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MICROSCOPE (Gr. µucp6s, small, asenre...

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Originally appearing in Volume V18, Page 392 of the 1911 Encyclopedia Britannica.
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MICROSCOPE (Gr. µucp6s, small, asenreiv, to %view) , an See also:optical See also:instrument for examining small See also:objects or details of such objects; it acts by making the angles of See also:vision under which the images appear greater than when the objects themselves are viewed by the naked See also:eye. Microscopes are distinguished as See also:simple and See also:compound. A simple microscope consists of a single See also:positive See also:lens, or of a lens See also:combination acting as a single lens, placed between the eye and the See also:object so that it presents a virtual and enlarged See also:image. The compound microscope generally consists of two positive lens systems, so arranged that the See also:system nearer the object (termed the See also:objective) projects a real enlarged image, which occupies the same See also:place relatively to the second system (the eyepiece or ocular) as does the real object in the simple micro-See also:scope. An image is therefore projected by the ocular from the real magnified image produced by the objective with increased magnification. See also:History of the Simple Microscope.—Any solid or liquid trans-See also:parent See also:medium of lenticular See also:form, having either one See also:convex and one See also:flat See also:surface or two convex surfaces whose axes are coincident, may serve as a " magnifier," the essential See also:condition being that it shall refract the rays which pass through it so as to cause widely diverging rays to become either parallel or but slightly divergent. Thus if a See also:minute object be placed on a slip of See also:glass, and a single drop of See also:water be placed upon it, the drop will See also:act as a magnifier in virtue of the convexity of its upper surface; so that when the eye is brought sufficiently near it (the glass being held horizontally) the object will be seen magnified. Again if a small hole be made in a thin See also:plate of See also:metal, and a minute drop of water be inserted in it, this drop, having two convex surfaces, will serve as a still more powerful magnifier. There is See also:reason to believe that the magnifying See also:power of transparent See also:media withconvex surfaces was very See also:early known. A convex lens of See also:rock-crystal was found by See also:Layard among the ruins of the See also:palace of Niinrud; See also:Seneca describes hollow See also:spheres of glass filled with water as being commonly used as magnifiers. The perfect See also:gem-cutting of the ancients could not have been attained without the use of magnifiers; and doubtless the artificers who executed these wonderful See also:works also made them.

Convex glass lenses were first generally used to assist See also:

ordinary vision as " See also:spectacles "; and not only were spectacle-makers the first to produce glass magnifiers (or simple microscopes), but by them also the See also:telescope and the compound microscope were first invented. During the See also:Thirty Years' See also:War the simple microscope was widely known. See also:Descartes (Dioptrique, 1637) describes microscopes wherein a See also:concave See also:mirror, with its concavity towards the object, is used, in See also:conjunction with a lens, for See also:illuminating the object, which is mounted on a point fixing it at the See also:focus of the mirror. Antony See also:van See also:Leeuwenhoek appears to be the first to succeed in grinding and polishing lenses of such See also:short focus and perfect figure as to render the simple microscope a better instrument for most purposes than any compound microscope then constructed. At that See also:time the " See also:compass " microscope was in use. One See also:leg of a compass carried the object, and the other the lens, the distance between the two being regulated by a See also:screw. Stands were also in use, permitting the manipulation of the object by See also:hand. See also:Robert See also:Hooke shaped the minutest of the lenses with which he made many of the discoveries recorded in his Micrographia from small glass globules made by fusing the ends of threads of spun glass; and the same method was employed by the See also:Italian See also:Father Di Torre. Early opticians and microscopists gave their See also:chief See also:attention to the improvement of the simple microscope, the principle of which we now explain.

End of Article: MICROSCOPE (Gr. µucp6s, small, asenreiv, to %view)

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