224 Sloan's Architectural Review and Builders' Journal. [Sept., CHARCOAL AND CHARRING. CHARCOAL is an exceedingly useful article in building, as well as the other arts. It is a non-conductor of heat; and hence, an excellent packing for surrounding water-pipes, in northern latitudes, where the power of King Frost is absolute. All piles and posts designed to be sunk in wet ground, should be charred as a precaution against rot. Charcoal, having the property of de- oderizing, is a desirable article to be used in filtration ; and may be thus applied to cisterns, by means of a false bottom, and passing the water through it, on its way up to fill the cistern. In this manner every drop of water is purified ; and every particle of matter left below. In the construction of ice-houses, charcoal packed in the surrounding- space, between the outer and inner walls, would tend to retain the solidity or frigidity of the ice. In fact, there are numerous ways in which charcoal becomes a ready aid to the builder ; and it would be well if its merits were a little more known ; or, if known, a little more generally applied. So it is with charring. How often, for instance, have we seen wells and cisterns, in cellars, with the unprotected joists of the floor above them rotting rapidly, from the effects of the ever- rising dampness, which impregnates the aii This is peculiarly the case in privies ; and it is not a little strange, that calculating, sensible builders will not take the trifling and most inexpen- sive trouble of carbonizing, or charring the exteriors of such timbers. How many fearful accidents have from time to time occurred (especially in those out- buildings belonging to school-houses) from this neglect ; and yet even the Superintendent of Buildings, of New York city — armed with full authority to insure sanitary and safe building — does not, that we are aware, ever look to this matter. What considerable trouble would there be in employing boys, to light little stick fires along a line, over which a beam might be laid, at a reasonable height, to admit of charring ; and this beam turned, until property coated on the sides requiring the precaution. In like manner, piles, shafts of pumps, gate- piers, and so forth. The Durometer. — The instrument for testing the hardness of metals, by drill- ing, is the invention of M. Behrens, an Engineer of Tarbes, in France. It has been thoroughly tried, and it is said that many French contracts for rails now contain a condition that they are to be tested by this apparatus. It consists of an upright cast-iron standard bolted down upon a bed-plate, and provided with a table for supporting the rail or other article to be tested. The spindle of the drilling-tool is capable of being raised and lowered in its bearings by turning a handle for that purpose, and the drill is held down to its mark by a weight fitted to the upper end of the drilling-spindle. Its rotary motion is derived, through a pair of mitre-wheels, from a driving shaft canying the "usual fast and loose pulleys. This shaft has a worm upon it which moves a train of mechanism, in connection with a signal gong, for the purpose of indicating the number of revolutions made by the drill. The apparatus is exceeding^ compact. Its use by French manu- facturers has led to a gradual increase in the hardness of the rails they pro- duce.
