A DISCOURSE OF NATURAL THEOLOGY. INTRODUCTION. ARRANGEMENT OF SUBJECTS AND EXPLANATION OF ference to obligation; and then it relates to rights and duties, and is synonymous with ethical. It seems advisable to use it always in this sense, and to employ the words spiritual and mental in opposition to natural and material; and psychological, as THE Words Theology and Religion are often used applied to the science of mind, in opposition to phyas synonymous. Thus, Natural Theology and Na- sical. Again, a distinction is sometimes made betural Religion are by many confounded together.tween the intellectual and moral powers or faculties But the more accurate use of the words is that which makes Theology the science, and Religion its subject; and in this manner are they distinguished when we speak of a "professor of theology," and a "sense of religion." the former being directly those of the understanding, the latter those of the will, or, as they are often called, the "active powers," that is, the passions and feelings. It seems better to use the word active for this purpose as opposed to intellectual. Thus, There is, however, as regards Natural Theology, we shall have these general terms, spiritual or mena more limited use of the word, which confines it tal, as applied to the immaterial part of the creato the knowledge and attributes of the Deity, and tion, and psychological, as applied to the science regards the speculation concerning his will, and which treats of it. We shall next have a subdiviour own hopes from and duties towards him, as an- sion of the mental faculties into intellectual and acother branch of the science, termed Natural Reli-tire; both form the subjects of psychological science. gion, in contradistinction to the former. Dr. Paley Moral science, in its restricted sense, and properly hardly touches on this latter branch in his book, so called, will then denote that branch which treats there being only about one-sixtieth part devoted to of duties, and of what is implied in those duties, it, and that incidentally in treating of the attributes. their correlative rights; it will, in short, be ethical Indeed, though in the dedication he uses the word science. Religion as synonymous with Theology, the title and the arrangement of his discourse show that he generally employed the term Natural Theology in Its restricted sense. Bishop Butler, on the other hand, seems to have used Natural Religion in a sense equally restricted, but certainly little warranted by custom; for that portion of his work which treats of Natural Religion is confined to a future state and the moral government of God, as if he either held Natural Religion and Natural Theology to be two branches of one subject, or Natural Religion to be a branch of Natural Theology. The older writers, Clarke, Bentley, Derham, seem to have sometimes used the words indifferently, but never to have regarded Natural Religion in the restricted acceptation. The ancients generally used Religion in a qualified sense, either as connected with an obligation, or as synonymous with superstition. This Discourse is not a treatise of Natural Theology: it has not for its design an exposition of the doctrines whereof Natural Theology consists. But its object is, first, to explain the nature of the evidence upon which it rests-to show that it is a science, the truths of which are discovered by induction, like the truths of Natural and Moral Philosophy-that it is a branch of science partaking of the nature of each of those great divisions of human knowledge, and not merely closely allied to them both. Secondly, the object of the Discourse is to explain the advantages attending this study. The work, therefore, is a Logical ore. We have commented upon the use of the terms Theology and Religion. As it is highly desirable to keep scientific language precise, and always to use the same terms in the same sense, we shall now further observe upon the word "moral" in relation to science or faculties. It is sometimes used to denote the whole of our mental faculties, and in opposition to natural and physical, as when we speak of "moral science," "moral truths;""moral philosophy." But it is also used in contradistinction to "intellectual" or "mental," and in connection with or in re95* Thus, the science of mind-say Metaphysical science-may be said to consist of two great branches, the one of which treats of existences, the other of duties. The one accordingly has been termed, with great accuracy, Ontology, speaking of that which is; the other, Deontology, speaking of that which ought to be. The former, however, comprehends properly all physical, as well as mental science.The division which appears upon the whole most convenient is this: That metaphysical science, as contradistinguished from physical, is either psychological, which treats of the faculties both intellectual and active, but treats of existences only; or moral, which treats of rights and duties, and is distinguishable from psychological, though plainly connected with it nearly as corollaries are with the propositions from whence they flow. Then physical truths, in one respect, come under the same head with the first branch of metaphysical truths. Physical as well as psychological science treats of existences, while moral science alone treats of duties. According to a like arrangement, Natural Theology consists of two great branches, one resembling Ontology, the other analogous to Deontology. The former comprehends the discovery of the existence and attributes of a Creator, by investigating the evidences of design in the works of the creation, material as well as spiritual. The latter relates to the discovery of his will and probable intentions with regard to his creatures, their conduct, and their duty. The former resembles the physical and psychological sciences, and treats of the evidences of