muscle. The contraction of this muscle diminishes the tension of the lens; and its surfaces, chiefly the front one, become more convex. The healthy eye, when at rest, sees distant objects distinctly; by contraction of the ciliary muscle it is accommodated to discern those which are near; thus, the images of objects, whether near or far off, are brought to a focus on the back of the dark chamber of the eye. This mechanism is sometimes disarranged, defects and different conditions of accommodation produce squinting, short sight, long sight, and no man can be said to have perfect sight. The failures are partly the result of our artificial way of life, partly of changes wrought by old age. The chromatic aberration of the eye is that defect by which, all the colours not being brought to a focus, a "dispersive image" is formed. In common use it is of little or no ill effect; and in scientific use, the fact of the eye not being achromatic is guarded against. Another defect is known as spherical aberration: the cornea of most human eyes is not a perfect symmetrical curve, but is variously bent in different directions. Owing to these two defects, chromatic and spherical aberration, we cannot see vertical and horizontal lines at the same distance perfectly clearly at once: in all eyes, it may be said, there are distinct though often slight deviations from accurate centreing. In consequence of this ill centreing, the image, say of a star, is not a single illuminated. point; but the focus is irregularly radiated, and the rays which we see around stars and other distant lights are images of the radiated structure of our lens. Another defect: the crystalline lens, though it looks so beautifully clear, is not optically uniform in structure. There are shadows and dark spots, chiefly due to the fibres and spots in the lens; corpuscles also, and folds of membranes floating in the vitreous humour, cause musca volitantes in our vision; so called, because they move with the movement of our eye. Lastly, there is that blind spot, the break or gap in the retina, where the optic nerve enters; and those smaller gaps of vision, caused by the minute shadows of the blood-vessels of the retina cast on the field of vision. These defects no more prove that the eye is not good, than moral evil demonstrates that no Divine government exists. Our contention is not simply, the eye is good enough—it might be contended that the world is good enough; but we contend that while Nature testifies of eternal power and Godhead (Rom. i. 20), it attests the mysterious fact that Nature partakes of vanity and trouble (Rom. viii. 20-23). Science, therefore, actually confirms Scripture as to the imperfection of all things: nevertheless, the defects described, which would be very troublesome in an artificial camera obscura, are not any real trouble or hindrance in the eye; in fact, it is very difficult to find some of them. We not only have two eyes, so one makes up for the defects of the other; but, as we are continually moving them, the field of vision is freed from those defects which irregularity and imperfection might occasion. Our eye has not only a very large field of vision, and all other optical instruments a small field which becomes smaller with the increased size of the image; but it is necessary for the image on the retina to be exactly over a very small surface merely, namely, that of the yellow spot. In this small part of the field, our power of vision is so accurate that it can distinguish the distance between two points, of only one minute angular magnitude, a distance equal to the sixtieth part diameter of the thickness of the finger-nail. Hence, the image which we receive by the eye, is a picture minutely and perfectly elaborated in the centre, with a rough sketching in all around. Every instant, with rapidity, we turn the eye from one point to another in the field of vision; and this rapidity, with perfection of the smaller field, and the rough sketching in of the larger, make the eye far superior to every other optical instrument. We turn our eye to one thing at a time; so soon as this has been taken in, we hasten to another; the sense of vision accomplishes all that is necessary. Whatever we want to look at we see accurately, and so quick is the transition from one object to another, that practically we possess the same advantages as if we viewed the whole field of vision at once. Just as quickly as the eye turns up or down, from side to side, the accommodation changes to bring the object looked at into focus; thus both near and distant objects pass with rapid succession into accurate view. The Lecture at Sion College. 45I eye shows them so rapidly that most people, who have not thought how they see, are not aware of any change at all. By the eye alone we discern the wealth of form and colour among flowers, the distant landscapes of our earth, all the varieties of sunlight that reveals them, and know the countless shining worlds that fill immeasurable space. It is the unsurpassed model of opticians, philosophers extol it as an organism full of wonders, poets and orators justly celebrate its praise. The following words are printed in an address on scientific education:" Some time ago I attended a large meeting of the clergy, for the purpose of delivering an address which I had been invited to give. I spoke of some of the most elementary facts in physical science, and of the manner in which they directly contradict certain of the ordinary teachings of the clergy. The result was, that, after I had finished, one section of