itself under the advantage of admitting of a strict comparison with optical instruments. The ear, it is probable, is no less artificially and mechanically adapted to its office, than the eye. But we know less about it: we do not so well understand the action, the use, or the mutual dependency of its internal parts. Its general form, however, both external and internal, is sufficient to show that it is an instrument adapted to the reception of sound; that is to say, already knowing that sound consists in 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. For of what does this structure consist? An external ear (the concha), calculated, like an ear-trumpet, to catch and collect the pulses of which we have spoken; in large quadrupeds, turning to the sound, and possessing a configuration, as well as motion, evidently fitted for the office: of a tube which leads into the head, lying at the root of this outward ear, the folds and sinuses thereof tending and conducting the air towards it of a thin membrane, like the pelt of a drum, stretched across this passage upon a bony rim: of a chain of moveable, and infinitely curious bones, forming a communication, and the only communication, that can be observed, between the membrane last mentioned and the interior channels and recesses of the skull of cavities, similar in shape and form to wind instruments of music, being spiral or portions of circles: of the eustachian tube, like the hole in a drum, to let the air pass freely into and out of the barrel of the ear, as the covering membrane vibrates, or as the temperature may be altered; the whole labyrinth hewn out of a rock; that is, wrought into the substance of the hardest bone of the body. This assemblage of connected parts constitutes together an apparatus, plainly enough relative to the transmission of sound, or of the impulses received from sound, and only to be lamented in not being better understood.

:

The communication within, formed by the small bones of the ear, is, to look upon, more like what we are accustomed to call machinery, than any thing I am acquainted with in animal bodies. It seems evidently designed to continue to wards the sensorium the tremulous motions which are excited in the membrane

of the tympanum, or what is better known by the name of the "drum of the ear." The compages of bones consists of four, which are so disposed, and so hinge upon one another, as that if the membrane, the drum of the ear, vibrate, all the four are put in motion together; and, by the result of their action, work the base of that which is the last in the series, upon an aperture which it closes, and upon which it plays, and which aperture opens into the tortuous canals that lead to the brain. This last bone of the four is called 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 office of the stapes is to repeat these vibrations. It is a repeating frigate, stationed more within the line.

From which account of its action may be understood, how the sensa tion of sound will be excited, by any thing which communicates a vibratory motion to the stapes, though not, as in all ordinary cases, through the intervention of the membrana tympani. This is done by solid bodies applied to the bones of the skull, as by a metal bar holden at one end between the teeth, and touching at the other end a tremulous body. It likewise appears to be done, in a considerable degree, by the air itself, even when this membrane, the drum of the ear, is greatly damaged. Either in the natural or preternatural state of the organ, the use of the chain of bones is to propagate the impulse in a direction towards the brain, and to propagate it with the advantage of a lever; which advantage consists in increasing the force and strength of the vibration, and at the same time diminishing the space through which it oscillates; both of which changes may augment or facilitate the still deeper action of the auditory nerves.

The benefit of the eustachian tube to

the organ, may be made out upon known pneumatic principles. Behind the drum of the ear is a second cavity, or barrel, called the tympanum. The eustachian tube is a slender pipe, but sufficient for the passage of air, leading from this cavity into the back part of the mouth. Now, it would not have done to have had a vacuum in this cavity; for, in that case, the pressure of the atmosphere from with out would have burst the membrane which covered it. Nor would it have done to

have filled the cavity with lymph or any other secretion; which would necessarily have obstructed, both the vibration of the membrane, and the play of the small bones. Nor, lastly, would it have done to have occupied the space with confined air, because the expansion of that air by heat, or its contraction by cold, would have distended or relaxed the covering membrane, in a degree inconsistent with the purpose which it was assigned to execute. The only remaining expedient, and that for which the eustachian tube serves, is to open to this cavity a communication with the external air. In one word; it exactly answers the purpose of the hole in a drum.

