panded, and by expelling some of the mercury from the tube at g" into the cup at g', it closes the aperture of the pipe e; thus cutting off the supply of air to the fire. In a few minutes (the fire in the mean time having abated its energy,) the air in the tube will return to its former dimensions, and the mercury subsiding in the cup, air is again permitted to enter the ash-pit.

The stove, of which we have thus attempted to convey a general idea, may be made of any required form or size. Instead of the self-regulating air valve just described, it is fitted up with others of a very simple construction, and which admit of being adjusted with the greatest accuracy by the hand.

FUNCTIONS OF THE EYE-ABUSE OF THE ORGANS
OF THE SENSES-CAUSES BY WHICH THE
EYE-SIGHT IS IMPAIRED.

HAVING already described the chief parts and funcconsider how it is that this apparently elaborate aptions of the eye, and its appendages, we come now to paratus performs its office. A pencil of light, that is, paratus performs its office. a bundle, or collection, of rays proceeding from any luminous object, falling upon the cornea, enters it, and is refracted or bent in its passage through the aqueous humour, by which means the rays of the We have seen Thermometer-stoves of various forms, some of them very beautifully designed, in operation. rays as can pass through the pupil are further pencil are brought nearer to parallelism; such of the We have attentively watched the process going on refracted by the crystalline lens, and the rays are within them, and have made ourselves acquainted with their capabilities as heating agents. The result out from a point, but begin, in passing through this now no longer divergent, that is, they do not spread of our observations leads to this conclusion; that if lens, to converge or proceed to a point, and this conthe Thermometer-stove be made in strict conformity vergency is perfected by means of the vitreous huwith the plain and simple rules which are so per-mour, which brings the converging rays to a point spicuously laid down by Dr. Arnott, it will prove one of the most economical as well as most useful inventions of this rapidly improving age.

Among the advantages of the Thermometer-stove, we may mention that it maintains an uniform temperature if required at night as well as by day, but which can be increased or diminished in a few minutes. The fire within it may be kept alight without requiring attendance or any additional fuel for ten, or even a greater number of, successive hours. To warm a moderate-sized room, the cost of fuel will not exceed a penny a day. No smoke, dust, vapour, or other products of combustion, can possibly escape into the room. The air is warmed, not heated, and hence it is not deprived of its health-preserving properties. There is no danger attending the use of the Thermometer-stove; it is more easily managed than an open fire; and there is no waste either of fuel or

of heat.

He who can imagine the universe fortuitous or self-created, is not a subject for argument, provided he has the power of thinking, or even the faculty of seeing. He who sees no design, cannot claim the character of a philosopher: for philosophy traces means and ends. He who traces no causes, must not assume to be a metaphysician; and if he does trace them, he must arrive at a First Cause. And he who perceives no final causes, is equally deficient in metaphysics and in natural philosophy; since, without this, he cannot generalize,-can discover no plan, where there is

no purpose. But if he who can see a Creation, without

seeing a Creator, has made small advances in knowledge, so he who can philosophize on it, and not feel the eternal presence of its Great Author, is little to be envied, even as a mere philosopher; since he deprives the universe of all its grandeur, and himself of the pleasures springing from those exalted views which soar beyond the details of tangible forms and common events. And if, with that presence around him, he can be evil, he is an object of compassion, for he will be rejected by Him whom he opposes or rejects. -MACCULLOCH.

COMPASSION.-Compassion is an emotion of which we ought never to be ashamed. Graceful, particularly in youth, is the tear of sympathy, and the heart that melts at the tale of woe; we should not permit ease and indulgence to contract our affections, and wrap us up in a selfish enjoyment. But we should accustom ourselves to think of the distresses of human life, of the solitary cottage, the dying parent, and the weeping orphan. Nor ought we ever to sport with pain and distress, in any of our amusements, or treat even the meanest insect with wanton cruelty.-DR. BLAIR.

HONOUR. He is worthy of honour, who willeth the good of every man; and he is much unworthy thereof, who seeketh his own profit, and oppresseth others.-CICERO.

exactly when they reach the retina. This process is undergone by every pencil of rays proceeding from any object to which the eye is directed, and an exact image of such object is depicted on the retina. If this convergent point do not quite fall upon the retina, but before it, in the vitreous humour, the eye is said to be short-sighted; if, on the contrary, these convergent points fall beyond the retina, the eye is then long-sighted; but these and other defects to which the eye is subject, will be discussed at greater length hereafter.

