hast ever caused the fond bosom that ventured its happiness in thy arms, to doubt one moment of thy kindness, or thy truth; if thou art a friend, and hast ever wronged in thought, word, or deed, the spirit that generously confided in thee; if thou art a lover, and hast ever given one unmerited pang to that true heart which now lies cold and still beneath thy feet; then be sure that every unkind look, every ungracious word, every ungentle action, will come thronging back upon thy memory, and knocking dolefully at thy soul; then be sure that thou wilt lie down sorrowing and repentant on the grave, and utter the unheard groan, and pour the unavailing tear,-more deep, more bitter, because unheard, and unavailing.

Then weave thy chaplet of flowers, and strew the beauties of nature about the grave; console thy broken spirit, if thou canst, with these tender, yet futile tributes of regret; but take warning by the bitterness of this thy contrite affliction over the dead, and henceforth be more faithful and affectionate in the discharge of thy duties to the living.-WASHINGTON IRVING.

PRUDENCE governs the wise; but they are few, and the most wise are not so at all times: passion actuates every body, and almost always.-ST. EVREMOND.

A MAN may be concise and utter much at the same time, especially in writing: for, in conversation, a great talker, and a sayer of nothing, do generally signify but one and the same thing.-COSTE,