The membrana tympani itself likewise, deserves all the examination which can be made of it. It is not found in the ears of fish; 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 an obvious resemblance to the pelt or head of a drum, from which it takes its name. It resembles also a drum-head in this principal property, that its use depends upon its tension. Tension is the state essential to it. Now we know that, in a drum, the pelt is carried over a hoop, and braced as occasion requires, by the means of strings attached to its circumference. In the membrane of the ear, the same purpose is provided for, more simply, but not less mechanically, nor less successfully, by a different expedient, viz. by the end of a bone (the handle of the malleus) pressing upon its centre. It is only in very large animals that the texture of this membrane can be discerned. In the Philosophical Transactions for the year 1800 (vol. i.), Mr. Everard Home has given some curious observations upon the ear, and the drum of the ear of an elephant. He discovered in it, what he calls it a radiated muscle, that is, straight muscular fibres, passing along the membrane from the circumference to the centre; from the bony rim which surrounds it towards the handle of the malleus to which the central part is attached. This muscle he supposes to be designed to bring the membrane into unison with different sounds: but then he also discovered, that this muscle itself cannot act, unless the membrane be drawn to a stretch, and kept in a due state of tightness, by what may

be called a foreign force, viz. the action of the muscles of the malleus. Supposing his explanation of the use of the parts to be just, our author is well founded in the reflection which he makes upon it: "that this mode of adapting the ear to different sounds, is one of the most beautiful applications of muscles in the body; the mechanism is so simple, and the variety of effects so great."

In another volume of the Transactions above referred to, and of the same year, two most curious cases are related, of persons who retained the sense of hearing, not in a perfect, but in a very considerable degree, notwithstanding the almost total loss of the membrane we have been describing. In one of these cases, the use here assigned to that membrane, of modifying the impressions of sound by change of tension, was attempted to be supplied by straining the muscles of the outward ear. "The external ear,"

we

are told," had acquired a distinct motion upward and backward, which was observable whenever the patient listened to any thing which he did not distinctly hear: when he was addressed in a whisper, the ear was seen immediately to move; when the tone of voice was louder, it then remained altogether motionless."

It appears probable, from both these cases, that a collateral, if not principal, use of the membrane, is to cover and protect the barrel of the ear which lies behind it. Both the patients suffered from cold: one, "a great increase of deafness from catching cold;" the other, “ very considerable pain from exposure to a stream of cold air." Bad effects therefore followed from this cavity being left open to the external air; yet, had the Author of nature shut it up by any other cover than what was capable, by its texture, of receiving vibrations from sound, and, by its connexion with the interior parts, of transmitting those vibrations to the brain, the use of the organ, so far as we can judge, must have been entirely obstructed.

former watch, would account for the skill and attention evidenced in the watch, so produced; than it would account for the disposition of the wheels, the catching of their teeth, the relation of the several parts of the works to one another, and to their common end, for the suitableness of their forms and places to their offices, for their connexion, their operation, and the useful result of that operation. I do insist most strenuously upon the correctness of this comparison; that it holds as to every mode of specific propagation; and that whatever was true of the watch, under the hypothesis above mentioned, is true of plants and animals.

1. To begin with the fructification of plants. Can it be doubted but that the seed contains a particular organisation? Whether a latent plantule with the means of temporary nutrition, or whatever else it be, it encloses an organisation suited to the germination of a new plant. Has the plant which produced the seed any thing more to do with that organisation, than the watch would have had to do with the structure of the watch which was produced in the course of its mechanical movement? I mean, Has it any thing at all to do with the contrivance? The maker and contriver of one watch, when he inserted within it a mechanism suited to the production of another watch, was, in truth, the maker and contriver of that other watch. All the properties of the new watch were to be referred to his agency: the design manifested in it, to his intention; the art, to him as the artist: the collocation of each part, to his placing: the action, effect, and use, to his counsel, intelligence, and workmanship. In producing it by the intervention of a former watch, he was only working by one set of tools instead of another. So it is with the plant, and the seed produced by it. Can any distinction be assigned between the two cases; between the producing watch, and the producing plant; both passive, unconscious substances; both, by the organisa

tion which was given to them, producing their like, without understanding or design; both, that is, instruments?

2. From plants we may proceed to oviparous animals; from seeds to eggs. Now I say, that the bird has the same concern in the formation of the egg which she lays, as the plant has in that of the seed which it drops; and no other, nor greater. The internal constitution of the egg is as much a secret to the hen, as if the hen were inanimate. Her will cannot alter it, or change a single feather of the chick. She can neither foresee nor determine of which sex her brood shall be, or how many of either yet the thing produced shall be, from the first, very different in its make, according to the sex which it bears. So far, therefore, from adapting the means, she is not beforehand apprised of the effect. If there be concealed within that smooth shell a provision and a preparation for the production and nourishment of a new ani mal, they are not of her providing or preparing: if there be contrivance, it is none of hers. Although, therefore, there be the difference of life and perceptivity between the animal and the plant, it is a difference which enters not into the account. It is a foreign circumstance. It is a difference of properties not employed. The animal function and the vegetable function are alike destitute of any design which can operate upon the form of the thing produced. The plant has no design in producing the seed, no comprehension of the nature or use of what it produces: the bird with respect to its egg, is not above the plant with respect to its seed. Neither the one nor the other bears that sort of relation to what proceeds from them, which a joiner does to the chair which he makes. a cause, which bears this relation to the effect, is what we want, in order to account for the suitableness of means to an end, the fitness and fitting of one thing to another; and this cause the parent plant or animal does not supply.