What we have above stated is the grand and important element in distinct vision; the convergence of the rays of a pencil to a point on the retina. An admirable adjustment of parts and of degrees of refractive power in the different humours of the eye sufficiently appreciate and understand the mechanism produce this perfect convergency, and the mind can and purposes of all this exquisite arrangement,—but here we have attained the utmost limit of our knowledge, we have traced upon the retina a picture of the forms presented to the eye, we see that this retina is an expansion of a nerve called the optic nerve, which proceeds from the retina into the brain, the seat of the mind;-but how the mind receives its impressions of light through the medium of this optic nerve, is a question that has never been answered, and probably never will be answered. The barriers beyond which he may not pass,-with cerstudent in science is constantly presented with certain tain limits to the inquiring powers of his mind, when subjects such as these are presented to him, which admit neither of demonstration or of analogical inference, and are therefore beyond the purposes of physical inquiry. Let him not, therefore, deal in vague conjectures, which, however ingenious, must still be unprofitable; but rather let him turn to the immense field which has already been cultivated so successfully, and from whence rich harvests of knowledge have been gathered. We cannot join in the utterance of the querulous opinion, which, because there is much that is unknown, denies the existence of any knowledge at all; nor could we ever assent to the conclusion of the philosopher, who said that his long life of study had taught him that he knew nothing; on the contrary, we can assure the reader, that the arena of modern science is so extensive, that a very long life and untiring industry, would be inadequate to a fair investigation of its contents.

The reader will now have some idea of the me

winking, as also by moving it about towards different objects: if the eye be kept open and rigidly fixed upon one object, its visual power rapidly declines.

There is so much sympathy between various physiological structures, that it often happens that a morbid or diseased action of one structure will seriously interfere with the functions of other structures which are healthy. In the healthy eye, the retina, the crystalline lens, the ciliary nerves, and the pupil, must harmonize in their action: the many diseased affections of the organ which include weakness or indistinctness of vision, result from a weak state of the retina, from the disordered action of the iris and ciliary apparatus; this is brought about mainly by inflammation of the eye or its appendages, resulting from injudicious use of the organs.

chanical structure of the eye, and how, as far as we
know, this structure assists the powers of vision. We
come, therefore, to the more direct purpose of our
subject, namely, the consideration of those employ-
ments of the eye by which its powers are impaired
or destroyed. And here we must remind the reader
of another law of nature as remarkable and beau-
tiful as any one in her code, if we may be allowed
such an expression, where all appear alike beautiful
and remarkable when we are quite sure that we read
and interpret them correctly; it is this-that the
perfect action of all the faculties, whether mental or
physical, can be assured and perpetuated only by
allowing them certain periodical intervals of perfect
repose. Now this may appear to be a truism, so
perfectly well known, that the necessity for its enun-
ciation in this place may be questioned by some:
but we must remind our readers, that a principle is
as important in its nature as it is unbounded in its
application; that it is the business of science not
only to discover principles, but to trace them to
effects where their presence is, perhaps, in no way
suspected; that we often recognise the action of a
principle in a few effects to which we are most obvi-
ously exposed, but we are often slow to recognise the
same principle in effects which afford us a larger
amount of pleasure or profit on the one hand than of
pain on the other, which minister to our cupidity, our
pride, our vanity; or which flatter one of those
"sins which do most easily beset us;" and, indeed,
we are frequently unable, from ignorance of the ex-bably cease.
tent of a principle, to apply it as a cause to effects,
which we often think have no cause at all, or at least
a very remote one, which, if discovered, we pro-
nounce to be irremediable. But this sort of argu-
ment is unjust and unreasonable: in nature there
are only a few principles or first causes; some of
these we are cognizant of-to all of them we are
subject our business, therefore, is to study the code
of laws by which we are governed, to conform with
the strictest obedience, since rebellion meets with
certain punishment, which, if ever it can be removed,
is removed only by a return to obedience.

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The senses, then, require perfect repose in order to their perfect action, and this repose implies a removal of every cause which excites them to action. By the perfect action of an organ, we mean its legitimate use and employment; the snuff-taker abuses his organ of smell, and its functions are manifestly impaired. The manufacturer of perfumes is a bad judge of odour from the same cause. A nauseous smell ceases to be nauseous unless it is judged of at intervals. The sense of hearing is subject to loss of power from abuse of its functions: a man accustomed to the din of noisy factories, and who sits down undisturbed by and even unconscious of the presence of that disturbance, which to a stranger is, at first, insufferable, is scarcely conscious of delicate sonorous impulses. Blacksmiths hear soft tones with difficulty, and examples have been abundant of old artillerymen who have become quite deaf from the long practice of their profession. The sense of touch is less perfect in the ploughman than in the watchmaker, and most perfect, perhaps, in the blind man, who by its means supplies in a great measure the loss of sight.

