SILBEE LIGHT 777 



capable of preventing the bottom from fouling, and at the same time resisting the 

 process of oxidation. To the solution of this problem Mr. Muntz, who was a metal- 

 roller at Birmingham, directed his attention, and commenced a series of experiments, 

 which resulted in his taking out a patent in 1832. This invention, slowly, but 

 steadily, attracted the notice of the shipping interest of the country, and it appeared 

 that in 1834, in the port of London, twenty ships were sheathed with metal prepared 

 by Muntz's patent process. The number gradually increased, until in 1843 there were 

 in the same port 257 vessels sheathed with the new composition, and now it is very 

 generally used. The improved metal sheathing is a mixture of copper and zinc, which 

 is cheaper than copper, more easily worked, and lasts longer than the pure metal. In 

 the specification of Mr. Muntz's patent, the nature of his invention is thus described : 

 ' I take that quality of copper known to the trade by the appellation of " best selected 

 copper," and that quality of zinc known in England as " foreign zinc," and melt them 

 together in the usual manner, in any proportions between 50 per cent, of copper to 50 

 per cent, of zinc, and 63 per cent, ot copper to 37 per cent, of zinc, both of which 

 extremes, and all intermediate proportions, will roll at a red heat ; but, as too large 

 a proportion of copper increases the difficulty of working the metal, and too large a 

 proportion of zinc renders the metal too hard when cold, and not sufficiently liable to 

 oxidation, I prefer the alloy to consist of about 60 per cent, of copper to 40 per cent, 

 of zinc.' See MUNTZ METAL. 



Various unctuous preparations and paints have been introduced for the purpose of 

 coating the sheathing on the bottoms of ships. The secret of all of them is the presence 

 of a metallic oxide which is offensive to both the vegetable and animal organisms. 



SK'KIiZiS. Hollow projectiles filled with combustible materials. See AETUXEHT. 



SHEXiIiS OF IVTOIiLUSCA. Many of these are used for ornamental manu- 

 facture. They will be found described under CAMEO. 



SKERRY WINE. See WlNE. 



SHIFT. Aminer's term. As used in Alston Moor and the Northern mines, a shift 

 is the quantity of lead ore contained in six or eight waggons, and amounts to about 

 240 kibbles of 14 quarts each; each waggon in a six-waggon 'shift' contains 40 

 such kibbles; while in an eight-waggon 'shift' each waggon contains only 30 kibbles. 

 In collieries a skiff is the time during which the men work in the pit. 



SHIWGXiIWG. Condensing the iron bloom by heavy hammers. See IRON. 



SHODDY, properly so-called, is the refuse of the willowing and scribbling process 

 in the preparation of mungo and wool, and is sold in large quantities for manure. 



SHODEING. Shades (related to the German schutten, ' to pour forth ') are loose 

 stones ; applied to such as are of a mineral character. Shodeing, is tracing those loose 

 stones from the valley in which they may be found up to the mineral lode from which 

 they have possibly at some remote time been removed. In this manner many mineral 

 lodes are discovered. 



SIEWWT Ai Clay coloured by the peroxide of iron and manganese. It is known as 

 raw and burnt Sienna, according to the treatment it has received. It is a good 

 artists' colour. 



SIXiBER XiXSHT. There is so much that is interesting in the progress of the 

 inquiry, which resulted eventually in the production of the Silber light lamps that, we 

 are pleased, at finding ourselves in a position to give a succinct record of that progress. 



The first invention of interest dated from December 20, 1869, and is a method of in- 

 dicating time at night. The figures of the hours are marked upon a glass globe, which 

 revolves, by means of clockwork, around a stationary index. At night, any ordinary 

 night-light is placed in a little glass tumbler which fits upon a platform, and is 

 enclosed by a chimney, around which the globe revolves, the figures then being 

 illuminated from within. 



The lamp used for this purpose is constructed upon the moderator principle, but 

 with a burner in which mineral oil may be used with safety. The moderator lamp 

 could be used, but the disadvantages arising from the liability of its pumps and springs 

 to get out of repair, and from the inconvenience of having to wind it up every four or 

 five hours, led to a search for the means of maintaining the oil-supply at a constant 

 level, not only in one burner, but in any number that might be required. In a patent 

 dated May 20, 1870, Mr. Silber devised the following plan: A ball-cock similar to 

 those used in all water-cisterns, but with a china float, and a new joint which connects 

 it with the elbow, and which, when properly constructed and adjusted, will work as 

 correctly as a clock movement. The china float is not affected by either mineral, 

 vegetable, or animal oil ; and it overcomes the difficulty of producing a float which 

 will act, as readily on petroleum as on water, notwithstanding the lightness of the 

 former, which is to water as 790 to 1,000. The china float is a circular double convex 

 disc, pierced with a hole in the centre. Into this hole is fixed a piece of hard wood to 

 which the arm or lever is attached by means of a metal pin. 



