526 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



by heating them in pans with two to ten per cent, of sulphur, 

 according to the nature of the oil, until the sulphur is melt- 

 ed, and then allowing them to cool. 14 (7, 1874, CCXI., 77. 



FINE MACHINE OIL. 



To prepare an excellent machine oil, mix 60 parts of 

 oleine with 40 of olive-oil; or 50 of oleine, 40 of clear paraf- 

 tine-oil, and 10 of olive-oil. 9 (7, ccvm., 109, 1873. 



POLISHING POWDER FOE GOLD ARTICLES. 



The following mixture, applied by means of a piece of 

 leather, is highly recommended by Belgian goldsmiths for 

 polishing true gold articles : -| pound of chalk, 3f ounces of 

 clay, 4 ounces of white lead, f of an ounce of carbonate of 

 magnesia, f of an ounce of polishing rouge, all finely pulver- 

 ized and intimately mixed. 14 C, 1874, 212, 80. 



DEVELOPING THE CRYSTALLINE STRUCTURE OF TIN-FOIL. 



The development of the crystalline structure of the tin of 

 tinned iron, for purposes of ornamentation, has been known 

 for a long time, this consisting essentially of the application 

 of a slight acid to the exterior. Tin-foil can also be made to 

 exhibit the same appearance, and in a still more characteris- 

 tic manner ; but the secret by which this was accomplished 

 has until quite recently been well kept. The actual process, 

 according to the English Mechanic, is as follows : 



A perfectly plain and polished cast-iron plate is heated, by 

 a number of small gas jets beneath, to a temperature of about 

 440, or just short of the melting-point of tin, and the gas is 

 so regulated as uniformly to maintain this temperature. A 

 sheet of tin-foil is laid on this plate, and, to bring it in per- 

 fect contact therewith, a roller made of felt or soft cloth 

 (similar to a printer's inking roller) is passed over the foil, 

 which at this high heat loses elasticity and touches the plate 

 all over. The next step is to fuse the tin-foil. To effect this, 

 a row of little gas jets is carried over the upper surface of 

 the foil with a small circling movement : this, in its passage, 

 completely fuses the tin, which quickly congeals again, and 

 may be at once raised, and the operation repeated on another 

 sheet. The movable row of gas jets is simply a small tube 

 perforated with a line of fine holes, and attached to a length 



