404 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



oxide, which, it is affirmed, by its great indifference to at- 

 mospheric and chemical agencies, effectually protects the 

 underlying metal from further change from these causes. 

 Dr. Percy lias confirmed the importance of this method; 

 and, in a paper read before the last meeting of the British 

 Iron and Steel Institute, laid down the general proposition 

 that the most effectual mode of protecting metals from at- 

 mospheric action is to impart to them " a coating of their 

 own oxides respectively." This very rational generalization 

 he demonstrated to be correct in the cases of iron, copper, 

 and lead. 



A new process of electroplating, which may become of 

 great utility, has been described in Sillimart's Journal, by 

 Professor A. W. Wright, of Yale College. It is based upon 

 the fact that the various metals may be volatilized by the 

 electrical current. He provides a hollow vessel, from which 

 the air has been partly exhausted, and arranges therein at 

 proper distances apart the poles of an induction coil the 

 article to be electroplated being suspended between the 

 poles. The negative pole carries a small piece of the metal 

 that is to be deposited, and a battery of three to six or any 

 number of cells is employed as may be necessary. The met- 

 al volatilized by the spark is condensed on the cold surface 

 (glass, etc.), forming a firmly adherent, brilliant, and uniform 

 coating. The invention has already been successfully ap- 

 plied in practice, and promises to become valuable. 



The prize offered by the Prussian Minister of Commerce 

 and Industry for a method of preparing plaster casts so that 

 they may be washed when necessary without impairing 

 their sharpness, was lately awarded to Dr. Reissig, of Darm- 

 stadt, who offered the following suggestions: 1st, to con- 

 vert the sulphate of lime into the sulphate of baryta by 

 washing the surface with strong baryta water; and, 2d, to 

 convert the sulphate of lime into silicate by the application 

 of silicate of potassa. The object to be attained is to form 

 a surface which shall not dissolve in water and shall prevent 

 dust from entering the pores. The above methods of treat- 

 ment render plaster casts indifferent to the action of hot 

 water and soap, but leaves them porous and capable of re- 

 taining dust, so that an additional treatment is necessary to 

 remedy this defect. This consists in the application of an 



