When _Distilled Water_ can be obtained, it should be used. It must have no smell, taste, or color; it must evaporate without leaving a residue; it must give no precipitates with solutions of nitrate of silver, chloride of barium, superoxalate of potash, caustic alkalies, carbonated alkalies, sulphurated hydrogen, or hydrosulphate of ammonia. _Rain Water_ generally contains carbonic acid, carbonate of lime, and chloride of calcium. _Spring Water_ contains the same impurities as rain water, superadded to chloride of sodium, sulphate of lime, carbonate of iron, &c. _River Water._--More free from salts than spring water, but often contains a large quantity of decomposing vegetable and animal matter. This is particularly the case with water taken from the Hudson, from Troy to its mouth; also, the Mississippi, and, in fact, almost all large streams which are navigated. _Lake Water._--All descriptions of stagnant water abound in half-putrified organic remains, as all well know, that the smaller the bulk of liquid, as in the case of the swamp or marsh, the more impure and the more unwholesome it is. _To purify Water._--Much has been said about purifying water for Daguerreotype use. We look upon this, so far as chemical agents are employed, in most instances a loss of both time and money; let every one _filter_ the water for use _often_ and freely and we will guarantee that _success_ will be his reward. We will class water in the following order:-- 1, Distilled water; 2, rain water; 3, brook water; 4, well water; 5, spring water; 6, river water: yet the water from some of our Western lakes would, we think be fully equal to rain water. We have used the water from Seneca lake, and have found it possessing less animal and vegetable matter, than found in the water from any well which we have been compelled to use. * * * * * Isinglass, as it is generally called fish glue, is prepared from the air-bladders of the sturgeon. It is found in commerce under various forms, such as large strings, small strings, and leaves. It is always white, semi-transparent, dry, fibrous, horny, of a faint odor and insipid taste. When a very thin leaf is moved between the eye and the light of the sun, a species of chatoyance is perceived. If macerated in cold water, Isinglass swells and softens; if boiled in water, it dissolves almost without any residue and forms a solution, which, on becoming cool produces a semi-transparent jelly. There are several counterfeits, but all are easily detected. * * * * * PAPIER-MACHE.