Dr. H. Wood describes a new cement invented by Dr. J. 6. Hunt, which seems likely to be generally useful, and in some cases extremely valuable. It is prepared as follows: - Take dammar gum, any quantity, and dissolve it in benzole; after obtaining a solution just thick enough to drop readily from the brush, add enough of the finest dry oxide of zinc previously triturated in a mortar with a small quantity of benzole, until the solution becomes white when thoroughly stirred. If not too much zinc has been added, the solution will drop quickly from the brush, flow readily, and dry quick enough for convenient work. It will adhere, if worked properly, when the cell cover is pressed down, even when glycerine is used for the preservative medium; keep in an alcohol-lamp bottle with a tight lid and secure the brush for applying the cement in the lid of the bottle. Its advantages lie in the circumstance that the glass cover can be placed upon the ring of it whilst still fresh and soft, and that in drying it adheres to both cover and slide, so as to form a joint between them of the width of the ring of cement, and not, as with asphaltum, gold-size, etc, simply at the edge and upon the outside of the cover.
The method of mounting with it is as follows: - A ring of any desired size is made by means of an ordinary Shadbolt's turntable, upon a slide, which is then placed to one side to dry; when required for use, the specimen, cover, etc, being all prepared and ready, the slide is again placed upon the turntable, and a new ring of cement put directly upon the old one. The specimen is immediately placed within the cell thus formed, and the requisite quantity of carbolated water placed upon it. The cover, which must be large enough to entirely or nearly cover the cement ring, is now picked up with the forceps, the under side being moistened by the breath to prevent adhesion of air-bubbles, and carefully placed in position. It is now to be carefully and equably pressed down with some force; by this any superfluous water is squeezed out, and the cover is forced down into the cement, which rises as a little ring around its edge. The pressure is best made with a stiff needle, at first on the centre, and then upon the edges of the cover, which may finally be made slowly to revolve beneath the needle point. The slide may then be put aside to dry; or, better, an outside ring of the cement put over its edge in the usual way.
If time be an object, and only a shallow cell be required, the first ring of cement may be dispensed with, and the whole mounting be done in a few minutes.