design, wisdom, and goodness exhibited both in the natural and spiritual worlds. The latter resembles rather the department of moral science, as distinguished from both physical and psychological. thus consider the science of Natural Theology as consisting, like all inductive science, of three compartments, Natural, Mental, and Moral; or, taking the Greek terms, Physical, Psychological, and Ethical. We may This classification is convenient, and its grounds 785 are very fit to be premised-at the same time that we must admit the question to be one only of classification and technology. Having so stated the divisions of the subject and the meaning of the terms used in relation to those divisions, I shall assume this arrangement and adhere to this phraseology, as convenient, though far from representing it to be the best. In such discussions it is far more important to employ one uniform and previously explained language or arrangement, than to be very curious in adopting the best. No classification, indeed, can, from the nature of things, be rigorously exact. All the branches of science, even of natural philosophy, much more of metaphysical, run into each other, and are separated by gradations rather than by lines of demarcation. Nor could any scientific language we possess help breaking down under us in an attempt to maintain a perfectly logical arrangement.* ANALYSIS OF THE WORK. The order of this Discourse is thus set out: The SECOND PART treats of the advantages derived from the study of the science. the mental constitution of living creatures, and in treating of the Soul's Immortality, it becomes necessary to enter more at large into the subject, and therefore, the third and the fifth sections are not, like the others, mere logical discourses in which the doctrines of Natural Theology are assumed rather than explained. The subjects of those two sections have not been sufficiently handled in professed treatises upon Natural Theology, which have been almost wholly confined to the first branch of the science-the proofs of the Deity's existence and attributes-and to the physical portion of that branch. This defect I have endeavored to supply. The Second Part, which treats of the advantages of the study, consists of the sections. The first shows that the precise kind of pleasure derived from the investigation of scientific truths is derived from this study. The second treats of the pleasures which are peculiar to this study. The third treats of the connection of Natural with Revealed Religion. PART THE FIRST. NATURE OF THE SCIENCE, AND OF ITS The former part is divided into seven sections.-The first is introductory, and treats of the kind of evidence by which the truths of Physical and Psychological science are investigated, and shows that there is as great an appearance of diversity between the manner in which we arrive at the knowledge of different truths in those inductive sciences, as there is between the nature of any such inductive INTRODUCTORY VIEW OF THE METHOD OF INVESTIGATION investigation, and the proofs of the ontological branches of Natural Theology. But that diversity is proved to be only apparent; and hence it is inferred, that the supposed difference of the proofs of Natural Theology may also be only ap parent. SECTION I. PURSUED IN THE PHYSICAL AND PSYCHOLOGICAL SCI- THE faculties, as well as the feelings of the human mind, its intellectual, as well as its active powers, are employed without any intermission, although with varying degrees of exertion, in cne of two The second section continues the application of ways; either in regard to some object immediately this argument to the Physical branch of Natural connected with the supply of our wants, or in reTheology, and shows further proofs that the first gard to subjects of mere contemplation. The first branch of Natural Theology is as much an induc- class of exertions relates to all the objects or necestive science, as Physics or Natural Philosophy.sity, of comfort, or of physical enjoyment: in the The first section compares the ontological branches of Natural Theology with all inductive science, physical as well as psychological. The second compares the physical branch of Natural Theology with physical science only. The third section compares the psychological branch of Natural Theology with psychological science, and shows that both rest alike upon induc tion. The fourth section shows that the argumentum a priori is unsound in a great degree-that it is insufficient for the purpose to which it is applied that it serves only to a limited extent-and that to this extent it is in reality not distinguishable from induction, or the argumentum a posteriori. The fifth section treats of the second or Moral, the deontological branch of Natural Theology, and shows that it rests upon the same kind of evidence with moral science, and is, strictly speaking, as much a branch of inductive knowledge. The sixth section examines the doctrines of Lord Bacon respecting Final Causes, and shows that he was pot adverse to the speculation when kept within due bounds. The seventh section examines the true nature of inductive analysis and synthesis, and shows some important errors prevailing on this subject. In treating of the proofs of design displayed by Note I. fursuit of these, the powers of the understanding, or the passions, or both together, are with nearly the whole mankind employed during the greater portion of their existence, and with the bulk of mankind, during almost the whole of their existence. The other class of mental exertions, which engrosses but a very few men for the greater part of their lives, and occupies the majority only occasionally and at considerable intervals, comprehends within its scope all the subjects of meditation and reflection, of merely speculative reasoning and discussion: it is composed of all the efforts