530 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



IMITATION OF MAHOGANY. 



A method of treating ordinary wood, so as to produce an 

 almost undistinguishable imitation of mahogany, as practiced 

 very extensively in France at the present time, consists in 

 first planing the surface so as to render it perfectly smooth, 

 and then rubbing it with diluted nitrous acid, which prepares 

 it for the materials subsequently to be applied. Afterward, 

 one ounce and a half of the gum called dragon's blood, dis- 

 solved in a pint of alcohol, and one third of that quantity of 

 carbonate of soda, are to be mixed together and filtered, and 

 the liquid in this state is to be rubbed, or, rather, laid upon 

 the wood with a soft brush. This process is repeated with but 

 little alteration, and in a very short interval afterward the 

 wood assumes the external appearance of mahogany. When 

 this application has been properly made the surface will re- 

 semble that of a mirror, and if the polish should become less 

 brilliant, rubbing the wood with a little cold-drawn linseed 

 oil will restore the former lustre. 18 A, Nov. 3, 1871, 165. 



IMPROVED STAMPING INK. 



An excellent red or blue stamping ink can be prepared by 

 making a saturated solution of fuchsin, or sublime blue, with 

 pure glycerine, and adding afterward, for the red color, mad- 

 der cake, and ultramarine for the blue, thickening with enough 

 dextrine to give the desired consistency. This color possess- 

 es all the peculiarities which are required for good stamping 

 ink. 14 (7,CCI.,278. 



SIMPLE CONSTRUCTION OF CONCAVE AND CONVEX MIRRORS. 



The German journals speak with approval of the invention 

 of ISTesmith, of Manchester, for the ready preparation of con- 

 cave and convex mirrors, which usually constitutes an expen- 

 sive and tedious branch of the glass manufacturer's art. For 

 this purpose a flat plate of glass, about forty inches in diam- 

 eter and three sixteenths of an inch thick, is first cemented 

 to an iron mould, hollowed out hemispherically. By means 

 of a tube attached to this mould all the air can be removed 

 from the hollow space beneath the glass. The simple act of 

 sucking away the air by means of the mouth will cause the 

 disk to bend under the pressure of the external air, so as to 



