"Let a thin slice be cut off from the fossil wood, in a direction perpendicular to the length of its fibres--the slice thus obtained must be ground perfectly flat, and polished. The polished surface is then to be cemented to a piece of plate glass (3 in. long and 1 in. wide) by Canada balsam--a thin layer of balsam must be applied to the polished surface of the slice, and also to one side of the glass--the slice and the glass are now to be laid on any thin plate of metal, and gradually heated over a slow fire, or a spirit lamp, to concentrate the balsam. The heat must not be so great as to throw the balsam into a state of ebullition; for if air bubbles be formed, it is difficult to get rid of them, and if not removed they will prevent the complete adhesion of the two surfaces when applied to each other; the heat of the metal should never be so great that the fingers may not be held in contact with it for a few seconds without inconvenience. When air bubbles are formed, they should be displaced by a small piece of wood tapering to a point; when the balsam is thought to be sufficiently concentrated, and all the air bubbles have disappeared, the slice and glass may be taken from the heated metal, and pressed closely together; a slight degree of pressure will suffice to expel the super-abundant balsam, and this will be facilitated by gently sliding the specimen to and fro on the glass; by this kind of motion any air that may have got entangled when the two surfaces were brought in contact, will also be removed. When the whole is cooled down to the temperature of the air, and the balsam has become solid, that part which adheres to the surface of the glass surrounding the slice should be scraped off with the point of a penknife; and by this operation, it will at once be seen whether the balsam has undergone the requisite concentration; for if it flakes off before the knife, it will be found that the slice and glass will cohere so firmly, that in the subsequent grinding, there will be no risk of their separating from each other; but if the balsam has not been sufficiently concentrated, it will slide before the knife, and in that case the two bodies will not adhere with requisite firmness. If the layer of balsam applied to the two surfaces be not too thick, its due concentration will be accomplished in four or five minutes, provided the application of the heat be properly regulated. The slice must now be ground to that degree of thinness which will permit its structure to be seen by the help of a microscope. This will be accomplished by rubbing the slice, by a rapid circular motion with the hand, on a piece of sheet lead, supplied with a little emery (_size_ No. 1.) moistened with water; when the emery ceases to act, the muddy matter remaining should be removed, and a fresh portion of emery applied; this must be repeated until the surface of the slice is perfectly flat; a sheet of copper must then be substituted for the lead, and the fossil ground as