which our understanding can make, and all the desires which we can feel upon subjects of mere science or taste, matters which begin and end in intellectual or moral gratification. branches of exertion have an intimate connection It is unquestionably true that these two grand with each other. The pursuits of science lend contical exercise of the mental powers constantly furstant assistance to those of active life; and the practhers the progress of science merely speculative. But the two provinces are nevertheless perfectly The corollary from a scientific discovery may be distinguishable, and ought not to be confounded.the improvement of a very ordinary machine or a common working tool; yet the establishment of the speculative truth may have been the primary object of the philosopher who discovered it; and to learn that truth is the immediate purpose of him who studies the philosopher's system. So, the better regulation of the affections or the more entire control of the passions, may be the result of an acquaintance of our mental constitution; but the object of him who studies the laws of mind is merely to become acquainted with the spiritual part of our nature. In like manner, it is very possible that the knowledge of a scientific truth may force itself upon one whose faculties or feelings are primarily en--and those objects of which we only know the exgaged in some active exertion. Some physical law, or some psychological truth, may be discovered by one only intent upon supplying a physical want, or obtaining a mental enjoyment. But here, as in the former case, the scientific or speculative object is incidental to the main pursuit; the matter of contemplation is the corollary, the matter of action the pro-him to be so far capable of reflection, as to know position. certainly think he had seized on a sound principle of classification, if he should divide the objects with which philosophy, Natural and Mental, is conversant, into two classes-those objects of which we know the existence by our senses or our consciousness; that is, external objects which we see, touch, taste, and smell, internal ideas which we conceive or remember, or emotions which we feel istence by a process of reasoning, founded upon something originally presented by the senses or by consciousness. This superficial reasoner would range under the first of these heads the members of the animal, vegetable, and mineral kingdoms; the heavenly bodies; the mind-for we are supposing that the proof of the mind's separate existence is, at the least, as short, plain, and direct as that of the body, or of external objects. Under the second head he would range generally whatever objects of examination are not directly perceived by the senses, or felt by consciousness. The merely contemplative pursuits, which thus form one of the great branches of mental exertion, seem again to be divisible into two classes, by a line that, to a careless observer, appears sufficiently defined. The objects of our inquiry and meditation appear to be either those in the physical and spi- But a moment's reflection will show both how ritual worlds, with which we are conversant through very short a way this classification would carry our our senses, or by means of our internal conscious- inaccurate logician, and how entirely his principle ness; or those things with which we are made ac- fails to support him even during that little part of quainted only by reasoning-by the evidence of the journey. Thus, the examination of certain vithings unseen and unfelt. We either discuss the sible objects and appearances enables us to ascertain properties and relations of actually perceived and the laws of light and of vision. Our senses teach us conceived beings, physical and mental-that is, the that colors differ, and that their mixture forms other objects of sense and of consciousness; or we carry hues; that their absence is black, their combination our inquiries beyond those things which we see and in certain proportions, white. We are in the same feel; we investigate the origin of them and of our-way enabled to understand that the organ of vision selves; we rise from the contemplation of nature and of the spirit within us, to the first cause of all, both of body and of mind. To the one class of speculation belong the inquiries how matter and mind are framed, and how they act; to the other class belong the inquiries whence they proceed, and whither they tend. In a word, the structure and relations of the universe form the subject of the one branch of philosophy, and may be termed Human Science; the origin and destiny of the universe form the subject of its other branch, and is termed Divine Science, or Theology. It is not to be denied that this classification may be convenient; indeed, it rests upon some real foundation, for the speculations which compose these two branches have certain common differences and common resemblances. Yet it is equally certain, that nothing but an imperfect knowledge of the subject, or a superficial attention to it, can permit us to think that there is any well-defined boundary which separates the two kinds of philosophy; that the methods of investigation are different in each; and that the kind of evidence varies by which the truths of the one and of the other class are demonstrated. The error is far more extensive in its consequences than a mere inaccuracy of classification, for it materially impairs the force of the proofs upon which Natural Theology rests. The proposition which we would place in its stead is, that this science is strictly a branch of inductive philosophy, formed and supported by the same kind of reasoning upon which the Physical and Psychological sciences are founded. This important point will be established by a fuller explanation; and we shall best set about this task by showing, in the first place, that the same