Taste also may be abused: the excited reveller scarce distinguishes the flavour of his " liquid fire," as the banquet approaches its end, and the pampered epicure is gratified only by allowing to his palate intervals of repose. The eye exhibits this principle in a beautiful manner. In its healthy state its function is being constantly intermitted in the process of

To discuss all the diseases of the eye resulting from abuses of its function, is manifestly a subject for a large medical volume, the study of which belongs to the medical pupil alone :—our purpose is more confined: we intend to point out some of the cases of every-day occurrence, wherein the organ is injured by an habitual irritable treatment. We do not intend to employ technical terms, except a few, which may be necessary to the comprehension of our subject, and still less do we pretend to direct remedies, except by pointing out causes of injury to the eye. In most cases our purpose will be effected, when, having clearly traced an ill effect to its cause, we say, remove or mitigate the cause, and the effect will pro

In the pathology of the eye the term amaurosis is employed, in which is comprehended all those imperfections of vision resulting from a morbid action of the sentient apparatus belonging to this organ. The term amaurosis is derived from a Greek word signifying to darken, and implies partial or total loss of vision, according as the optic nerve, or retina, is partially or totally paralyzed. This injury, or paralysis, is not generally manifested by external symptoms, and is therefore clearly distinguished from cataract, opacity of the cornea, and closed pupil. This disease is due to a variety of causes which it is not our business to discuss; such as disorganization of the retina, vascular turgescence, injury of certain nerves, &c. Our purpose is, as we have already stated, to point out those common causes, of every-day occurrence, which the exercise of many arts and professions is calculated to induce, and these causes may be conveniently arranged into five heads, namely:

1st. Sedentary employments in which the head is bent over work of various kinds; including those cases in which the eye is customarily employed on minute objects.

2nd. Where the eye is employed upon too strong or too little light: upon polished or reflecting surfaces. 3rd. The habitual exposure of the organ to high temperatures.

4th. The habitual exposure of the eye to acrid fumes.

5th. The customary employment of optical glasses.

By the light of Divine revelation, Christianity enables us

accurately to discriminate between good and evil, right and
wrong: it teaches us to see things according to their own
nature and in their proper colours: to behold those qualities
which are really vicious, deprived of the dazzling bright-
ness, wherewith reason, impaired by passion, had invested
them; and to contemplate those which are virtuous, disen-
cumbered from the clouds of worldly prejudice, and arrayed
in their native beauty. In a word, it teaches us to see
things, as they are in the sight of God, and not as they
BISHOP MANT.
appear according to the erroneous conception of men.-

ON THE PERPETUATION OF PLANTS. THE care which the Creator has bestowed on the perpetuation of plants offers a wide field of inquiry. The collateral as well as the direct means of propagation are very numerous, and the results very extensive and valuable.

The circumstance which is, perhaps, most striking in the mode of propagation by seeds, is the apparent anxiety for their production, in the means adopted. This is less sensible to common observation, where the magnitude, the duration, and the uses of the plant itself, are conspicuous; but it becomes striking in the smaller and more perishable ones, and is often very remarkable in the lowest parts of the scale. Thus in the oak, we pay little attention to the production of seeds; or if noting it, we still know that there is before us a being, destined to a life of so many centuries, that we scarcely think of its death, or of the necessity of a system of perpetuation.

:

It is in the biennial and the annual plants that this anxiety for the continuation of the races is most obvious to common observation. Millions of individuals seem to be utterly worthless and there are even species without end, for which we can discover no use, though desirous to find at least an insect attached to each. Amid the hundreds of lichens and mosses, a very few would, as far as we can see, have fulfilled the purpose which they appear solely to serve, in producing soils on naked surfaces. Yet in these we trace the same care and the same anxiety. The annual seems to grow for no other purpose than to produce seeds; and that being accomplished, it dies. For this it struggles against every difficulty: | and under every check, every accident, every mutilation, it still labours for this end, as if it were a conscious agent. We cut off its flowers, or cut down itself, obstruct, impede it, in every manner, but it still resists, proceeding with an obstinacy of determination to effect this great object; while if, tired of opposing it, we cease, it recommences, and having at length gained its purpose, dies. We can often even prolong the annual life for another year, or more, by the same opposition; as if it was determined not to part with existence till it had obeyed its orders and fulfilled its destiny.

