subject very briefly, because it would require a whole week's lectures to enter with minuteness into it, we nevertheless have seen what are the general ideas. What I deduce from it is this, that if, throughout a book of such antiquity, such wisdom, such grandeur as the Bible; if throughout such a book we find these trees, flowers, animals, birds, fishes, and so on, mentioned not so much for themselves, as to convey spiritual instruction; and if we find that they in every place convey just the same meaning, although the writers were so various, although they lived at such widely separated intervals-then there must have been something behind these writers guiding their minds, and impelling them always to use the same kind of language, and the same kind of allusions. If we were to look at the history of our own country, and read some of old King Alfred's writings in the AngloSaxon, and some of venerable Bede, and then some of Chaucer, some of Shakspere, and now some of Macaulay, we should not find that they always used the objects of nature in the same sense; nor should we find that they used them to express some distinct and lofty spiritual idea. And yet that would embrace a period of only 800 years. How much vaster then the period occupied by the writers of the Bible, and when there were no books, not as now, plenty of libraries and means of intercommunication, but each writer living alone and detached from the others— how much more may we regard this as strange, wonderful, and suggestive of divine illumination on the part of those writers, when we find that, under all these disadvantages, still they concur. One of the proofs to my mind of the divine inspiration of the Bible, is to find that such trite and common things, as we consider them, the mere flowers of the field, and the mere trees of the forest, shall yet be used by these writers on the most solemn occasions, and always to mean precisely the same thing; and that we cannot possibly get the spirit of those prophetical

writings where they are mentioned, until we translate the allusions in the way I have briefly instanced. Just as by gathering the stalk of some large and beautiful plant, we secure a whole posy of flowers at once, and thence learn that one single juice has come up from the earth and fed all those flowers, however numerous and different, the same sap spreading throughout all, and making all the flowers alike; or just as we may look at a great oak tree with its millions of leaves, some of them many yards away from the others, yet all fed from the same sap, SO we may infer from the resemblances in the scripture allusions to natural objects, and from the identity in the meaning of all those allusions, that, like the clustered flowers, or the myriad of leaves, they have all come from one great central root, one stream of sap has fed them all; they are far apart, and yet they are all connected by one heart; one life blood circulates through the whole. That one

great fountain that has made them alike is that whence flow the streams that make glad the city of God. That is the inference I would draw; and that I think is the true way to apply the Natural History of the Bible.

ON THE STEREOSCOPE,

BY J. B. DANCER, ESQ., F.R.A.S.,

OPTICIAN, MANCHESTER.

[Read before the Manchester Photographic Society, at the Royal Institution, Jan. 10, 1856, Dr. FRANKLAND, F.R.S., &c. presidin;.]

Th Stereoscope derives its name from two Greek word signifying "Solid" and "I see." This instrument was first introduced to the scientific world by Eofessor Wheatstone, in a memoir published in the hilosophical transactions of the Royal Society, in the year 1838. The memoir is entitled "Contributins to the Physiology of Vision." The author stats that when an object is viewed at so great a distnce that the optic axes of both eyes are sensibly parlel, when directed towards it, the perspective projctions seen by each eye separately are similar, andhe appearance to the two eyes is precisely the sam as when the object is seen with one eye only. The is in such a case no difference between the visul appearance of an object in relief, and its perspecve projections on a plane surface; and hence pictial representations of distant objects, when

those circumstances which would prevent or disturb the illusion are excluded, may render such perfect resemblance of the objects they are intended to represent, as to be mistaken for them. The Diorama is an instance of this. But this similarity no longer exists when the object is placed so near the eyes that to view it the optic axes must converge. This fact may be easily verified by placing an object of three dimensions, such as an outline cube for instance, at a distance of eight or ten inches from the eyes. The appearances which this simple experiment will render so obvious, may be easily inferred from the established laws of perspective, for the same object in relief is, when viewed by a different eye, seen from two points of sight, at a distance from each other equal to the line joining the two eyes. This appears to have escaped the attention of every philosopher and artist who has treated on the subject of vision and perspective. This inattention is ascribed to the circumstance, that the results were contrary to the opinion which was generally maintained by optical writers, viz; that objects can be seen single only, when their images fall on corresponding points of the two retina. It will now be observed why i will be impossible for an artist to give a faithful epresentation of any near solid object, that is, to produce a painting which shall not be distinguished in the mind from the object itself. In a painting vewed by both eyes, two similar pictures are projected on the retinæ. On looking over the works of nany authors who might have been expected to make ome remarks relating to this subject, Professor Wheatstone was able to find but one, viz; a Treatie on Painting, by Leonardo da Vinci, in 1500. This great artist observes that a painting, though condcted with the greatest art and finished to the last prfection, both with regard to its contours, its light, its shadows, and its colours, can never shew a rlievo

equal to that of the natural objects, unless these be viewed at a distance, and with a single eye. (See Diagram.)

F

"For" says he, "if an object C be viewed by a single eye at A all objects in the space behind it, included as it were in a shadow ECF cast by a candlé at A, are invisible at A; but when the other eye at B is opened, part of these objects become visible to it; those only being hid from both eyes, that are included in the double shadow CD, cast by two lights at A and B, and terminated in D; the angular space EDG beyond D being always visible to both eyes. Thus the object C seen with both eyes, becomes as it were more transparent according to the usual definition of a transparent thing, namely, that which hides nothing beyond it. But this cannot happen when an object whose breadth is larger than that of the pupil, is viewed by a single eye. The truth of this observation is therefore evident, because a painted figure intercepts all the space behind its apparent place."

Had Leonardo da Vinci taken a cube instead of a sphere, he would have not only observed that the object obscured from the eye a different part of the more distant field of view, but the fact would also perhaps have forced itself upon his attention, that the object itself presented a different appearance to each eye. He failed to do this, and it was reserved