$ 1. Reflections on the Heavens. The planets and comets which move round the Sun as their centre, constitute what is called the Solar System. Those planets which are near the Sun not only finish their circuits sooner, but likewise move faster in their respective orbits, than

Now

those which are more remote from him. The motions of the planets are all per formed from west to east, in orbits nearly circular. Their names, distances, bulks, and periodical revolutions, are as follow:

The Sun, an immense globe of fire, is placed near the common centre of the or

bits of all the planets and comets: and turns round his axis in 25 days 6 hours. His diameter is computed to be 763,000 miles.

goes

Mercury, the nearest planet to the Sun, round him in 87 days 23 hours, which is the length of his year. But, being seldom seen, and no spots appearing on his surface, the time of his rotation on his axis, is as yet unknown. His distance from the Sun is computed to be 32,000,000 of miles, and his diameter 2,600. In his course round the Sun, he moves at the rate of 95,000 miles every hour. His light and heat are almost seven times as great as ours; and the Sun appears to him almost seven times as large as to us.

Venus, the next planet in order, is computed to be 59,000,000 miles from the Sun; and by moving at the rate of 69,000 miles every hour in her orbit, she goes round the Sun in 225 of our days nearly. Her diameter is 7,906 miles; and by her motion upon her axis the inhabitants are carried 43 miles every hour.

The Earth is the next planet above Venus in the system. It is 82,000,000 miles from the Sun, and goes round him in a little more than 365 days. It travels at the rate of 1,000 miles every hour on its axis; is about 8,000 miles in diameter. In its orbit it moves at the rate of 58,000 miles every hour; which motion, though 120 times swifter than that of a cannon ball, is little more than half as swift as Mercury's motion in his orbit.

The Moon is not a planet, but only an attendant upon the Earth: going round it in a little more than 29 days, and round the Sun with it every year. The Moon's diameter is 2,180 miles, and her distance from the Earth's centre 240,000. She goes round her orbit in about 27 days, at the rate of near 2,300 miles every hour.

Mars is the planet next in order, being the first above the Earth's orbit. His distance from the Sun is computed to be 125,000,000 miles; and by travelling at the rate of 47,000 miles every hour, he goes round the Sun in about 687 of our days. His diameter is 4,444 miles, and by his diurnal rotation the inhabitants are carried 556 miles every hour.

Jupiter, the biggest of all the planets, is still higher in the system, being about 426,000,000 miles from the Sun; and going at the rate of 25,000 miles every hour in his orbit. His annual period is finished

in about 12 of our years. He is above 1,000 times as big as the Earth, for his diameter is 81,000 miles; which is more than ten times the diameter of the Earth. Jupiter turns round his axis in near ten hours, and his year contains upwards of 10,000 of our days. His equatorial inhabitants are carried nearly 26,000 miles every hour, besides the 25,000 above-mentioned by his annual motion.

Jupiter has four moons. The first goes round him in about two of our days, at the distance of 22,900 miles from his centre: the second performs its revolution in about three days and a half, at 364,000 miles' distance: the third in a little more than seven days, at the distance of 580,000 miles: and the fourth in near 17 days, at the distance of 1,000,000 miles from his centre.

Besides these moons, Jupiter is surrounded by faint substances, called belts, in which so many changes appear, that philosophers are not agreed either concerning their

nature or use.

Saturn, the next to Jupiter, is about 780,000,000 miles from the Sun; and travelling at the rate of 18,000 miles every hour; performs its annual circuit in about 30 years. Its diameter is 67,000 miles; and therefore it is near 600 times as big as the Earth.

