If cement be used to fix the rock-work of the miniature marine landscape, let it be the best Portland cement, which, when dry, must be soaked by filling the vessel with water, and the water changed several times before the tank will be fit for use. The best sand for the artificial beach, or bottom, is the Thames’ sand, used by builders; but this must be washed several times, till the water runs off quite clear, before it is fit for use—any other kind of sand, if that cannot be procured, must be submitted to similar washings. Sea-water can be procured by furnishing the steward or captain of any Thames steamer, or the guard of a railway in connection with the coast, with a clean barrel; the charge, in either case, for carriage and trouble, would not exceed two or three shillings. The artificial salt water has been found sufficient for Zoöphytes, but not for fish and other of the higher class of marine animals, except for a certain given time. The composition for artificial sea-water is as follows:— Common salt 3-1/2 oz. Epsom salts 1/4 oz. Chloride of magnesium 200 grs. } troy. Chloride of potassium 40 grs. } To these are added four quarts of water, and when the salts are thoroughly dissolved, say on the following day, the liquid must be filtered through a sponge; it is then fit for use. Care must be taken to observe whether, when the sun shines and the light is bright, the silvery bubbles of oxygen form upon the fronds of the marine vegetation; and if not, it is certain that the marine plants are not in a healthy state, and must be renewed. Mr. Gosse gives the following final directions as to the class of animals and plants that should be selected in preference for the experiments of beginners. With regard to sea-weed, he observes, do not take Oar-weeds or Tangle; all the Fuci are of a slimy nature, which it is difficult to manage, and as their size is inconvenient, and they have but little beauty, their absence is not to be regretted. Of animals, he says, take:—_Of Fish_—Blennies, Gobies, Wrasses. _Of Mollusca_—Aplysia, Periwinkle, Chitons, Scallops, and Burrowing Bivalves, such as Venus, Pullastra, &c. _Of Crustacea_—Eurynome, Portunus puber, Carcinus mænas, Ebalia, Corystes, the Paguri, Porcellana platycheles, and the Crangones, the Palæmones, that is, Shrimps and Prawns. _Of Annelids_—Pectenaria, the Sabellæ, and the Serpulæ. _Of Zoöphytes_—the Madrepores, and _all_ the Actiniæ.