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branes with which they are lined: also some very minute bones, and the auditory nerve.

The external ear, as it is called, consists of two parts, viz. the pinna or ear, popularly so called, and a tube called the meatus auditorius, which leads from the pinna to the membrana tympani, or from the external to the internal ear. These parts serve for collecting and conveying sounds to the organ of hearing. The passage just mentioned is of considerable length, and it is lined with a fine membrane, furnished with small hairs for guarding the parts within from the entrance of insects; and it is moistened by an oily secretion called cerumen or wax. The lower part of the external ear, or that which is often pierced for ear-rings, is called the lobe. The inner extremity of this canal is closed by a thin transparent membrane, which is set in a bony circle, something like a drum-head, hence it has been called the drum of the ear.

The internal ear consists of two divisions, viz. the tympanum and labyrinth. The tympanum is an irregular bony cavity, hollowed out of the temporal bone, just within the membrana tympani, which has several communications with the neighbouring parts. Opposite to the membrana tympani are two openings that lead to the labyrinth, which consists (1) Of an irregular cavity, (2) Of three semi-circular canals which open into this cavity, and lastly, of a spiral canal, something like the shell of a snail, making two turns and a half from the basis to the apex, and likewise opening into the former cavity. All these parts of the labyrinth are lined with a fine membrane, which transmits the vibrations it receives from the membrane that separates the labyrinth from the drum of the ear. Besides these parts, there is the Eustachian tube, that opens iu front of the tympanum. It takes its rise by an expanded cartilaginous orifice at the back of the nostrils, passes through the substance of the temporal bone, and terminates by a contracted orifice in the tympanum. Its office is to convey air into the cavity of the tympanum, The membrana tympani is thrown into vibrations by the impulse of the sonorous undulations of the air; but these vibrations could not take place unless there were air in the inside as well

as on the outside of the membrane; nor could the purpose have been answered, had the space been occupied by confined air, because the expausion of that air by heat, or its contraction by cold, would have distended or relaxed the covering membrane, in a degree not consistent with the purpose which it was designed to execute. The only expedient, then, and that for which the Eustachian tube serves, is to open to this cavity a communication with the external air: it, in truth, answers the purpose of the hole in a drum.

The cavity of the tympanum contains a chain of small bones, called ossicula auditûs, the use of which seems to be that of transmitting the vibrations of the air from the membrana tympani to the labyrinths. These little bones are called (1) The malleus or hammer, being larger at one extrewity, which is the head, than it is at the other, which is the handle. (2) The incus, less like an anvil, notwithstanding its name, than a grinding-tooth with its two fangs diverging; in the body of this is a hollow exactly adapted to receive the head of the malleus. (S) The stapes, which has an exact resemblance to the iron part of a stirrup.

The sense of hearing, which requires the assistance of all the parts which have been described, is occasioned by a certain modulation of the air collected by the funnel-like shape of the external ear, and conveyed through the meatus auditorius to the membrana tympani. The air vibrating on the latter communicates its vibrations to the different parts of the labyrinth, and by means of the fluid contained in this cavity, affects a nerve called the auditory nerve, so as to produce sound. Sound is more or less loud in proportion to the strength of the vibration; and the variety of sounds seems to depend on the difference of this vibration, for the more quick and frequent it is, the more acute will be the sound, and vice versa.

It should be observed, that the filaments of the auditory nerve pass from the meatus auditorius, through a number of very small apertures which lead to the labyrinth, and they ter minate on the vascular membrane of the labyrinth, so that the nervous pulp is exposed, almost bare, to a con

tained fluid. The distribution of the auditory nerve on the cochlea is parti cularly beautiful. The aqueducts of the ear are two very fine tubes, passing from the vestibulum and cochlea to open on the surface of that part of the brain called the dura mater.

From this account of the structure of the ear, it will appear that the organ is no less artificially and mechanically adapted to its office than the eye. Its general form is evidently adapted to the reception of sound, that is, knowing that what we denominate sound consists of pulses of the air, we perceive, in the structure of the ear, a suitableness to receive impressions from this species of action, and to propagate these impressions to the brain. The external ear, as we have seen, is calculated, like a trumpet used by the deaf, to catch, collect and convey onwards, the pulses just mentioned: it consists of a tube which leads into the head, lying at the root of this outward ear; of a thin membrane like a drum-head, stretched across this passage upon a bony rim; of a chain of moveable and highlycurious bones, forming a communication between the membrane and the interior canals and recesses of the skull; of cavities, similar in shape and form to wind instruments of music, being either spiral or portions of circles; of the Eustachian tube, like the hole of a drum, to let the air pass freely into and out of the barrel of the ear, either as the membrane vibrates, or as the temperature may be changed; and the whole labyrinth is wrought into the substance of the hardest bone of the body.