the assembled ecclesiastics attacked me with all the intemperance of pious zeal, for stating facts and conclusions which no competent judge doubts; while, after the first speakers had subsided, amidst the cheers of the great majority of their colleagues, the more rational minority rose to tell me that I had been taking wholly superfluous pains, that they already knew all about what I had told them, and perfectly agreed with me. A hard-headed friend of mine, who was present, put the not unnatural question-Then why don't you say so in your pulpits?' to which inquiry I heard no reply. In fact, the clergy are at present divisible into three sections: an immense body who are ignorant and speak out; a small proportion who know and are silent; and a minute minority who know and speak according to their knowledge." The assembled ecclesiastics were not irritated at the statement "of facts and conclusions which no competent judge doubts:" their "pious zeal" was aroused by the assertion that these facts were in opposition to Revealed Truth. It is no wonder, when a learned professor insults the common sense and attainments of educated men-men in the habit of encountering unbelief and misbelief that they regard him as trifling with them; and say, with some little warmth-"No one doubts the elementary facts in physical science:" no wonder that the more courteous minority think and say-"We know all about what you have told us." The same professor writes flippantly, as if glad to announce his belief that Christianity is false. "In this nineteenth century, as at the dawn of modern physical science, the cosmogony of the semi-barbarous Hebrew is the incubus of the philosopher and the opprobrium of the orthodox. . . . Extinguished theologians lie about the cradle of every science as the strangled snakes beside that of Hercules; and history records that whenever science and orthodoxy have been fairly opposed, the latter has been forced to retire from the lists, bleeding and crushed, if not annihilated; scotched if not slain. But orthodoxy is the Bourbon of the world of thought. It learns not, neither can it forget; and though, at present, bewildered and afraid to move, it is as willing as ever to insist that the first chapter of Genesis contains the beginning and the end of sound science; and to visit with such petty thunderbolts as its half-paralysed hands can hurl, those who refuse to degrade Nature to the base of primitive Judaism" ("The Origin of Species," Westminster Review, April, 1860). The professor reminds us "Intelligence and courtesy not always are combined, Often in a golden house a wooden room you find." * "The fire of rage was in him, and 'twere good You leaned unto his sentence with what patience He states the saddest thing in the world—if it be true. We are a duped race led by knaves, or fools taught by maniacs. Is it possible any true man can be glad that there has been no revelation of God to men? that Christ's spotless life, wise words, mighty deeds, possess no truth, no reality? that all good men, past and present, who made the world better, who enlarged our views and use of Nature, made life happier, death more peaceable and hopeful, were deluded? Such conviction were enough to make the merriest-hearted weep and mourn. Every one, even but a little acquainted with history, is well aware that science and true doctrine are never opposed. Science and True Doctrine not Contrary. 453 Religious, intellectual, industrial progress culminates in the most splendid series of researches when God's glory and man's welfare are the motives which unitedly urge devout and thoughtful men to fearless investigation of truth. The fanatical and ignorant, in all ages, have been rash, violent, unjust, cruel. They seem to think that the face of Truth is full of dread. They are afraid to unveil her statue, they say— "We will none of this dogma, none of that science." The great and good have no fears that, perchance they may encounter a ghastly death's head: they know that the beaming countenance of the image of Truth, raised by God Almighty, is the face of Jesus Christ where Divine glory and human purity meet in rarest beauty. Feeling their way, as best they can, into that limited portion of facts lying within their reach, they interpret the Two Books of Revelation, the Works of God and the Word of God, as they are-not as men might like them to be. The medieval conception of the material and spirit world, as presented by Dante, was somewhat in harmony with the best science and the urgent wants of the time; but the Copernican revolution displaced all that, and scientific light enables us more largely to understand Providence, and to see that God's plan is written in the physical laws of the universe and in the pure morality of Holy Scripture. It is time that all good and true men, whether students of Science or of Religion, put down every feeling of antagonism. The roll of names, illustrating the annals of science, of itself ennobles that pursuit; the Newtons, the Wallises, the Wollastons, the Davys, the Rumfords, the Faradays, confer imperishable renown. Will not praise be added to their successors if, enfranchised from narrowness, they recognise those other lights of charities and moralities which shine in the path of human life that wayfarers may walk cheerily onward to their future home? For those who would falsify our high lineage, make us cunning casts in clay," and require that we discard, as a romantic delusion, the ennobling conviction that we are little lower than the angels; we have an answer in the words of |