Note A — Front matter

In these directions "11⁄2 in. power" means a lens having a focus of 11⁄2 inches; "1⁄2 in. power" means a lens or combination of lenses having a focus of 1⁄2 inch; and so on. All the different powers mentioned in the directions may be obtained in the small-sized 3-lens, bellows form magnifier, either by using the lenses singly or combined in different ways. The magnifying power of any single lens or simple combination is easily found by dividing 10, by the focus in inches. Thus the magnifying power of a 1⁄2 in. lens is found in this way: 10÷1⁄2 = 10×2⁄1 20. The lens magnifies therefore 20 diameters i. e. makes an object appear twenty times as long and twenty times as broad as it is.