This planet has five moons: the first goes round him in near two days, at the distance of 140,000 miles from its centre; the second in near three days, at the distance of 187,000 miles; the third in four days and a half, at the distance of 263,000 miles; the fourth in about 16 days, at the distance of 600,000 miles: and the fifth in about 80 days, at the distance of 1,800,000 miles.

Besides these moons, Saturn is attended with a thin broad ring, as an artificial globe is by an horizon; the nature and use of which are but little known at present.

Georgium Sidus, the remotest of all the planets yet discovered, is near 40,000 miles in diameter, and upwards of 83 years in performing its revolution. How many moons this planet is attended by is unknown. Two have been already discovered. And, if the ingenious ard indefatigable Mr. Herschel is spared with life and health, we may expect to be favoured with still further discoveries.

Every person who looks upon, and compares the systems of moons together, which

belong

belong to Jupiter, Saturn, and the Georgium Sidus, must be amazed at the vast magnitude of these three planets, and the noble attendance they have in respect to our little Earth; and can never bring himself to think, that an infinitely wise Creator should dispose of all his animals and vegetables here, leaving the other planets bare and destitute of rational creatures. Το suppose that he had any view to our benefit, in creating those moons, and giving them their motions round their respective primaries; to imagine, that he intended these vast bodies for any advantage to us, when he well knew that they could never be seen but by a few astronomers peeping through telescopes; and that he gave to the planets regular returns of day and night, and different seasons to all, where they would be convenient; but of no manner of service to us, except only what immediately regards our own planet, the Earth; to imagine, I say, that he did all this on our account, would be charging him impiously, with having done much in vain and as absurd, as to imagine that he has created a little sun and a planetary system with the shell of our Earth, and intended them for our use. These considerations amount to little less than a positive proof, that all the planets are inhabited for if they are not, why all this care in furnishing them with so many moons, to supply those with light, which are at the greater distances from the sun? Do we not see, that the further a planet is from the Sun, the greater apparatus it has for that purpose? save only Mars, which being but a small planet, may have moons too small to be seen by us. We know that the Earth goes round the sun, and turns round its own axis, to produce the vicissitudes of summer and winter by the former, and of day and night by the latter motion, for the benefit of its inhabitants. May we not then fairly conclude, by parity of reason, that the end and design of all the other planets is the same? And is not this agreeable to the beautiful harmony which exists throughout the universe? Surely it is and raises in us the most magnificent ideas of the Supreme Being, who is every where, and at all times present: displaying his power, wisdom, and goodness, among all his creatures! and distributing happiness to innumerable ranks of various beings!

The comets are solid opaque bodies,

with long transparent tails or trains, issuing from that side which is turned away from the Sun. They move about the Sun in very eccentric ellipses, and are of a much greater density than the Earth; for some of them are heated in every period to such a degree, as would vitrify or dissipate any substance known to us. Sir Isaac Newton computed the heat of the comet, which appeared in the year 1680, when nearest the Sun, to be 2,000 times hotter than redhot iron, and that, being thus heated, it must retain its heat until it comes round again, although its period should be more than 20,000 years; and it is computed to be only 575.

It is believed, that there are at least 21 comets belonging to our system, moving in all sorts of directions. But of all these the periods of three only are known with any degree of certainty. The first of the three appeared in the years 1531, 1607, 1682, and 1758, and is expected to appear every 75th year. The second of them appeared in 1532 and 1661, and may be expected to return in 1789, and every 129th year afterwards. The third, having last appeared in 1680, and its period being no less than 575 years, cannot return until the year 2225. This comet, at its greatest distance, is about 11,200,000,CCO miles from the Sun; and at its least distance from the Sun's centre, which is 49,000 miles, is within less than a third part of the Sun's semi-diameter from his surface. In that part of its orbit which is nearest the Sun, it flies with the amazing swiftness of 880,000 miles in an hour; and the Sun, as seen from it, appears an 100 degrees in breadth, consequently 40,000 times as large as he appears to us. The astonishing length that this comet runs out into empty space, suggests to our minds an idea of the vast distance between the Sun and the nearest fixed stars; of whose attractions all the comets must keep clear, to return periodically, and go round the Sun: and it shews us also, that the nearest stars, which are probably those that seem the largest, are as big as our Sun; and of the same nature with him: otherwise, they could not appear so large and bright to us as they do at such an immense distance.

The extreme heat, the dense atmosphere, the gross vapours, the chaotic state of the comets, seem at first sight to indicate them altogether unfit for the purposes of animal