MAGNIFYING

, is the making of objects appear larger than they usually and naturally appear to the eye; whence convex lenses, which have the power of doing this, are called Magnifying Glasses.

The Magnifying power of dense mediums of certain figures, was known to the Ancients; though they were far from understanding the cause of this effect. Seneca says, that small and obscure letters appear larger and brighter through a glass globe filled with water; and he absurdly accounts for it by saying, that the eye slides in the water, and cannot lay hold of its object. And Alexander Aphrodisensis, about two centuries after Seneca, says, that the reason why apples appear large when immersed in water, is, that the water which is contiguous to any body is affected with the same quality and colour; so that the eye is deceived in imagining the body itself larger. But the first distinct account we have of the Magnifying power of glasses, is in the 12th century, in the writings of Roger Bacon, and Alhazen; and it is not improbable that from their observations the construction of spectacles was derived. In the Opus Majus of Bacon, it is demonstrated, that if a transparent body, interspersed between the eye and an object, be convex towards the eye, the object will appear magnified.

Magnifying Glass, in Optics, is a small spherical convex lens; which, in transmitting the rays of light, inflects them more towards the axis, and so exhibits objects viewed through them larger than when viewed by the naked eye. See Microscope.