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54 MCINTOSH BATTERY AND OPTICAL CO., CHICAGO, ILL., IT. S. A. MAGNIFYING POWERS—In Diameters for Tubes ten inches in length. THE CARE AND USE OF MICROSCOPIC LENSES. The risk to valuable objectives from handling, by those unac- quainted with the delicacy and care required to prevent serious injury, calls for some suggestions to those who are about to commence the study of Microscopy. A paper on this subject, read by William Wales before the New York Microscopical Society, contains so many good points we copy it entire: “ However good the lenses of an instrument may be, they will not do their best work except when properly cared for and properly used. Yet I have met with reputable microscopists who do not in practice appreciate this obvious truth. Let me show you how a lens is cleaned. My implements are four—an old, soft, silk handkerchief, a small stick of soft wood, a phial of alcohol, and a watchmaker’s glass ol two powers. I have here an eye-piece. I will first examine it with the magnifying glass, by reflected light, to learn its condition. If it be found to need cleaning, alcohol is to be applied with the handker- chief. This liquid must not be allowed to touch the lacquer, but the cell which holds the lens will not be harmed by it, since that haS been burned black with acid. If, after the cleaning, fibers from the cloth be found adhering to the lens, they may be blown off by a quick breath. “I have brought an objective which was sent to me to be cleaned. I will attach it to an instrument, and will place under it a slide of familiar diatoms. Now view the object through the lens. It looks so obscure that you will all exclaim, ‘ Well, this is a very poor objective;’ whereas it is of excellent quality, as you shall presently see. In it are eight pieces of glass. The back combination is composed of two crowns and the flint; the middle of a double concave flint and a double convex crown ; the front of two crowns, with a flint between them. It has, probably, not been cleaned for twenty years. Suppose your watch to have been thus neglected ! I will now clean this ob- jective. I begin the work by unscrewing the cells. I then moisten a