The first mark of care, if a remote one, is found in the contrivances for protecting the future flower through the Winter, wherever such protection is necessary. In the buds, the beautiful packing, the investing scales, the down or hairs in some cases, and the varnish in others, are familiar: and, by these contrivances, aided by that vital power, the action of which in resisting cold has not been explained, the most complete protection is afforded. In the bulbous-rooted plants, the bud is not less effectually protected beneath the ground, partly by the depth of earth, and partly by the singular chemical properties of the coverings, aided by the same resisting vitality. In other cases, the flower bud is not produced till the frosts are passed; and our attention may now be directed to the provisions within it for the formation and ripening of the seeds. In a certain sense, indeed, the flower is a superfluity, an example of gratuitous beauty, while it also contains provisions for the feeding of insects; yet with these are always combined some uses for the seed itself, as, in many cases, they are so numerous and remarkable that they cannot be overlooked. The reader need only be reminded of the various ways in which they protect the essential parts of the fructification, the stamina, and the pistils, on which the future seed depends; and of the contrivances for bringing the pollen into contact with the latter.

The essential protection which the calyx affords, by enveloping everything while yet in a tender state, must not be forgotten; apt as we are to look on it as a superfluous part, from attending only to the expanded flower. It would be endless to point out the numerous forms and modes under which it guards the unopened flower, and above all from the access of water. The calyx of the rose, so useless when expanded, is a familiar instance of protection afforded by a structure which, compared to the purpose, is very inartificial; and yet in this, and all similar forms, that protection is complete. In the cistus, possessing a flower of unusual tenderness and delicacy, a varnish is superadded, for the purpose of warding off the rains. The monophyllous calyces present a structure more apparently efficacious, yet the protection is not more complete. And if the scale calyces of the grasses offer a much simpler contrivance, the security which they afford is not the less perfect. The calyx of the poppy is lax, and not very firmly closed; but as a counterbalance to this, the flower bud is bent down by a curvature of the stem, and erects itself only when the protection of this deciduous guard is no longer wanted. The obstinacy with which this bud refuses to flower till it can erect itself, belongs to a still more interesting circumstance in the physiology of plants: but under the present view, the inverted position enables the back of the calyx to ward off that water which might have penetrated the less perfect junction at the summit.

That provision may here be pointed out in the liliaceous flowers, which, as a sheath, forms the substitute for the absent calyx, while the leaves also are sometimes arranged to perform the needful function. Under many different modes, the tulip, the genus Allium, the grasses, and far more, will afford examples of protection, given either to supply the want of a calyx, or to add to the security which that affords. And thus the seeds of the mosses are so embosomed in the plant, at first, as almost to elude the botanist; while they escape the chance of injury; to be elevated for dispersation, only when all hazard of failure is past.

It is under all this care and concealment, that the essential parts, destined to produce the perfect seed, are growing within; free from all hazard, till the expanding flower opens to the light that the work may be completed. And then do we begin to perceive the utility of many other preparations towards this great end, the purposes of which we might not have understood before, and which he who looks on this interesting part of creation with a common eye, never sees. The vanity of philosophy may smile, if it pleases, at what it may choose to term fanaticism, but it is he who seeks for the hand of the Creator in every one of His works, who has found the true clue of investigation; since the purpose is that clue, and, that to study the design and the Designer, are one. And if the care of a parent for its offspring, the anticipations, the preparations, the watchfulness of a mother, are objects of our admiration, shall we not at least investigate the contrivances, the thought, the anxiety, of the Great Parent of all, for the safety and the life of these, His beautiful, but His lowest children; not inquire of his care for their perpetuity, that not one shall be lost? Could more have been done; and if He has not done it, by whom then was it effected? Who is it that contrived, who is it that watches over the lilies of the field, that not one of them should perish from his land? Who is it that guards to maturity, even the minutest moss, and ensures it a posterity, that it shall not fail from the multitude

Fig. 2.

