90 ANNUAL OF SCIENTIFIC DISCOVERY. 



IMPROVED MODE OF TEMPERING EDGE-TOOLS. 



FOR heating axes, or other similar articles, a heating-furnace is con- 

 structed in the form of a vertical cylinder, the exterior being made of 

 sheet-iron, lined with fire-brick, 4 feet 8 inches in diameter. In the 

 interior of this cylinder four fire-chambers are formed, the inner wall of 

 each being 18 inches long, 4 from front to back, and 4 deep, forming in 

 the whole a circle 3 feet 4 inches in diameter ; under each there are 

 grate-bars, and air is supplied through a pipe connected with a blowing 

 apparatus. A circular table of cast-iron is made to revolve slowly on 

 a level with the upper part of the chambers, and when the articles are 

 to be heated, they are placed upon the table with their steeled party 

 projecting so far over its edges as to bring them directly over the centre 

 of the fire, and the table is kept slowly revolving. The hardening- 

 bath consists of a circular vat of salt water, within which, a little above 

 the surface of the liquid, is a wheel mounted horizontally, with a 

 number of hooks around the outside, on which the articles to be 

 hardened are suspended. The height of the hooks from the surface of 

 the liquid is such as to allow the steeled part only to be immersed. As 

 soon as the hardening is effected, the articles are removed and cooled in 

 cold water. With the best cast-steel a temperature of 510 has been 

 found to produce a good result in hardening in about 45 minutes. 

 Scientific American. 



NEW METHOD OF AMALGAMATING ZINC. 



THE following method of amalgamating zinc was discovered by Pro- 

 fessor Stoddard of Ohio, and communicated to the editor of SUlimaris 

 Journal. It consists in the employment of double chloride of zinc and 

 ammonia (the same solution which is so useful in soldering iron and 

 steel). The zinc to be amalgamated is heated to about 450 or 500 

 Fahrenheit, and the liquid applied by a cloth or pponge, and the mercury 

 suffered to flow immediately over the surface while still moist. The 

 union is instantaneous and complete, and the depth of the amalgamation 

 is easily regulated by the quantity of mercury suffered to remain in 

 contact with the zinc. This method is applicable even when the zinc is 

 thoroughly oxydised on the surface ; but if it has been previously used 

 in a galvanic battery, it is best to cleanse the surface first by immersion 

 in somewhat concentrated hydrochloric acid. A set of Grove's 

 cylinders thus amalgamated, it is stated, has been used at Miami 

 University during a long course of lectures without serious injury and 

 without reamalgamation. 



TO ZINC COPPER AND BRASS. 



PROFESSOR BOETTINGEK, of St. Petersburg, has published a new 

 process for covering plates and wires of copper, brass, &c., with a 

 brilliant coating of zinc. Pour melted zinc into a mortar of heated 

 iron and keep stirring it until it becomes solid. Then place it in a 

 porcelain or other non-metallic capsule, and pour a saturated solution 



