M. TECHNOLOGY. 519 



bare (where the writing is, therefore), and the prussiate solu- 

 tion acting upon the iron, there is found prussiate of iron or 

 Prussian blue characters corresponding to those scratched 

 upon the plate. The number of copies that may be pro- 

 duced by this electro-chemical action is almost unlimited, 

 and the formation of the Prussian blue lines is, of course, in- 

 stantaneous. 12 A, February 8, 1872, 292. 



IMITATION OF MAHOGANY. 



A method is now in use in Paris by which almost any kind 

 of wood of close grain can be made to imitate mahogany so 

 closely as to render it almost impossible to distinguish be- 

 tween the real and false article. The w r ood is first planed so 

 as to render it perfectly smooth, and is then rubbed with di- 

 lute sulphuric acid. Afterward an ounce and a half of drag- 

 on's-blood dissolved in a pint of alcohol, and half that quan- 

 tity of carbonate of soda, are mixed together and filtered, and 

 this liquid is then rubbed, or rather laid, on to the w T ood with 

 a soft brush. This process is repeated until in a short time 

 the wood will be found to have the appearance of mahogany. 

 A little cold-drawn linseed oil will restore the polish, which 

 becomes dimmed. It js said that this substitute is now ap- 

 plied with success in Paris to all purposes for which mahog- 

 any was formerly used. 17-4, March 1, 1872, 236. 



LONG LEATHER BELTS FOR MACHINERY. 



A manufacturer of Munich, to obtain belts of great length 

 from the hides of oxen, skins them as hunters do fur-bearing 

 animals, namely, by making a comparatively small opening 

 behind, and stripping the hide off entire. After removing 

 the feet, a kind of bag is left, which is tanned, and then cut 

 round in a continuous strip of the desired width. 5 C\ 1872, 

 xix., 152. 



UTILIZATION OF SUINT. 



In nothing is the spirit of the age more clearly shown than 

 in the efforts made to utilize waste substances. This is be- 

 ing done with such effect that what was formerly got rid of 

 with great difficulty and at considerable expense may become 

 one of the most important objects of manufacture. We need 

 only point to such matters as sewage, the slag of furnaces, 