But the inversion can be corrected by taking a little more pains. Let A be a piece of looking-glass fixed in a wooden or brass frame, and connected with a piece of clear glass, B, so that the angle C BA shall be an angle of one hundred and thirty-five degrees, the image of an object placed at r will be reflected from the looking-glass at A, and proceed to the clear glass at B: from this it will be reflected upwards to the eye at G, and the glass being transparent, the image and the hand will be seen at the same time; in this case the image is erect. But, in general, neither of these plans are resorted to, for in both cases, as there are two reflecting surfaces from the glass, there will necessarily be two reflected images, one of them certainly much less vivid than the other, but still sufficiently visible to distract the eye

of His children, who, even in the vegetable world, | simplest construction, but possessing the disadvantage look to Him for their food, their life, and their enjoy- of reflecting an inverted image. ment? Was it He: and is it He who cares not for man, provides not for him, governs him not, watches him not? Be it so, if it can afford satisfaction to think that so it is: but it will not be so to him who will open his eyes on the world around him, and who has learned, in everything, to look to the Cause, the Parent, of the universe. Would that I could persuade him who has hitherto walked through creation without eyes, without thought, without a heart, to take into his hand the first flower that shall present itself, and examine it as the work of some Being at least who intended, and wrought, and cared. If eloquence has long done its worst for this unfortunate cause, there must be one who can sit down with the next flower that meets him in his Summer walk, and ask himself, Whence came this, why is it here, why all this beauty, why all this care? I have seen it rise from a minute seed, I trace a series of cares and contrivances that seed shall spring from it again, I trace these under a thousand forms, I marvel at their ingenuity and their wisdom, I am astonished at an anxiety which has neglected nothing, I see that an end was intended, and I find that end attained. What more does man ever do to attain his objects, when does he labour with more care and more knowledge, and when does he succeed with more certainty? Does woman show more anxiety, more contrivance, for her offspring, than the Parent of this little flower has displayed? And who can that careful, that affectionate parent be? No one! Even so was it no one that reared me from helplessness to maturity, I knew no parent's thought, no mother's care: there is no God. Can such a conclusion ever have entered the heart of man? We know not how to believe him who has declared it.

[Abridged from MACCULLOCH's Proofs and Illustrations of the Attributes of God.]

THE CAMERA LUCIDA. THE Camera Lucida, an invention of Dr. Wollaston, like the Camera Obscura, is an instrument employed in making copies of drawings, and in portraying distant objects; but it is of greater service than the Camera Obscura, being much more portable, and, if properly used, reflecting the image of the object without the least distortion.

If a piece of thin glass is held at an angle of fortyive degrees with the horizon, at a small distance from the table, and a sheet of white paper is placed immediately beneath it, the reflected image of an object before it will be visible, by looking downwards upon it; and as the glass is transparent, the hand and pencil can also be seen, and an outline of the image can be made upon the paper. In this case the image is inverted. Such an instrument as this can be made off-hand very easily. Let в be a piece of thin plate-glass, about an inch and a quarter long, and three-quarters of an inch wide; A a piece of wood in which the glass is fixed, and c a piece of pasteboard with a small hole in it, forming an eye-piece to keep the eye directed to one point.

D

B

Fig. 3. A

The optical portion of the Camera Lucida which is usually sold consists of a prism. Fig. 3 is a section of the prism employed; the angle A is equal to 224 degrees, C to 135 degrees, D 22 degrees, and B is a right angle of 90 degrees. The solid nature of the prism will not allow the hand to be seen through its thickness, and the instrument is used in a different manner to the last contrivance. A is the prism, в a moveable piece of brass, having a small eye-hole in it at B; the reflected ray from c is received near to this corner of the prism, and reflected upwards to the eye; the eye-hole is so adjusted that one-half only is over the prism,

B

A

Fig. 4.

the other half leaves a free space through which the hand and pencil can be seen. In using the instrument a vast deal depends on the proper adjustment of this eye-hole.

If the light is very powerful on the object, and much less so on the paper, the part of the prism exposed through the hole should be small, and the opening through which the paper is seen large in proportion. On the other hand, if the light on the drawing is weak, a larger part of the prism must be uncovered. In copying a print, great care must be taken that the print itself is perfectly flat and perpendicular to the horizon, and that the side of the prism at B A, fig. 3, which is opposite the print, shall be parallel to it. If this is not attended to, the print will be thrown into perspective and the copy be distorted.

If the object is to be copied of its natural size, its distance from the prism in front must be equal to the distance from the eye to the paper; if it is to be reduced it must be placed at a greater distance; if to be enlarged, it must be brought nearer.

The Camera Lucida has been fixed to the eye-hole of a telescope or a microscope, in such a manner as to allow the objects within the field of vision to be copied on paper.

LONDON:

JOHN WILLIAM PARKER, WEST STRAND. PUBLISHED IN WEEKLY NUMBERS, PRICE ONE PENNY, AND IN MONTHLY PARTS,

PRICE SIXPENCE.

Sold by all Booksellers and Newsvenders in the Kingdom.

THE SOLAR SYSTEM.