The RED CEMENT, which is employed by instrument makers for cementing glass to metals, and which is very cheap and exceedingly useful for a variety of purposes, is made by melting five parts of black resin, one part of yellow wax, and then stirring in, gradually, one part of red ochre or Venetian red; in fine powder, and previously _well dried_. This cement requires to be melted before use, and it adheres better if the objects to which it is applied are warmed. A soft cement, of a somewhat similar character, may be found useful for covering the corks of preserved fruit and other bottles, and it is made by melting yellow wax with an equal quantity of resin, or of common turpentine (not oil of turpentine, but the resin), using the latter for a very soft cement, and stirring in, as before, some dried Venetian red. Bearing in mind our introductory remarks, it will be seen that the uniting broken substances with a thick cement is disadvantageous, the object being to bring the surfaces as closely together as possible. As an illustration of a right and a wrong way of mending, we will suppose a plaster of Paris figure broken; the wrong way to mend it is by a thick plate of plaster, which makes, not a joint, but a botch. The right way to mend it, is by means of some well-made carpenter’s glue, which, being absorbed into the porous plaster, leaves merely a film covering the two surfaces, and, if well done, the figure is stronger than elsewhere. On carefully reading over our article, we find one useful substance has been omitted, namely, what is termed _mastic_ cement, which is used for making a superior coating to inside walls, and which must not be confounded with the _resin mastic_. It is made by mixing twenty parts of well-washed and sifted sharp sand, with two parts of litharge, and one of freshly burned and slaked quick-lime, in fine _dry_ powder. This is made into a putty, by mixing with linseed oil; it sets in a few hours, having the appearance of light stone; and we mention it, as it may frequently be employed with advantage in repairing broken stonework (as stairs) by filling up the missing parts. The employment of Roman cement, plaster, &c., for masonry work, hardly comes within the limits of Domestic Manipulation. V. DIVIDING, POWDERING, GRINDING, ETC.