68 ANNUAL OF SCIENTIFIC DISCOVERY. 



rolled of any length, and tapered to any required degree. The principle 

 of the action of the machine consists in keeping one of the rollers fixed 

 on its bearings by hydraulic pressure. A valve, regulated by a fine screw, 

 permits the water to escape, and thus, as the operation proceeds, the rollers 

 become more and more separated, and the iron bar less flattened. By regu- 

 lating the valve, so as to allow of greater or less escape of the water, the 

 degree of tapering can be very accurately adjusted. 



NEW PROCESS OF WHITENING PINS AND NEEDLES BIADE OF IRON , 



AND STEEL. 



It is well known that pins made of brass wire, are deficient in strength 

 and elasticity, and accordingly they have been replaced by pins made of 

 iron or steel ; but it is necessary to tin them over. This operation, how- 

 ever, cannot be performed equally well with iron as with brass ; the pins 

 have a rough, uneven surface, which renders them inconvenient to use, as 

 they are liable to tear the cloth. 



Messrs. Yantillard and Leblond, wishing to avoid this defect, formed 

 the idea of first covering the iron with a thin coating of copper, or other 

 metal having a greater affinity for tin than iron has ; but in order that this 

 result should be satisfactorily attained, it is necessary to polish and pickle 

 the pins before coppering them. The above- named manufacturers have 

 most ingeniously effected the polishing, the pickling, and the coppering, 

 by one single operation. To treat, for example, 2 kilogrammes, (a little 

 more than 4 pounds Qh ounces,) 4 litres (about 7 pints) of water, 300 

 grammes (10 ounces 9 drachms, avoirdupois, by weight) of oil of vitriol, 

 30 grammes (15 ounces, 13 grains, avoirdupois) of salt of tin, 40 grammes 

 (1 ounce 4 drachms 17 grains) of crystalized sulphate of zinc (white cop- 

 peras), and 7 grammes (about 108 grains avoirdupois) of sulphate of copper, 

 are mixed together; this mixture is allowed to dissolve during twenty-four 

 hours. The bath being thus prepared, it is to be introduced into a barrel 

 of wood, made pitcher-like, and mounted upon an axis. Into this barrel, 

 which has a capacity of about thirty-five pints, the pins are now to be put ; 

 it is then turned rapidly during half an hour, when the pins will be found 

 to have received a pickling, a polishing, and a slight coppering. After the 

 lapse of this time, 20 grammes (about 10 drachms 8 grains, avordupois) 

 of sulphate of copper, in crystals, (blue stone,) are to be added, and the 

 barrel again turned during ten minutes, when a solid coppering will be 

 effected, with a finely-polished surface. This done, the liquid in the bar- 

 rel is to be decanted off, and may be used repeatedly for the same purpose ; 

 the pins are washed in cold water, then put in a tray containing a hot solu- 

 tion of soap, and agitated for about two minutes. The soap lye is decanted 

 off, and the pins put into a bag, with some fine sawdust, and shaken, by 

 which means the coppered surface assumes a brilliant appearance. The 

 pins thus prepared may be tinned in the ordinary way. The articles made 

 in this way are far more beautiful and useful than those made in the ordi- 