The communication within, formed by the ossicula, or small bones of the ear, is perfectly mechanical, and seems evidently designed to continue towards the sensorium the tremulous motions which are excited in the membrane of the tympanum or drum of the ear. The compages of the bones are so disposed and so hinge upon one another, as that, if the membrane of the drum of the ear vibrate, all the four are put in motion together, and by the result of their action work upon the base of that which is the last in the series, upon an aperture which it closes, and upon which it plays, which aperture opens into the winding canals that lead to the brain. This last bonc is the stapes.

The office of the drum of the ear is to spread out an extended surface capable of receiving the impressions of sound, and of being put by them into a state of vibration. The business of the stapes is to repeat these vibrations. Hence it may be understood how the sensation of sound is excited, by any thing which communicates a vibratory motion to the stapes, though not, as in ordinary cases, through the intervention of the membrana tympani. This may be done by solid bodies applied to the bones of the skull, as by a metal bar held at one end between the teeth and touching at the other a tremulous body. It appears to be done, likewise, by the ear itself, even when this membrane, the drum of the ear, is greatly damaged; so that either in the natural or preternatural state of the organ, the use of the chain of bones is, no doubt, to propagate the impulse in a direction towards the brain, and to propagate it with the advantage of a lever. This mechanical advantage consists in increasing the force and strength of the vibration, and at the same time diminishing the space through which it oscillates: both these changes may augment or facilitate the still deeper action of the auditory nerves.

The advantage of the Eustachian tube may, as we have seen, be made out upon known pneumatic principles, being intended to bring a supply of air, when wanted, into the cavity called the tympanum; which cavity could not have answered the end required had it been left as a vacuum, or filled with an aqueous fluid, or been occupied with confined air.

The membrana tympani is not found in the ears of fishes, which furnishes an additional proof of what indeed is indicated by every thing about it, that it is appropriated to the action of air, or of an elastic medium. It bears, as we have seen, a resemblance to the head of a drum in this, that its use depends upon its tension. In the drum the skin is carried over a hoop, and braced as occasion requires, by means of strings attached to its circumference. In the ear the same purpose is provided for, more simply, by a different expedient, viz. by the handle-end of the malleus pressing upon its centre.

To demonstrate the wisdom of the

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Natural Theology. Creator in the structure of the ear, it has been observed, that it is situated in the most convenient part of the body, and in a part near the common sensory in the brain, to give more speedy information: in a part where it can be best guarded, and where it can be most free from annoyances, and where it gives the least hindrance to the exercise of any other part-in a part appropriated to the peculiar use of the principal senses-in the most elevated part of the body, where it can perceive the greatest number of objects, and receive the greatest information, and also in the neighbourhood of the eye, with which it has a peculiar and admirable communication by its nerves. Thus, with regard to its situation and place in the body, the sense is admirably designed and contrived.

The external ear in different quadrupeds is very differently framed, but always exactly calculated for the creature's manner of life. Hares and such other animals as are daily exposed to insults from beasts of prey, have large ears directed backwards, their eyes warning them of any danger before: rapacious animals, on the other hand, have their ears placed directly forwards, as may be seen in the lion and cat. In hounds and other other animals, that are designed to hear most distinctly the sounds coming from below, the ears hang down wards, or they are flexible, because they move their heads, for the most part, with greater difficulty than man. Man, who must equally hear sounds coming from all quarters, has his external ear placed in a vertical manner, somewhat turned forward. Moreover, as the form of this organ is various in various animals, so in each of them its structure is very curious and observable, being in all admirably contrived to collect the wandering impressions and undulations of sound, and to convey them to the sensory

within.