apparent diversity of evidence exists in the different subjects or departments of the branch which we have termed Human science. It seems to exist there on, a superficial examination: if a closer scrutiny puts that appearance to flight, the inference is legitimate, that there may be no better ground for admitting an essential difference between the foundations of Human science and Divine. The careless inquirer into physical truth would performs its functions by a natural apparatus resembling, though far surpassing, certain instruments of our own constructing, and that therefore it works on the same principles, But that light, which can be perceived directly by none of our senses, exists, as a separate body, we only infer by a process of reasoning from things which our senses do perceive. So we are acquainted with the effects of heat; we know that it extends the dimensions of whatever matter it penetrates; we feel its effects upon our own nerves when subjected to its operation; and we see its effects in augmenting, liquefying, and decomposing other bodies; but its existence as a separate substance we do not know, except by reasoning and by analogy. Again, to which of the two classes must we refer the air? Its existence is not made known by the sight, the smell, the taste; but is it by the touch? Assuredly a stream of it, blown upon the nerves of touch, produces a certain effect; but to infer from thence the existence of a rare, light, invisible, and impalpable fluid, is clearly an operation of reasoning, as much as that which enables us to infer the existence of light or heat from their perceptible effects. But furthermore, we are accustomed to speak of seeing motion; and the reasoner whom we are supposing would certainly class the phenomena of mechanics, and possibly of dynamics generally, including astronomy, under his first head, of things known immediately by the senses. Yet assuredly nothing can be more certain than that the knowledge of motion is a deduction of reasoning, not a perception of sense; it is derived from the comparison of two positions; the idea of a change of place is the result of that comparison attained by a short process of reasoning; and the estimate of velocity is the result of another process of reasoning and of recollection. Thus, then, there is at once excluded from the first class almost the whole range of natural philosophy. But are we quite sure that any thing remains which, when severely examined will stand the test? Let us attend a little more closely to the things which we have passed over hastily, as if admitting that they belonged to the first class. SECTION II. COMPARISON OF THE PHYSICAL BRANCH OF NATURAL It is said that we do not see light, and we cer- | tween the method of investigation, the nature of the tainly can know its existence directly by no other evidence, in the two departments of speculation? sense but that of sight, but that we see objects va- Although this Preliminary Discourse, and indeed riously illuminated, and therefore that the existence the work itself which it introduces, and all the illusof light is an inference of reason, and the diversity trations of it, are calculated throughout to furnish of color an object of sense. But the very idea of di- the answer to the question, we shall yet add a few versity implies reasoning, for it is the result of a particulars in this place, in order to show how precomparison, and when we affirm that white light is cisely the same fallacy which we have been expos composed of the seven primary colors in certaining, in regard to the classification of objects in ordiproportions, we state a proposition which is the re-nary scientific research, gives rise to the more gesult of much reasoning-reasoning, it is true, found-neral classification or separation of all science into ed upon sensations or impressions upon the senses; two distinct branches, Human and Divine, and how but not less founded upon such sensations is the rea- erroneous it is to suppose that these two branches soning which makes us believe in the existence of a rest upon different foundations. body called light. The same may be said of heat, and the phenomena of heated bodies. The existence of heat is an inference from certain phenomena, that is, certain effects produced on our external senses by certain bodies or certain changes which those senses undergo in the neighborhood of those bodies; but it is not more an inference of reason THE two inquiries-that into the nature and conthan the proposition that heat extends or liquefies stitution of the universe, and that into the evidence bodies; for that is merely a conclusion drawn from of design which it displays; in a word, physics and comparing our sensations occasioned by the exter-psychology, philosophy, whether natural or mental, nal objects placed in varying circumstances. and the fundamental branch of Natural Theology, But can we say that there is no process of reason- are not only closely allied one to the other, but are to a ing even in the simplest case which we have sup- very considerable extent identical. The two paths of posed our reasoncr to put; the existence of the three investigation for a great part of the way completely kingdoms, of nature, of the heavenly bodies, of the coincide. The same induction of facts which leads mind? It is certain that there is in every one of us to a knowledge of the structure of the eye, and these cases a process of reasoning. A certain sen- its functions in the animal economy, leads us to the sation is excited in the mind through the sense of knowledge of its adaptation to the properties of light. vision; it is an inference of reason that this must It is a truth of physics, in the strictest sense of the have been excited by something, or must have had word, that vision is performed by the eye refracting a cause. That the cause must have been