78 ANNUAL OF SCIENTIFIC DISCOVERY. 



various decorative purposes. For one such application, the thin 

 plates are first purified by treatment with strong sulphuric acid, 

 and then silvered by the ordinary process adopted with looking-- 

 glass. The mica thus acquires a beautiful silver lustre, and it may 

 easily be cut into any shape to be used for inlaying work. The 

 flexibility of the mica will, of course, allow of its being applied 

 to round surfaces. When a sheet of mica is heated to full redness 

 for a time, in a clay muffle, it loses most of its flexibility, and is 

 changed considerably in appearance. Under reflected light it has 

 a dead silver-white look ; but viewed by transmitted light it is 

 seen covered with gray spots. This latter appearance is lost 

 when two or three pieces are superposed, and the transpar- 

 ency i$ lost. The mica after heating is also a beautiful material 

 for inlaying work. It should be cut into the, shapes required be- 

 fore it is heated. Another very pretty effect is obtained by scat- 

 tering small fragments of mica on freshly poured sheets of gela- 

 tine, and varnishing it with a dark-colored solution of gelatine. 

 Finely ground mica on colored gelatine also shows very pretty 

 effects ; and a very finely ground material mixed with a solution 

 of gum-arabic may be used, Puscher says, for silver ink. Mech. 

 Magazine. 



IMITATIONS OF GOLD. 



* 



A beautiful alloy resembling gold, manufactured in Waterbuiy, 

 Conn., a French discovery, consists of pure copper 100 parts; 

 tin, 17 parts ; magnesia, 6 parts ; sal ammoniac,, 3.6 parts ; quick- 

 lime, 1.6 parts; tartar of commerce, 9 parts. The copper is first 

 melted ; then the magnesia, sal ammoniac, lime, and tartar in 

 powder are added little by little, briskly stirring for about half au 

 hour, so as to mix thorough.!} 7 ; after which the tin is thrown in , 

 stirring until entirely fused ; the crucible is then covered, and 

 the fusion maintained for about 35 minutes, when the dross is 

 skimmed off, and the alloy is ready for use. It can be cast, 

 rolled, drawn, stamped, chased, beaten into a powder or leaves, 

 and none but excellent judges can distinguish it from gold, ex- 

 cept by its inferior weight. Another beautiful alloy, rivalling the 

 color of gold, is obtained with 90 per cent, copper and 10 per 

 cent, aluminium, which must be perfectly pure, of the best 

 quality, and in exact proportion. It is little affected by the atmos- 

 phere, and is strong, malleable, and homogeneous in structure. 



MERCERIZING COTTON. 



To Mr. Mercer must be attributed the discovery of the peculiar 

 action of caustic soda and sulphuric acid upon cotton. This sin- 

 gular process, now called "mercerizing," has the efi'ect of un- 

 twisting the normally twisted flattened tubes of cotton filaments, 

 and converting them into cylindrical tubes. When colors are 

 applied to the cotton so treated, they pass more readily through 

 the minute pores of the tubes, and are precipitated in denser lay- 

 ers in the interior of the latter, whereby darker and more per- 

 manent shades are produced. Cajico so treated becomes greatly 



