Most microscopes are furnished with a revolving diaphragm, with three holes, of different sizes, to diminish the quantity of light that is admitted to the object. This instrument is of some use, and offers a ready means of obtaining a very soft agreeable light for transparent objects, viewed with low powers. For this purpose cut a circular disk of India or tissue paper, rather larger than the biggest aperture; scrape a few little pieces of spermaceti, and place them upon it, then put the whole on a piece of writing-paper, and hold it a few inches above the flame of a candle, moving it gently. If this is dexterously done, the spermaceti will be melted without singeing the paper, and when it is cold the disk will be found transparent. Place it over the hole in the diaphragm, send the light through it, and the result will be a very soft agreeable effect, well suited for many purposes, such as viewing sections of wood, insects mounted whole, after being rendered transparent, many small water creatures, etc. Another mode of accomplishing this purpose is to place a similarly prepared disk of paper on the flat side of a bull's-eye lens, and transmit the light of a lamp through it. This plan may be used with higher powers, and the white opaque light it gives may be directed at any angle by means of the mirror beneath the stage. An ordinary lamp may be made to answer for microscopic use, but one of the small paraffine lamps now sold everywhere for eighteen-pence is singularly convenient. It is high enough for many purposes, and can easily be raised by one or more blocks. A paraffine lamp on a sliding stand is still more handy, and all the better for a hole with a glass stopper, through which the fluid can be poured.