external, light, and making it converge to a focus upon the may possibly be allowed to be another inference retina; and that the peculiar combination of its which reason could make unaided by the evidence lenses, and the different materials they are comof any other sense. But to discover that the cause posed of, correct the indistinctness which would was at any the least distance from the organ of vi- otherwise arise from the different refrangibility of sion, clearly required a new process of reasoning, light; in other words, make the eye an achromatic considerable experience, and the indications of other instrument. But if this is not also a truth in Natusenses; for the young inan whom Mr. Cheselden ral Theology, it is a position from which, by the couched for a cataract, at first believed that every shortest possible process of reasoning, we arrive at thing he saw touched his eye. Experience and rea- theological truth; namely, that the instrument so soning, therefore, are required to teach us the ex- successfully performing a given service by means istence of external objects; and all that relates to of this curious structure, must have been formed their relations of size, color, motion, habits, in a with a knowledge of the properties of light. The word, the whole philosophy of them, must of course position from which so easy a step brings us to this be the result of still longer and more complicated doctrine of Natural Theology was gained by strict processes of reasoning. So of the existence of the induction. Upon the same evidence which all namind: although undoubtedly the process of reason-tural science rests on, reposes the knowledge that ing is here the shortest of all, and the least liable to the eye is an optical instrument: this is a truth deception, yet so connected are all its phenomena common to both physics and theology. Before the with those of the body, that it requires a process of days of Sir Isaac Newton, men knew that they saw abstraction alien from the ordinary habits of most by means of the eye, and that the eye was conmen, to be persuaded that we have a more undeni-structed upon optical principles; but the reason of able evidence of its separate existence than we even have of the separate existence of the body. It thus clearly appears that we have been justified in calling the classifier whose case we have been supposing, a careless inquirer, a superficial reasoner, an imperfect logician; that there is no real foundation for the distinction which we have supposed him to take between the different objects of scientific investigation; that the evidence upon which our assent to both classes of truths reposes is of the same kind, namely, the inferences drawn by reasoning from sensations or ideas, originally presented by the external senses or by our inward conscious ness. If, then, the distinction which at first appeared solid, is found to be without any warrant in the different kinds of Humane Science, has it any better grounds when we apply it to draw the line between that branch of philosophy itself, and the other which has been termed Divine, or Theology? In other words, is there any real, any specific difference be its peculiar conformation they knew not, because they were ignorant of the different refrangibility of light. When his discoveries taught this truth, it was found to have been acted upon, and consequently known by the Being who created the eye. Still our knowledge was imperfect; and it was reserved for Mr. Dollond to discover another law of nature-the different dispersive powers of different substances, which enabled him to compound an object-glass that more effectually corrected the various refrangibility of the rays. It was now observed that this truth also must have been known to the maker of the eye; for upon its basis is that instrument, far more perfect than the achromatic glass of Dollond, framed.These things are truths in both physics and theology; they are truths taught us by the self-same process of investigation, and resting upon the self-same kind of evidence. When we extend our inquiries, and observe the varieties of this perfect instrument, we mark the adaptation of changes to the diversity of circum stances; and the truths thus learnt are in like man- | uppermost, roll the egg how you will; consequently, ner common to Physical and Theological science; the chick is always kept nearest to the breast or that is, to Natural History, or Comparative Anato- belly of the mother while she is sitting. Suppose, my, and Natural Theology. then, that any one acquainted with the laws of moThat beautiful instrument, so artistly contrived tion had to contrive things so as to secure this pothat the most ingenious workman could not ima-sition for the little speck or sac in question, in order gine an improvement of it, becomes still more in- to its receiving the necessary heat from the henteresting and more wonderful, when we find that its could he proceed otherwise than by placing it in the conformation is varied with the different necessities lighter liquid, and suspending that liquid in the of each animal. If the animal prowls by night, we heavier, so that its centre of gravity should be above see the opening of the pupil, and the power of con- the line or plane of suspension? Assuredly not; centration in the eye increased. If an amphibious for in no other way could this purpose be accomanimal has occasionally to dive into the water, with plished. This position is attained by a strict inducthe change of the medium through which the rays tion; it is supported by the same kind of evidence pass, there is an accommodation in the condition of on which all physical truths rest. But it leads, by the humors, and the eye partakes of the eye both of a single step, to another truth in Natural Theology; the quadruped and the fish. that the egg must have been formed