We must conclude this article with some observations on the nature of sound, which is of such admirable use in the animal world. It is known from very simple experiments, that air is the vehicle of sound, for if the clapper of a bell be made to strike the side when it is under a glass receiver full of air, the sound will readily be heard, but if the experiment

No. V.-The Ear.

be made in a receiver that has no air within it, the sound can scarcely be heard at all; aud in a receiver containing condensed air, the sound will be much stronger. There is no doubt, therefore, that it is the air that conveys sounds to the organs of hearing. Sound propagates itself on all sides in right lines, when obstacles do not hinder it; so that every point of a sonorous body may be considered as being the common summit of a great number of very sleuder cones of an indefinite length. Sound employs a certain time to diffuse itself through the air, and it is longer in arriving at the ear, as that organ is farther from the sounding body. The velocity of sound is at the rate of 1143 feet in a second of time, and this, according to Dr. Derham, is the same in all weathers, whether the sky be clear and serene, or cloudy and turbid; whether it snows or rains, thunders or lightens; whether cold or hot, day or night, winter or summer; whether the mercury in the barometer rises or falls, in all changes of the atmosphere, wind only excepted.

"Who but an intelligent Being," says Derham, "what less than an omnipotent and infinitely wise God could contrive and make such a fine body, such a medium, so susceptible of every impression that the sense of hearing hath occasion for, to empower all animals to express their sense and meaning to others; to make known their fears and their wants, their pains and sorrows in mournful tones; their joys and pleasures in more harmonious notes; to send their minds at great distances in a short time; or to express their thoughts near at hand with a gentle voice or in secret whispers. Who less than the same most wise and indulgent Creator, could form such an economy as that of melody and music; that the medium should so readily receive every impression of sound, and convey the melodious vibration of every musical string, the harmonious pulses of every animal voice, and of every musical pipe, and the ear be as well adapted and as ready to receive all these impressions, as the medium to convey them; and finally that music should not only affect the fancy with delight, but also give relief to the mourner, and peace to those who are excited by strong passions. Who then can

of the sense of hearing, and not give the great Creator his due praise? Who can survey all this admirable work, and not as readily own it to be the work of an omnipotent and infinitely-wise and good Being, as the most artful melodies we hear, are the voice or performances of a living creature."

Extracts from the Bishop of London's

Charge.

[The following passages from the Bishop of London's Charge (1814), are curious and important. Designing in our Review department to take notice of them and of the strictures which they have drawn from the press, we give them at length and entire. The reader's attention is invited particularly to the paragraph relating to the Unitarians. ED.]

ROM these considerations of do

now called to concerns of universal importance to the interests of the Christian world. The convulsions which threatened to subvert the hallowed and ancient fabrics of religion, of social order, and of civil and political liberty, are happily allayed. The storm has ceased to roar. In the sight of the nations assembled from the ends of the earth to be the ministers of God's justice, and the witnesses of his power, the pillar of usurped domination, erected on the ruin of thrones and the wreck of principles, has crumbled, at the bidding of the Almighty, into dust, and the tyranny, which made the world as a wilderness, and destroyed its cities,* exists only in recollection, like the horrors of, an oppressive dream. The restoration of peace has followed the triumph of truth and justice; and the moderation which has tempered the glories of victory with a milder radiance, may be hailed as an auspicious presage of settled and durable tranquillity. But prosperity has its dangers: the Spirit of evil is always busy-though often confounded, he is never dismayed; though baffled, he returns to the contest with new arms; prepared alike to seduce or to intimidate, to succeed by violence or by fraud.

At so momentous à crisis, which I

nent. On this head I conceive we have little to apprehend for the sound, or even the reclaimable part of our pulation. There is indeed but too much

po

reason to fear that the state of reli

gion and morals in a neighbouring country is by no means satisfactory to the friends of piety and virtue. The French Revolution was not an accidental explosion, a burst of momentary passion or frenzy, but a deliberate and premeditated rebellion against authority human and divine: It was the

shake off the salutary restraints imposed by religion and law on the worst passions of human nature. The conception, and still more the successful accomplishment, of a project thus singular in atrocity, bespeaks an unexampled inveteracy of corruption diffused through the vitals of the community; and it is not unnatural to infer, that the evil has derived an accession of extent and malignity from the systematic encouragement of licentiousness by a despotic government; from the destruction of churches; the neglect of public worship; and, above all, from the abolition of the Sabbath, and the blasting influence of an unchristian education on the minds of youth. But the grossness of vice without disguise will be rejected with disgust by the habitual feelings of virtuous decency incorporated with our national character. The common sense of the nation will form a security equally strong against the deadly contagion of irreligious principle The cause of avowed infidelity has never prospered in this country: Attached by reflection and feeling to the interests of religion and virtue, we smile with contempt at the sophistries and sarcasms of the wretched literati, who, prostituting the powers of a dazzling wit and seductive eloquence to the gratification of public de ravity, obtained a cele