TUBES FOR EXPOSING SUBSTANCES TO HEAT AND GASES.--This instrument consists of a tube bent in the middle into a U. Pl. 3, fig. 3. It is much employed in chemistry, for containing substances which we wish at the same time to expose to an elevated temperature and to the action of certain gases. This tube can also be employed for cooling gases, or liquids, in distillation; the bent part being, in this case, dipped into water or a freezing mixture, or enveloped in wet paper or cloth. * * * * * TUBES FOR THE PRESERVATION OF OBJECTS OF NATURAL HISTORY, OR OF CHEMICAL PREPARATIONS.--Take a tube of which the width and length corresponds with the object which is to be enclosed; draw it out at one end, and, after having obstructed the point, twist it into a ring. Introduce the object by the open extremity, which you must afterwards draw out; fill the tube with the liquid necessary to preserve the object, and then seal the point. See pl. 2, fig. 27. If you desire to have the power of taking out the object at will--as, for example, when grain is preserved, or when, in chemistry, the tube is employed to contain salts and other compounds, of which small quantities are now and then required for use--you do not seal the end of the receiver, but border it in such a manner that it can be closed by a cork. In some cases a cork is not sufficient to secure the substance from the action of air: it must then be assisted with a little cement. By melting together two parts of yellow wax, one part of turpentine, and a small quantity of Venetian red, a very useful cement for such purposes is obtained. It is sometimes necessary to _suspend_ the objects enclosed within the tube: you then introduce a little glass hook, the tail of which you solder to the upper extremity of the tube; managing this operation at the same time that you make the external ring for the support of the instrument. By turning the hook round cautiously, which is done when the end of the tube is in a soft state, and by cooling the whole with care, you may succeed in fixing the hook in the centre of the tube. See pl. 3, fig. 20. * * * * * TUBE FOR EMPTYING EGGS.--It is a simple tube, drawn out to a capillary point at one end, and bent there into a V. See pl. 3, fig. 23. The application which the author has made of this instrument, and of the tube represented by pl. 3, fig. 26, has been shewn in a memoir inserted in the _Annales des Sciences Naturelles, Tom. XV. Novembre_ 1828, concerning a new method of preparing and rendering durable collections of eggs destined for cabinets of Natural History. * * * * *