by some hand skilful in mechanism, and acting under the knowledge of dynamics. The forms of the bones and joints, and the tendons or cords which play over them, afford a variety of instances of the most perfect mechanical adjustment. Sometimes the power is sacrificed for rapidity of motion, and sometimes rapidity is sacrificed for power. Our knee-pan, or patella, throws off the tendon which is attached to it from the centre of motion, and therefore adds to the power of the muscles of the thigh, which enable us to rise or to leap. We have a mechanism of precisely the same kind in the lesser joints, where the bones, answering the purposes of the patella, are formed of a diminutive size. In the toes of the ostrich, the material is different, but the mechanism is the same. An elastic cushion is placed between the tendon and the joint, which, whilst it throws off the tendon from the centre of motion, and therefore adds to the power of the flexor muscle, gives elasticity to the bottom of the foot. And we recognise the intention of this when we remember that this bird does not fly, but runs with great swiftness, and that the whole weight rests upon the foot, which has but little relative breadth; these elastic cushions serving, in some degree, the same office as the elastic frog of the horse's hoof, or the cushion in the bottom of the camel's foot. So, having contemplated the apparatus for protection in the human eye, we find that in the lower animals, who want both the accessory means of cleaning the eye and the ingenuity to accomplish it by other modes than the eyelids, an additional eyelíd, a new apparatus, is provided for this purpose. Again, in fishes, whose eye is washed by the element in which they move, all the exterior apparatus is unnecessary, and is dismissed; but in the crab, and especially in that species which lies in mud, the very peculiar and horny prominent eye, which every body must have observed, would be quite obscured were it not for a particular provision. There is a little brush of hair above the eye, against which the eye is occasionally raised to wipe off what may adhere to it. The form of the eye, the particular mode in which it is moved, and, we may say, the coarseness of the instrument compared with the parts of the same organ in the higher class of animals, make the mechanism of eyelids and of lachrymal glands unsuitable. The mechanism used for this purpose is discovered by observation and reasoning; that it is contrived for this purpose is equally a discovery of observation and reasoning. Both propositions are strictly propositions of physical science. The web-foot of the water-fowl is an inimitable paddle; and all the ingenuity of the present day exerted to improve our steam-boats makes nothing to approach it. The flexor tendon of the toes of the duck is so directed over the heads of the bones of the thigh and leg, that it is made tight when the creature bends its leg, and is relaxed when the leg is stretched out. When the bird draws its foot up, the toes are drawn together, in consequence of the bent position of the bones of the leg pressing on the tendon. When, on the contrary, it pushes the leg out straight, in making the stroke, the tendons are relieved from the pressure of the heel-bone, and the toes are permitted to be fully extended, and at the same time expanded, so that the web between them meets the resistance of a large volume of water. The same remarks apply to every part of the animal body. The use to which each member is subservient, and the manner in which it is enabled so to perform its functions as to serve that appointed use, is learnt by an induction of the strictest kind. But it is impossible to deny, that what induction thus teaches forms the great bulk of all Natural Theology. The question which the theologian always puts upon each discovery of a purpose manifestly accomplished, is this: "Suppose I had this operation to perform by mechanical means, and were acquainted with the laws regulating the action of matter, should I attempt it in any other way than I here see practised?" If the answer is in the negative, the consequence is irresistible that some power, capable of acting with design, and possessing the supposed knowledge, employed the means which we see used. But this negative answer is the result of reasoning founded upon induction, and rests upon the same evidence whereon the doctrines of all physical science are discovered and believed. And the inference to which that negative answer so inevitably leads is a truth in Natural Theology; for it is only another way of asserting that design and knowledge are evinced in the works and functions of nature. It may further illustrate the argument to take one or two other examples. When a bird's egg is examined, it is found to consist of three parts; the chick, the yelk in which the chick is placed, and the white in which the yelk swims. The yeĺk is lighter than the white; and it is attached to it at two points, joined by a line or rather plane, below the centre of gravity of the yelk. From this arrangement, it must follow that the chick is always grain. In another class of birds, those which roost upon the branch of a tree, the same mechanism answers another purpose. The great length of the toes of these birds enables them to grasp the branch; yet were they supported by voluntary effort alone, and were there no other provision made, their grasp would relax in sleep. But, on the contrary, we know that they roost on one foot, and maintain a firm attitude. Borelli has taken pains to explain how this is. The muscle which bends the toes lies on the fore part of the thigh, and runs over the joint which corresponds with our knee-joint: from the fore part its tendon passes to the back part of the leg, and over the joint equivalent to our heel-bone: it * Hence called Sesamoid from Sesamum, a kind of |