with the gold size applied to the edge must then be carefully laid upon the cell, and slightly pressed down, so that all air-bubbles may be displaced. The two portions of gold-size will now be found to adhere wherever the liquid does not remain, although the whole ring may have been previously wet. The outer edge of the thin glass and cell must now be perfectly dried, and a coating of gold-size applied. When this is dry, the process must be repeated until the cement has body enough to protect the cell from all danger of leakage. When some preservative liquids are used, a scum is frequently found upon the surface when placed in the cell, which must be removed immediately before the cover is laid upon it. I believe this method to be perfectly secure against leakage when carefully performed; and some of my friends have told me that their experience (some years) has been equally satisfactory. In using some of the particular kinds of preservative liquids, it will be found necessary to make slight change in the manipulation. This will be best explained by mentioning a few objects, and the treatment they require. For the preservation of the Mosses, Algæ, &c., Deane’s compound is much used, and considered one of the best media. The specimen to be mounted should be immersed in the compound, which must be kept fluid by the vessel containing it being placed in hot water. In this state the whole should be submitted to the action of the air-pump, as it is not an easy matter to get rid of the bubbles which form in and around the objects. The cell and slide must be warmed; and heat will also be necessary to render the gelatine, &c., fluid enough to flow from the stock-bottle. The cell may then be filled with the compound, and the specimen immersed in it. A thin glass cover must then be warmed, or gently breathed upon, and gradually lowered upon the cell, taking care, as with all liquids, that no bubbles are formed by the operation. The cover may be fixed by the aid of gold-size, Japan, or any of the usual varnishes, care being taken, as before, that all the compound is removed from the parts to which the varnish is intended to adhere. The glycerine jelly of Mr. Lawrance, before mentioned, requires almost a similar treatment. “The objects to be mounted in this medium should be immersed for some time in a mixture of equal parts of glycerine and dilute alcohol (six of water to one of alcohol). The bottle of glycerine jelly must be placed in a cup of hot water until liquefied, when it must be used like Canada balsam, except that it requires less heat. A ring of asphaltum varnish round the thin glass cover completes the mounting.”