Note:  Do not rely on this information. It is very old.

Solar Microscope

Solar Microscope is really a form of lantern used for obtaining upon a screen immensely-magnified images of minute objects. It is necessary that a small object should be enormously illuminated, for the greater the magnification obtained the less bright is the image compared to the object. For this reason it is convenient, when possible, to use the rays of the sun. A plane mirror is so placed that it reflects the sun's rays down the tube of the instrument, and the tube is often conveniently fixed in a hole in the shutter of a window. These rays, being parallel, are refracted by a powerful convex lens of short focal length to its principal focus, near which the object is placed. The rays then pass through another convex lens or set of lenses, from which they diverge on to the screen. This arrangement can only be used for objects through which the light can pass; if opaque objects are used, a device is employed by means of which the sun's rays, after passing through the first convex lens, are reflected by a second mirror on to the back of the object. and thence proceed to the magnifying lenses as before. Since the sun's rays are seldom at our disposal, another source of light has frequently to be used; the most brilliant substitute is the electric arc, but, in the absence of this, the oxyhydrogen limelight is employed.