Another method of making these cells is as follows:--Two “punches,” similar to those used for cutting “gun-wads,” are procured, of such sizes that with the smaller may be cut out the centre of the larger, leaving a ring whose side is not less than one-eighth of an inch wide. These rings may be readily made, the only difficulty being to keep the sides parallel; but a little care will make this easy enough. For this purpose close-grained cardboard may be conveniently used. It must have a well-glazed surface, else the varnish or cement used in affixing the thin glass cover sinks into the substance, and the adherence is very imperfect. When this takes place it is easily remedied by brushing over the surface of the cardboard a strong solution of gum or isinglass; and this application, perhaps, closes also the pores of the card, and so serves a double purpose. But, of course, the gum must be _perfectly_ dried before the ring is used. For cardboard, gutta-percha has been substituted, but cannot be recommended, as it always becomes brittle after a certain time, never adheres to the glass with the required firmness, and its shape is altered when worked with even a little heat. Leather is often used, and is very convenient; it should be chosen, however, of a close texture, and free from oil, grease, and all those substances which are laid upon it by the “dressers.” Rings of cardboard, &c., have been rejected by persons of great experience, because they are of such a nature that dampness can penetrate them. This fault can be almost, if not totally, removed by immersing them in some strong varnish, such as the asphalt varnish hereinafter mentioned; but they must be left long enough when affixed to the glass slide to become _perfectly dry_, and this will require a much longer time than at first would be supposed. There has, however, been lately brought out what is termed the _ivory cell_. This is a ring of ivory-like substance, which may be easily and firmly fixed to the glass slide by any of the commonly-used cements, and so forms a beautiful cell for any dry objects. They are made of different sizes, and are not expensive.